It has been a very long time since I've posted here, but life has calmed down enough that I can get back to my build log. I decided to change direction a little on the electronics and built my own board with the motor drivers built in. Hacking the moshi board like I did worked fine, but the allegro motor driver chips that everyone is using on the pololu boards are so cheap it doesn't even make sense to keep any of the moshi electronics.
I designed up a board using a PIC16F1937 (that's my favorite PIC right now), using an MCP2200 USB to Serial converter and 4 Allegro A4984s. The Pololu boards that everyone is using use the A4988. I chose the A4984 instead because I could get it in a TSSOP package (easier to solder) and the A4988s had a super long lead time. The laser is only using 2 of the motor drivers right now. I put down 4 so that I could use this same board to build a 3D printer in the future. I also have a header on board to get to my E-Stop and limit switches. I bought my boards from iteadstudio.com. I'm very happy with the quality of their 2 sided boards, and they are very low cost. Shipping takes a long time to NY.
- Stepper Driver
I originally bought my DC-KIII with the intention of building a much bigger laser. I wanted a 2' x 4' work area and planned to transition all the electronics, tube, mirrors and power supply to the new laser. That plan ended up panning out quite well. I spent the month of September designing up my dream laser and buying parts. The month of October was consumed with building. By the middle of November I was back up with an operational laser. Here is the computer rendering of my design:
- ProD Complete Laser Design
All the aluminum extrusion is from misumi. The total bill was $913 at misumi. I didn't expect it to cost that much, but I did use a lot of it. I decided to build a complete base so that that laser would be free standing, which drove the cost up. I decided to swap out the DC-KIII's focusing optics for a one of the adjustable ones that LightObject.com sells. That allowed me to have a fixed table, which I think is a terrific idea if you are going to build a 2'x4' laser. My linear rails are maker slide that I purchased from inventables. I bought 2 1800mm rails and cut one of them in half to make the y axis. The gantry is just a solid piece of makerslide. When I bought it I wasn't sure it would hold up running the whole 4' of the table ( I thought it might sag) but it has worked out great.
- Laser Frame
One of the key pieces of my design is that all the custom brackets and connectors were designed to be laser cut on my DC-KIII to build the new bigger laser. This saved a lot of money as several of the parts had to be remade a few times when I changed my mind during the build or something wasn't measured correctly. I remade the gantry mounts several times when I found that acceleration of the gantry was causing the brackets to flex. I had to widen them quite a bit and changed from 3 v wheels to 4 v wheels.
Original gantry mount - only 3 vwheels and not wide enough:
- Original gantry mount
Wider gantry mount and laser head mount:
- Laser Head Close
Trouble Shooting Electronics:
- Trouble Shooting Electronics
Everything is finised enough to get back to production!
- Laser Complete before installing the lid panels
I decided to skip the expense of Alupanel and skin the laser with luan plywood. I bought to alumium foil to cover the insides of the wood panels with in case of a beam alignment problem. I don't really want the sides to start on fire. I haven't actually installed my safety aluminum foil yet though.
I'll save the rest of the info of my build for another post.