How to cut a rack on a PCNC 1100?

[avayan]

Hi guys,

I just got my PCNC1100 about 2 months ago and have been learning all the material, which has been keeping me quite busy. I am just dying to get some chips flying and I thought of cutting a rack for a plasma cutter rack and pinion linear drive. However, I am wondering what is the best technique to do such a part on a 3 axis milling machine.

Is this something that can only be done on a horizontal milling machine or is there a vertical blade I can use to cut it? I imagine that with the awesome resolution on the PCNC 1100, the output should be quite accurate as well, right?

Thanks for sharing your thoughts on this topic.

[philbur]

A vertical mill, as you have realised, is not really suitable for cutting a rack. It can be done but depends on the DP, the material and how much your time is worth.

1) You can make of buy a right angle drive. (not very rigid)
2) You can use the z axis as a shaper. (not very rigid)
3) You can make a special tapered endmill. (can you make end mills)

I have done none of the above. There maybe others, we shall see.

Phil

[StephanWenger]

Hi,

Option 4: use a tapered end mill.

I vaguely recall that a rack is an involute gear with infinite diameter. It has been 25+ years since I studied this stuff, so I might be wrong. However, if I'm right, the flanks of a rack tooth are straight lines, at an angle to the perpendicular of the rack that is the pressure angle (20 degrees in most cases).

What you can do is to get a tapered end mill (like this one Enco - Guaranteed Lowest Prices on Machinery, Tools and Shop Supplies) and cut the flanks of the teeth.

Also take a look at this:Rack and Pinion

Stephan

[keen]

Hi - If the material is to be steel using a HSS tapered cutter is challenging.

When cutting many teeth the cutter easily becomes dull and crabs over giving form and angle errors. If you choose this approach in steel first gut out the bulk with another cutter and just finish off with the sharp taper cutter. Or you could buy 2 and use one as a rougher. You will need a cutter slightly smaller that the tooth to allow a side shift and more accuracy.

[asuratman]

Hi avayan,
Check gearotic motion, they have software to cut gear, I think they will release one to cut rack.