questions; print size limitations + top-down vs bottom-down

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nicanor76
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questions; print size limitations + top-down vs bottom-down

Postby nicanor76 » Mon Feb 23, 2015 1:46 am

I'm really considering building a DLP printer instead of buying one. I've built some 3-axis CNC machines in the past so, I think these 3d printers won't be as (mechanically) complex as the CNC machines so am not afraid to go that route.

First question. What's the positive and negatives of a top-bottom and a bottom-up setup? I know top-bottom would require more resin and a deeper vat container, but most I've seen are small print areas.

Second: what's the limitations of the print area? Projector resolution seems to change the print size. Curious why couldn't we just set the projector further away; does it reduce the light required to cure the resin? I'm aiming to have a 7" x 7" print area but seems like most are in the 5"x3" size?

For those that built their printers, what's the time you've spent to get it up and running? A couple weeks, a couple months? I know it will vary pending on how long you spend on it, skill levels, etc.

jkao
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Joined: Sun Jan 04, 2015 5:42 am
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Re: questions; print size limitations + top-down vs bottom-d

Postby jkao » Mon Feb 23, 2015 8:56 am

Resolution will be inversely proportional to size. The highest resolution commonly available projector is 1920 x 1080 pixels.

Your size and resolution will depend on how you distribute those pixels over space.

So if you want 100 micron (0.1mm) XY resolution, you project to 192 mm x 108 mm. For 50 micron resolution, you'd project to 96mm x 54mm, etc...

You can probably achieve the size you want going up to 150 micron resolution, although your maximum printable area will always by 16:9, in proportion to the aspect ratio of the projector.

Light intensity on a given point will go down as area goes up, so your exposure times will get longer as you project bigger.

nicanor76
Posts: 25
Joined: Sun Feb 22, 2015 3:35 pm
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Re: questions; print size limitations + top-down vs bottom-d

Postby nicanor76 » Tue Feb 24, 2015 4:30 am

Thanks for the info on resolution, definitely helps explain the basics.


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