Very long cure times for MakerJuice SF for LRP, seems more translucent

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Scatterplot
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Very long cure times for MakerJuice SF for LRP, seems more translucent

Postby Scatterplot » Thu May 11, 2017 11:26 am

So I got my first batch of resin a month or so after the original Kickstarter for the LittleRP and have only printed very small things; as a result my resin lasted me a very long time (I also don't use my printer THAT frequently). If I remember right my settings were in the 3-4 seconds per layer cure range with Red SF for LittleRP.

About 6 months ago I got a FlexVat and installed it with no issues. It had been a good while since I'd used the printer, and the focal distance was a bit different, so I had some trouble with my initial prints; I had cure times around 11-12 seconds and was still having some trouble, so I figured my resin had gone bad and I ordered a new batch a couple of months ago for a project that got bumped to this week.

I opened up my Red last night after shaking it hard for a couple of minutes and put some in my vat. It seemed to be noticeably more translucent than I remembered my original batch of Red being. I did a calibration test and found that it, too, seemed to need about 12 second cure times to get a decent layer.

I did a normal print with it but a 35 mm tall object took around 5 hours, and it had enough light bleed around some thin gaps (0.010"-0.015") to close them up completely. The finished parts seem a bit more translucent than I remember as well.

Did Makerjuice change their formula? Could my projector (Acer 6510BD) need a new lamp already (after roughly one liter of use)? Any other thoughts on my very long cure times and translucent parts?

C3DC
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Re: Very long cure times for MakerJuice SF for LRP, seems more translucent

Postby C3DC » Thu May 11, 2017 2:33 pm

Going from petri to flexvat, your cure times will increase just because of the distance. An inch farther away from the projector will make a big difference, but maybe not as drastic as you are describing.

Did you ever try switching back to petri after you were having troubles with the original resin and flexvat?

Scatterplot
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Re: Very long cure times for MakerJuice SF for LRP, seems more translucent

Postby Scatterplot » Thu May 11, 2017 5:14 pm

I haven't had a chance to really play around with it yet but I can give it a shot. Do you think a 2-3x change is to be expected? I know the area is larger and thus gets less light, but I guess I haven't really done the math to know exactly how much I changed things.

Mattasmack
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Re: Very long cure times for MakerJuice SF for LRP, seems more translucent

Postby Mattasmack » Thu May 11, 2017 7:55 pm

You should be able to figure the change in exposure time from the change in printer resolution, right? If, say, switching vats changed your xy resolution from 25 um to 50 um, then each pixel is covering four times more area (25x25 um to 50x50 um), so exposure time should be four times longer as well. (i.e., exposure time goes with the square of the xy resolution.) Assuming you've measured the new resolution with the flexvat, how does that jibe?

Also, how sure are you of your exposure time? I don't have experience with MakerJuice SF specifically, but significant light bleed could indicate overexposure. I've been using B9 Emerald, off and on, for a bit over a year for jewelry work. I recently discovered that I've been using waaay too long an exposure time -- I'd been using 3 s for the past year, but found that I can print successfully with ~1.2 s of exposure. I used to have trouble with parts coming out over-thick and with fine details filled in (i.e., light bleed), but with the correct, shorter, exposure that's mostly fixed.

Scatterplot
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Re: Very long cure times for MakerJuice SF for LRP, seems more translucent

Postby Scatterplot » Fri May 12, 2017 11:07 am

I haven't compared resolutions, that's a good idea. I'll check it when I get home tonight.

I'm definitely seeing a little bit of light bleed right now but I know it's not significant overexposure. I ran the exposure test at 1 second increments and ended up needing at least 11 or so seconds; I tested in 1 second increments and didn't dial it in SUPER tightly but it's at least within a second or so (10%).

I'm starting to wonder if my projector has a bad bulb or something- might be time to rig up a light meter :)

Edit: A main reason I asked this was because the resin itself looked much thinner than I remembered, and I was wondering if MakerJuice had changed their formula. I didn't want to waste 10 hours tracking down a non-existent bug because MakerJuice changed some slight thing with their resin. I'd heard they were going to start using dies instead of pigments to fix settling issues and didn't know if that was a rumor or if I just misunderstood something.

Scatterplot
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Joined: Mon Jan 12, 2015 12:09 pm
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Re: Very long cure times for MakerJuice SF for LRP, seems more translucent

Postby Scatterplot » Fri May 12, 2017 11:28 am

Did my best to get some comparison pictures... sorry for the crappy quality, it's hard to get my phone to get a good comparison picture of translucent parts.

The parts here are identical with the exception that one was printed probably 8-10 months ago and one was printed 2 days ago. The old one was a stock LRP with my old batch of resin. The new one is on a LRP with the flexvat and new resin. Certainly the old one would have been more cured over time just from sitting around but neither have been in a UV oven or anything to post-cure.

Image

You can see the one on the right is a different color (not a problem, it's just a little older) but in person it's noticeably more translucent.

Trying to catch the thin wall area (maybe 0.8mm or so wall) with a light behind it... old one:
Image

New one:

Image

The light REALLY shines through the newer one. I wouldn't have expected this to be a cure time issue; this seems like a resin issue. Any thoughts on that? Do these get more opaque as time goes on?

I usually use a syringe to suck up resin from the bottle and squirt it into the plate, and I really think it looks different- I wonder if it's just due to age or a change in formula.

Mattasmack
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Re: Very long cure times for MakerJuice SF for LRP, seems more translucent

Postby Mattasmack » Tue May 16, 2017 11:21 pm



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