I'm been doing some steam loco bodies in British OO9 scale (4mm scale 9mm gauge) I've just printed out my first batch of 5 in FD of which 4 came out really well but the 5th is a mess. But the 5 th has a rough crystalline feel to one side where it should be flat It is twisted front to back but about 5 degrees Its sprayed outwards in the middle by about 2mm and it has ridges across the back So why did this one go so wrong when the other parts of the print worked fine ? Tom
It could be that these are large enough that they had to print the 5th one in a separate batch, and that it ended up with a different orientation. As to the splaying of the sides.. the models are cleaned in 150 degree water.. if your sides are too thin for their length, then you need to either make the sides a bit thicker, or, what I've done for a couple of models is add a couple of horiontal sprues from one side to the other to help keep everything in line during the (hot) process.. it's worked well for me.
The sides are .72 mm thick and the back part has a strengthening angle attached to it. Given that the side is only 10mm wide at the front and 14 mm at the back this would seem to be more than the material rules suggest as minimum. Do you think it should be thicker still? Tom
stonysmith is right on both counts - it looks like models 1-4 were printed as the back of the cab as the bottom, 5 looks like the side was oriented to be the bottom. Couple of things here - while models 1-4 were being built you have 3 sides of a box enclosed, whereas model 5 only has 2 sides of a box enclosed (weaker). Using the minimum wall thickness (.72mm isn't all that different from .6mm) and affected model 5 more due to the weaker orientation. Personally, I would only use the minimum wall thickness of .6mm for supported walls, and would at least double it for unsupported walls. Having thicker walls with horizontal sprues (like stonysmith mentioned) would take care of both build orientation and the hot cleaning.
I don't think it has anything to do with orientation, the fourth loco has the same striations on the back of the cab. I looks more like it has been slightly overcooked when the wax was melted out. FUD will soften in almost boiling water, and often just getting it to soften will take the stress out of the plastic and it will return to it's intended shape.
It's not just the warping that is the problem it's also missing a few minor details and has what look like crystals of resin on both the side shown and between the boiler and the tank I have though just realized what the ridges on the back are. There are a line of rivets down each side, represented by a hemisphere . These protrusion has been have been joined across the back to make the ridge line you see. Now the question is why ? Tom
Stony, really! 150 degree water... what unit of measurement, or is it that the water has done 30 degrees shy of a half turn? afaik, FUD (& FD) is post-print processed in an oven at about 59 celcius. To me it looks like the '5th' was placed upsidedown in aforementioned oven after being printed sideways up - crystaline structure is lower print side, lines across back are support material and the bowing with twist are wrong oven placement. example vid - fast forward to ~ 6:20
I apologize.. that was "oven" not "water".. that'll teach me to answer forum questions after a day of travelling to the wrong time zone. And.. I meant 150F which is about 65C
Rather than trying figuring out why Shapeways and its partners can't figure out how to maintain quality control and machine calibration on UD and FUD, just ask for a re-print through customer service. This has been a problem since day one, and thicker walls and gussets can't fix a bad print.