1/4" Cast Acrylic: Craiglist Find

[marmak3261]

My picker texted me at the end of January that there was a Craiglist post in St. Louis selling 19 x 32" 1/4 cast acrylic for $5.00 a sheet. I texted back and forth with the seller and got a pic of the masking. Looked it up and it checked out. The acrylic looked pristine.

I was not able to get it picked up myself do to the Mexico trip. @cynd11 to the rescue! I let her know about the find and she was able to go and pick some up for her and get me 10 sheets. $5 per sheet. Inventables sells 1/4" clear cast acrylic for $9.00 a square foot. Do the math. It’s quite a find. Glowforge does have 1/4" clear acrylic in the shop but I hadn’t picked any up yet it got buried under other material and I forgot I had it. Will process this in Proofgrade Acrylic to see how the auto settings handle it.

I went to St. Louis for a funeral on Friday and let @cynd11 know I’d be coming through. I got to visit with her and her husband and her beautiful 4 cats. What a lovely home.

Once again I got food treats and gifts from her, including some laser amenities to help with my projects. I do not know which shop impressed me more, @cynd11’s stamp and card room or husband’s jewelry shop. Arg! I wasn’t able to stay long, but was there long enough to get a lesson in making a jump ring out of drawn silver wire for making jewelry. And I got a lesson in jewelry pliers.

Glowfriends are the best friends!

So now we need to figure out how to cut this acrylic. Engraving is no biggie because surface wise it is pretty much the same. I have never done 1/4" acrylic before but I know it has been done. As I looked through old posts I got a sense for what to shoot for. One thing I can note again: @dan has been so active in this forum and has liberally left tidbits of help and info all over the place.

Keep in mind I have a pre-release so your results may vary. I did three sets of cutting to test this out. The first set was too slow and under power. Didn’t quite go through the acrylic. Not even points on the corners came through.

The next set got a successful through cut at 100% power, 10 inches per minute, but the kerf was wider than I would have liked…

So I did one more test but this time with a lower power faster speed and doing the cut twice. 80/20 worked and 75/15 worked perfectly, barely making it through the masking on the other side. Kerf was nice. And the acrylic looked beautiful.

Next step is to make something out of it. I did the acrylic night lights with Proofgrade 1/8" but had do make a spacer piece so that the acrylic was firmly in the base.

I can use this 1/4" acrylic to make the reflector and engrave a slight depression in the mount section so that it fits snuggly.

Finished night light.

Only thing left is to find a source for the electronic bases.

[takitus]

I have a lot of chemcast from my local supplier as well. Its good stuff! Nice find!

[jamesdhatch]

Is it focusing on the surface or halfway through the material (1/8" below the surface). If it’s focusing on the surface you’ll get a wider kerf and a sloped edge. If it’s in the middle the kerf will be narrower and you’ll have an hourglass shaped edge.

The latter is preferred for minimum power, highest speed clean cuts.

Can you specify which in the UI?

[takitus]

@marmak3261

So I did one more test but this time with a lower power faster speed and doing the cut twice

I think its worth the extra time to do a second cut instead of trying to power through on one. Ive been using 2 passes on 1/4" acrylic as well. It makes it sooo clean. You just have to watch out for flashback.

[cynd11]

This whole Glowforge process has been an amazing opportunity to make new friends–the most valuable part of the experience. Thanks for your visit @marmak3261. And for the awesome acrylic find!

[rpegg]

Not yet.

[Clone]

great find

[marmak3261]

Hard to get a shot of the edge with the iPhone. Maybe this will help. Or obfuscate.

The left side is the bottom of the cut.

[mpipes]

@takitus

You just have to watch out for flashback.

For the laser newbs here, flashback? I’m assuming this is the laser bouncing off the crumb tray and back into the underside of the material, causing marks in areas you dont want them?

[takitus]

Off the honeycomb. Definitely a pain

[Jules]

You lucky duck! (Nightlight looks fantastic!)

[marmak3261]

There is something in the file that I missed before and it has those weird specs by the moon and a few on the angel. Couldn’t see anything in the PNG so I took it into Inkscape and did a trace. Must have been some white pixels or something funky. I cleaned it up and finished the left side of the pillow/cloud that was cut off in the drawing.

[mpipes]

What about placing the acrylic on top of some other sacrificial material? This way the laser cuts through the acrylic but then the excess energy gets absorbed by something else?

Or maybe placing the acrylic on top of a glass plate (invisible to IR) then a sacrificial layer, might keep smoke at bay.

Edit Sorry, this was in response to @takitus post above.

[dan]

@jamesdhatch

Can you specify which in the UI?

You can specify a manual focus point, but it’s not very well refined yet.

@mpipes

Or maybe placing the acrylic on top of a glass plate (invisible to IR)

Glass plates are not invisible to IR at those wavelengths; they absorb it almost 100%.

[mpipes]

@dan

Glass plates are not invisible to IR at those wavelengths; they absorb it almost 100%.

Oh that’s right… brainfart, spent too much time in the heat today and still am not thinking 100%.

[jamesdhatch]

Can you take a square and set it against the edge to see whether it slopes the thickness of the edge or if the high spot is in the center of the edge and slopes inward above & below?

If it’s the former then it’s focusing on the surface. If the latter then it’s focusing in the center.

[kennethclapp]

Quick question, where did you find the night-lite base? Was it scavenged or did you find a supplier. It looks a lot like one I have that’s branded by GE, but for the life of me I can’t find a supplier anywhere. Just thought I would ask.

[curt]

He has a link to the original topic of them in the post. It’s just above the picture of the one torn apart.

Goes here:

Upgraded LED Nightlight: Clear Proofgrade Acrylic

Posting this to document a few things regarding design, materials and workflow. My materials picker (a parishioner who drops by the office just about every day with some materials or ideas for the Glowforge) came up with some on-sale nightlights at Menards. $10 for three, reduced to $8 and then add a 10% discount if put in the big shopping bag. [image] Although it is tempting to throw the reflector shield in the Glowforge, I would guess this is polycarbonate and not acrylic. Not wanting to me…

[kennethclapp]

Thanks for that, as soon as I clicked on it I remembered the post. Must be Monday or something the way my brain is working

[marmak3261]

When I find a bulk supplier I’ll post it. I have GE ones and I have Intertek, Ningbo Home Automation products. I have gotten these at Menards on sale. I have one that was a garage sale find. Menards said that if I bought them in the bulk 8 packs with three lights in each pack they would give me a deal that would get them down to less than two dollars a piece. But then I’d still have the original reflector to deal with as waste. Sawmill Creek has a thread about them but the info is outdated. I’ve tried to find something in Alibaba but my search skills with them are not that great. Walmart carries something like that. At least one store in Mexico that I saw.