Casting Tips

Don’t ask, “Can you cast this feature?” Instead ask, “Should this feature be cast in the prototype?”

Most configurations can be cast effectively. However it can often be considerably more cost and time affective to incorporate some features into a secondary machining operation. In order to do this right you must assemble a team that understands both the intricacies of die casting as well as secondary machining. Missing either of these components can lead you to try to cast features that are too difficult, or to eliminate features that could have been readily and easily cast.

The production alloy may not necessarily be the right alloy for your prototypes.

An example might be the designer of a structural component who went through a prototype program and initial prototypes failed in mechanical testing. A subsequent redesign yielded parts that performed well. The designer however, had prototyped the initial parts in an alloy and process that was not representative of the eventual production process. Although on the surface this resulting redesign may not seem to be a big deal, it may have been totally unnecessary. Imagine also, that this over design caused by the non-representative prototypes added $4.00 to the production cost of each part. Certainly an issue if you are looking at an annual production rate of 500,000 parts.

Another is the designer that prototyped in a material whose heat dissipation characteristics were greater than that of the eventual production material. Imagine the anguish as parts "in the field" failed after prototypes had performed well. This is obviously another situation to avoid.

Determine your prototype quantity requirements.

Is your prototype quantity requirement 10 pieces or is it 250 pieces? Is it 10, and then 250? Is it 10 and then maybe 250? It is helpful for you to try to determine this, and to share this information with your prototype supplier at the quoting stage.

I have often witnessed low quantity prototype projects grow to larger quantity prototype needs. As the need for additional larger volume requirements arise for additional testing, pilot builds, marketing tests, etc., these parts are often produced with tooling that was really more affective in low volumes. If at all possible, you may want to discuss these known or possible quantity requirements with your prototype supplier. If a larger run will be required, the lower volume tooling my be able to be designed in such a manner so as to minimize the cost and timing associated with a tooling upgrade.

Furthermore, you can avoid the possibility that the lower volume tool is designed in such a way that it is not able to be upgraded in a cost affective manner. This could force you to re-tool or to live with the cost penalty of running the larger volumes from a tool designed for low volumes.

Is your casting the pacing item of your company’s prototype build?

You are approaching your prototype build and your casting design is not complete. How many of you have been in this situation?

One course of action is to quickly finish your design and hope for the best. Another possible solution is to contact your prototype supplier regarding your needs and share with them your design issues. Often the prototype source may be able work with the partial design (staying away from areas of potential change) and save time for you. The prototype source may also be able to design the tool in a generic form and allow secondary machining to complete the part when the design is firm. Unfortunately, not all prototype processes allow this, however it is worth investigating.

Time Constraints — when do you really need the part?

Virtually all prototypes are exceedingly time sensitive, some more so than others. It is important for the prototype supplier and design engineer to talk about time lines early in the developmental process. Holding back releasing the prototype build until the last minute, for whatever reason, is not beneficial to a successful prototyping process. The earlier you can bring the prototype supplier into your confidence the better for everyone.

There are often very good reasons for not releasing a design for prototype production. As a prototype supplier, you will be ahead of the game if you level with your prototyping source and lay all your concerns out on the table. Believe me, I am just as interested as you to make sure that your prototype is a resounding success.

We can and will work 24 hours a day to get a prototype done if you absolutely need the part in record time. But, it will cost more. Also, as you know from your own experience, when you are rushed the likelihood of mistakes increases. And when the time available to get the job done is curtailed, then there is also less time to think something through and to deal with unforeseen events.

At times the casting is the pacing item. At other times it is not. Some people will present their part as though it were the pacing item even when it is not. They’ll ask for it in a protracted timeframe. So to be on the safe side they tell the prototype supplier they have to have the part much sooner than they really do. The prototype supplier may have to really scramble and work overtime to get the prototype done only to find out after the fact that the imposed urgency wasn’t necessary. This is generally due to a lack of trust between the designer or buyer and the prototype supplier. The solution is for the prototyper and designer to start working together long before the project release crunch time. The designer can gain valuable insight that will not only expedite the prototyping process but could also help improve the production efficiency of his part.

Selecting the Prototyping Process right for your Application

There is no single prototyping process that is right for every application. But for every application there is a prototyping processes that is the most optimum solution. The critical question to ask yourself is: "What is the primary purpose or use of my prototype?"

If you simply need a three dimensional part to hold in your hand, display at a trade show or have it to serve as the center piece for an early-stage engineering design and production meeting, then there are several options available to you.

But if the prototype is to be used for testing and analysis of critical performance characteristics then your choices are headed in a different direction.

In upcoming tips I will explore some of the prototyping options available to you and when to choose one over another.

In the meantime, if you have concerns about a specific project or application call me, or send me an email. Looking forward to hearing from you.

Hog-out Prototyping Process - The Pros & Cons

A hog-out may, in certain situations, be a quicker way to create a prototype that will ultimately be die cast. But, like any other metal prototyping process hog-outs offer distinct advantages in certain cases and disadvantages in others. The following are simply guidelines to help the designer make a decision as to which process to choose for his specific situation.

Advantages:

• Cost effective in low quantities
• High precision due to the machining process
• Parts can be produced in a very short time once programming is complete
• Strength - parts are very strong structurally

Disadvantages:

• Cost increaes with volume of parts to be produced
• Some configurations are not cost effectively machined
• May not accurately reflect the characteristics of die cast part
• Distortion of test results. Caution should be used if using the hog-out for mechanical testing. Strengths may vary from the eventual die cast component

We do not favor any one prototyping process. The process you choose really depends on a variety of factors and conditions. For more guidance on this subject, please review our Prototype Casting Guidelines and if you have any further questions do not hesitate to send us an email. We are always happy to answer questions.

What is your primary reason for creating the prototype?

Let us assume that the decision has been made that a prototype will be needed before releasing a part for production. So the next question is what type of prototype will you need? Or to phrase the question another way, What is the primary reason for creating a prototype?

