Category Archives: tools

laser cutter design portability

I’ve had my full spectrum engineering gen5 hobby laser for about 8 months, and I’m enjoying using it. I’m not a total newb to using a laser. I had a couple months of intensive usage at Tech Shop years ago.  After that, I bought a CNC Router, and after that a 3d Printer.  I tinker with a lot of different things.

Over the years, I’ve seen a range of design files that people have shared.  For the 3d printer, typically you’d go to Thingiverse to get and share designs that you can use in your device.Thingiverse has some design files for CNC routers…   Some things make sense to share for a 2.5D personal manufacturing device.  And I guess if you’re making 2d things with the laser cutter, then of course you can share all kinds of clip art and whatnot.

A 3d printer is fairly straight forward.  The output is handled by the media you’re printing with. Your slicing software just accounts for everything and spits out machine code to do the right thing.  And things usually go well and you end up with what you were trying to end up with.

If you’re making 3d things from 2d media with the laser cutter, things get more complicated. If you pick up someone’s design on thingiverse, it’s designed for a specific thickness sheet good to cut the shapes out of.  If the design has finger joints or cross braces or is a box of any kind, it has to be designed with parts precisely cut to fit with whatever you’ve chosen to make your project out of.

Exhibit A:

The iPhone 5 stand by Kip


I like this design. A lot. It’s clean, thoughtful, and looks like it would take all of 10 minutes to cut out.  The description says it’s cut from 4mm thick plexiglass.

I guess “plexiglass” is the same thing as a sheet of acrylic.  So I’d go with a sheet of acrylic. I just went out to my garage and measured easily 20 pieces of acrylic, and NONE of them are 4mm thick.  So if I threw a 4.75mm thick sheet of acrylic onto the laser and ran this file as-is, none of the joints would fit because they’re expecting a thinner material.  So it would be a total waste of time and materials.

So, I’m here to do some wishing.

I wish there was a 3d cad program that would let me draw an abstracted design without specific thicknesses until I know what material I have in my hand that I’m going to use in my project. For the iPhone stand above, we know there are 4 pieces.  So if my wish came true, I could say “here’s the overall dimensions, this piece should have this critical angle, this edge should not be programmatically variable, but the rest of these pieces are dynamic.


Oh. I guess that would be a parametric cad program. Anyone ever heard of a parametric cad program aimed at designing for a laser cutter?

april 2013 works in progress

I helped kickstart Full Spectrum Laser’s 5th gen 20×12 hobby deluxe laser last year. They delivered the laser, and I tried and failed really quickly at building my own fume extractor.  I bit the bullet and purchased an industrial strength fume extractor, and now I can use the laser without polluting the air. Yay!  So: game on!

Cuts so nice you gotta hear it twice.
ideas taking flight
hard to see cousin

My head is overflowing with new ideas that feed off these initial tests. All very exciting!

an OpenSCAD script for 3d printing potentiometer knobs

I learned some OpenSCAD!

OpenSCAD - potknob_parametric.scad-7
OpenSCAD - potknob_parametric.scad
OpenSCAD - potknob_parametric.scad-1-1
OpenSCAD - potknob_parametric.scad-2-1
OpenSCAD - potknob_parametric.scad-3-1
OpenSCAD - potknob_parametric.scad-4
OpenSCAD - potknob_parametric.scad-5
OpenSCAD - potknob_parametric.scad-6
MeshLab v1.3.0-1
MeshLab v1.3.0-1-1
MeshLab v1.3.0-2

This script has a *lot* of variables you can tweak.  I don’t even feel like I’ve put everything into this script that I want to, either.

an incomplete list of parameters you can adjust:

  • knob radius
  • knob height
  • shaft hole radius
  • shaft hole height
  • set screw inclusion, radius, and location
  • flatness of shaft hole
  • rounding on top (thanks very much to for the articles on edge rounding!)
  • indentations
  • directional indicators
  • plus a lot more!


One of the most stressful things about making multiple copies of an electronics project is reliably locating interface controls that you like. Maybe you can locate them one time, but can you locate them a year from now? two years from now? And how much do they cost?

