SLA / DLP printing - Beginner help needed

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StephanK
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Joined: Mon May 22, 2017 11:16 am

SLA / DLP printing - Beginner help needed

Post by StephanK » Mon Jun 26, 2017 11:08 am

Inspired by Toms Wanhao 7 unboxing, I decided to give it a go with a "moderately" priced SLA printer (UV Laser based). Only to find out: all I learned with FDM printing is next to useless when it comes to SLA / DLP printing. Is there anybody here who could help get me started.

For starters, I got some questions. Please excuse me if i sound like an idiot, i am literally starting at 0 and trying to get up to speed here.

1) Why is it so bad if your object touches the build plate? I get the point about keeping the cross section area small and all. But most sla slicers seem to go to strange lengths to raise a whole object off the plate and use a Forrest of supports to do so (for no apparent reason)

2) I am trying to print a rectangle: 80mm long, 60mm wide 3mm thick. I think i printed it 5 times now and it failed every time. My collection of twisted shiny things is growing rapidly :-)

If you follow the logic of least cross section are you would basically angle it from one corner and support the heck out if it. (that's how PreForm does it in auto mode - i run my stuff thru Preform to get an idea how PreForm would do it). The problem is, if i print it this way it "wobbles" and i get layer shifts. It also starts warping. In FDM i'd just slam that dang thing flat on the buildplate and be done with ;-)

3) hollowing out models. If i understand correctly, you place vent holes "upwards" towards the buildplate - to avoid the suction cup effect. Do i also need to put in drain holes facing towards the tank? It would seem to me, that for the most part, the drain hole is not that necessary.

4) My printer is "peeling" by lowering the right side of the resin tank. In order to counter this.. i would raise the left side of model up a bit? cause if i then turn it upside down, the angle would offer less resistance to the peeling.. erm.. help? Does it really matter?
Last edited by StephanK on Mon Jun 26, 2017 6:26 pm, edited 1 time in total.

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kojote
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Re: SLA / DLP printing - Beginner help needed

Post by kojote » Mon Jun 26, 2017 1:55 pm

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bringho
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Re: SLA / DLP printing - Beginner help needed

Post by bringho » Fri Jun 30, 2017 11:04 pm

Over a month with no answer may indicate not many SLA / DLP users are around here (yet?).

I've only owned / used a YHD-101 for a few months (FDM since May 2013) and though it produce great prints I'ts not perfectly dialled in yet...

A few fast answers based on my limited experience:

1. Don't know... Never done anything with supports yet.

2. Sounds like you should cure the resin more, how that is done in your printer I don't now as my machine use a hires mobile screen and a 40W UV led for curing the resin.

3 The vent holes should be pointed towards the bottom of the tank to allow excess resin to flow out of the model as it is raised out of the tank while printing.

4 Why do you want to counter the peeling movement?

StephanK
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Joined: Mon May 22, 2017 11:16 am

Re: SLA / DLP printing - Beginner help needed

Post by StephanK » Fri Jun 30, 2017 11:31 pm

Hey, glad you joined in. Its only been a couple of days, but yeah, i guess SLA/DLP isn't mainstream yet.

2. It cures with 405nm UV Laser light during the print, post processing instructions suggest additional curing under a UV lamp. I did find out that my printer has a setting to increase laser strengths, this helped a bit. As for additional curing under UV lamp, I guess you gotta approach this carefully, if you overdo it, it will crack. Took a few ruined prints to notice the pattern there ;-)

3. Since my printer is printing upside down, a drain hole doesn't exist until it prints the last few layers. So I was wondering what the point is. The "top" holes (facing outwards, not against the buildplate) I got confirmation by Formlabs is a good idea to allow the resin to actually flow back out of hollow areas of the part without a vaccuum building during the peeling right when it starts printing a hollow part. They been nice and helpful even though I do not own a Formlabs printer. (Maybe "yet".. They did impress me by contacting me and offering help.. but boy are they expensive..)

4. "Counter" was probably not the proper wording. The manual of my printer suggests to add stronger supports where the forces of the peeling are greatest.. Without mentioning what side that would be and with all the upside down stuff, I was getting dizzy ;-) By trial and error, it seems when looking at the slicer, the right hand side needs extra support, the left hand side should be angled steeper. Does yours do this peeling motion with the resin tank as well? Sounds to me, that alot of DLP work without this peeling motion.

bringho
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Joined: Fri Jun 30, 2017 10:19 pm

Re: SLA / DLP printing - Beginner help needed

Post by bringho » Sun Jul 09, 2017 2:59 am

Really dunno what to say next...

I did this test on my YHD-101 the other day: Mounted a 60mm square frame with 4mm beams to measure the difference when increasing the cure time: Started with 20 seconds. All ok. then in increments of 5 seconds up to 45 seconds, a total of 6 prints.

Result: The result did not change particularly in size indicating that no particular "overcure" was happening, but the embossed text in the beams got harder and harder to read. "Overcuring" did not get the FunToDo SnowWhite resin to get any more flat when post curing in a UV chamber.

Trying 15 seconds/layer meant that one corner of the frame did not cure at all...

Also I did two test putting the frame on supports and the result was not what I expected so I stopped that experiment immediately

StephanK
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Joined: Mon May 22, 2017 11:16 am

Re: SLA / DLP printing - Beginner help needed

Post by StephanK » Sun Jul 09, 2017 3:14 am

Unfortunarely, i have no answers.. :-(

and no printer atm. I returned this one, cause it was "losing" resin. Out of a 500ml bottle, 300ml disappeared into nowhere. I have absolutely no clue how this could have happened - unless the automated pump was leaking and somewhere in its guts is now a resin lake.

I've now got a Wanhao D7 on order, eta in about a week or so. The experimts shall continue then ;-)

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