If you are working as a member of a design team, you may have one specific reason for wanting a prototype. Another member of the team may have a completely different reason. Be sure that everyone is in agreement on what needs the prototype will have to satisfy. Don’t assume. Assumption is the mother of many failures.

It is important to understand all criteria that are pertinent to each particular prototype. So you may ask yourself, Are we creating this prototype simply for appearance or “fit” only? Will this part be subjected to mechanical testing? Will we be testing for RF leakage? Is corrosion resistance an issue? Is weight and strength a linked issue? These answers to these and other related questions will guide you in the direction of the most suitable prototyping process and subsequently the success or failure of your project.

Some of the options available to you include but are not limited to Sand Casting, Plaster Mold Casting, Investment Casting, Machined Hog-outs, Direct Shell Casting, among others. Now, add to this mix of possibilities the attachment of one of the Rapid Tool options and you get a feel for how confusing a prototyping program can be.

New processes, materials and technologies have only served to add to the options and the pitfalls. If you are facing some tough decisions about a prototype you are contemplating, do not hesitate to give us a call. We are always glad to help any time.

Are you using the right prototyping technology?

Sometimes people make choices that appear to be right but in retrospect find that the choice was made for the wrong reason. Over the years I have witnessed people choosing the wrong prototyping technology in an attempt to shorten their prototype lead-time.

An example of this might be a situation where the size of the prototype exceeds the build envelope of a particular rapid prototype machine. Parts to be used as patterns are constructed in pieces and assembled manually. The sacrifice of dimensional integrity alone might make this process suspect. Now factor in the additional time and labor required and you quickly realize that things are definitely headed in the wrong direction.

Sometimes the desire to utilize the “new” technology entices people to ignore existing processes that not only would have worked just fine but done so more efficiently and effectively in both cost and time.

Another example may be when particular part geometry suits one type of technology but another type is used. Thin walled parts may be better suited to particular types of Rapid Prototyping equipment but we still see people attempting to use technologies better suited for thicker walled components.

A simple way to avoid the trap of using the wrong prototyping process is to ask yourself honestly why you favor one process over another. Honestly review the reason(s) behind the choice, and don’t be fooled by fancy rationalizations. If the process is not ideal for that particular prototype and you are not fully convinced that your prototyper is giving you the best advice then take the time to investigate it further. The characteristics of the part and the reason for producing the prototype (such as mechanical testing) should guide your final choice of process.

How many castings do you really need?

Cost is always a factor when it comes to prototyping. You know you need to produce a certain number of prototypes to test your design. Where do you draw the line on quantity? Is ten castings the right number or should you consider ordering fifteen or twenty just to be safe? Sometimes the limitation on quantity is drawn so tight that there aren’t enough parts to go around for proper testing and evaluation.

The concern is spending too much on the prototypes. This is an understandable concern. But if you address the need up front and in all fairness give yourself enough leeway to have the quantities you truly need for thorough performance evaluation then lay your program out and discuss it openly with the prototyper to find the most cost-effective solution.

Even in the prototyping process where the cost of each part is significant enough to make you think twice about quantity, there is room for maneuvering. There are things that can be done in the prototyping process to give you sufficient quantities without breaking the bank.

Problems don’t get solved in the production casting process

As a designer of a part that will be die cast, you must switch gears mentally when it comes to prototype casting. Do not assume that everything will be accomplished in the casting process. The question that isn’t asked may be the one that trips up the project.

For example: Should this seal groove be cast? Although seal grooves are readily cast in the die casting process, they are more cost-effectively machined in the prototype casting process.

Sometimes the right casting design decision is completely contrary to popular belief. For example: It is commonly accepted that fewer parts in an assembly generally means a lower production cost. That logic would stipulate that it is more cost-efficient to create one casting rather than two. But that theory does not always hold true. When you are struggling with the design for a complex part to make it work as one casting, you may experience the nagging thought that this should not be that difficult.

That nagging inner voice is telling you to try another approach. Once in a while it is more cost-efficient to change a design from a single complex casting into two simple castings. The question is, could that part have been successfully cast as one complex casting? Absolutely! But just because something can be cast does not always mean it should be. So, if you find yourself really struggling with a casting design, you may save yourself time and money talking with an experienced prototyper who can offer his counsel to help you achieve not only the best part design but also the most cost-efficient method of casting it.

What should your prototype cost?

Cost is relative. Something is either expensive, cheap or a good buy depending upon the value received. And so it goes with prototyping. Obviously every buyer, no matter what, wants to make sure that he gets the best value for the money invested. So in the prototyping process, how do you quantify value received?

Since no two prototypes are exactly the same it is difficult to compare the cost of one to another. Well, you can compare the estimate from one prototyper to that from another and compare the price differential. But that will not tell you which one has more value.

So, as an informed and savvy buyer you take into account past experience. You ask yourself: How good do the castings look? What kind of advice did I get from the prototyper? Did the prototyper’s advice make a difference in the final outcome? Can I lean on his expertise to ensure a successful prototype? Did he deliver on his promises? Does he truly understand what I am trying to do or does he just want a sale? Does he ask probing questions? Does he offer recommendations? Do I hear only “yes” or is he qualified enough to say “no” once in a while and support it with wisdom?

Only after having sorted through this array of assessments are you ready to quantify the real value of your prototype sources and decide whether the lower dollar figure is indeed the better value.

The Designer’s Prototype Alloy Guide

356
By far the most common alloy used in prototyping die-castings is Aluminum Association 356. It offers good cast ability, pressure tightness, and surface appearance. When combined with a T6 (solution heat-treated and artificially aged) it provides the following typical mechanical properties as minimums.
Tensile Strength – 35,000 to 40,000 PSI
Yield Strength – 25,000 to 30,000 PSI
Elongation 3 - 6%

A caution regarding 356 Aluminum is that its heat dissipation characteristics are approximately150% those of die cast 380 (in other words it offers greater heat dissipation than the die cast 380). This can deem it inappropriate for some heat sensitive prototypes. Its heat transfer does match die cast 443 Aluminum.

