In most of our direct customer relations, we hardly get the approval for releasing the practical use of our LCD / DLP / SLA resins in customer projects. But when it is the case and we get the approval for a summary of the test results and applications with our resins, we are extremely glad to share this with the community. The use case as described in this article was presented to us by one of our appreciated customers, Philadelphia Scientific UK, represented by Mr. Aaron Darlow.
Since 1983, Philadelphia Scientific has brought advanced technology solutions to the industrial battery industry. Specialized in the research, design, development and manufacturing of products for motive power, standby and automotive batteries in addition to tools that maximize battery Performance. Philadelphia Scientific serves a global marketplace from multiple locations around the globe and holds an extensive patent inventory that reflects the creative and inventive spirit of their employees.
As the creator and manufacturer of many market-leading products, Philadelphia Scientific continuously develop new innovations to serve the industry. This excellence in engineering, combined with their passion for quality, has made Philadelphia Scientific one of the most trusted brands in its marketplace today. Thanks to Aaron and Philadelphia Scientific for sharing your results and enabling this real scientific summary.
The Challenge of 3D Printed Injections Molds
The need to cover plastic enclosures with injection molded parts is the most common way, cost-effective and mechanically strong enough to protect internal sensitive parts. But depending on the stage of development or the need for a mold that is only needed for a few injection molding operations, the cost of a mold made of metal for injection molding drives up the cost and strains the budget.
3D printed parts that serve as such injection mold are a real option, if several requirements can be met, to name a few:
- withstand the temperature of the injected thermoplastic (such as HDPE)
- resist the mechanical pressure during the injection
- hold space, distances, dimensions of the model (low shrinkage)
- allow a certain re-usability (no „one-time shot“)
Application of High Temp UV Resin as Injection Mold
First of all, let’s describe some details of the mold/part made: The lead probe is used for checking the electrolyte levels in lead acid batteries. „We solder the cable to the lead then over mold to protect the connection and simultaneously make it into a fitting to mate with a holder. For this prototype we were looking at fitting the probe into an existing specialist holder that doesn’t yet have the capability to mount the lead probe. As the holder is an existing part we couldn’t change this to make the design easier so ended up with a fine detail part needed“, describes Aaron Darlow. The front face is approx. 1 mm thick.
As the part needed to cover the lead and cable so the are connected, it couldn’t be simply printed as a prototype, so it had to be made as a mold. Another reason why the mold is not milled, is that the resolution is limited by bit size, the speed would be slow as a long 1mm bit would be needed which could easily break, if cutting too much or too fast. Also any changes would start to incur large cost as new aluminum billets would be needed for each iteration.
Aaron adds: „I could make a mold from Polycarbonate on the FFM printer. However the resolution is slightly less than the resin printer, the finish layer pattern gets transferred to the part, The polycarbonate (PC) molds take longer to print than the resin and the PC mold degrades faster.“ Although the resin shown in the photos has some crazing that marks the prototypes, it will still produce useful prototypes, a PC mold would not be able to do that with the same number of uses.
This leaves the resin as the best solution. The herewith presented results are based on the use of DruckWege Type D High Temp UV resin, indicating a heat deflection temperature at 260°C (HDT).
Experiences With the 3D Printed Mold and Injected Thermoplast
DruckWege shared 4 different materials (v1…V4) for some test runs, whereas V1 is the current formula that is used in the DruckWege Type D High Temp UV resin.
All molds were printed on a Original Prusa SL1 3D printer.
V1 (DruckWege Type D High Temp)
From the first look V1 seems the most robust. The mold made from Type D High Temp started to degrade near the injection inlet with visible crazing after about 5 shots. The material used is Polypropylene, heated to 190° C with ram pressure of 80 PSI.
V2 (New Development Formula for High Temp Applications of DruckWege)
V2 showed some more versatile performance in general. With a quick degradation, it’s more usable for prototyping only, whereas the Type D High Temp had potential for short production runs. Due to its easy application, no issues with adhesion and very fast printing time; „V2 is certainly useful as a prototyping tool“, states Aaron Darlow.
V3 (DruckWege Type D Pro)
Printing was easy and no noteworthy issues were spotted also machining V3 was possible, however at the edges it would shatter in few small areas leaving a rough finish after the injection. When molding with V3 it showed no ill effects from the material contact. However, the mold shattered on the first use causing a failure. On a second try the mold did not shatter.
V4 (like V2, but with further Additives)
From the calibration test: V4 had the lowest exposure time of the resins so would be the quickest to print with. It did have some failures and more warping, but these defects could be traced back to over exposure. When tweaking the exposure time it was still less than used for the other resins but gave a good print quality like V2 & V3. V4 machined well and was easy to work with without any ill effects on the mold. When molding the surface layers in contact with the material began to ‘flake’ away from the first use especially where the injection port opens up into the main chamber.
With focus on prototyping, V4 turned out working fine ahead of all the materials. „It has the greatest printing speed, a good initial print and can be adapted after if needed. Although it does deteriorate immediately it is not to an extent it would cause issue with the function of most of the products I was making and the cosmetic finish wouldn’t be so bad it couldn’t be looked past.“, summarized Aaron Darlow.
Summary of the Test Results of High Temp UV Resins
V1 as Type D High Temp takes the high temperatures the best, especially in combination with the high load of pressure. The robustness in the environment allows a set of molds for short production runs. In the end all materials were working to allow the making of 3D printed molds, however they have different characteristics on printing s and after the plastic injection. High Temp is hard to print, but has the least wear. The material takes some experience to print well. Unlike a standard resin. V2 is easier to print, but showed quick wear after injection molding and showed frayed corners. The Type D Pro is not significantly better than V2 in single-luff behavior from temperature and pressure. V4 was easy to print, but had no improvement in corners (compared to V1).