CNC tweaks

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pictsidhe

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Jul 15, 2014
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I had a Chinese 3040 4-axis cnc turn up today. A first look and it looks pretty useable. With one exception, the chuck timing pulley has been made with too small a PCD, the belt doesn't mesh properly. The seller is a drop shipper and I got it 25% off after someone else bought it then returned as they didn't have a parallel port. I'm therefore thinking that I should just put a new pulley on. I can't find a stock replacement so I'm thinking why not make it larger. That the means a pulley and a belt. With another pulley, I could change belt type. It currently has a good 12T stepper pulley and a no-good 27T chuck pulley. belt is 3/8"XL. What do the experts think of changing to 2mm GT2? Perhaps 20T and 100T It's only a 80mm chuck, but with a larger reduction could be useful. Steppers are nema 23 about 2 1/4" long.

I'd also like a much higher rpm spindle for it for grinding cutting tools. I would like to make my own fly cutters to cut ribbed belt pulleys and no doubt other things. Any suggestions for high rpm spindle motors than aren't hundreds of dollars? I'd prefer something that will take 1/4" shaft tools as there is a wide selection of diamond burrs in that size. I have a Makita router but it seems a bit big for a 3040?
 

FritzW

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Jan 30, 2011
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Las Cruces, NM
Ebay seems to have every imaginable drive pulley and belt you could ever need. And you can get a 500w chinese spindle with PWM for under $100.

I've been using (and abusing) the same cheap chinese 2.6kw spindle and PWM for 7 or 8 years and it's as tight as the day I got it.

Just a thought: water cooled spindles are soooo much quieter than air cooled. I've been waiting for mine to wear out so I can replace it with a water cooled.
 

pictsidhe

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Jul 15, 2014
Messages
7,426
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North Carolina
Aliexpress has even more pulleys. Custom ones too, which this will need. I need a 25mm bore with 5mm keyway. Add an OTS stepper pulley and I can upgrade the whole drive for increased torque. I'm dubious about the 2.25:1 ratio on a nema23. The XYZ steppers move the head 4mm for 360degree stepper rotation. The 4th axis is 2.25 stepper turns for 1 chuck turn. With a 60mm workpiece, that's 84mm per stepper turn. Perhaps this a cheap version of a 4th axis with a gearbox on the stepper...
 

Winginitt

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Joined
Apr 5, 2019
Messages
176
I had a Chinese 3040 4-axis cnc turn up today. A first look and it looks pretty useable. With one exception, the chuck timing pulley has been made with too small a PCD, the belt doesn't mesh properly. The seller is a drop shipper and I got it 25% off after someone else bought it then returned as they didn't have a parallel port. I'm therefore thinking that I should just put a new pulley on. I can't find a stock replacement so I'm thinking why not make it larger. That the means a pulley and a belt. With another pulley, I could change belt type. It currently has a good 12T stepper pulley and a no-good 27T chuck pulley. belt is 3/8"XL. What do the experts think of changing to 2mm GT2? Perhaps 20T and 100T It's only a 80mm chuck, but with a larger reduction could be useful. Steppers are nema 23 about 2 1/4" long.

I'd also like a much higher rpm spindle for it for grinding cutting tools. I would like to make my own fly cutters to cut ribbed belt pulleys and no doubt other things. Any suggestions for high rpm spindle motors than aren't hundreds of dollars? I'd prefer something that will take 1/4" shaft tools as there is a wide selection of diamond burrs in that size. I have a Makita router but it seems a bit big for a 3040?
How do you cut ribbed pulleys with a fly cutter ? How bout a picture of the machine.
 

pictsidhe

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Joined
Jul 15, 2014
Messages
7,426
Location
North Carolina
Maybe I'm using the wrong term. I need a form tool with a 60 degree angle and and a radiused nose. The plan is to braze an old piece of file onto some drill rod, reharden it, grind it (slowly) with diamond burrs. I may well have to use a 2 point cutter, one point for each side of the groove. Once I have the cutter, I can mill in circles around a piece of stock clamped to the bed. I'm not expecting my machine to like plunging the whole rib at once. As good as a lathe job? No. Good enough? Should be.

the CNC is one of these:

It's not great, but looks quite useable. I have been measuring up the standard 4th axis pulleys, the motor pulley has some run-out, so I will change the whole set. I could cut new pulleys on the machine, if my 4th axis wasn't so badly belted...
 
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