319
When used as a prototyping alloy 319 closely mimics heat transfer characteristics of die cast 380. It offers the following typical mechanical properties as minimums when produced with a T6.
Tensile Strength – 30,000 to 36,000 PSI
Yield Strength – 21,000 to 24,000 PSI
Elongation 2.5%

Although its copper content matches 380, its elevated levels of other trace elements produce a part that does not paint, chem. film, or coat as well as some other alloys. This along with some susceptibility to corrosion has relegated it mainly to prototyping of heat sinks and cylinder heads.

380
In circumstances where strength is not a particular issue for protyping, 380 Aluminum can be used. Examples of this could be switch plates, electronics enclosures, bezels, and other non-structural components.

Others
Other alloys can at times be used to test for a narrower range of characteristics. Examples of this might be 355 Aluminum for minimized elongation of some trans axle components. 360 and or 390 may be suited for clutch or other “wear sensitive” components. Depending upon testing required sometimes the same casting design would be produced in multiple alloys.

Zinc
#12 gravity cast zinc mimics mechanical properties of die cast 3, 5, or 8 zinc. Die cast #12 zinc can be prototyped in #27 zinc.

You need how many parts by when?

Once in a while all the time you thought you had to get a part out of design, through prototype, testing and into production just evaporated. The deadline for required production parts is approaching like a speeding train and you are in a real time-crunch. If you’ve been there before, you know it’s not where you want to be. So is there a way out when caught in this time dilemma?

Here is a way to recapture lost time. If you are coming up on the eleventh hour and need to get production parts quickly, then low volume production of parts by your prototyper is a viable solution. Now, the per-part price for a low volume run will definitely be higher through the prototyping process than production die casting process. You will have to weigh the benefits of having production parts on time versus holding up production and becoming the fall guy.

The per-part cost can vary substantially in low volume production depending upon the prototype supplier’s process. Some prototyping processes are prohibitively expensive to consider for low volume runs. Even if you do not think you will need a small volume of production parts it will be to your advantage to discuss this possibility with your prototype supplier up front. You prototype supplier should then be in a position to offer you the best alternatives and provide you with some cost references so that you are prepared when the need actually arises. Needless to say, it is better to be prepared for such contingencies rather than be caught short and have no way out.

Lost in translation

Have you ever wondered what makes one vendor an absolutely terrific asset to your company and another vendor is just run-of-the-mill. Your vendor’s expertise in specific areas such as prototyping can be your insurance policy for new product success.

However, for this to work efficiently requires that communications be clear, well-thought-out and organized. I’m not talking about the part drawings or files. I’m talking about how well the expectations are communicated. Without precise marching orders for all the parties involved in a prototyping process, chances are something will get lost in the translation especially if you are getting your information filtered through several departments or vendors. It’s “possilbe” is translated into “can do, no problem,” or it can be interpreted as “very difficult” to do.

As the designer and specifier you want to be sure that you are talking to the people actually doing the work. Ask your vendor to bring the expert into the meeting so that you can be certain everyone understands what needs to get done. Make sure your prototype supplier asks lots of probing questions. The tougher the project the more likely he will seek clarification, and possibly offer up options that might prove the difference between success and failure.

We all know that as information gets passed from one vendor to another, by the time it gets to the third, fourth or fifth vendor, something invariably will get lost in translation. And the biggest loser in that situation is the customer, because no matter which way the fingers point his product either doesn’t perform to expectations or misses the production deadline.

It is always better when everyone can be in the same meeting and get the same information. Even if some of the members are on a speaker phone, it is better that they listen in on the critical discussion that will affect their function. But even so, nothing beats having the information spelled out in detail and copying everyone. And if changes need to be made to the design during the prototyping process, make sure the changes are detailed in writing for everyone involved. And by all means consult the experts before sending out change orders.

If your prototyper is truly skilled in his craft, he may be able to save everyone time, money and finger-pointing. After all, no one wants to be part of a failure. Rely on the experts, consult with them, bring them to the important meetings to ensure the success of your prototyping project.

What is the real purpose of your prototype

If this seems like a silly question, it’s not. We all know that prototypes are created to accomplish a variety of things such as testing the mechanical strength of a part, measuring heat dissipation characteristics, fit and whatever else may be required to ensure the success of the design before it goes into production.

Is the prototype being created for design confirmation or design testing? This is more than a semantic difference. Confirming a design may cause one to proceed through the prototyping process in a routine manner. The process becomes a formality tacked unto the tail end of the design process. It’s akin to a quality check at the end of a production run. You really don’t want to discover any problems because there isn’t much time left before the part has to go into production.

However, when one enters the prototyping process with the intent to truly test the part rigorously in order to uncover any potential shortcomings, then you are truly entering the process without preconceived notions. This means you don’t hold back. You push the performance envelope to discover under what conditions the part will fail. In essence, you are looking to fail the part to take a real measure of it’s design characteristics. You huddle with the design team to make sure nothing has been overlooked. You check and double check to make certain that the simulation was exacting.

To properly test your prototype you need time, and time is often in short supply when it comes to prototyping. And you want to get more than a handful of parts to make sure you have enough to go around. You don’t want to hoard your prototypes as though they were ancient artifacts, but get them into the hands of enough people involved in the project to make certain that each has sufficient parts for the testing process. Only after you have been able to measure the breaking point of your design can you truly be confident you know its complete performance characteristics.

How long does it take to produce a prototype casting?

Well, that's a good question and the answer you get will vary. Some folks will tell you it will take four to six or maybe even eight weeks to deliver prototype castings. They could be right. Some jobs are more challenging than others. But what you, as a designer, need to know is that when someone tells you, "I can have this prototype casting for you in about four to six weeks.." I would suggest you make a few more phone calls.

The average time-frame for producing a prototype casting should be about two weeks. Now, that is not to say that on occasion more time might be required due to certain complexities, but two weeks is a good average. That is two weeks from the time the prototyper gets your materials in his hands. In our operation we figure two weeks including casting, machining and parts delivered to your door.

