Hi! I'm quite new to 3d printing and am creating a couple of large models to be used as props in a short film. By large I mean roughly 500x500x500mm in size. This means I will have to print them in parts. The model is kind of like a vase, so I cut it in half and plan to print it lying down on the cut side – since this side will be flat. I plan to glue it along this line afterwards. I have 3mm wall thickness. I have created areas especially for glueing and aligning the part after printing. My question is, does anyone have any experience with printing this kind of large parts to be assembled later? How accurate will the part be if I print the two halves separately? Strong and Flexible says 0.15mm AND 0.15% of the longest dimension, which will amount to 0,8mm, which is quite a lot when two parts need to align perfectly. – Is the most accurate print layer the one closest to the floor/base. In which case my setup should be fine? (Meaning I will get 0.15mm accuracy as opposed to 0.15% of longest side?) – Is the print then also less accurate the higher we get above the ground, the top layers? Mats
That's an interesting challenge. If you could somehow get them printed on the same printer in back-to-back runs, you'd likely have close to the same accuracy. But, if they're printed on separate printers at the different times, then the difference might be noticeable. 3mm for WSF is quite thick.. that's going to cost more than $3,000.00 http://stonysmith.com/wired/VolumeEstimator.asp?L=500&W= 500&H=500&T=3&S=1 If you were able to divide it into say 8 or 16 pieces, you might be able to stack them such that it could all get printed in a single run. That way the accuracy would be uniform across the pieces.
Ah, I see. So the accuracy is a calibration issue more than just "natural variation"? I will have to check with Shapeways if I can request a back-to-back print on the same machine – if not I might have to try your idea. Thanks!
OK, so I'm arranging the 8 parts like you suggested, but then I realized that the parts might not be able to stand firmly on the ground by themselves. Or will they... I realize I sound a bit dumb right now. I'm using Lightwave and can't simulate anything. I cut the egg in half both vertically and horisontally so the pieces are 90 degree slices. I suspect they will fall. And if I arrange them another way I wont free up the space like in your example. I don't know too much about how the print process works, but I reckon the pieces need to be stable otherwise they will fall over during printing? Or is there something I don't know about that helps the models stand up? Best, Mats
Watch the video in the "How it works" link at the bottom of the webpage (you will also see it on the upload page). WSF parts grow layer-by-layer from a bed of nylon powder, and the unsintered powder acts as their support material.
The parts do not need to stand on their own for wsf. If your model is good, it will print just fine. Check out this page https://www.shapeways.com/about/how_does_it_work and specifically this video for an idea of how wsf works. Other printers, notably home printers, may need support structures, but with the SLS (Selective Laser Sintering) technology the material that has not been sintered acts as the support. Also ceramic at Shapeways needs a proper base that it will stand on, but I think this may be more to do with the glazing process. Edit: Dang! mkroeker is too fast for me!
You both beat me to the punch. <grin> @aktuba: They are correct.. for WSF and a couple of other materials, the parts "can't" fall over.. see the referenced videos.
Great! Does this then mean that hollow parts with no openings will trap powder? (Which might explain why this other part I have shows the same price for a solid print as with a 3mm wall thickness). Mats
Exactly - which is why the design guidelines specify minimum parameters for what they call "escape holes" If there is no opening connecting the inside and outside of your model, the software will simply eliminate the internal geometry. If an escape tunnel for the trapped material is provided but too small to be actually useful, the model will upload without problem but will be rejected by the print operators later. (The only exception being the "ultra detail" materials, where ultra-tiny holes are allowed to trap the milky raw material inside the translucent resin for special effects like ship-in-a-bottle)