B9-red and Spot-A-HT?

A lost wax capable resin tuned for 70 - 200 micron slice thickness
WalterMo
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B9-red and Spot-A-HT?

Post#1 » Tue Aug 13, 2013 1:30 am

I have a remainder of B9-red. Can it be mixed with Spot-A-HT?
If yes, what mix ratio?

Thanks!

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tim.yoshi
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B9-red and Spot-A-HT?

Post#2 » Tue Aug 13, 2013 11:37 am

Give it a try.
1:1 should be nice start point.
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ah3000mk1@sbcglobal.net
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B9-red and Spot-A-HT?

Post#3 » Mon Aug 19, 2013 1:55 am

Tim,

I've had some great results with a 50-50 mix of Spot-A GP and B9R, detail wise. However, I'm going mad trying to keep parts from delaminating. I get layers of orange cheese slices in the vat with anything but the smallest items on most prints.

I'm using 4 attach layers, and a 42-sec attachment time at 75 micron x-y resolution and 50-micron slices. I've got open/close speeds down to 15%. Exposure times were 19 T-base, 3 or 4 T-over. I'm using low (stock) over-lift settings.

Can you suggest exposure settings to try for this mix, at both 75 and 50 micron slices?

The Spot-A is "faster", and produces a finer part, but is brittle, and seems to have difficulty adhering to the vat. With a mix, I've tried a linear (averaging) set of exposure times, risking having gooey B9R components in the cured part. I've found the mix renders a more crisp, sharper result than B9R alone, but again, the lower layers just peel away. I'm not sure if I'm over-curing, under-curing, or just running down a rabbit hole...

Appreciate your insight, you've got very impressive parts coming out... I aim for the same.

-ah3000mk1

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tim.yoshi
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B9-red and Spot-A-HT?

Post#4 » Mon Aug 19, 2013 2:59 am

If you'll overcure it it will certainly stick between the PDMS and the build table (if I correctly understood and we are speaking about first layers) and make it to stuck. If you see this then you might lower the exposure. If no maybe try to bump it a little.
Also double check that you have precise build table calibration on the shallow end of the VAT without resin.

Also try to disable overlift at all - I disabled it month ago and all of my prints I made so far was without it.
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ah3000mk1@sbcglobal.net
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B9-red and Spot-A-HT?

Post#5 » Mon Aug 19, 2013 5:00 am

Tim,

Any suggestions on overcure time? I thought I had it set for base layers at 42 sec or so for the 75XY, 50z attempt. I've tried 2,3, and 4 base layers with the following results...
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WalterMo
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B9-red and Spot-A-HT?

Post#6 » Tue Aug 20, 2013 4:58 am

I have given it a try and it works!

The mix ratio was 1:1 as Tim suggested some posts above.
The print is called Nautilus Gear, its 3D data came from Thingiverse:
http://www.thingiverse.com/thing:27233

The chosen axial distance of the two wheels is 65 mm.

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tim.yoshi
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B9-red and Spot-A-HT?

Post#7 » Tue Aug 20, 2013 7:19 am

WalterMo, can you share your overcure times? :)
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WalterMo
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B9-red and Spot-A-HT?

Post#8 » Tue Aug 20, 2013 5:49 pm

I am not using a 'real' B9C, it's a self-built one. So I am not sure what 'overcure time' exactly means.

The first two layers with a thickness of 75 µm each are exposed at 30 sec. All the other layers have a thickness of 105 µm and 15 sec exposure time. And the print directly stuck to a PVC build table.
Projector is an Infocus 3118HD, means sliced and printed at 1920 x 1080 pixels.

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tim.yoshi
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B9-red and Spot-A-HT?

Post#9 » Wed Aug 21, 2013 9:08 am

Wow... You are using Full HD projector! Cool... Also very cool is that you already have "variable cure timing" of which we are talking. That should probably be very handy, like VTEC on Honda engines :)
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kirkrhino
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B9-red and Spot-A-HT?

Post#10 » Wed Aug 28, 2013 11:54 am

WalterMo! Would love to see some pics of your setup! : ) Awesome print!

WalterMo
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B9-red and Spot-A-HT?