A word of caution: just because we can produce prototype castings within a two-week time-frame does not mean you should wait until the last minute to release materials for prototyping work. Leave yourself some breathing space. If things can go wrong, they will, and they generally go awry when you are under tight deadline. Give yourself the security of knowing that there is sufficient time to not only produce the prototype casting but also enough time to make changes if necessary to meet production deadlines.

Part overheats in prototype testing

Having your part fail in prototype testing may seem like a minor catastrophe, but in reality it is a blessing in disguise. It is better to discover part weaknesses in the prototype process than in the production process, with hundreds, if not thousands of parts out in the marketplace. After all, prototyping is done to test the design.

Let us assume for a moment that heat dissipation is critical to your part’s performance. What if your part overheats in prototype testing? The problem could be in the design, but it could also be in how the prototype is cast and how the test is conducted. Before you rush back to the design computer, take a close look at the prototype itself. In what metal was the prototype cast? Does the casting accurately reflect the characteristics of a production casting? Remember, the prototype casting is only a simulation of the production casting. Take the time to examine the details of the prototype process that is being applied to ensure an accurate simulation. To modify the design without thoroughly analyzing all the issues relating to your prototype may cause you to over-design the part, which may lead to other complications in the production process.

Release the part to prototype supplier before the design is complete?

Here are some of the advantages of releasing your part files to the prototyper before you complete the design.

Releasing the part files to the prototyper before the design is finalized assumes that you haven’t waited until the very last minute to choose the prototyper. This can save you time, especially in the critical final stages before product launch. By collaborating with the prototyper early on, you give him a heads-up as to when the design will be finished, when sample castings will be needed, and how many. This avoids the inevitable scramble at the 11th hour as well as the potential for mistakes caused by haste. Early preparation also respects the prototyper’s need for lead-time in his production schedule. Give him enough time to do the best job with time to spare in case everything does not go according to plan.

Early release of your design also suggests that you are bringing the prototyper into the process to spot potential pitfalls. This, by the way, is a good way to evaluate your prototyper’s expertise and commitment. A sharp prototyper may identify potential issues with the design that could undermine prototyping and production success. Having the prototyper review the design from a production perspective a little earlier than usual allows time for adjustments as needed. Remember, prototyping is done for a number of reasons, not the least of which is to avoid making a “CLE” (career limiting error). While you focus on finishing the design for the part, let the prototyper focus on the production aspects. By working together, you will save time, money and potential headaches.

At Alumacast our experience has shown that early collaboration with the designer reduces stress at crunch time and results in a smoother process and assured success.

How much time will your prototype part require?

That is the nagging question, especially when it comes down to crunch time. Every prototyper has a story about speedy turn-around of a prototype casting project and he may assure you that record turn-around of your casting is not a problem. But be careful about accepting this kind of promotional bravado at face value, especially if you are banking the success of your project on a record turn-around because you have run out of time.

Find out more about what type of casting was involved in this glowing report. If the part you are designing is an “airfit” part, meaning that it does not require close tolerances for a precision fit with a mating part of an assembly, then a shorter than standard turn-around time is quite possible. This is especially true if you only need one or two parts with less than critical dimensions and where a raw casting will be sufficient for the job. However, if your part requires very tight tolerances and has to fit perfectly with another part (in other words, tolerances are critical) then most likely machining will be needed and that will require a secondary operation, consequently more time to complete.

Every part presents a different set of challenges, and seldom, if ever, are the project requirements identical. So remember, whenever tight-fitting tolerances are required for mating parts, allow more time for secondary operations and the potential for unanticipated issues to arise.

Can prototype cast parts be produced in two or three days? Yes they can under special circumstances. However, one of the best ways to avoid unpleasant surprises and high levels of stress is to let your protoper see your design and offer production feedback before you hit crunch time. At Aluma Cast we partner with designers to work out any anticipated production issues well before deadline. This makes everyone’s life a little less stressful and ensures a successful outcome. Call Aluma Cast any time with concerns about your prototype.

What should you do when things don’t go according to plan?

The very purpose for producing a prototype is to uncover potential problems in the product being prototyped. But what happens when problems you did not anticipate occur in the prototyping process?

Sometimes we need to remind ourselves that the prototyping process by its very nature is a combination of art and science. Generally it is a good idea to allow a little extra time in case everything does not go according to plan. If you have factored a little extra time into your prototyping schedule to account for unexpected difficulties, then there is no stress. But if you are up against a hard deadline and your time allotment is tight, then the stress level does increase substantially. So what are your options when you find out some unexpected issues have arisen that will require extra time and attention?

You can camp out on the prototype supplier’s doorstep and hover over his shoulder, watching every step he makes and asking a million questions. If travel is not an option, then you can call him every couple of hours to find out what he is doing. In either case, anxiety tends to move us to micro-manage in the belief that two heads are better than one, as well as the feeling it gives us that we are doing something actively to fix the problem. That sounds good in theory, but generally is terrible in practice. Nobody likes to be micro-managed, especially not when they have a problem to fix.

Here is a simple solution. Leave your prototyper alone. You gave him the job because you believed in his expertise. The trust was established early on. This is not the time to pull your trust in him. If he indeed is an experienced prototype supplier, he will fix whatever the issue is in order to deliver a prototype to you that is satisfactory. In all honesty, the real test of the worth of your prototype supplier is when a problem arises in the process. So give him the support he asks for and the time he requires to fix the process. The outcome, with or without your hand-wringing and micromanaging will determine whether your faith in his expertise was well placed. As long as your prototype supplier is aware of your ultimate deadline, give him the time and space he needs to solve the issues, and solve them he will.

