The following is taken from the webinar: Break out of the traditional mold – Speed up production using 3D Printing. Here, DSM Application Development Manager, Brigitte Jacobs covers rapid tooling, the use of 3D printed molds, and a recent study comparing stereolithography with other types of 3D printing. This article has been edited for length and clarity.
DSM is a large, global, science-based company that employs over 25,000 people worldwide. They are active in health, nutrition, and materials, and they focus on creating brighter lives for people today and generations to come. How do we do this? We do it by connecting our unique competencies in both life science and material science to create solutions that nourish, protect, and improve the performance of people’s life.
As I mentioned before, I work for the group of Somos within DSM and that group is part of the material science cluster. So this material science cluster consists of three different business groups, and one of them is the engineering plastics groups.
Also, this group recently entered the arena of 3D printing and started to offer filaments based on Armitel and Novamid. The group of Somos I work for is part of the DSM resins and functional materials business group. This group is predominately made up of coating resins. We are a small player in this business group that makes proto-polymer resins for the 3D printing technology.
Somos has been in 3D printing for a long time. We were one of the first players in material development in 3D printing, and have over 30 years experience in this area. In those 30 years, we’ve grown quite a bit. We now have a business center together with our RND group that is based out of Elgin, Illinois close to Chicago and we have recently moved our manufacturing location to Hoek van Holland in the Netherlands.
Rapid tooling is a mold making process that can create tools quickly and without much direct labor. It’s basically a technology that is applied for prototype and low volume production injection molding. So let me make it clear, it’s not a technology that can give you millions of finished parts. In other words, not manufacturing. t’s typically used when the quantity of parts is limited.
It’s a technology that allows you to get injection molded parts to get the real parts in a matter of days rather than weeks. It’s a technology that allows you to test your designs faster or possibly allows you to do more iterations before the final design is finished.
With that said, normally when I give this presentation at a conference, I pass around a mold that was used by an electrical OAM to make switch gears in glass-filled nylon. This printed mold was able to make 47 parts. And I will talk more about this mold and the process conditions that it was run under during the end of the presentation when I discuss some application stories. One can imagine the mold gives an audience a great opportunity to basically feel what a mold feels like and also get an idea of what a finished part coming out of such a mold looks like.
So now let me tell you a little bit about what a rapid tooling stereo lithography mold can offer you. As I’ve explained, it’s a technology that allows you to get the real injection molded part in a matter of days rather than weeks. Typically, when you 3D print your finished part, either through the SMS technology or the FDM technology, you will always have a fairly large discrepancy from the original part. That is because this technology doesn’t start from the original material. So the rapid tooling technology isn’t yet intermediate 3D printing technology whereby your printing the mold and the injecting your real finished material into the mold.
We already talked about the short lead times that can be achieved with this technology, so this can obviously shorten your qualification cycle. This can be very important when you have challenging deadlines or trying to bring new products to the market faster than the competitor.
Another advantage that you could get from this technology is that you could save and tooling costs. Especially when the tool design is more complex and requires multiple steps such as EDM and CNC. The cost advantage can be significant. In one example, the customer did some benchmarking studies on costs for a complex mold requiring EDM and CNC. This customer found that actually, the cost difference for a 3D printed mold versus a traditional tooling was 70%. The form printed mold was 70% cheaper than that traditional form tooling. Obviously, when the mold design is less complex and would only require a simple CNC step, then the cost difference becomes less significant.
I have to say that I’ve never seen a technology being more extensive than traditional tooling. But Another advantage that you could get from a 3D printed mold is the design freedom. Especially for those familiar with making molds themselves, it can sometimes be difficult to use CNC technology to make like rounded forms or curved forms. With a 3D printed mold, you won’t have those difficulties or challenges.
All in all, there are quite a few benefits from rapid tooling with 3D printed molds made using stereolithography. What I usually encourage the customer to do is make the technology work for them. So consider perhaps combining technology or redesigning the mold slightly to think outside of the box, or the mold in this particular case.
