Designing gears, cogs, sprockets in illustrator for laser cutting

I really enjoy building mechanical movements, and I am terrible at it. It is really difficult to build things that move without relying on expensive pre-built mechanisms. Thus I am always looking for cheap ways to design and build cogs, gears, and sprockets.

For gears it is tough to beat the online wooden gear generator at woodgears.ca. It lets you specify size and number of gears, and also lets you see how they mesh and tweak a bunch of variables. I usually print these to pdf and then import them as vector to illustrator. With this site you can build any number of compatible gears. They have rather large teeth because they are meant to be cut out of wood with a bandsaw, but they will work very well for low-precision work. There is also an inkscape plugin that generates gears as described here by MAKE.

One note on importing all of these files into illustrator. Illustrator has strange import prefs, and if you import a dxf that is in mm, and your preferences are in inches, centimeters, or anything else, then it will scale your drawing on import. Be careful. This is an easy way to mess up at the very first step.

Timing belt cogs are another deal entirely. There isn’t an online generator. There are a few python scripts that purport to build cogs, but they never seem to work right. One other way to do it is with blender and a plugin, but then you end up doing more 3d modeling than cutting.

To build one in illustrator you will need to know the belt you plan on using and the number of teeth you want the cog to have. You will also want to go to sdp-si and download an example any cog that uses your belt pitch. Set your units to mm in illustrator>preferences>units. Grab the dxf of that cog and open it up in illustrator.

More than likely you will see something similar to the image below. It has two example teeth showing the tooth spacing, but the entire cog isn’t drawn out as a time saving measure.




here’s how to duplicate out the rest of the teeth and more.

Thank you for voting / Ponoko test fit pieces!

First – a big thank you to everyone who voted for me in the sparkfun / ponoko / Geekdad contestI won!

From here on out I will be documenting my process as I go from rough prototype to finished laser cut beer vending machine!

There will be an upcoming longer piece on how to design for laser cutting. I have been amazed as to how many variables you need to keep in your head, and I haven’t even gotten the pieces yet! It seems like once you get it all figured out it is very systematic, but my design wasn’t nearly as tight as it needed to be in order to be laser cut.

This post is all about prep work. I have been talking with Josh at ponoko, and he suggested that I cut a few test pieces to figure some things out. I am planning on using t-bolt assembly. The good thing about that is that it ought to withstand both the thermal rigors of being refrigerated and the physical stress of having 12 oz cans banging around in the machine. The bad thing is that it adds another unknown to the design. I decided to test a bunch of different slot and tab widths to find one that fits as close to perfect as possible.

One interesting thing about designing for laser cutting is that you can easily control the cut dimensions within 0.1mm, but you don’t have any control over the thickness of the acrylic. Due to variances in manufacturing, the 3mm sheet could be +_ 15%! On a 3mm sheet your thickness could be off by up to 0.4mm. This means that for a tab and a slot, you have to make the short sides precise, and the wide sides a bit sloppy. Definitely an interesting twist.
hit the jump for more laser-cut plastic action!

Get yer lase on

As of last night I got my 16x sony diode all plugged in and turned on! I’ll have some pictures to prove it in a bit. I’m excited, but I really was expecting a bit more danger in the process. It’s bright, and it cuts very thin, dark things. It might even do a decent stencil if cut out of black paperboard, but I was hoping for something with a bit more killing power. I guess I had my hopes a bit high for a laser that cost $30!
I’m still gonna try to mount it to the cnc router and see what it can do. Hopefully I can find a type of wood, or a stain that makes wood “singe-able” I’d be pretty happy about that.
Here’s a pic of the laser diode and enclosure(silver thing in mid-air) and the power supply (thing on the breadboard) Yep, it’s not pretty.
sony 16x diode DIY 620nm red burning laser

Here’s a pic of the output. Shining gloriously on my hardwood floor.

laser dot on floor

Lastly, I went out and got drawer slides for the z-axis (at lowes), and bought a hitachi trim router (at ReconditionedSales.com)
With the exception of one L shaped piece of metal I should have everything I need to fully assemble this monster.
If there aren’t any posts for a few weeks, either my body is frozen out in the garage, or I’ve become even more fascinated with the fully functional router.

Treatise on living and loving lasers

In case you haven’t caught on yet. I love projects, and I am always starting a new one in order to abandon an old one. Recently I have become fascinated by the DIY laser movement propagated by the fine people over at laserpointerforums.com. My interest was piqued initially by “lamedust” who posted an instructable here that showed how to build a laser powered stencil cutter out of 2 scanner corpses and a sony16x diode.

My previous post showed my homemade laser driver (ie regulated power source)

I bought a laser focusing tube/heatsink and a sony 16x laser diode from stonetek. Stonetek is run by a frequent commentor from laserpointerforums.com, and is highly recommended over there.

I’m really excited about seeing what this sucker could do if I were to hook it up to my cnc router. Right now it only has an x and a y axis, so this laser fits in nicely without the need for a z axis!

I havent been able to get a precise answer regarding how useful this laser will be. It certainly will not be more powerful than I need! It might be strong enough to burn (but not cut) wood and to possibly cut paper, paperboard, or etch plastic. I’m really excited to find out what it’s capable of.

Here’s to the start of another project, and hopefully the smell of burning things is in my future!