Early decisions in the design process have the greatest financial impact

“A designer's primary objective is to design a functioning product within given economic and schedule constraints. However, research has shown that decisions made during the design period determine 70% of the product's costs while decisions made during production only account for 20% of the product's costs. Further, decisions made in the first 5% of product design could determine the vast majority of the product's cost, quality and manufacturability characteristics. This indicates the great leverage that Design for Manufacturability (DFM) can have on a company's success and profitability.”
by Kenneth Crow, www.npd-solutions.com

In our experience early collaboration with designers is the best insurance to avoiding major pitfalls in the prototyping and die cast production process. As noted in the paragraph above early decisions can make or break your project. Talk to us early on and gain peace of mind.

Casting vs. Fabrication

It is not uncommon for a part to be designed for fabrication only to find that it is more economical to cast the part, especially when quantities are needed.

Shifting from fabrication to casting for the production of a part is no small decision especially once all the production drawings are completed. What seemed like the right decision early on becomes obviously wrong. So what is the most efficient way to change direction at such a late stage?

Some prototypers, such as Aluma Cast, are capable of redesigning your part from fabrication to casting production. How do you determine whether it is better to fabricate a part or cast it. These are all case-by-case determinations based on the complexity of the part, size, production quantities and so forth. Production decisions made at the onset of the design process may seem absolutely correct at that moment in time, and later may prove incorrect. It is therefore advisable to revisit the production decision for a part throughout the design process to make sure that the early decision is still valid as you get closer to the completion of the project.

Tweak Part Design while Prototyping Your Part

Alumacast is able to begin prototyping work before a part design is completely finalized. Due to our uniquely flexible mold making process we can begin work on your prototype while you are completing some minor revisions in one area of your part design. This type of flexibility gives the designer more time to tweak the part design in what may be a critical area without seriously delaying the start of the prototyping process and running the risk of becoming the key factor in delaying the launch of a new product.

How quickly can a prototype be cast?

Remember, no two parts or projects are identical. Therefore, can a part be prototype cast in two days? Absolutely! Does that mean your part can be cast in the shortest possible time? Not necessarily. To avoid unforeseen complications that can derail a well-designed part, it is best if you work in concert with a trusted prototyper early in your design process.

At Aluma Cast we look at a part design from the manufacturability perspective. We ask some of the following questions:

• Is the part going to be machined after casting?
• Will the part be coated?
• Is heat treating being considered?
• Are there mating parts?
• What are the tolerances for the mating parts?
• What mechanical stresses will the part be subjected to?
• What temperature variances will the part be exposed to?
• What aluminum alloy have you chosen for the product part?
• How many parts will be needed for production?
• How soon will the first castings be needed?
• Will the production part be die cast?
• Does the production quantity required justify die casting?

Remember, if time is of the essence, you can get production-quality castings in quantities to meet the immediate demand for parts to avoid holding up initial production. Alumacast can also provide production parts in sizeable quantities on a just-in-time basis to meet long term parts requirements.

Call us if you have any questions, we are in business to give you the best prototype aluminum casting solution. We want our customers satisfied. Satisfied customers keep coming back.

Features that should be machined

In the prototyping process there are certain features on a cast part that should be machined even though they will be cast in the production process. For example:

Small holes should be machined in the prototype casting process. In the die casting process small holes are not an issue, but in a gravity-feed prototype casting process you are time and money ahead by simply drilling the holes in the prototype.

Mating surfaces can also create unwanted challenges in the prototype process that can cost you valuable time and money and lead to avoidable production delays. Quite often prototypes cannot be cast as flat as a production die casting. In many instances mating surfaces on die cast components will fit without secondary machining. But rather than waste precious lead-time getting involved in straightening fixtures and procedures, you are money ahead by simply planning to have the mating surfaces machined in the prototyping process. The end result will be cleaner, more precise, and more time- and cost-effective.

Control the cost of the production die

The prototype process serves many functions, but seldom is it perceived as a way to minimize cost and save time in the production process. But approached the right way the prototype process can be instrumental in clearing your way to production, and it can minimize the cost of the production dies.

As a rule of thumb prototype tooling is approximately 10x to 20x cheaper than a production die. So unless you are absolutely convinced that your part requires no design changes, it is cost-efficient to prototype, test and prototype again, making tooling modifications as needed to perfect and finalize your part design.

Caution: Do not rush through the prototyping phase. Allow yourself enough time to properly test the part, to tweak the design and to retest it before moving forward with building the production die.

It is far more economical to make the necessary design modifications in the prototype tooling than in the production die. There are several factors to consider when making last-minute changes to the production die. Modifications of any kind to the production die are costly. Production must be stopped to pull the die. This means costly down-time while the die is modified. Furthermore, the production life of the die decays with each rework; thus, your cost per part will begin to rise sharply.

Knowing the immediate and longer-term costs associated with making changes to the production die can provide the designer with the information needed to properly test and refine his final design before committing huge sums for the creation of production dies.

The importance of understanding simulation in prototyping

It is important to remember that the prototyping process is often being used to simulate a product die casting. Although this seems rudimentary and obvious to any designers of cast metal components, it does merit mention here. Mechanical and physical properties can be significantly different from the prototyping process to the production process. These differences are often due to different solidification rates of the cast material in the differing processes. As an example, 380 Aluminum cast in a production die will have differing mechanical properties than 380 cast in a prototyping process. An alloy switch and subsequent heat treatment can result in mimicking the production alloy for mechanical properties, but the prototyping alloy selection may have differing heat transfer, vibration dampening or corrosion resistance properties than the eventual production alloy.

For more information on how various aluminum alloys perform in the prototyping process versus the die casting process, please visit casting tip number 13. If you need answers to questions not covered by any our casting tips or have a need for more clarification relating to your specific design, do not hesitate to contact us.

Do you know what design changes will cost you in the prototype process?

It is an understood fact that the whole reason for prototyping is to ensure the best possible part design before committing to the cost of building permanent tooling. Design changes in the prototyping phase of product development can be a normal part of the process. On average 25% to 30% of prototypes result in design changes. For this reason it is important for you to know what kind of changes the prototyper can handle and the approximate cost to make changes to the original prototype tool. In the final analysis the prototype process you choose can greatly affect the cost of design changes during prototyping.

