X Axis Travel Accuracy

Jason wrote:

Hi Leon,

The Rack and Pinion system does use a preload spring to pull the pinion against the rack.

I'll pull one of the pinions off the machine today and post some pictures of the wear. I guess it's better to wear the pinion than the rack.

Cheers,
Jason.

Yes better to replace a small gear vs a 4ft+ track.

It may be considered a "wear" item or maybe try some type of grease lubricant. If they are cheap enough it may be worthwhile to try a new one and check it with the indicator

Yeah I think they do consider it a wear item. I was thinking that a dry lubricant might be helpful. Normal grease would probably catch too much dust and crap causing other problems.

Cheers,
Jason.

Here are some pictures of the R&P setup and the wear on the pinion.

The wear seems to be concentrated on one side of the tooth. I’ll check the other side of the gantry too. Maybe the pulleys can be swapped side to side to alleviate some of the wear.

Cheers,
Jason.

Do you climb cut or conventional cut.

Conventional cutting will always be pushing back on the tooth.

Climb cutting the forces will accelerate the gantry with the rotation of the tool.or even possibly make it rattle back and forth if it's really loose

Hi Leon,

I’m using conventional cutting.

I have recently been cutting Aluminium which puts more strain on the machine. My loss of accuracy and hole shape being off probably coincides with some of this activity...

Cheers,
Jason.

Your wear pattern on the pinion looks like poor alignment with the rack. The overall design looks rather weak and prone to wear issues. Any slop in the pinion bearing or the plate pivot is going to result in the issues you are describing.

Yes, having the spring on the side like it is would put the alignment out and is most likely the reason for the odd wear I’m seeing.

The pinion runs on a bronze type bushing and the pivot point is the same. Both bronze bearings run against a ground shoulder bolt.

When removing the pivot bolt it did seem like the bolt was bent. I’ll check that before reassembly and correct it if need be.

I’ll have a think about the tensioner to see if there might be a better solution.

Cheers,
Jason.

Hi Guys,

I’m after plenty of mucking about and measuring I have fixed my machine.

The worn pinions haven’t been replaced yet. During the measurement process (scale and backlash) I discovered the root cause of my X axis issue. The X and Y axis of my router run on hardened V rail with V bearings. The bearing pressure against the V rail is adjustable. Turned out that the bearings on the X axis were too tight. Bugger!

Anyway, all fixed now and the machine is working much better. I now have round holes.
Both the X and Y axis ended up with 0.001” backlash compensation. The Z axis uses a ball screw. It required 0.0005” of backlash compensation.

Cheers,
Jason.