What are the benefits of prototyping? A lot of technology will allow you to make a 3-D part quickly and cheaply, but the key is to be able to functionally test it. Our zinc die casting prototypes are typically about 85% of the strength of the actual die cast part. So if the prototype passes your mechanical application testing, the actual die casting will only be that much stronger.
Other prototype processes will give you a warm fuzzy feeling and something nice to look at, but you're not really learning, not answering the questions: Have I designed this for functionality and manufacturability? Is it going to perform at the appropriate level of safety and reliability? And so on. Our goal is to make sure the part you designed is going to perform in the application. That's where the value is.
What's the average cost of a prototype? Depending on the quantity required, typical costs will run from approximately $1,200 to $2,500.
How long will my prototype take? Most rapid prototyping in zinc will take 2½ to 3 weeks from the receipt of the high resolution '.STL' model (stereolithography format) and a purchase order.
A plastic prototype tool, can be turned around in a 3–6 weeks depending on complexity, though we have done them as quickly as 2–3 weeks.
What do I need to send you to get a quote? We need a high resolution stereolithography 3-D model, which is a .STL format model. We also need the quantities that you want quoted.
How many parts can I get from the prototyping process and how good are they? Typical quantities range from 6, to 12, to 25, to 100, and up to 500. As for quality, we actually get better average results than the standard quoted tolerances for rapid prototyping processes. Very often, you'll get quoted ±.005" or ±.010", which is too much variation for most small part applications. But resolution holds better for small parts than it does for much bigger parts, and we can often get down in the ±.003" or ±.004" range on most small part features.
What is the difference between investment and spin casting? Depending upon the precision needed, the investment cast process is more accurate, but also more expensive. It is typically used when real precision is needed and for small quantities. We do a 3-D print part that has ±.0005" (half-thousandth) resolution. That model becomes the sacrificial part for investment casting. So you need one 3-D print part per investment casting and the resulting prototype parts will probably hold in the ±.002" range.
Spin casting is less expensive as it uses a rubber mold, but it is also less precise. However, we typically investment cast one or two parts, then use those castings to build the rubber mold. This preserves much of the accuracy of investment casting, but allows higher quantities of 25, 50, or even 100 or more. We've done prototype runs as high as 500 pieces, which is still much less expensive than taking the step into production tooling.
Can I prototype a very thin-walled part? A frequent problem with prototyping is wall thickness. Typically, the minimum prototype wall has to be .070"–.080", although, depending upon geometry, we can sometimes get as low as .055"–.060". The problem is that with the die cast version walls can be much thinner.
Die casting injects much faster and under pressure, so you can fill thinner walls. Typical NADCA recommendations are approximately .025" thick walls, but we've gone as low as .010" walls on some miniature parts where the tooling and gating have been designed to maximize flow through those zones.
So if you've got thin walls and need to prototype, what we can do is beef up the walls into the .070"/.080" range—i.e., make the prototypes with excess material—then machine that back down to the required dimensions for testing. The trick is not to alter the design, but to alter the model for the prototype process.
Can a prototype be machined? Occasionally, we machine prototypes from zinc alloy bar stock. This is a special bar stock that has some compressive stress built in—by what's called a “gravity drawn bar process”—specifically for machining zinc prototypes. So if you have thin walls, sometimes straight machining is a better way to get the geometry. However, most of the parts that lend themselves to die casting have complex shapes that, although possible to machine, tend to be difficult to machine and/or very expensive to machine.
How does prototyping work with a plastic part? Plastic prototypes tend to take a little longer, but our goal is still to give you a functional part. Most plastic prototypes will require a prototype tool because we actually injection mold the prototypes to get all the mechanical properties of the process into the part for functional testing. We use the actual material you're designing with, including color concentrate or fillers, so the prototype is truly going to be representative of the production process of injection molding. We keep costs down by using frames and inserts instead of complete molds. Many of our customers actually continue to use these tools for initial production, until sales levels are better known and the capital risk of building multiple cavity production tools is reduced.
What advantage does a pre-hardened steel tool have over aluminum? We do not typically build aluminum molds for injection molding because we've seen too many prototypes end up becoming initial production tools. Then, just when things get going, the tool wears out and you're forced to spend more money. For an additional 15 to 20% you can go right into a pre-hard steel tool which is going to have better durability and much longer life for production.
What is the difference between a prototype and production tool? Production tools are significantly more expensive because a lot more goes into them than the prototype tool. For example, on a prototype tool, very often if there are through holes or “side actions,” we can use inserts to keep the cost down and simplify the mechanics. Once you go into production, however, you need to get labor out of the process, so we'll go with a cam action mold or a core pull mold. These mechanical actions add a lot of cost, as does using hardened tool steel for longer life. You may also have water cooling, or sub gates as opposed to a simple edge gate, and so on.
