Top down Sagging :(

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kakapoopie
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Top down Sagging :(

Postby kakapoopie » Mon Jan 19, 2015 4:11 pm

Hi all, I'm running a homebuilt Top down DLP over saltwater and have been struggling with sagging...top sides of my model look perfect but the bottom sides droop down :(

I've tried curing times from 10s down to 5s and it doesn't seem to ever get sharp

Anyone have tips for this?

Thanks,
Vaughan

IMG_20150219_211308.jpg

IMG_20150219_211255~3.jpg
asdasd

IMG_20150219_211128~2.jpg
asd
Last edited by kakapoopie on Fri Feb 20, 2015 1:53 am, edited 4 times in total.

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PomeroyB
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Re: Sagging

Postby PomeroyB » Mon Jan 19, 2015 11:19 pm

When FDM prints "droop", the answer is more support material, so you may try that. However, the rules are a bit different with DLP, so I'm not sure here.


Do you have any pictures?

kakapoopie
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Re: Top down Sagging :(

Postby kakapoopie » Fri Feb 20, 2015 1:53 am

Thanks for the tip...I've tried adding tons of supports but anything facing down still looks...mushy in general

Glacian22
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Re: Top down Sagging :(

Postby Glacian22 » Fri Feb 20, 2015 3:24 am

I've never used a top down setup, but maybe floating more resin on the saltwater would help?

jkao
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Re: Top down Sagging :(

Postby jkao » Fri Feb 20, 2015 4:44 am

When you say "droop", does that mean that on the bottom side, there is more solid material cured than you expect?

You may be experiencing overcure/light bleed where the light for a layer is penetrating through and curing the previous (lower) layers.

If so, there isn't really a settings-based solution for that. The only way to mitigate light bleed is to add pigments to the resin mix to make it more opaque and reduce the amount of excess light penetration.

kakapoopie
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Re: Top down Sagging :(

Postby kakapoopie » Fri Feb 20, 2015 12:39 pm

Exactly JKAO. Isnt it weird that its only happening on bottom sides though? Tops side looks very nice and crisp

jkao
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Re: Top down Sagging :(

Postby jkao » Fri Feb 20, 2015 3:27 pm

If it is light bleed, it would only affect one side of the part. The side closer to the projector would be fine and the side away from the project is getting an extra dose of light in this case. For some types of transparent or translucent resin, the cured part itself acts as a light pipe that directs the excess light down to the bottom of the part. For instance, if the whole part glows while you're curing, that would be a hint that light is being carried through the part and may be being directed to unintended locations.


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