For example, I found some slide potentiometer knobs at for about $0.50 apiece two years ago, and they ran out of them… forever. I tried sourcing them elsewhere, and the best I could find was a seller that had them for $4.00 apiece (!!wtf!!). So that really sucks.

One strategy is to buy in bulk. But, buy too few and you may run out and pay twice for shipping.  Buy too many and you  end up with unused knobs sitting around not making your money back. That also sucks.

Round potentiometer knobs are somewhat readily available. But still, they can be from $0.80 to $5.00 each, and if you can’t find enough for your project, that can be problematic. Mostly I’m tired of paying multiple dollars for things that should basically cost $0.25 apiece. Aesthetics are important too, so having options beyond what’s out there is nice.

A different strategy is to print them yourself as you need them.  No shipping, no running out, and you get to call the shots on how it looks and how it fits. Now, I like this way. Plus, for my project, making the knobs just goes along with the rest of the stuff I’ve done myself.


Well… some are better than others. Limited success is better than no success at all.


Click here to download the parametric potentiometer knob generator OpenSCAD script.


Creative Commons License
parametric potentiometer knob generator by steve cooley is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License.
Based on a work at
Permissions beyond the scope of this license may be available at

makerbot thing-o-matic y axis drift video

My makerbot thing-o-matic has a problem with a drifting y axis, but only when a layer is complete. There’s lots of vague advice about how tight or loose the timing belt should be, but I’ve tried a dozen different tension guesses, and nothing seems to work without shifting the print mid-way through.

edit 2012-02-01 : my voltages were set to the makerbot motors, where the should have been set to the moons motor voltages. :-

sCCweet for korg iMS-20

sCCweet for the Korg iMS-20

sCCweet (cheesily said: “shweet”) for the Korg iMS-20 is a MaxMSP compiled application for mac os x that connects to your iMS-20 app through your existing MIDI connection (figure that out ahead of time). It randomizes the parameters of the iMS-20 at an adjustable rate so you can explore different combinations of settings that you might otherwise never run into on your own. It’s pretty random. There aren’t a lot of controls. :) Think of it as a spelunking tool for this synth. Enjoy!

Download “sCCweet for the Korg iMS-20″

Silicone Rubber test results and comparison

Trial, meet error:
Trial, meet Error

I’ve been working for about 6 months on finding a suitable silicone rubber material to use when making the keys for my beatseqr project. I started on this journey right after I’d set up my blacktoe cnc router. I knew I wanted a clear rubbery material to put in between the LED Tact switches on my circuit board for the user to push. This is a pretty well understood paradigm, so I figured there had to be a low-volume, relatively low-cost way to at least do some research into the feasibility of being able to do this. Of course you never know everything you need to know when you just start stabbing wildly at solving a problem that doesn’t have an obvious solution.  So, below is a small sampling of the attempts I’ve made.

TAP Platinum Silicone

When I started, I thought I knew what I needed. A clear silicone rubber. Right? Should be easy to find. I didn’t really know what exactly to look for, but then I saw that TAP had one! I drove on down to one of my local TAP stores and was a little sticker shocked at the price. Oh well, one credit card swipe later, I was ready to test it out. The product is really simple to use. It’s a 1:1 mix ratio, so you pour parts A and B in equal amounts, mix it all up, and start pouring it into your mold. It’s super runny before it cures so it pours easily.

Once I had tested it out, I realized that there was a critical third qualifying attribute to the silicone that would ultimately win the day: hardness. Smooth-on has an excellent FAQ posted about this topic. It explains everything you need to know and has a printable visual aid. Ok, so with that new knowledge, I can see that this TAP silicone has a Shore hardness of A8, which explains why it feels like floppy gelatin. I’m going for a push button with some give, without being squishy. So this silicone was not going to work. (It did, however, come back later as an excellent mold making material, its intended use anyway.)

