View Full Version : Need Help! 4896crp pro. Nema 34.

07-14-2013, 09:14 PM
Quick question from anyone with a who has a crp with nema 34 motors. wanting to know acceleration and speed are suppose to be set at. I have spun two bearings in the x and a axis pinions. I ordered two more replacements from cnc routerparts and installed them, but still having issues even after slowing down acceleration rate. I do a lot of carvings which I'm sure doesn't help much.
I did download the mach 3 xml configure files for the pmdx 126 when I did the build. I'm not sure if the info was stored in there or not, if so I have already over written them.

I also have a legacy cnc with lots of hours on it with no issues but it only is a 58" machine. I really need to get my crp 4896 working right or invest in another commercial machine. Right now my z axis sounds like horrible grinding. Even cutting small flat work files my motors get to hot to touch.
I only have a handful of hours on it.

PS. This is the old pro not the v bearing pro.

07-15-2013, 12:54 PM
I don't think the bearings die because of speed or accel, but because of being clamped too tight to the rail.
The trucks will never line up perfectly to the rails, and there will be high and low spots.
I have cracked 1 bearing and it was because they were adjusted too tight.

For your Z grinding, if it isn't a skate bearing that is making the noise, check the thrust bearings for the leadscrew, they need some lube.
I forgot to lube mine and they were load because of it. some grease made a good difference, quiet now.

I have set speed as high as 1500 ipm, and 150 in/s/s accel for x and y. Z maxed about 600ipm and 150.
It was crazy fast, and the whole table shakes because of the accel.

I run 600ipm limit with accel at 50 for all axes usually.

Edit- oops. I see you said pinion bearing problem.
scratch what I said. Have any pics of the damage?

07-15-2013, 03:09 PM

Thanks for the reply. I will reset speeds, re-cal and give it a shot. As far as picture goes it's the best I could do. The two x axis shoulder bolts and needle bearings are toast. When I ordered the two replacement pinions I thought I ordered pro model but I received the bushed style that seams to be holding up fine so far. The originals failed on my very first test carvings. Yes I did pack them with grease.
I did repack the z axis thrust bearing seams to have calmed the noise. Better put some new ones in my spare parts list to order.


07-15-2013, 06:06 PM
Is your belt tension too high? I don't think there is a spec or an easy was to measure tension, but on mine I pulled the motor firmly with my hand, then tightened the bolts.
If you use a clamp or something, maybe it is too tight?

07-15-2013, 06:22 PM

I think I did use a clamp the first time I assembled for belt tension. Replacements I did by hand just in case.

07-22-2013, 12:14 AM
I noticed a noise from my X axis prime drive today..my 4896 was finished not long ago and has maybe an hour or so of run time...I removed the shoulder bolt and it looks the same..chewed up...my belt and rack tension were NOT overly tight...the large drive spindle had started to rub on the edge of the aluminum plate because of the bolt wear...

I contacted Ahern about replacements..I hope he takes care of this problem..

07-22-2013, 12:40 AM
I had the same problem today with my y axis. I confirmed last week that belt tension was only hand tight. I never had much faith in needle bearings, but maybe we just got a bad batch of soft shoulder bolts. All I know is that this is getting old quick. all three pinions with less than 20 hrs. probably closer to 10 of run time.

07-22-2013, 07:35 AM
I contacted Ahern at CNCRP and they are sending replacement spindles with the updated design...hardened shaft and oilite bearings.....

I am going to remove the other 2 today...

I am also going to update to the new Z axis once I get going with a large project I have ready to cut...

Myrtle Beach SC

07-22-2013, 11:52 AM
As far as Nema 34 stepper heating..I have the Digital Leadshine AM882 drives..they are amazing!!....driving CNCRP 960 motors...Even when running back and forth full travel several times at 1000 ipm they only get warm to the touch...when idle they are barely warm...the reduction in amps is adjustable..I have it set for 50%

The Z has the smaller 640 oz/in nEMA 34 motor ... I use Teflon grease on the screw, also installed the new oldham coupling..makes a BIG difference...everything runs very quiet,

When test cutting in the air at say 100 ipm the motors sound like servos..almost silent.

The drives have stall detection and it works..if I try to run the Z too fast or with high accel/Velocity settings it will shut down and indicate stall/missed steps...when everything is set correctly it runs perfect.

07-28-2013, 09:21 PM
The new updated pro spindles arrived Sat. and I installed them..running very smooth!!..

They should take care of the wear problem...

07-29-2013, 10:42 AM
193928193930193932Glad to hear all went well with the replacements. Mine seems to be running okay now. Slowed acceleration Alan had recommended after seeing that mine was set the same as his. I have a customer coming this morning to cut out 5 patters out of Masonite. I hope all goes well. Friday I cut a plenum for my vacuum table. That is as soon as I come up with a good deal on a vacuum pump.

08-06-2013, 08:07 PM
Hi all,

Just found this thread. We changed the design on the PRO spindles as of the beginning of 2013, so if anyone has any further trouble with the bearings, let us know and we'll take care of it. We can retrofit current spindles to the super oilite bushings and hardened shafts, and if you have an arbor press you can do the retrofit yourself. Just let us know!

Best regards,

CNCRouterParts (http://www.cncrouterparts.com)

08-07-2013, 05:03 PM
That looks great ..I want one for my table!!...what is the material you are using??


Myrtle Beach SC

11-08-2013, 12:51 AM
how is your vacuum holddown coming along? I'm very interested in the setup you will assemble.

12-05-2013, 08:09 AM
how is your vacuum holddown coming along? I'm very interested in the setup you will assemble.

+1 here!