Top Down, Wiper needed?

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Phife
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Top Down, Wiper needed?

Postby Phife » Mon Aug 25, 2014 6:39 pm

Hey all,

After many many hours of testing my new bottom up LCD/LED based printer I have decided its just too much trouble dealing with part release from the VAT. I cannot get a successful complete print, part detaches from the build platform and this is with small parts and a FEP flex vat. I can only imagine how much harder it will be once I get to 400x300mm prints.

I will be switching to top down with floating resin. My concerns are with the wiper, is this needed? Im already using the low viscosity resin from Spot-A, its almost like water. Im wondering if I will have issues with layer control if I do not use a wiper.

Can people who have experience with top down chime in and tell me what they think? My assumption is that with the large vat I have, The problem with resin leveling will be greatly reduced. Perhaps just waiting a few seconds between layers is enough for it to level off?

Let me know what you guys think.

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PacManFan
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Re: Top Down, Wiper needed?

Postby PacManFan » Tue Aug 26, 2014 11:45 pm

From what I've read and understand, there are several important factors in top-down printers to ensure consistent thickness of the layers. A heater in the vat can be used to raise the viscosity of the resin so it flows better. A wiper mechanism can be used in conjunction with dipping the object in the vat and raising it up to a level to wipe off the excess resin from the current level. After that, the projector exposes another layer and the process repeats. I have actually just received a prototype top-down unit from a vendor that I'm going to be working with over the next few weeks. I'll report my findings.

Phife
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Re: Top Down, Wiper needed?

Postby Phife » Wed Aug 27, 2014 10:53 am

The problem I face is that my LCD needs to be close to the resin for it to work right. I dont have a projection lens so I cant project the image onto the resin. I only have a few mm of space between the LCD and resin surface so using a wiper will be difficult. I hate to have to change the system to be able to project the image a longer distance and still be in focus, that would make the machine much larger and much more complicated/costly.

Im hoping the large area, low viscosity resin and maybe a little heat will be enough to maintain proper layer thickness.

kakapoopie
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Re: Top Down, Wiper needed?

Postby kakapoopie » Wed Aug 27, 2014 1:40 pm

I've just started testing my top down and have been very happy with the Z behavior so far, no wiper. Just letting the resin self level works great

greglab61
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Re: Top Down, Wiper needed?

Postby greglab61 » Sun Feb 15, 2015 7:59 pm

The wiper also helps to calm turbulence after the build plate has dipped.


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