A few noob questions..

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heyarn
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A few noob questions..

Postby heyarn » Tue Jan 27, 2015 8:06 pm

Hi Everyone,

Noob here.. Hope you guys can take the time and help me with these few questions that I have:


Question #1:
I wanted to make a laser SLA, and initially wanted to use an x-y gantry. I wanted to simplify the setup, and was wondering if I could use some cheap stepper motors with 18deg steps, and 100:1 gear reduction as galvos. I noticed that there isn't much talk about using steppers as galvos for SLA application, so I'm assuming that perhaps there are weaknesses in that approach. Would someone care to educate me? Is it a speed limitation? backlash issue? reflection issues? cost? firmware/software? Why don't I see a lot of stepper galvo designs out there?

Question #2:
This is about the top down and bottom up approach.. Quality wise, is there a difference? It seems to me that the top down approach is the simplest and most cost effective way to do it, especially that you can pour the resin back into your storage container after use. Thinking about it a little bit more,
If I go with the top down approach, if the part being printed is large enough, wort shrinkage alter the level of the resin's meniscus in the container? How do top down systems account for that? (or do they not?)

I'm looking to start building soon, and have all the parts on hand. I just want a 3.5x3.5x6 inch build dimension.

Thanks in advance :)

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PomeroyB
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Re: A few noob questions..

Postby PomeroyB » Wed Jan 28, 2015 1:46 am

The issue you'll hit with #1 is speed. Stepper motors (especially ones geared down 100:1) can't go nearly as fast as a galvanometer setup. This is partially due to the relatively cheap stepper drivers we use... but even with high end drivers I doubt you'd be able to match galvos.

As for #2, both top down and bottom up are about on par for quality... provided money is no object. Most high end systems use top down laser scanning, with a dedicated wiper to keep the resin level (To avoid the meniscus effect you mention). On a small scale, top down is indeed simple and effective, but maybe not quite as precise as bottom up. The general idea is that bottom up printers have a barrier on both sides of the layer (The resin tank base and the previous layer), which let's you make very consistent layers. You're at the mercy of the resin surface when it comes to cheap top-downs.

By the way, welcome to the forums!


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