In some prototyping processes if you have to make design changes after initial parts have been produced you might have to start all over again with brand new tooling to effect the changes. Aluma Cast uses rigid tooling that in addition to being more dimensionally stable than some softer materials, also allows for quick and economic design changes.

Contact Alumacast for a consultation on your part design.

Understand the parameters of the prototyping process

Every process has inherent advantages as well as limitations, and prototyping processes are no exception. Understanding the capabilities of the process you choose will avoid undesirable surprises and allow you to achieve optimum results in minimum time. Always seek to work within the proven parameters of the chosen prototyping process; doing so will result in quality prototype components at a reasonable cost. Push the envelope of the technology only when you need to, not because you can.

Cost-effectiveness of low volume production

Besides making a handful of parts for testing, the prototype casting process is also suitable for low volume production. The quantitative limit on our process is its cost-effectiveness as compared to the production-oriented processes such as die-casting or the permanent mold process. The prototype casting process becomes suitable as a production casting process when the quantities you require do not justify the cost of expensive production tooling.

Nanotechnology in Aluminum Prototypes

Alumacast is following the developments in the application of nanotechnology in metal castings. Nano particles offer the potential to greatly increase the strength of lightweight alloys like aluminum while maintaining the inherent properties of aluminum, such as the ease of machining the material. It appears that early successes will be in the casting of small batches of material. We are keeping a close watch on these exciting developments especially as they pertain to prototype aluminum casting and short run production castings.

Alloy heat transfer characteristics in prototyping

Aluminum alloys exhibit different heat transfer characteristics when die cast versus gravity cast. To compensate for that difference Aluma Cast Foundry has developed a heat transfer chart to demonstrate the alloy options available in order to more accurately simulate the heat transfer characteristics the part will exhibit as a production cast part.

Aluma Cast, Inc. Heat Transfer Chart

If heat transfer is an important issue for your cast part, it is vital that you raise the issue before proceeding with the prototype process.

Contact Alumacast for a consultation on your part design.

Thin-wall castings in Aluminum Prototypes

During the course of completing the design for a heat-sensitive, thin-wall casting the engineer was mistakenly advised to thicken the walls of the part design from 3mm to 5mm to accommodate prototyping process limitations. Thin wall prototype castings can present a challenge in the prototype world, but that does not mean that thin-wall parts cannot be cast and properly tested in prototyping processes. The engineer should not be asked to revise the design of the part in order to accommodate the limitations of a select prototyping process. Instead of changing the design to meet prototype process limitations, we recommend working with a proptotype supplier who produces more representative prototypes.

If you have concerns about the prototype castability of your thin-walled design, call us for a free consultation.

When CAD models don’t tell the whole story

Solid models play a useful role in the engineering design world. There are many benefits to using solid models in the design process, not the least of which is the three dimensional perspective of the design. But as good as solid models are, they have their limitations.

Solid models are instrumental in helping the prototyper to more clearly picture the part from various perspectives. That certainly has its advantages. But the solid model cannot replace the specifications provided on a drawing, especially for critical dimensions, and above all, the solid model is no substitute for a thorough briefing by the designer. Calling attention to critical dimensions in the part design that must be achieved in order for the part to function as intended in the final assembly is not something you want to leave to chance.

The best insurance for a successful prototype is to start with a carefully structured checklist that is itemized and covers every little detail in the design from the critical on down. Nothing ever should be left to chance.

Contact us for a free consultation.

Choosing the right vendor for your prototype

There are many prototypers to choose from and a variety of prototyping processes. Selecting the right supplier and/or process can sometimes be a daunting exercise in frustration with questionable results. Every prototyping process has attributes that make it the right choice under certain circumstances. For example, Alumacast is the right choice for your prototype project if the following primary criteria exist:

1. The part is designed for die cast production. The Alumacast process is well suited to simulating part characteristics achieved in the die cast production process.
2. The part design incorporates thin walls. Die casting is often used to produce thin-walled castings. Faithful simulation of the die cast process in gravity prototypes is critical to achieving accurate prototype castings for testing.
3. You require quick turn-around. The day an order is received it goes into the production. There is no queuing up of orders.

There are of course other factors that come into play in making your final selection of a prototype supplier and/or process for your project. If you have concerns about a specific project or application call me, or send an email. We look forward to hearing from you.

What drives the cost of cast prototypes?

As a designer you are aware that every prototype is a one-of-a-kind product, which means there is no standard pricing chart to follow. But here are some of the factors that determine the ultimate cost of your prototype:

• Time – are you allowing enough time to cast the prototype, test it, modify the design if needed, recast and retest?
• Process — is the prototyping process you have chosen right for your design or are you making accommodations to fit your prototype into a process available? The extra time and effort required to make things work in the wrong process may cost you.
• Briefing — have you prepared a check list of critical items to discuss with the prototyper. The list should include things that are not shown on the drawing such as performance requirements? You may want to create your checklist throughout your design process making notes of questions and concerns as they arise.
• Secondary operations — some features should be machined in the prototype process even if they will be cast in the production process. To do otherwise is to waste time and money.
• Simulation — does the chosen alloy provide proper simulation of the production part characteristics?

These five simple steps can help you avoid unnecessary frustrations, anxieties and sleepless nights, and ensure you of a successful outcome. But if there is a nagging concern as you finish your design, call us, we will be glad to give you the benefit of our many years of prototype casting experience.

When do you finalize the design of your component?

Knowing what you really want in your cast part is not just a matter of design, but revealing the reasons behind the design. Is there an outstanding feature in this part? If so, what is the purpose of this feature? What is the best way to cast this part to ensure cost-effective manufacturability.

For the prototyper it is absolutely critical to understand the functionality of the part he is being asked to cast. Occasionally we find that a part design is more complex than it needs to be. As a prototype supplier, we bring a different perspective to a meeting with the customer. Many questions should be asked. The questions that are not asked on the front end will haunt you on the back end.

