"Gearing up" for another CNC build thread - RC Groups
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Mar 21, 2012, 03:58 PM
Father of Fr3aK, DLG Pilot
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"Gearing up" for another CNC build thread

Kinda... over the next week or ten days I'll be converting my Joe's 4x4 CNC from lead screw to rack and pinion. I originally started building my machine in November of 2009 and have been cutting with it regularly for just over two years.

The pictures seen here are taken on the current machine, and are parts that I'll use to convert it to RnP.
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Mar 22, 2012, 08:12 AM
Father of Fr3aK, DLG Pilot
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Belt reduction kits showed up yesterday... very nice stuff from cncrouterparts.com

BTW the rack came from Moore gear. Thursday call and Tuesday UPS truck with a custom drilled rack. GREAT service.
Mar 22, 2012, 09:55 AM
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I was Harry's Cast CNC #44

I am in the final stages of finishing up a smaller V 2.5, looks like my cut area will be 22.5 x 48 inches.
Mar 22, 2012, 10:40 AM
Father of Fr3aK, DLG Pilot
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Very nice. A friend of mine is doing a Harry's cast CNC too...
Mar 22, 2012, 02:23 PM
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Originally Posted by tom43004
I'll be converting my Joe's 4x4 CNC from lead screw to rack and pinion. .
Neat, thanks for sharing. CNC's helping to make their own replacement CNC's!
Dumb question, but what does the rack & pinion enhance? rigidity... positioning... backlash issues... transit time...?
Mar 22, 2012, 03:47 PM
Father of Fr3aK, DLG Pilot
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Yeah, my CNC has spawned parts for half a dozen or so others, as well as cutting some part modifications for itself.

As for RnP...

It's a little more forgiving of slight racking issues on a homebuilt machine, and increases my rapids since I'm not spinning a 6 foot long leadscrew anymore. It also eliminates couplers which can be a PITA to keep from slipping.

The big reason is that it increases my cutting area by about 40% without changing footprint since the pinion can run right to the end of the rack, where the leadscrews have boxes that carry a bearing on each end and the stepper, all of which deduct from travel. Right now I have seven inches of unusable table at the front and back of my machine and with RnP on the Y/A axis I get to reclaim all of it in the front and most of it in the back.

Gearslop is very similar to or a little better than the backlash on standard ACME screws, and drag is quite a bit lower, especially if you upgrade to a ball screw for more accuracy. All of this makes a more maintenance free, faster, cleaner machine with a larger cutting area.
Mar 22, 2012, 05:55 PM
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Merk's Avatar
Tom Looking good.
Soon I will be calling you for some simple test files for my CNC.

Mar 23, 2012, 12:17 AM
Father of Fr3aK, DLG Pilot
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I have you covered Russ. Just let me know when.

You should probably start with a 1/2 ballnose, a 1/4 endmill, 1/4 ballnose, 1/4 endmill .060 radius, and maybe a 1/8 collet with 1/8 endmill and 1/8 ballnose. Those will cover most situations for now.

I probably have over 100 different bits now and 5-6 different collets. It's really a bad addiction. You start losing sleep trying to figure out how to match a tool to a part (of a part) so that the machining is perfect. Next thing you know your credit card is maxed out on little chunks of carbide.

Mar 23, 2012, 11:04 AM
Father of Fr3aK, DLG Pilot
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One of my favorite uses for my CNC is as a router table. I'm using a 1/8 roundover here to clean up the edges of the parts for my new X axis carriage.

Time to paint on 8-10 coats of wood sealer so I can do finish sanding and assemble with epoxy.

My McMaster order arrived yesterday so it's officially on this weekend.

DSCF4578.AVI (0 min 24 sec)
Mar 23, 2012, 03:40 PM
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I to rounded all the edges before gluing it all up. Makes it look a litlle better.

That wood hardener stuff is great but don't get it on your hands.
It turns them a nice shade of black for a few days.

Mar 23, 2012, 03:50 PM
Father of Fr3aK, DLG Pilot
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Yeah, I have used it a bunch of times in the past, including on my current CNC.

I think the roundover and a good coat of paint keeps it from looking like a homebuilt machine. No sense in building something ugly after all.

BTW... I should have a box ready for you by mid week next week.
Mar 25, 2012, 10:42 AM
Father of Fr3aK, DLG Pilot
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Sealed, Painted (first two coats) parts

Today I get to glue together the carriages. If I didn't have to play hockey tonight I'd probably get the wiring harnesses updated. Today the Y/A axis motors are fixed at the back of the machine, on bearing blocks mounted to the 8020 and hardwired back. With the RnP mod, the motors will be on the carriages, moving with the gantry so I need to reroute cables, probably make new ones, and wire more "stuff" into the gantry wiring harness.

BTW... this is how messy your machine will look in a couple of years if you actually use it. It's surprising how much static electricity the dust removal hose generates (even with a ground) and how the statically charged particles stick to the wall behind the machine.
Mar 26, 2012, 10:08 PM
U down with EPP? Ya U know me!
Aerogance's Avatar
A few moments with a push broom will have that wall looking like new
Mar 29, 2012, 08:13 AM
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Tom is it all together?

Like to see some pics.

Mar 29, 2012, 08:40 AM
Father of Fr3aK, DLG Pilot
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I'm taking lots of pics Russ. I had an issue with the paint not wanting to dry over the weekend here (raining / humid) so I have all of the carriages painted and assembled now.

I had to find a local supplier for bushings since Ahren sent me the R&P kit with a 1/2 pivot instead of the 3/8 that I'd ordered. I just got the bushings last night and I'll press out the old ones / press in the new ones tonight. Assembly doesn't look like it will take long so I may take a stab at it tonight.

The wiring will take longer than anything else.

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