Engraving Acrylic to Cast Silicone - let's do this!

projectinspo

#1

I wanted some custom stamps for my product packaging and envelopes, and I had been trying to make them with the 40 watt Versa Laser at my Makerspace by cutting individual letters out of a sheet of silicone that the Silhouette company makes for you to use on their cutters. I had very mixed results and for no good reason some letters wouldn’t cut all the way through or they would fall through the holes if the pieces were too small and I would have to go try to fish them out. You obviously couldn’t do anything really detailed or it would fall through the cracks or just obliterate itself from the power of the laser. It also is really freaking messy leaving white powder everywhere.

I’ve been doing a lot of playing around with molding and casting and had some liquid silicone Alumilite high-strength 3 used for mold making (it can be bought at Hobby Lobby in the model section with a 40% off coupon!) and thought duh why don’t I CAST the stamps. I hadn’t messed with acrylic yet and realized silicone will not remotely stick to it when it’s curing, so why don’t I use all of that scrap getting thrown away up at my Makerspace and cast stamps with it!

But since doing this, I realize how many amazing things I can do with the acrylic and silicone combination and I’m looking forward to trying some of them out next time I can get up there. Once I have my Glowforge I won’t have to wait. This whole waiting is painful to a right brain that doesn’t shut off. Next thing I want to engrave and cast are rings or bracelets…

Please note my guessing on placement on the scrap…where the Glowforge would have saved me from my own stupidity. lol

I found something else that brown boxing tape sticks to as viciously as it does to paper and skin… ACRYLIC. I was not expecting that, but it worked flawlessly to make little edges around the designs. When it sticks it is INCREDIBLY bonded. Comes off, but not if you don’t want it to.


I filled in the etch…and don’t try to turn around to talk to someone if you have silicone in your hand… it ends up on your table. Not helpful. lol

Things I learned…

  • Do a trial and fine tune your depth of engrave with your chosen silicone strength and denseness. Using something like I did makes it come out flawlessly from the cut because it’s super stretchy and strong. I didn’t lose a microscopic piece to the acrylic using this. But, on the really skinny stuff I engraved too deep so it won’t hold up if I go to press on it. If you were to do something with less flexibility it would probably work better but not stand up to having to pull. I will update this thread as I try different types so that it may save somebody time and money. If you’re doing a really detailed design you don’t want it to be very deep because no silicone will be dense enough. If it’s really really fine, then do a negative space image where the design is removed. I was stunned with the level of detail I got. This isn’t with a Glowforge, so I can’t speak to is ability yet.

  • Depending on your settings, you are going to have striations in the solid portion unless your design lends itself to working ok defocused. (See awesome other post on forum) If that bugs you, and if you do it deep enough you could just pour in some resin and it would completely smooth it out before you put your silicone in.

  • The finer detail in the design the more likelihood you’re going to get bubbles, so you want to use a initially thinner silicone (pourable vs caulk) it will release the bubbles and so you can pop them when you see them. You can spot the tiny bubbles in the too small detail.


    Just cut them apart and put them on clear acrylic blocks… I will try to do this with clear acrylic next if I can find some that works well.

  • I wish I would have cut each stamp out of the acrylic completely by themselves so that I have stamp blocks to put them on the reverse side. Oh well… I guess I’ll just have to do it on the bandsaw. But it will be very cool to just just be able to color fill in the word (if you don’t want to recast from it) and be able to know what the stamp is on the shelf.

  • I will design in empty spaces to begin pouring the silicone on to the flat surface. You always want to pour in one spot and allow it to fill in itself to prevent bubbles. The one I didn’t do this on was full of them.

  • Having a Glowforge will be nice because I love recycling and using scrap. I’m a scrap hoarder. Here is an example where I went had to head with placement with the VersaLaser and lost. 20 minutes on a deep engrave I’ll never get back. Yeah yeah measure twice cut once. I know. I know. :slight_smile:

  • Talking into Google Docs is so much faster than typing.