Accurately Simulate Cast Parts in the Hog-Out Process

In Casting Tip #7 we cited the advantages and disadvantages of using the hog-out process for prototyping parts to be produced in the die cast process. As noted there are pros and cons to every process.

One of the advantages to using the hog-out prototyping process is that there is no tooling involved. Changes in the prototype design are more easily accommodated by re-programming the machine making the part.

If testing the prototype for mechanical strength is vital, then note that hog-out parts tend to be stronger than cast parts. This could misrepresent the mechanical strength of the die cast part. Simulating fillets has an effect on the strength of the entire component, depending upon the location of the stresses and loads in the part design.

When testing for heat transfer in the hog-out prototype, keep in mind that the presence of draft can change the volume of mass of the part and thus skew the heat transfer test results. If you have your part made by a machine shop as a hog-out, the shop may or may not include the draft angles in the prototype. Including the draft angles, fillets and radii, which are inherent in the cast part, makes it more difficult to machine the prototype as opposed to machining the part with straight up-and-down walls. But eliminating the draft, fillets and radii in the hog-out prototype will result in an inaccurate simulation of the die cast part.

Additionally, be aware that the material used to produce the hog-outs might have different heat transfer characteristics than the material used to create the production part in the die cast process.

In the final analysis the selection of the prototyping process should not be based on what is expedient, but which process will simulate the desired characteristics of the die cast component most accurately.

Using the investment casting process for your prototype

Although primarily a production process, die cast designs are occasionally prototyped through the investment casting process. An advantage can be cost effectiveness on longer runs of smaller parts such as hinges, valves and switch enclosures. One disadvantage could be longer lead times or the inability to produce large complex geometries.

The investment casting process can produce some excellent prototype castings; however, there are certain part configurations that do not lend themselves to this process. When the parts are larger or considerably more complex, you may want to consider other prototyping processes.

Turnkey Product Delivery

Does your prototype part call for secondary machining and maybe even powder coating? It can save you time and money if the prototyper can handle these secondary functions for you and deliver a finished product for review. Knowing what you need and expect up front, and discussing these issues with your prototyper can mean the difference between making your deadlines versus losing valuable time in the review and testing of your prototype. At Alumacast, secondary functions are taken into account and managed to provide the customer with a high quality turnkey product delivery.

Meeting Time Constraints in the Prototype Process

Time is always a factor in the production world, but even more so in prototype casting. Recently Alumacast quoted a prototype for a customer that had a compressed timeline. The part was quite complex and producing it quickly was going to be a challenge. In a follow-up conference with the customer we discussed the part and its use. During that discussion we discovered that many of the problematic and time-consuming features were not really needed in the prototype. Although desirable in the production die casting, for cost savings and metallurgical concerns certain design features were not vital in producing the prototypes. In the course of the meeting we agreed to eliminate some features and moved others to secondary operations, salvaging the timeline for the customer.

If you have concerns about a specific project call me, or send an email. We look forward to hearing from you.

Production quantity determines process

The higher the quantity of parts to be produced the more production process options are available to you. Therefore, it is essential that serious consideration be given to the eventual production quantities needed before venturing too far into the design of the part. Know and fully understand the eventual production process so that you can maximize the advantages the chosen process has to offer.

The art and science of sand casting

Recently someone asked how the Aluma Cast process works. "Precision Fine Grain" describes the variation on the sand casting process Aluma Cast uses to achieve high quality sand castings that simulate the die casting process. We apply a super fine grain sand, almost a powder, that is chemically bonded to construct a tool that looks just like the cast part except that it is built as a positive...a die casting die is, of course, a negative. The tool is also slightly larger than the cast part to allow for material shrinkage during solidification. With this tool we can produce an unlimited number of sand molds into which we pour the molten aluminum or zinc. After casting we break the sand mold away, exposing the resulting casting. Further processing may include heat treatment, machining and coating to end up with a part that looks like a die casting and closely mimics the mechanical and/or physical properties of the eventual die cast product. The part is now a viable representation suitable for design integrity verification. This is the process reduced to its basic components. The process is a science because of its predictable, repeatable and measurable results. It is also an art in that it takes craftsmanship to create consistently high quality parts every time.

Looking beyond the prototype

In the design stage of the process, it may not be possible to anticipate what types of changes may develop along the way during a new product introduction. However, where there is the expectation of later changes, the prototyping process can be used to satisfy a variety of contingencies.

For example: Your part may be slated for die cast production, but the product launch team may decide to take a more measured approach to the product introduction, calling for a limited production of parts in stages. The number of parts needed immediately, and the quantity in weeks or months later has yet to be decided. One of the ways to address this uncertainty is to bring your prototype supplier into the picture. He should a able to formulate a production strategy with a variety of options. By making accommodations in the construction of the tooling your prototype supplier will be in a position to meet a variety of production requirements. You may not need to implement this plan, but it can provide immeasurable peace of mind knowing that you are prepared for a variety of outcomes.

Casting draft angles in aluminum prototype castings

Recently claims have been made that sand castings, when used to prototype die castings, require more draft than the eventual die castings. This is absolutely false. Some prototype suppliers may even advise the engineer to change the design to accommodate the prototyping process. The precision fine-grain sand casting process used by Aluma Cast does not require such a change.

Sand castings mimic surface finish of die castings

Contrary to a common misconception, the sand casting process can provide the surface finish typical of die cast parts. Aluma Cast uses a fine-grain sand casting process designed specifically for prototyping die castings. Our typical as-cast surface finish is a 100 RMS.

Sand castings mimic surface finish of die castings

Contrary to a common misconception, the sand casting process can provide the surface finish typical of die cast parts. Aluma Cast uses a fine-grain sand casting process designed specifically for prototyping die castings. Our typical as-cast surface finish is a 100 RMS.

Changing part design to suit the prototype process is not necessary

Contrary to popular misconception, thin-walled castings can be produced in the sand casting process. Thin-wall prototype castings can present a challenge in the prototype world, but that does not mean that thin-wall parts cannot be cast and properly tested in prototyping processes. If you have any concerns about the cast-ability of your thin-walled design, call us for a free consultation. Or contact us through this site.

