Laser cut gears from mdf and windup toys

[Joshua Merrow]

Hi all

We're experimenting with our new laser cutter. A few questions about gears:

1. Is MDF the way to go for largish (2 to 12" diameter) gears? We have 1/8" and 3/16" thicknesses. I don't think our 60W helix will go much past 1/4".

2. What's the easiest way to do shaft collars? We'll need two kinds - a simple collar that locks to the shaft (most likely 1/4" wood dowel, though we could use acrylic), and one with a flange that locks to the gear as well (see attached illustrations). We're not talking about heavy loads here. I think I've seen such pieces in plastic, perhaps inside toys, but I'm not exactly sure where. Anyone have a source, or a better way?

3. Finally, we're thinking about making windup toys with 9-12th graders. Has anyone tried this and/or know of a source for beefy windup mechanisms?

Thanks!

Josh Merrow

Maker Dept.

Riverdale Country School

[Joshua Merrow]

Oops, here are the sketches of what I'm thinking about.

[Diego Fonstad]

If you have a 3D printer this is a great use of it.  These are small and easy to design in Tinkercad.

Size the screw holes using a Die Tap chart and most screws can self-tap their own threads or you can easily use a tap into the plastic for the threading.

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[Kenton Hoover]

I wouldn't carve gears in MDF as I don't think they will survive,
between friction just rubbing them to dust, that they won't take any
torque to speak of, and if you drop it, it's garbage. I've had lots of
success with acrylic and thin plywood sheets. If you need to go
thicker, I'd just cut multiple gears the same way and laminate them.

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Kenton A. Hoover
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The Tehiyah Day School
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[ndigiorgio]

I've played around a bit with gears for a guitar-shaped-clock that is scaled to the actual Stratocastor size and then scaled 300+% to be almost 5 feet tall. 

The website isn't really complete but you get the basics of the project. http://nickdigiorgio.com/clock-guitar/

I agree with using layers of acrylic. 

FYI, Inkscape has a gear generator built-in but the best purchase I've made is the gear generator (link) program. 

Steal shafts, set screw collars and mini bearings are the way to go!!!. 

I purchased mine from amazon and VXB.com

606ZZ: 20 Bearing 606ZZ 6x17x6 Shielded Miniature Ball Bearings

 

[Kenton Hoover]

Love your clock.

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[Joshua Merrow]

Thanks for the ideas everyone!

[Joshua Merrow]

Update. After experimenting with different materials we went with 5/32" mdf, available from home depot. We had the home depot guy panel saw it into 24 x 20" pieces that fit on our laser cutter (Helix 60W). There is some sticky residue left on the laser bed, and it smells bad, but it's cheap and hard enough for gears and other moving parts.

For the project, each kid gets a 2rpm 12V coffee grinder motor (found on http://surpluscenter.com for about $4-5 each) and has to make a working clock. Emphasis on funky, original designs. They use geargenerator.com (free) to generate gears and save them as .svg files, which they edit in Illustrator. They also browse http://507movements.com/, a century-old archive of mechanical solutions to different problems with images that you can trace in Illustrator. We're in the middle of the project now and the kids (grades 11 and 12) are engaged. Gallery show in the cafeteria once they're done, will post.

One weak point is Illustrator - it does everything, but its learning curve makes me hesitate to use this toolchain with younger kids. Does anyone have an easier way to edit gears, design parts, trace images into vectors for output to laser?

Thanks

Josh

[Kate McAdams]

Hi Josh- I have been using laser cutters for ten years- we have never used MDF in a laser the fibers are too small, my suggestion would be Plywood (laser ply ideally) or pine if you can afford it.

On Monday, May 18, 2015 at 9:51:22 AM UTC-4, Joshua Merrow wrote:

[Kenton Hoover]

I would avoid MDF on the laser cutter myself as it's also a big soot generator which means more mirror cleaning. I've used model plywood in 1/8" - 3/8" as it cuts cleanly and usually with a single pass (more than 3/8" I find I have to recalibrate the laser and do two passes).

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[Ryan Barnes]

I've always avoided MDF for the formaldehyde component. I've been using 12"x12" panels of 1/8" baltic birch I get for about $1 a sheet from Kencraft. Cuts like butter on our 40w machine. 

-Ryan 

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Ryan Barnes

Drexel University, College of Engineering

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[Joshua Merrow]

Good call on avoiding MDF. I've tried 3/16" plywood and it does seem to cut more cleanly.

Thanks,

Josh