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Keith Downing
12-13-2016, 12:46 AM
Had a guy contact me about cutting acrylic to use to stamp his logo into concrete. I'm going to go ahead and make him one to try, but has anyone done anything like this?

It looks like most of the "professionals" use some type of plastic/rubber/silicone stamps with a laser or cnc for custom designs. But the blanks I found were all ~$300+.

I also found this product to make your own: https://www.smooth-on.com/tutorials/custom-concrete-stamp-urethane-rubber/

Has anyone ever used anything like this? Any chance it is laser engrave-able?

Even if not, I would think I could still cut a negative in wood to use as a mold... Maybe?

Love to hear any experience anyone might have had with this type of project.

Neville Stewart
12-13-2016, 6:49 AM
A rubber stamp for detail in concrete just don't seem to go together in my mind. Visible detail in concrete would have to be large and that's seems inefficient for a laser, possbile certainly. If they're paying who cares but if it's just a 5"stamp for his company name then rubber for durability, acrylic for disposable.

Brian Lamb
12-13-2016, 10:23 AM
I have molded parts using this product:

https://www.aeromarineproducts.com/product/aeromarine-concrete-molding-stamping-rubber/

I haven't tried lasering into it directly, but making a mold out of wood should be pretty easy and then cast it in rubber from there.

The first laser we had back in my machine shop days we used for making rubber part marking stamps a lot.... of course the rubber sheets we were using were only 1/8" thick or so, and the stamps were maybe 3/4" x 1 1/2", but I don't see why you couldn't get thicker rubber and cut out whatever you want. My ULS drivers have options all set up for rubber stamps. Laserbits sells this and it's 1/4" thick:

http://www.laserbits.com/stamp-products/hot-stamp-die/rus-003-hot-stamp-die-material.html

And evidently delrin for embossing dies, so you could just get thicker delrin:

http://www.laserbits.com/stamp-products/delrin-sheet/aus-100-delrin-sheet-white.html

Keith Downing
12-13-2016, 12:47 PM
A rubber stamp for detail in concrete just don't seem to go together in my mind. Visible detail in concrete would have to be large and that's seems inefficient for a laser, possbile certainly. If they're paying who cares but if it's just a 5"stamp for his company name then rubber for durability, acrylic for disposable.

I've seen the larger ones. They are almost like rubber mats that are applied with a light pattern (like a tile mold, or inverted cracks) on top of the cement a section at a time. They can usually support a persons weight and look very durable. The link I posted shows how you would do this for imitating tile on a freshly poured concrete slab.

I guess if you think of it less as a stamp, and more as a reversed mold it makes more sense.

Keith Downing
12-13-2016, 12:50 PM
I have molded parts using this product:

https://www.aeromarineproducts.com/product/aeromarine-concrete-molding-stamping-rubber/

I haven't tried lasering into it directly, but making a mold out of wood should be pretty easy and then cast it in rubber from there.

The first laser we had back in my machine shop days we used for making rubber part marking stamps a lot.... of course the rubber sheets we were using were only 1/8" thick or so, and the stamps were maybe 3/4" x 1 1/2", but I don't see why you couldn't get thicker rubber and cut out whatever you want. My ULS drivers have options all set up for rubber stamps. Laserbits sells this and it's 1/4" thick:

http://www.laserbits.com/stamp-products/hot-stamp-die/rus-003-hot-stamp-die-material.html

And evidently delrin for embossing dies, so you could just get thicker delrin:

http://www.laserbits.com/stamp-products/delrin-sheet/aus-100-delrin-sheet-white.html

Thanks Brian,

The first product looks a lot like what I was looking at. I think it could be the ticket. The others might work as well, but he needs this thing closer to a square foot. And the price on the laserbits products is already high for just tiny little stamps.

Brian Lamb
12-13-2016, 1:26 PM
Agreed, that is pretty pricey, a quick google search turn up this, and I'm sure you might find local suppliers.

http://www.rubberstampmaterials.com/laserengravablerubberandpolymer.aspx

You might need two 8.5 x 11 sheets, but they are a lot cheaper at roughly $13 each. It doesn't say what thickness they are, so check first.

Keith Downing
12-13-2016, 1:30 PM
Agreed, that is pretty pricey, a quick google search turn up this, and I'm sure you might find local suppliers.

http://www.rubberstampmaterials.com/laserengravablerubberandpolymer.aspx

You might need two 8.5 x 11 sheets, but they are a lot cheaper at roughly $13 each. It doesn't say what thickness they are, so check first.