How much will my production tools cost? Average tooling for a zinc die-casting part can run from $5,000 to over $20,000 depending upon complexity and additional cavities if we're trying to drive high volume. One of the real advantages of zinc die casting is you really don't need as many cavities (which results in less overall part-to-part variation) as you would if you were going to injection mold the part because zinc has a faster cycle time. Plastic molding tends to have a slower cycle, so you need more cavities to get production quantities and still retain responsiveness in production.
Average tooling costs for plastic molds range from $3,000 to over $50,000 depending upon complexity and cavitation. We have been molding for over 45 years and have many standard frames we can use to help our customer save dollars. Instead of buying a complete stand-alone mold, they can just buy cavity inserts.
How long will tooling last? Most of our tooling consists of class A molds geared for high volume production and long life. We have tools that have been running for over 20 years and will typically guarantee a tool for so many million pieces. The trouble is, customers don't want to buy tools, they want to buy parts. Unfortunately, the tool is a necessary evil. It's the path to get good parts, and if it's not built right, we suffer in production and can't offer competitive pricing. That's why we build quality tooling that's going to last.
The other side of this issue is maintaining tooling while it is in production. A lot of shops will take a tool out of a machine and put it on the shelf. Then next time it's needed, they discover a problem. We're very pro-active. When tools come out, they get inspected. We have a detailed check list. We look at any quality issues throughout the run and create a feedback loop to get any of those problems corrected so we can be on time and responsive to future orders. Our tools are always ready.
Will tools for zinc parts last longer than tools for aluminum? Zinc is a heavier, denser material than aluminum, but there is a big advantage to it if your application can tolerate the weight. That is, zinc casts below the tempering point of die steel, so a zinc die cast tool can be good for 5 million shots plus. A typical aluminum tool will run about 150K shots before it starts showing signs of heat checking, or the orange peel effect, as it becomes annealed. By casting at elevated temperatures, you start to draw the hardness out of the tool steel, so it doesn't last as long. So, if you have equal part pricing, over the long haul, zinc is going to be the less expensive.
How do zinc and aluminum compare in terms of part performance? Fairly similar, outside of weight. If you look at tensile strength properties, aluminum is the stronger material, depending upon the grade. But I have actually converted aluminum parts to zinc that have actually outperformed aluminum. With zinc, you pick up some strength in the die casting skin, so if the walls are fairly thin and uniform, zinc can perform equal to or even a little better than aluminum.
What zinc materials do you use? We cast with Zamac 2, 3, 5, 7, and ZA 8. See our section on Zinc Alloys for complete details.
What plastic resins is Fielding familiar with? Our Injection Molding Resins section lists all the different materials we've run, from commodity resins all the way up to very highly engineered resins with fillers and high flow liquid crystal polymers, as well as all kinds of colors.
In general, if a resin is made for injection molding, we've probably run it. But we also have a very open mindset to testing new materials. For example, a lot of our customers are in the electronics and telecommunications fields. Shielding is a big issue in that industry and there are a number of new conductive plastics with shielding capabilities. Recently, we worked with XTech (Extrusion Technology, Inc.) of Randolph, MA, to develop expertise and learn the best molding condition properties to give them the best conductivity and shielding properties. Anyone can mold a material, but to optimize the performance of some high end engineering materials requires designed experiments and downstream testing to get data on the best process parameters. There are subtle nuances in the molding process that we learn only through designed experimentation and testing.
Can you recommend a material for my application? We can help, especially when you consider production. There are all kinds of material resins out there—as well as fillers—and it's important to understand the mechanical properties and what the requirements are. Is it tensile strength that's important? Is it impact resistance?
As an example, we recently took a tool in from a customer that one of their prior molders had brought in from China. They'd had all kinds of trouble running it, and had a 3–4% failure rate. But it was a fairly complex part and nobody could really nail down what was going on. We sampled it, and ran tests on our Instron Tensile tester. We identified some weaknesses in the tool design and came up with four or five fairly minor modifications to improve the processability of the existing material. But as we learned more about the application, it became clear they had an impact strength issue. We recommended an impact modified material. This involved a modest increase in the price of the material, but it was the correct solution and solved the problem permanently. They had no more failures and ultimately no more rework costs.
How can I figure out what quantity is cost effective for zinc die casting? It takes a combination of factors. There are some parts we run only 2,000 to 5,000 parts per year, but because the geometry is so difficult to machine, tooling costs get amortized and the payback on the production tooling is very rapid. For a part with simple geometry, typically it takes 15,000 to 25,000 pieces per year before the numbers start to make sense. Our typical production runs are 100,000 to 500,000 per year. Very often we'll tell prospects, “there's no way we're going to be competitive. We're not going to beat a screw machine, or a stamping. (Part of the value we offer is being able to know when to quote and when not to quote, so we don't waste our time or our prospect's or customer's time.)”
How do you define “small,” “miniature,” and “micro?” The definition of small is a changing target. As technologies advance, the size of component it is feasible to manufacture shrinks: But here's a good rule of thumb we use to differentiate “small,” “mini,” “micro,” and “nano:”
A Small part is generally one that will fit inside a 3" cube
A Miniature part will fit inside a 1" cube
A Micro part will fit inside a ½" cube
And a Nano part will fit in a .100" cube, down to wherever.
