New Machine Build- Rack & Pinion

[captainkirk]

All,

I have asked similar question in past but now I am down to actually purchasing and installing so I will ask with more detail this time.

I am building a CNC router that has a 4' x 4' operational area. It is a gantry type so there will be dual racks on one of the axis. Here are the questions:

1. What ration / pressure angle is best for the application?? Plan to do a gear redution drive on the steppers for increased resolution.

2. Where is the best place (most cost effective) to purchase the racks and pinions.

3. Any other ideas for driving this size of machine. It will also be a plasma so it will need to have jog rates at 1000ipm and drive a plasma at 800ipm.


Any advice / help is appreciated.

Thanks,

Kirk

[Mike Nash]

By far the best pricing I found on rack was here http://www.stdsteel.com/gr_stock.htm and I had zero problems with the purchase. But you have to ask for pricing and shipping and send a check, no credit cards. I have heard they have gone to per piece cost on shipping based on two shipping zones lately. I bought a gear blank from McMaster that's 12" long that I intend to make my own pinions from. Lot's cheaper and I can get the 1/2" bore that I need that way (I sure love my 12x36 lathe!.) I went with the 20DP and 20 tooth pinion but have yet to build. I've gotta finish the mill first.

You need to check out the MechMate at http://www.mechmate.com/ and also be sure to scan the forums. They've already got a motor/rack/pinion combo worked out. Plenty of info and it's free.

Disclosure: The preceding two paragraphs were flagrant cut and pastes from previous posts I made.

[dmoore]

Originally Posted by captainkirk 1. What ration / pressure angle is best for the application?? Plan to do a gear redution drive on the steppers for increased resolution. 2. Where is the best place (most cost effective) to purchase the racks and pinions.

Here is a link to the entire pricing, web links, etc for all the rack, steppers, etc you will need:

MechMate 4'x8' Comprehensive Bill of Materials

Originally Posted by captainkirk Any other ideas for driving this size of machine. It will also be a plasma so it will need to have jog rates at 1000ipm and drive a plasma at 800ipm.

The links to the rack and 7.2:1 geared motors will do about 1,400 IPM *IF* you use something like the Gecko G100 or SmoothStepper, it's not possible with those motors/gearing to get above about 600-800 IPM with a standard parrallel port and a current PC without loosing steps.

Here is a video of cutting at 450 IPM with jogs at 800 IPM with my Machine:

YouTube - MechMate at 450 Inches/Min

YouTube - MechMate at 450 Inches/Min