Using the latest PreForm 3.8.0, I’ve had a few prints fail due to parts breaking off during the print using Tough 2000. For the first time in a long time, I found myself running a tray full of resin through a filter (now twice in quick succession).
Since I’ve had great success with Tough 2000, I looked closer at the prints that caused the problems (in all cases, minor revisions of parts that have printed perfectly before in identical orientations). The root cause of the failures seems to be that the auto-generated supports (with default settings for density, touchpoint size, etc.) have left unsupported minima in the print.
Interestingly, PreForm’s “printability” analysis shows no errors and concludes that the part is printable. “Show Minima” (enabled, of course) has a green thumbs-up next to it.
In spite of that, zooming around the model shows quite a few red blotches indicating unsupported areas of the print. When I manually Edit Supports so that I can add them myself, PreForm then complains that it is unable to add a support in that location (probably the reason that the automated process didn’t add them to begin with). Interestingly, once I am in Edit Support mode, PreForm suddenly notices the unsupported minima and tells me that the printability check has failed.
In all cases, the points where I need to add supports are on flat surfaces about a centimeter from another flat surface directly below it. There are other supports close by connecting the same two flat surfaces. In other words, it looks identical to nearby areas that have supports. After some trial and error, it is possible to add enough supports in the vicinity to satisfy PreForm’s printability check.
Has anyone else experienced this? I’ve had it happen with a few different parts that have little in common structurally (other than being generated via OpenSCAD).