Smooth-on Sorta clear 40

So while we were showing Beatseqr at the Bay Area Maker Faire 2010, I was able to locate the Smooth-on booth and discovered a couple of clear silicone rubbers that were MUCH firmer than the silicone I’d tried. Sorta clear 40, and Dragonskin 30. (Note that those product pages contain more than one shore hardness in the same product line!) I figured I’d go with the firmest one they sold, so I located a local dealer and bought a quart sized trial kit of Sorta clear 40.  As you can see from the photo above, the optical properties are excellent with this product.  However, after running a couple of test castings with this product, I discovered a fourth critical qualifying property that I’d need to consider: viscosity.

Always mix more than you need

Sorta clear 40 is an excellent material. I really like it.  It does, however, trap air bubbles… permanently, if you don’t do something about it.  That something you can do is called “degassing”.  Degassing essentially means that you use a vacuum chamber to forcibly remove trapped gasses, usually air, but sometimes other gasses depending on what you’re working with.  Well, I didn’t have a degassing vacuum chamber, and the ones that I found when searching for them seemed to cost multiple hundreds of dollars on the low end, and thousands on the high end. Definitely not within my budget for this test.

I found an article explaining how to build one, so I did that.  I’ll save the explanation for another post, but I managed to cut the price down from $800 down to about US$250.  I’ve always been interested in different materials, and I knew I could use this degassing chamber for other stuff later, so I justified the cost and assembled the parts.  

The viscosity of sorta clear 40 is pretty high, meaning, it does not pour like water. More like honey. Or taffy. The way you combine the 10:1 mix ratio parts is to open the canister of the part A liquid and scoop out 10 parts into a cup on a scale, and then add drops of part B to the mix until you reach the 10:1 ratio. I say “scoop” because the part A liquid is barely a liquid. If you hold the container upside down, it does not pour out. It’s perfectly happy to stay there without pouring at all. When you mix parts A and B together, it does become a somewhat pourable liquid, but before you get there, you have to stir stir stir for 3 minutes to get it fully mixed. Then the material has a bazillion air bubbles in it. So off to the degassing chamber it goes for several minutes, all while the “pot life” is ticking away. Pot life, meaning that you have a certain number of minutes after you combine the parts before they start to cure and solidify, so you need to work pretty quickly to get everything done once you start the process. So, out of the degassing chamber, and into the casting mold, quick!

Incomplete casting of sorta clear 40

above, you can see the worst case scenario of rushing to get the silicone into the casting mold, and not being thorough about making sure all of the cavities are filled and big air bubbles are out. Not only does this produce an unusable finished product, it wastes time and money. :P

Degassed sortaclear 40

Above is a test I ran to mix, degas, pour, and then degas in the mold. It sorta worked. Small bubbles were reduced significantly, but big bubbles formed and by the time the silicone started setting up, they were trapped forever.

Degassed sortaclear 40 mottled back

Above is another test I ran in a similar fashion. I got pretty good clarity by working faster and leaving more time for the silicone to sit in an uncured state in the mold, but while working feverishly to make sure all big bubbles were eliminated, I overworked the material past the pot life, and so the back of the flange is mottled and uneven. This might be usable, but seems like waaaay too much work to get it right every time.

Casting acrylic. Smelled awful.

Originally, the first beatseqrs had acrylic bar stock cut into rectangular shapes and hand sanded to be used as the button interface. The look and feel was pretty good, but the amount of work it took was too much for any kind of mass production, so I thought I’d try a casting acrylic to get the same/similar results without having to do so much hand work finishing. For all of the silicone castings, I am using machinable wax as the negative casting mold. Casting soft rubbery materials into a hard mold is fine, but… you can’t do that for rigid materials. So I made a “master positive” casting out of the TAP silicone, and then a silicone negative from that master positive. Actually, i did two. the first time, I didn’t adequately spray down the master positive with release, and silicone loves being cast on top of silicone, so I adequately destroyed the first silicone negative mold that I needed to do it again. The second silicone negative worked fine, and I was able to do the above casting in the casting acrylic I found at Michael’s.