Post#11 » Wed Aug 28, 2013 6:57 pm

In this thread I have mentioned some infos of my self-built printer:

http://www.b9c.com/support/?mingleforumaction=viewtopic&t=387

Also some links to pics and details are given. The device is still under development.

kirkrhino
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B9-red and Spot-A-HT?

Post#12 » Fri Aug 30, 2013 2:33 pm

Cool, all the best with that project!

WalterMo
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B9-red and Spot-A-HT?

Post#13 » Tue Oct 08, 2013 8:45 pm

My last print with a mix of B9-red and Spot-A-HT was a failure. I printed this cannon from GrabCad:
http://grabcad.com/library?per_page=20&query=canon-model

All came out fine, even the thin explosive fuse. But after two days the cannon tube bursted. It is well known that Spot-A-HT cures faster and is more brittle but I didn't believe that a 2.3 mm thick wall would burst.
I have printed several hollowed objects of similar size with B9-red but never seen such a burst.

Could it be due to the mix or is Spot-A-HT generally not suitable for hollowed prints?

PS. Exposure time was 12 seconds, diameter of the wheels 57 mm, layer thickness 75 µm.

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ah3000mk1@sbcglobal.net
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B9-red and Spot-A-HT?

Post#14 » Wed Oct 09, 2013 3:10 am

May I ask how well cured the part felt coming off the printer? And what method of post-cure did you use? The surface might be prone to shrink at a higher rate, due to pigment masking the material beneath. I couldn't tell you if a faster (UV) forced cure or a slower (window on a cloudy day) cure method would avoid this.

Did the part split along a layer interface?

I had a similar issue with splitting due to shrinkage of a Spot-A GP/HT hybrid mix. Ended up doubling wall thickness. And, actually, using a B9R Spot-GP mix (50/50). (See photo, left part is before design change-spokes pulled the rim apart over 1-2 days).

Could you reduce the bore depth to maybe 1-1.5 calibers down the barrel, and leave the rest solid? Or, since no one else will know, carve out the bore to a uniform wall thickness as it tapers away from the muzzle?

I'd like to help you work through this one as I've got some thick section bits coming up.

ah3000mk1@sbcglobal.net
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B9-red and Spot-A-HT?

Post#15 » Wed Oct 09, 2013 3:12 am

The pic...

WalterMo
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B9-red and Spot-A-HT?

Post#16 » Wed Oct 09, 2013 5:00 am

The cannon was cured fine when it came off the printer. I removed it together with its supports from the build table and washed it in ethanol. Then, after drying, it was post cured by a sunlamp. This was the same procedure as I did for all my other prints.
Then I removed the supports and smoothed the parts on the cannon where they were mounted. Up to this time all was ok. But one day later I saw the disaster.

No, the barrel didn't split along a layer interface. It was printed standing vertically on its muzzle. Its surface is very fine, layers are only to see by a magnifying glass.

Of course I can reduce the bore depth or increase the wall thickness and print it again. But it is a general question if this mix or Spot-A-HT alone is suited for hollowed objects. I had printed mainly bigger (up to 200mm) objects which were hollowed out to save resin. With B9-red I never had a problem.
I would have sticked to B9-red but a lower price due to no customs duty and less portage made Spot-A-HT interesting. We should have a reseller for B9 equipment in the EU!

In the meantime I have glued the crack with a two component epoxy resin adhesive. Hope it's stable.
You mentioned a posted photo, but where is it?

ah3000mk1@sbcglobal.net
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B9-red and Spot-A-HT?

Post#17 » Thu Oct 10, 2013 2:26 am

Another upload attempt
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ah3000mk1@sbcglobal.net
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B9-red and Spot-A-HT?

Post#18 » Thu Oct 10, 2013 2:34 am

AHHH, got the pic in at a lower resolution.

WalterMo,

You can see where the rim split on the left part; my theory is as the spokes contracted, a radial stress was put on the rim. Took a day to split, even after UV cure. The wall thickness was raised, and the part (right-side) reprinted in the same vat of material. No split. Even small stresses seem to affect the mix. The 60 spokes on this part are 0.3mm in diameter, as I recall.

I'd be curious as to whether a much higher overcure (perhaps higher than the base) time might help on this, perhaps the cannon, too.

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