✂️Week 3: 3D Printing

Both of the students enrolled at this lab in 2024 have extensive experience with 3d printers and both have their own 3d printers dialled in to perfection (this is a lie but we like to think so). As we both know the characteristics of our printers extremely well through many years of printing, we used this as an opportunity to characterise the printers at the fablab which fortunately happen to be the same printers we both can access at our place of work.

The 3d printer we are using is the UltiMaker S7 and we printed the test files off of the 2024 site (files also linked at the bottom).

We started by slicing the models in cura with the default settings at a 0.2 mm layer height, and them printed them via USB.

Dimensional Accuracy

The S7 did remarkably well with the dimension.stl cube. Each dimension of the outter surfaces printed withing 0.05 mm of the 20mm cube it should be and we saw very little elephant footing or print artifacts.

The inner dimensions of the cube were a little less accurate with the thinnest axis coming in at 0.1 mm smaller than the 10 mm it should be. This is still a decent result.

Tolerances

We printed the clearance.stl test file with default cura supports and after printing and removing supports, all of the 1 mm to 0.4 mm rings had freed themselves. We managed to get the 0.3 mm ring free with a small amount of force, but weren't able to get the 0.2 mm ring free no matter how hard we tried, it feels like it was very close though, maybe a more granular test would be revealing.

Minimum Feature Thickness

The S7 (and also probably Cura doing much of the heavy lifting here) performed really well on the minimum thickness test. It was able to print a free standing wall at 0.2 mm, but it wasn't dimensionally accurate at this point and was printing the wall at a thickness of 0.27. all of the thicknesses below 0.6 suffered from similar dimensional accuracies. All walls thinner than 1 mm also produced a blob print artifact on one side, this blob was about 0.4 mm across the board. The slit test also was performed well and light can be seen through the 0.2 mm slit.

Overhangs

To start with overhang angle, we printed angle.stl and found that the S7 could print geometrically accurate (enough) overhangs to a 60 degree angle. From 60 to 70 degrees we started to observe some deformities, and below 20 degrees there was significant drooping and spaghetti-fication. This machine will be geometrically accurate with the 45 degree rule, and if accuracy isnt an issue, we would be confident to print upto a 65 degree overhang.

Then we printed free.stl which tests for overhang lengths at a 90 degree angle. This is a difficult test for printers and upto a 2mm overhang, it appeared quite clean. This quickly changed though and beyond 5 mm, we experienced significant drooping, but upto 5mm it wasn't too bad.

Bridging

Finally we printed bridging.stl to test bridging capabilities and the S7 didn't even flinch. Even at the 20mm bridge on the test piece there was no observable print defects and it only bowed down an extra 0.04 mm which may be the dimensional innacuracies rather than drooping from the bridging. I would be confident in pushing the s7 to 30 mm of bridging without worrying about any deformities.

Final Results

All in all the S7 is quite a capable machine and it is a bit of an upgrade from our hobbyist-level printers. The final results are

Dimensional Accuracy: +/- 0.1 mm
Minimum part-to-part tolerance: 0.2 mm
Minimum Feature thickness: 0.2 mm
Maximum Accurate Overhang Angle: 60 degrees (50 degrees for REALLY accurate overhangs)
Maximum Accurate 90 degree Overhang: 2mm
Maximum Bridge Length: 20+ mm