Yeah, I'll look around some more. I actually have some laserable rubber (for regular stamps) but I think it's too thin for what he is trying to do. It's well under 1/4".

Kev Williams
12-13-2016, 5:02 PM
Why rubber? Get a cheap piece of hardwood, laser-hack it into a reverse relief stamp, then coat the whole thing with fiberglass resin. It'll stamp great, clean up nice and will last practically forever...

Brian Lamb
12-13-2016, 6:30 PM
I don't know about your machines, but I don't think I'd want to wait around for mine to do a 1 foot square chunk of hardwood to 1/4" deep in raster cutting. Now, vector cut it out and glue it to another piece of wood... maybe, but depending upon detail that might be a royal pain in the ass.....

Keith Downing
12-13-2016, 7:15 PM
Why rubber? Get a cheap piece of hardwood, laser-hack it into a reverse relief stamp, then coat the whole thing with fiberglass resin. It'll stamp great, clean up nice and will last practically forever...

I think most use the rubber so you can flex it when you need to and easily pull it off. The professionals often use large pieces (like the size of 6 to 8 tiles).

But the fiberglass resin idea may be a winner! I had been trying to think of a way to coat wood to use it as a base for the stamp. I wonder if the west epoxy I already have would be too thick to use?

I agree with Brian too. I think the best implementation (for my needs of cost vs durability) may be an acrylic cutout, glued to a flat piece of 1/2" wood. Then coated with some kind of resin or sealer that will go on smooth and thin. I should be able to laser that in a few minutes, and glue and coat it pretty easily.

Brian Lamb
12-13-2016, 7:29 PM
West epoxy will work, no problem. Most concrete forms are raw wood that they spray with diesel fuel as a release. Given a stamp will only be in contact with the wetness of the concrete for a few minutes and then washed and dried.... it wouldn't be a high issue as long as it was half ass sealed.

I do agree with the rubber for removal, I can't imagine the suction you might get with a 12" square form tamped into wet concrete, getting that sucker loose without destroying the mark would be a feat in my opinion.... unless you drill some "vent" holes in the wood form and then be willing to hand flatten the crete after the fact, which they might do anyway....

charlie wade
12-14-2016, 11:48 AM
We built a log home, and when it came time for the front walk didn't want something as "formal" as pavers. So, we went with stamped concrete. The installer used rubber mats for the texture, and I cut the ship's wheel for him out of a scrap piece of acrylic. It'll look sharper once we seal it for the winter -- probably next week... Can't seem to post pics though.
349460349461

Keith Downing
12-14-2016, 12:40 PM
We built a log home, and when it came time for the front walk didn't want something as "formal" as pavers. So, we went with stamped concrete. The installer used rubber mats for the texture, and I cut the ship's wheel for him out of a scrap piece of acrylic. It'll look sharper once we seal it for the winter -- probably next week... Can't seem to post pics though.
349460349461

Don't know if you are interested in this for the ships wheel, but our client intends to use a colored grout in the impressed area for his design. and then seal it. So it will be flat/level but the pattern will be visible essentially forever.

I like the look of the walkway a lot btw. They did good work.

Lee DeRaud
12-14-2016, 1:13 PM
I do agree with the rubber for removal, I can't imagine the suction you might get with a 12" square form tamped into wet concrete, getting that sucker loose without destroying the mark would be a feat in my opinion.... unless you drill some "vent" holes in the wood form and then be willing to hand flatten the crete after the fact, which they might do anyway....I watched them do my patio: the molds were some sort of rubber with a solid steel backing plate and a socket for a handle. The concrete wasn't anything I'd call "wet" when they stamped it, more like the point where you'd brush it for a non-skid finish. (Hint: they were able to walk on it to get to the far edge when they started stamping.) And they're not kidding when they say "stamped", the guys really put some serious force into getting the 24"x24" molds down. The only hand touch-up was around the edges and joints where the sections come together, plus a few spots where the concrete was still too wet and got pulled up by the mold.

Kev Williams
12-14-2016, 1:38 PM
If the mud's too wet rubber will pull it up too, need to be a snick more set--

For removing a solid mold, drill a dinky hole thru somewhere near the middle that's in the cavity and not the stamping part. On the top side, blow some pressurized air thru the hole...