Supports for production models?


#1

Hi folks, curious for your thoughts on something. I am making my first few runs of pennywhistles on the Form 3 before looking at other mass production, and I’m wondering if I can a) optimize the supports manually for critical surfaces, and b) use manual supports to make the whole thing easier to descaffold. Currently there is no way to tell Preform NOT to put a support on a given surface (where they’re attached to your model rather than the scaffolding), and this has led to some very dicey support placement around the airblade. I’m thinking of modeling in my own supports for these final models.

Mere thousandths of an inch will kill these instruments, so it’s really important that the highlighted areas come out as close to perfect as possible. In this case I have deliberately outset the windway exit somewhat so I can polish it back flat to get a guaranteed 90deg angle on the windway exit, but again that is suboptimal from a labor perspective.

I’ve highlighted these areas below:


My printing orientation with the best results is nose-up (so pointing down into the tank when viewed in action) on maybe a 10deg angle from vertical, with the windway exit overhanging the blade (which seemed to be the only way to keep Preform from attaching supports to the end of the blade).

Any ideas about what a custom support approach would be?


#2

I’m not sure if I understand your problem correctly, but you can edit the supports manually when hitting “edit” in the support window of PreForm. Each touchpoint of a support is then displayed as a grey sphere and you can deselect a touchpoint by clicking on a sphere or you can just place your own spheres.
You can also check off the tick mark for “Internal Supports”, so that the support structure’s base is not attached to the model. But this feature only works if the overhanging part is close to the overall edge of the part, otherwise the supports don’t reach in far enough and you end up with unsupported minima(s).


#3

Yes, I understand how to edit supports. The issue is that there is no way to “protect” a surface or feature from supports that originate on the surface. Turning off internal supports entirely is not what I want, because they are required elsewhere in the piece.

My question is whether anyone here has experience modeling custom, optimized supports directly into the workpiece “by hand” aka in their 3D modeling program of choice.


#4

Yep…

The green is the model, blues and purple are supports. This is built directly on the build platform, but need some extra supports in various places.

Maybe if you show us what you are trying to achieve, we could give you more help.


#5

On the support front, you can edit the preform auto supports by editing and deleting individual supports. Go into edit supports then you are left with the touch points. Click on a touch point and it is deleted. Apply.

Like @billb we often design our own supports down to 300 microns. Our supports were sacrificial sheets instead of columns and these were further supported by a more rigid framework. We also orientated the sacrificial sheets parallel to the sheer direction of the tray on a F2. (the shear forces are different on a F3) Our output was a membrane 80mm long by 8mm wide and 300 microns thick. We did carry out a simple FEA to under stand the forces being transmitted to our part! Bit of overkill but fun. We printed at 25 microns in CLEAR

For your device, my inclination would be to bridge the gap with a sacrificial window ( in your design software) and remove in post processing. You can add supports to your sacrificial window

You seem to be doing all the right things. Printing vertically to get your knife edge right but you will have a compromise on your o-ring grooves!

Out of curiosity, what are your critical absolute dimensions and tolerances?

What we tend to do for a new design is to let preform give its best effort (it is good but not perfect) modify it from our experience then print. As we have a lot of internal structures we more often than not support the external cosmetic surface and clean that up post processing that way we minimise internal supports that are more difficult to clean up.

For precision and stable prints, my go to resin is DENTAL MODEL printed at 25 microns layers.

We are printing some columular parts with a dia of 3.8,mm ht 28.65mm and wall thickness of 300 microns with cross shafts that we ream out afterwards. We have to print vertically to maintain the concentricity of the part. We also print directly onto the platform, but we add a sacrificial thin walled cylinder with a mouse hole to vent and machine off afterwards.

ATB


#6

Interesting information - thanks all for your detailed suggestions! I like the idea of a sacrificial window, since that’s something I had considered but was unsure if it was a good idea. O-ring grooves have come out fine so far printing vertically, but I am already VERY sick of sanding the adjusted windway exit after 6 prints. It’s achieved consistent results, but “not allowing that part to warp in the first place” would be a far better solution. I’m going to work up a few things based on the suggestions here and try again.

If anything, though, I am pleased with my ability to correct the various inconsistencies in printing for a uniform sound across what I’m making. I’m relatively new to instrument making, and this was an element I was worried about.