DVD-CNC DIY Laser cutting project

[ElectroNick]

Just a small update about the project.

Tried to combat the issue of low positional accuracy by controlling the steppers with simpler drivers that do not support microsteps and chopping 'cause chopping cuts the power - it Allegro A3967 chip runs at 70% power in 1/2 step setting  and I just wanted to try what's possible with a non-chopping driver.

Well, the results are not terribly good, basically there's no difference. I'm thinking these DVD stepper motors are just not powerful enough to move the body of the cutter in half steps. They still seem to only respond to full steps and some half-steps  and that ambiguity just makes the cuts look weird and strangely deformed.

I'll try to find and post a better picture of the test cutting pattern I used which was supposed to exaggerate the steps (with slightly slanted lines). Here you can see the pattern cut out of the lime green foam. Don't know how well you can see it, but the circle in the middle is not quite a circle and the slanted lines around it aren't straight lines either. This is not even mentioning that none of the text, also present in this pattern, is  easily recognizable.

I have the pattern in GCode and SVG formats if anyone's interested, and will post a better picture of the inaccuracy later.

[msurguy]

To answer your questions :

By the way, I wanted your input on the best size of a laser cutter specifically designed for those flying models you make. My models are in an odd tiny 1:212 scale but only because of the size limitation of the DVD slide (1.5″ travel). I would like to use some of the same components but forgo the slide. So, I’m looking for the best correlation between the sizes of the finished airplanes, the sizes of the sheets the foam comes in and the sizes of the new design elements of the cutter (which I’ve yet to pick). I’m very interested in your real-life based input, if you can post in the forum. Actually, I think it deserves a new topic in its own right. Thanks!

The models I made were in 1:72 scale I believe, the perfect size cutter would be A4 or Letter Size just like any printer or scanner. The foam comes in sheets 12x12 inches I believe.

Lots of info on the thin foam airplanes can be found here on the forum : http://www.rcgroups.com/forums/showthread.php?t=922636&highlight=spitfir+diy
http://www.rcgroups.com/forums/showthread.php?t=611386&page=22

The foam is now available only from one place as far as I know: http://www.microflight.com/Durobatic-Foam-Uncoated-3-Sheets

[ElectroNick]

The models I made were in 1:72 scale I believe, the perfect size cutter would be A4 or Letter Size just like any printer or scanner. The foam comes in sheets 12x12 inches I believe.

Do you remember off the top of your head the wingspan of that Spitfire model?
Also, if it comes 12"x12", this is what I'd stick with. It does not have to be any particular paper-standard size ('cause there's no hope for it to ever cut any paper except for the thinnest and darkest specialty papers) although it looks more like A3 - I actually have a plotter I may be willing to sacrifice for that