Minor inconsistencies in prints

I have had my Form 2 for some time and have no issues. But now I have two, seemingly related problems:

  1. We are using Tough resin to print small wheels to fit on a McMaster Carr 3mm dowel pin (tolerance .002-.008mm). The bore hole in our design is 3.2mm, which is .2mm larger than the diameter of the dowel pin. This means that the axle should have plenty of room on the bore hole. However, this is not always the case and some of the wheels are quite tight on the axle.

  2. Our SolidWorks model has the wheel thickness as 3.1mm. However, when we measure with calipers the are anywhere from 3.7mm to 3.88mm. This is a big problem for us as we need them to fit within a 3.7mm slot (0.025 mm tolerance). The prints look perfect otherwise.

I am washing in a Form Wash - 20 minutes and curing in a Form Cure for an hour at 60°C. We have many of these wheels to print and they are small, so automating the wash/cure process is critical. Of course, we could sand them, but that seems to defeat the point of CNC fabrication.

Any advice or thoughts as to what’s going on?

How are you orientating the wheels in preform?

I hope the image helps.

As the pdms wears you will have a spread on exposure. Just the nature of the beast. If your using really tight tolerances then you may want to use a polyjet machine or laser sinter depending on feature detail as those don’t degrade over a series of prints.

The PDMS is crystal clear with no visible signs of wear. I’ve used one liter on it but move the models around on the build plate so the PDMS wears relatively evenly. Any sense for tight tolerance how much I can print before it starts to spread? I’ll try it out on a new tray to make sure.


On a fresh tank I don’t think I ever experienced variations like your experiencing across the build platform. For kicks did you try printing a simple shape such as an opened end cube and put a few across the build platforms such as 1 in each corner and one in the middle and compare them. Maybe your getting some sort of optical distortion.

As far as cleaning parts, I found that IPA can distort parts horribly and even shrink them a little. I only use IPA on regions where I need to repair or adhere another part with raw resin.

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