I’m looking forward to the plethora of the knowledge all of you folks can add to this and impart on me and also when this and the other hundred projects I have either done or am planning can be put in the made on a Glowforge category. I could finally start making my YouTube videos :slight_smile:

@jules made me realize I didn’t post the actual stamping. OOPS! Silicone will not stick to acrylic when curing, but once cured it sticks perfectly to a clear acrylic block you can buy with a grid for alignment (we can easily make ourselves) that you can change your stamps out as you wish. I am using a not so new charcoal colored solvent stamp pad, but it still worked great. I will for sure try a little less flexible silicone and or not engrave so deeply. Those words I really had to hold rather still to keep from blurring… the saw blade not hard at all. With this particular ink, it is REAL obvious to see the engraved texture of the solid space… this will need to be fiddled with once I have my own. I am not spending more time learning this thing. lol


#2

Very cool! Thank you for sharing your process and discovery :smiley:


#3

Fantastic idea! Does the silicone hold the ink well as a stamp? (I need to put this one in the tuts.) :smile:


#4

Those turned out really well!

Adding a slight draft angle would allow you to use a little tougher silicone material and still release from the master without losing the tiny bits, plus it will lend more support to those smaller areas while printing.

Once the 3D engraving option is turned on in the Glowforge software, that draft angle will be more of a possibility.

Otherwise, there’s a few tricks for avoiding trapped air on mold surfaces in those tiny areas.

  1. Brush silicone into the detailed areas to help break the surface tension. The silicone that flows in afterwards it more able to settle in without air voids.

  2. If you build a mold box that you can move around while the silicone is curing, you can tap the mold on the table to help shake the bubbles loose.

  3. Place the mold into a pressure chamber and use air pressure to squeeze the bubbles out. This will take care of bubbles at the surface and all through the thickness of the material.


#5

Most stamps you buy these days are silicone… those clear see through ones they sell in sheets. I realize I didn’t take a pic of them on the block or being used… doh! Let me go test one out and I shall post it real quick!


#6

Ahh. I need to note that in my write up if I didn’t. The tape was acting as the mold box. Super stiff. I totally tapped it pretty heavy handed on the table and the bubbles came up nicely. The only bubbles that happened were in MINUSCULE lines and dots… so small I don’t think the silicone would have even gone into them… I wouldn’t do designs with anything that small again.


#7

Silicone will reproduce every unimaginable detail, it is completely unforgiving. If you make a master with a surface you want to keep glossy, you can’t even touch it because silicone will reproduce fingerprints and smudges.


#8

Really nice work! I was hoping to play with making silicon molds and this is so inspiring to see.

Very good tip. I suggest using Legos to make great temporary boxes that are easy to pull apart. Just get a lego base plate and a bunch of legos and you’re good to go.


#9

I’ve got a box full for just that purpose. :slightly_smiling_face:


#10

I need to get some Lego! I always have MDF or melamine and foam core laying around so I’ll hot glue boxes together right quick, but reusable Lego would be nicer.


#11

:[quote=“mpipes, post:7, topic:9018, full:true”]
Silicone will reproduce every unimaginable detail, it is completely unforgiving. If you make a master with a surface you want to keep glossy, you can’t even touch it because silicone will reproduce fingerprints and smudges.
[/quote]
Yeah… it’s stunningly amazing how detailed they are. If you were to use a thicker ink or one with a paint like consistency it would smush a little more to blur them. I think I am going to try my resin flood on the bottom in a few and then recast and see if it actually works like I think it will.


#12

I have seen this many times and it is really the best possible way to make boxes around objects. I need to remember and try it when I am mold making next!

This application didn’t lend itself to that as I didn’t like how all of it came out and the tape allowed me to make little walls around what I wanted and what I didn’t and since I was too tired at the end to cut them out of the sheet individually and I just pulled it out in one piece and trimmed it to how I wanted it. When I am not just experimenting, I might do it the slightly more proper way…maybe. lol


#13

Mind blown


#14

Wow. That is really, really brilliant. One other thing you can do (sometimes) for bubbles is to degas your silicone by pulling a slight vacuum on it and leaving for a while.


#15

Oooo, very nice! This would be a much faster process than engraviving away a rubber stamp.


#16

Such a great idea! Thanks for all the details and in process photos!


#17

Excellent idea! Thank you.


#18

These turned out Great! Thanks for sharing the process and what you learned. I’m gonna have to come back to this one later and try to make my own sometime!


#19

Neat adventure! Casting sure beats vulcanizing. Gonna have to try that stuff.