What are the keys to miniature part design and production? As a designer, you have to think differently for real small parts. You've got to put all your disciplines together: part design, tooling, and processing. If you don't think about all the required downstream processes and design for them up front, you're going to build in some real headaches going forward. You need a much more integrated approach to design and engineering to successfully make very small parts. For a more in-depth look at zinc die casting for miniature parts, see our recent article, “Miniature Zinc Die Casting: New Promise From an Old Process.”
What size parts does Fielding make? In plastic, any part that will run on a 100 ton machine, down to true miniature and micro parts at 5 tons injection molding. With zinc, the rule of thumb on the high end is any part that will fit within a 3" cube, and on the miniature side, down to parts that will fit on the tip of a pencil… very small.
Production And Experience
What happens if I get a sudden surge in demand for my products? In today's marketplace, everything tends to be Just-in-Time, or full demand. People don't want to build a lot of inventory so we try to work with our customers to be sure we have enough sprint capacity to meet their high end-demand. That's where our cavitation strategy comes in, making sure we don't have to run a job 40–50 weeks a year just to meet average demand. Our goal is to be able to meet annual demand in less than six months. That way, we're sure to have sprint capacity within our tooling scheme, so that if our customer gets a surge, we can service it in a very timely manner: they can grab market share and continue to grow.
If we see that the maximum number of cavities we have means we are going to be tapped out, we recommend a second set of tooling. However, most of our tooling process throughput can cover up to 3 million parts a year, so you'd only consider back up tooling if you were up to 3–6 million plus quantities, which are very high numbers.
What Secondary Processes does Fielding offer? We offer a number of value added processes on our zinc parts, such as internal tapping of threads, reaming holes to tighter tolerances, and general machining. We also handle plating and painting. We have partnered with some of the top platers on zinc die castings in terms of quality, delivery and cost-effective bulk processing. They are all environmentally sound and safe, and we rate them on a quarterly basis. Handling the finishing ourselves simplifies things so our customers don't have to deal with two vendors. And if there are any quality issues, we take accountability. That works out very well and our customers have seen great value in that.
We also do light sub assemblies and hot stamping. Some of our customers provide mating assemblies, and our system is able to keep track of inventory and bills of materials with many different part numbers. So even if something isn't high volume, if it helps us add value in the eyes of the customer, we'll often do it. We do light packaging, cell packaging, plastic bags, sealed bags, kitted packages—i.e., a little package of something like screws that gets packaged with our part—that can simplify a customer's inventory and tracking.
How does Fielding's 45 years of experience help me? Our extensive production to market knowledge can have great value for our customers. We help by learning the intangibles, having a conversation with the customer and understanding what their market is, whether it's mature, and what their needs are. For example, a Fortune 1000 company may have all the engineering talent and resources they need but are interested in automating. In that case, it's knowing what it takes to make parts for automation—that if they end up with slight defects, or part to part variation it's going to cause them problems—and being sensitive to that.
An advantage of zinc die casting is that it is a very good process for automated production lines because it produces parts with very little part to part variation. Zinc parts shrink isotropically, and you can make a high volume of parts with tooling that has tremendous life. You can end up having a really tight standard deviation and that's very important if you have high value automation lines.
At the other extreme is the inventor who has an idea, but doesn't really know anything about intellectual property or patenting, or market research. He might want to jump right into tooling something, and we'll advise how prototyping can be used for market tests or even raising capital if you're looking for investors.
In 45+ years, we've dealt with both extremes and everything in between. That market knowledge allows us to interface intelligently with a prospect and possibly add value. We've been through that process ourselves as inventors, working with other inventors, going through the patent process, bringing a product to market, licensing. You've got to have been there to offer good concrete advice. These things can add significant intangible value in the eyes of our customers. They trust the information they're getting.
What are some of the other intangibles I can get from Fielding? We get five or six emails a day from companies in China that want to build us molds. Their average age is probably five to ten years. Our company is in its 45th year, so there's a lot of corporate knowledge in our systems, and in the way we design. We have documented and codified our knowledge and experience through our ISO documentation, so it's not just in our tool engineers' and process techs' heads. That way, those coming up through the ranks and still learning don't have to make the same mistakes. This is of real value to our customers and helps them get better products to market quicker. In today's market very often the company that wins is the one who hits the market first and doesn't have quality issues; the one that can grab market share and hold it.
Our vision statement preaches flawless execution from start to finish. We often say our customers will pay us a profit—because they understand we have to be profitable in order to serve them—but they won't pay us for our mistakes. Margins are very thin and very often, it's the dumbest vendor who sets the price in the market place, the one who doesn't really know his cost structure. We're not always the lowest priced vendor in the market, but we'll stand toe to toe with anybody in terms of overall value. That's what comes from experience.