Can anyone explain why the automatic support generation capability in PreForm leaves some support hot spots (red zones) that require manual insertion of supports?
The red shading is not a good indicator of parts that require additional support, in fact it’s best to ignore it because even while it might not work that well, there’s cases where it’s completely wrong and highlights parts that are clearly supported. The most important thing is that it places supports on islands which it is able to do. In all of my experience you can get much better results by placing supports by hand rather than using the automatic method. This is because you can usually use fewer supports and space them so that they are more easily removed and so that they don’t require as much cleanup.
Thanks for such a helpful and comprehensive response!
Have you come across any online resources that will help me to understand how to optimize my use of manually inserted supports. I assume I can figure it out eventually by trial and error, but I’d prefer to avoid re-inventing the wheel if there is some way to accelerate my ability to intuitively place supports in the right locations.
It’s just from experience, haven’t seen any guides.
I do an automatic generation first with a 1.5mm base and 8mm spacing so that there’s a good amount of room underneath the print. After the initial automatic generation go into edit mode.
You first want to make sure all islands have support, the automatic generation should be able to catch all the required points. Then you want to make sure any fragile parts have support, then you would want to add supports just for general strength which will keep the print in place. If you have a large area that needs support, place them diagonally so that you get better coverage and they’re easier to remove. Use the red coloring as a hint but remember it’s not always correct. Also, sometimes the automatic generation will place points on the inside of the print (if you have intersecting parts) so after the supports are generated do a check to see if it looks like any supports are going through the print which can indicate a point on the inside. You can go back into edit mode and then scrub through the layers to find things like that.
Also, for smaller objects you can get away with a much lower support density. Fewer supports are easier to remove and require less finishing of the print after removal. I often print smaller parts at 0.70 support density. Lower density makes it much easier to break away the model from the supports. But it’s the spacing between the supports that matters so the object has got to be reasonably small with no large surfaces parallel to the tank bottom.
In a similar vein, you can also reduce the support point size quite a bit. I typically go to 0.5mm.
Combined with a reduced density, models printed with smaller point sizes can often be just “unzipped” from the supports by hand. Hold the base in one hand and the model in the other and give it some gentle twisting and the support points break free of their own accord. No need to use the flush cutters (which I find typically results in a marred surface from the cutters making contact in hard to reach places).
As far as support removal, it can be easier to remove the supports right after the print is finished, but for some parts they will warp over time so I leave them on to try to help with that, like right now I have a bunch of small parts I’m not ready to assemble yet so they’re still on the supports and I’ll remove them when I glue them together.
Also, if you’re going to paint it, it can help to keep supports on if they don’t get in the way so that you have something to hold the object while you paint.
Really appreciate so much helpful advice related to my question! I hope to learn enough to be able to contribute back to the community so effectively.
You may want to consider adding a video on your site with some examples of how to optimize support placement and density for different scenarios. I am sure it would be appreciated by newbies like me.
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