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source: Bauke Janssens

Introduction

3D printers have taken quite a flight last decade and if you have been paying a bit attention you will have noticed that 3d printers have become mainstream, evolving from heavy expensive machinery to consumer products and even gadget-like products for as little as two hundred dollars upwards with printing quality good enough for most hobbyists. In my previous and current work I used B2B printing-services and have investigated the acquisition and maintained of professional Stratasys Dimension FDM-printers, worked with several Makerbots and as well several FormLabs resin-printers.
This article will focus on resin printers and printing parts that can be used as inserts in molds to be used during injection molding.

Resin Printers

Stereolithography (SLA), the technology on which resin-printers such as the FormLabs ones is built, has the benefit of printing with much greater accuracy and detail then FDM-printers (such as the Makerbot, the most known hobby-brand). Because resin-prints are much stronger than filament prints it lends itself for machining afterwards, for inserts during injection molding or for metal casting. In this article we will discuss how to create a print for injection molding and what issues you can expect during this process. For our resin-prints we worked with a FormLabs 2.

High Temperature Resin

When working for one of our clients we were investigating if it would be possible to use the high temperature resin from FormLabs to use during injection molding. Swapping the design part in the mold instead of building the whole mold over again would significantly reduce the costs for production.


Before you start, you should know that FormLabs provides two high temperature resins: one that deforms at 289 and the other that deforms at 238 degrees Celsius. The type you plan to use depends on the material you plan to use during production, the mold-temperature during production and the pressure during the process which should not exceed 0.45 MPa. We printed our part with the 289 degrees Celsius resin at 100 micron layer height and with 100% infill as recommended for inserts during injection molding. The expected printing time for our build was twenty-six hours.

A second thing to be aware of is that the resin is highly viscous and if you plan to print the part flat on the building plate it is almost impossible to get it off afterwards. We had to use a rubber hammer to detach the printed block, leading in one occasion to a completed built with a chipped off corner. Given that we waited twenty-six hours for the print to finish you'll hate yourself for this. To avoid this you should add a support structure in between the building plate and the to-be-printed-model so after printing you are able to seperate the model from the building plate.

During printing we experienced several times that the model got stuck to the bottom surface of the resin-tray, refusing to come off. This malfunction doesn't get detected by the printer itself, leading to a sweeper-mechanism hitting the halfly printed build continuously for hours in a row and other mechanisms in the printer jamming and stalling. You don't want this. Unfortunately you cannot print blocks requiring too much contact surface and after several trials we oriented the entire block vertically so it only printed a small cross-section at a time. The last, successful, print was used as insert during injection molding.

More information

I hope our experience and recommendations for High-Temperature resin-printing can help you during printing. If you have similar problems with resin-printing or want to know more about this topic, feel free to contact us for more information.

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