Printing horizontally, or vertically, or diagonally?

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orangezero
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Printing horizontally, or vertically, or diagonally?

Postby orangezero » Wed Jan 14, 2015 12:25 am

First post, but I've been trying to do a lot of reading first. I've built a filament 3d printer and cnc machine, but I've only seen videos of SLA.

If I wanted to print a 5mm cylinder that was 150mm long, would I want to do it vertically, horizontally, or diagonally to get the best chances of success and with the best print quality?

I would guess that the vertical print would take quite a bit longer, but if I only ever wanted to do narrow parts theoretically I could have a longer z-axis and a smaller vat. If horizontal, I'd need less support structure and there would be more force needed to lift each layer, but 5mm x 150mm layers don't seem that bad (a standard screw driven nema17 would work). If vertically diagonal, I'd be using a lot more resin to build support. I'm unsure if it would matter if it was top down or bottom up.

The reason I ask is that some of the kits or pre-built units don't seem to be able to do 150mm very well unless you do them diagonally, so I'm leaning towards building my own. From a cost perspective, it seems much better to build a larger vat and print everything as low as possible, assuming the z-axis could produce the force to separate. Is there a good rule of thumb for a max in regards to surface area for each layer (nema17 vs nema23)?

Thanks for any clarifications or corrections in my thinking.

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PomeroyB
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Re: Printing horizontally, or vertically, or diagonally?

Postby PomeroyB » Wed Jan 14, 2015 1:07 pm

The forces required to move up one layer are nothing to the motor. Leadscrews have huge mechanical advantages, and the people building machines out of Nema 23 sized motors are just wasting money. You could probably even use a Nema 14 or Nema 11 for the Z axis... but the ubiquity of Nema 17s means that they are probably your most cost effective option.

The main problem with large XY build spaces is build plate adhesion. A large amount of surface area will exert a vacuum force that's greater than the force of adhesion to the build plate, causing your part to delaminate. People usually put these large prints at 45 degree angles to cut down on the vacuum force, and different machines can handle different forces... no good rule of thumb, unfortunately.

Another problem (that plagues both bottom-up AND top-down) is resin shrinkage and warping. Shrinkage is a constant percentage (Around 3% for quality resins). This means that a 10mm long rectangle will shrink 0.3mm down the long axis, but a 100mm long rectangle will shrink a whole 3mm!

But to answer your question... the vertical print would hands down be the way to go. The optimal setup for a long cylinder like you want would be a tall top down, with a very thin tank (to save on resin)... But that's a pretty specific setup!


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