I am printing cores and cavities for use in an injection molding machine. There are approximately 3 X 4 X 1 inches thick. They frequently come out of the printer with a slight warp. Because the material is so brittle, it easily cracks when the press closes. It is impractical to try to sand or machine the parting face so the parting face must try to flatten when closed or it will flash. Neither is a good option.
I have been printing at an angle with supports. They are warped as printed prior to curing. The material handles the heat well but warping and poor tensile strength are not a good mix. I am primarily injecting Polypropylene using the lowest pressure and speeds I can.
Any advice would be greatly appreciated.
Are these cavities or cores sacrificial?
Or are you expecting them to be reused?
Do you need them to be printed because you need to iterate frequent design revisions?
do they always warp in the same direction and approximately by the same amount? ( if so- then you can try and warp the model in the opposite direction prior to print so that they will warp closer to tolerance rather than away from it. )
Have you tried clamping them flat WHILE post curing? Or getting them hot first- ( before turning on the UV lights ) and then clamping while baking under UV. The idea being that the heated resin might flatten more readily without cracking- and the subsequent UV exposure “set” the cure in that shape.
I am planning on running 100 or so shots per core and cavity set.
It makes sense that they if I clamp them flat uncured and then cured while clamped I may have better chance of getting them flat without cracking.
I haven’t found a predictable warp amount or direction at this point. There may be but I haven’t identified it yet.
I did print one where the parting face was parallel to the build platform. I used supports. The parting surface was much higher quality printed in this orientation but the back side of the part was pretty wavy.
I am using them in a tool design course I teach in a tech school. All the students design the part and mold and hopefully have injected molded parts to show an employer.
well you might not have found a repeating warp direction because each time you set up a part you are changing its orientation slightly.
If the parts are always aligned in exact same way- the effect of layer shrinkage ought to be very close to the same from one part to another,
If they crack when clamped for curing, you can try an extra long soak in solvent prior to clamping- but this might change dimensions when the solvent has boiled entirely out.
How about adding more supports? I noticed that my parts come out looking much sharper and without any visible seams/lines when adding more supports or even thicker contact points. Since the opposite sides of the mold isn’t aren’t going to mate then it shouldn’t cause you too much problem.
I have also noticed that raising the part very high (from the raft) could cause some wiggling while it’s being printed so you can lower it a bit. I haven’t used High Temp resin until now although I have one cartridge in supply but these are my observations when it comes to the other Standard resins.
Good Luck and keep us updated on your results!
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