Plastics that can be handled with the PerFORM molds
Our customers have tested their molds with a variety of different materials. And typically what we see is many different materials can be run on those molds. Usually, for the more simple plastics such as polyethylene and polypropylene, you can easily get a few hundred parts out of a form printed mold.
However, as you go up the plastic pyramid to materials such as ABS, glass-filled nylon, they can still be run on a PerFORM mold, but you won’t get as many parts out of that mold in that particular case. An ABS usually yields in about 50 to 100 parts whereas a glass-filled nylon will give you somewhere in between 30 to 50 parts. Typically, more challenging materials are possible, however, the number of parts will decrease. It’s really a combination of materials that you try to run, design, and the part’s design.
The PerFORM material is a stereolithography resin. It’s filled resin that is made up of over 50% of silica. It’s a great product for testing and can be used in tooling application.
Some of the properties of PerFORM are rigidity and smooth surfaces. It also has good heat resistance, as it has a heat distortion temperature of about 500 Fahrenheit. It’s the composition of stereolithography technology and PerFORM material that provides a great combination of surface quality, accuracy, and part size.
In one study, we compared PerFORM printed molds with other 3D printing technologies in the market. We ran the test with different materials, including the glass-filled nylon and we looked at the quality and the quantity of both finished parts. We ran the test at a slightly lower pressure than normal, and what is important to stress here is that during this test, we did not cool the mold in between cycles. What did learn from this test? The Somos PerFORM clearly outperformed the object mold. It was able to run significantly more cycles and, importantly, the quality of the finished parts was much better with the Somos PerFORM.
We also kept track of the temperature in this experiment and we noticed the temperature increase across the mold was significantly faster with the object mold than with the PerFORM mold. Demonstrating that the thermoconductivity and the heat dissertation with the PerFORM mold was much better than with the object mold.
This product was used by an electrical OEM to make switch gears out of polyamide 6 with 30% glass-filled nylon. This mold was successful in making 47 parts. In this particular case actually the customer decided to run fairly traditional pressure, so in this particular case it was 650 bars, however, as I said, we normally recommend to lower the pressure a bit. We usually keep pressures around the 400, 450 bars.
After each cycle, the mold was opened and it was cooled down with compressed air to bring back the original mold temperature to 80 degrees. This took about 40 seconds. Obviously, this adds some time to each cycle. The process brought the whole cycle, per part, to about a minute. So it’s very important to keep this mold temperature stable and under control, which means that you will have to cool down the mold in between cycles, and we’ve come to learn that the most effective way to cool down this mold is using the compressed air.
Here’s another example. There was a mold used by an OEM to make finished parts in ABS. We ran and injected the material under the recommended temperatures of the product data sheet, and also, in this particular case, each time after a cycle we opened up the mold, cooled it down with compressed air to bring back the mold temperature to original starting temperature.
In another example of a mold used by a medical packaging company, the company’s intention was to make a low-volume production run. So they used a mold to make living hinge parts out of polypropylene, and they were able to make few hundred parts. The mold actually didn’t veer much and was able to be used.
The last mold that I would like to share with you is a mold for a customer specializing in manufacturing components for electric side view mirrors. We organized a design contest and we asked customers to submit a mold design. This particular customer won the contest and we offered to 3D print their mold design in PerFORM. It was quite a challenging design with some overhanging clip mechanisms allowing it to fit on the actuator, as well as having a connection to fit in some wiring, so for the customer, it was really important to have the real part to perform this functional testing before moving to full production with the finished part.
We printed this challenging mold design and were able to run 50 finished test parts out of ABS on it. After that, we were able to run another 18 parts of glass-filled nylon through that same mold.
In summary, let me start by saying that this is a technology that is predominately used when part sizes are relatively small, so, less than five inches. This is more driven by cost and time of the mold than performance. Therefore, I would not recommend this technology for really large parts such as desk boards. The technology is great technology when you’re not sure about your final product yet. So there’s still a chance that your part design or your toolings design might change.