Can solidification modeling software eliminate the need for an actual prototype casting?

If you need to test the mechanical strength of the cast part, measure heat dissipation or any other mechanical properties you can only accomplish that with an actual metal casting. The software simulates the molten metal flow through the gating systems and how the metal fills the casting cavity of the mold. However, the software simulation can certainly help focus your prototyping process and ensure a successful outcome.

Is your production process locked in at start of design?

Sometimes components are designed in advance of the production method chosen which on occasion places the designer and production team into a potentially compromising situation. Not knowing the production process while designing a part can create unwanted obstacles and at times unnecessary extra work and cost. As a prototype supplier we are in a unique position to guide the designer to the proper production methods allowing the designer to take full advantage of the characteristics of the eventual production process.

Casting complex geometries in prototype

New technologies have proven instrumental in facilitating the production of complex geometries by combining our conventional fine-grain sand casting process with 3D printed cores/molds. Used in combination this allows us to take advantage of some of the positive characteristics of each process.

If you need answers to questions not covered by any of our casting tips or have a need for more clarification relating to your specific design, do not hesitate to contact us.

If you want something specific, ask for it

When communicating the requirements for your prototype, there is always the risk of either under-specifying or over-specifying. Too many details, and you may end up paying for more than you need. If you are dealing with a qualified, professional prototype supplier, make sure to provide enough details on the “must haves,” and trust them to use their expertise and proper judgement on these details.

Meeting the needs of structural loads in prototype

Is the part you are designing going to be subjected to significant structural loads? Talk with Aluma Cast engineering about prototypes with enhanced mechanical properties.

Test your prototype in two materials with one tool

Occasionally we get requests to produce prototypes in both aluminum and zinc. A little known fact is that at Aluma Cast we can cast parts in either zinc or aluminum from the same tool. If you have a desire to test the parts in both materials we can accommodate you with one tool for both materials. Call us if you are interested in exploring this Option.

Do aesthetics matter in prototype castings?

Capturing the aesthetics of a finished die casting in the prototype process can be very important. Some prototype processes would not satisfy these specific requirements. Prototype castings produced with the Alumacast process not only perform like die castings, but also have the look and feel of a production die casting.

Enhancing Part Performance

Grain refining and heat treatment are just two of the tools and techniques used at Alumacast to create prototypes that perform mechanically as close as possible to the performance of the eventual die casting.

If you have concerns about a specific project or application call me at 920-596-1988, or send an email.

Production determines the prototyping process

The operating parameters and characteristics of the eventual production process should be an integral part of the design process. This will help the designer throughout the design development. Keeping the production process in mind will guide design decisions as well as determine the prototyping process best suited to simulate the ultimate production part characteristics.

What to do when your production tooling is no longer available or functional?

There comes a time when your production tooling May no longer be usable. What can you do? You only need a couple hundred parts, but your die casting die or permanent mold is no longer available. Aluma Cast’s low volume casting process may be a viable option for you.

Which prototyping process is right for you?

Every process has inherent advantages as well as limitations, and prototyping processes are no exception. New processes, materials and technologies have only served to add to the options and the pitfalls. Be sure to familiarize yourself with the pros and cons of the various prototyping processes available. And then clarify the reason(s) for creating the cast prototype before releasing the design for production.

To determine which prototyping process is best suited to meet your needs. Ask yourself:

• Are we creating this prototype simply for appearance only?
• Is fit essential with critical tolerances?
• Will this part be subjected to mechanical testing?
• Will we be testing for RF leakage?
• Is corrosion resistance an issue?
• Is weight and strength a linked issue?
• Does heat dissipation play a role?
• Do you anticipate possible design changes?
• Do you know what design changes will cost?
• How many castings will you need to satisfy everyone on the team?

The answers to these and other related questions will guide you in the direction of the most suitable prototyping process and subsequently the success or failure of your project.

Accurate Simulation

These are the two most important words in prototyping.

Regardless of the reason for creating the prototypes, the guiding principle should always be without exception—ensuring accurate simulation of the final production part. Everything else is secondary. Cost? What is the point of saving money on prototypes that do not accurately reflect the production casting? Whatever testing you plan to do with your prototypes make sure that it accurately represents the performance characteristics of the die cast production components.

When does low volume production using the prototyping process make sense?

In the prototyping process there are things that can be done to give you sufficient quantities of production castings without breaking the bank.

If you need to get production parts quickly, then low volume production of parts by your prototype supplier can be a viable solution. You will have to weigh the benefits of having production parts on time versus holding up production.

The per-part cost can vary substantially in low volume production depending upon the prototype supplier’s process. Some prototyping processes are prohibitively expensive to consider for low volume runs. But even if you think you will not need a small volume of production parts it is worthwhile to discuss this possibility with your prototype supplier up front. Your prototype supplier should be able to offer you cost references so that you are prepared if the need arises.

The prototype casting process becomes suitable as a production casting process when the overall quantities you require do not justify the cost of expensive production tooling. Depending upon the size and complexity of the casting quantities of 300 to 500 castings a year is generally the volume that is cost-effective in Aluma Cast Foundry’s fine-grain sand casting process.

How will your part be used?

This is one of the most important questions to ask before beginning the prototyping process. The answer to this question may determine your choice of prototyping options. Below is a real-life situation where neglecting to ask this all-important question unfortunately resulted in a Career Limiting Decision (CLD).

The initial prototypes failed in mechanical testing. A subsequent redesign yielded parts that performed well. The designer, however, had prototyped the initial parts in an alloy and process that was not representative of the eventual production process. Without knowing the real cause of the part failure, the company decided to redesign the part to make it stronger. As a result of over-designing the part, the real expense revealed itself later when the unnecessary redesign added $9.00 to the production cost of each part. With an annual production rate of more than 1,000,000 parts, such an added cost is certainly an issue.