Ok, BUT … when I went to do the acrylic casting, I discovered the downside to this material immediately. It basically smelled like a chemical factory took a crap, exploded, and died. And it stayed like that for upwards of 3 weeks. I asked a guy from Smooth-on about that and he said it sounded like it was a polyester casting material. Ok, so as pretty as it looks, I will definitely avoid using that again. The jury’s still out on rigid keys… Smooth-on has a material I may run some tests with, but maybe later if some customers dislike the silicone keys. So far, that hasn’t happened too much.

Hot melt glue!

I had these silicone negative molds, and started looking around my garage. I noticed how nice and translucent hot melt glue sticks are. After I realized that silicone would more than withstand the heat, I did a test and got some interesting results. Maybe this is a good fast casting material in some cases. It’s relatively cheap and easy to work with. But… really… not what I was going for.

Smooth-On Dragonskin 30

Enter the dragon. Smooth-on Dragonskin 30, to be precise. While at World Maker Faire 2010 in NYC, I got a great recommendation to try dragonskin 30. It seemed to have the right properties for this need:

1. translucent. Not transparent like sortaclear 40, but early tests indicate that LED light transmission is pretty good, which is what I want.
2. shore hardness A30, which is pretty firm. Not quite as much as sortaclear 40, but firm enough.
3. 1:1 mix ratio, so easy peasy mixing.
4. low viscosity, easy pouring. Less trapped air bubbles, should be easier to degas.
5. good working time and self leveling. Here, take another look:

Dragonskin 30 nice smooth casting

The flange is super smooth. That lets it sit perfectly flat on the LED Tact buttons so they they’re all seated evenly. There are some air bubbles trapped in the casting, but that’s because I didn’t bother degassing the early tests. I’m confident that if I need to get more clarity in the final castings, degassing will go well because this silicone is so much less viscous than sortaclear 40.

Dragonskin 30 translucence

Full castings in the mold cavities. Awesome. Minimal hand-working to get it to that state. Since the material pours much more easily, it doesn’t need much coercion to fill all the nooks. I declare a winner! Dragonskin 30.

There are a few loose ends to tie up on this story, so maybe when I complete all of the research I want to do on this process, I’ll post up the results. I’m hopeful my market for beatseqr is just starting, and I’ll need to keep refining my products to meet demand. If that happens, I will have more to post.

UPDATE … it occurred to me that you might be interested in see what the casting mold looked like (or, one similar to the current one I’m using) and how the casting mold looks when it’s filled, and how the casting looks as it’s coming out of the mold, so here you go!




UPDATE 2: just a reminder to never leave your CNC program running unattended. I stepped away for one minute right at the end of this run, and KABLAM… ruined casting mold. I was lucky it was just wax!

Ouch - cnc crash

blacktoe cnc usage: silicone casting mold

alrighty, then.. so I’m starting to get my bearings with how all the software works to run jobs through the blacktoe CNC router. I switched from cambam over to sheetcam and now I’m getting really good results. There’s still a certain amount of strangeness, probably all my fault, so I’m still learning what works and what doesn’t. Here’s a video I did to show how the blacktoe does with machinable wax:

The end result is a mold to use for casting translucent silicone into for use in my beatseqr project, as a replacement for the hand-cut-and-sanded acrylic buttons that I’m currently using. You never know how an experiment will really go until it’s over, and now that this experiment is over, I’ve learned a lot and will make a bunch of adjustments:

1. change the silicone product from tap plastics platinum cure translucent (way too wobbly for this application) to smooth-on sorta clear 40. I saw this product at the Maker Faire this past weekend and really liked the firm quality of the cured product. I think it will be a really good candidate. Smooth-on dragon skin 30 was my second-best candidate.
2. cut a new button mold using the techniques I’ve learned by doing this one.
3. adjust the height of the button to be not as tall as this test.
4. adjust the flashing surrounding the buttons to be not nearly as tall. I had it set to be 0.1″ tall, and that’s probably 0.08″ too much. all I need is for it to basically be thick enough to keep all of the buttons together, and that’s it.
5. think about how to diffuse the LED light going into the button… this new silicone is water-clear… so … I’ll need a way to adjust that quality so it looks good. maybe just a sheet of paper under the silicone flashing… we’ll see how that goes.

So… progress continues. I’ll post the result of the next prototype when it’s done.