Racks not square to Pinon gears - C-channel tops not flat, twisting rail down

[sailfl]

Gerald,

I have know for some time that my racks are not square to the pinon gears. I believe that is why I am getting the noise that I talked about in the past. I am ready to take some action on fixing the problem.

Sean has suggested using UMHW tape in 0.01 thickness to raise the rail to make it square with the pinon gear. It comes from McMaster in .5, .75, 1 and large widths. I am thinking .5?

I would like to hear what your suggestion would be or others.

Thanks

[Gerald D]

I don't see how raising something will change its angle?

[sailfl]

I think the idea is to put it on one side of the rail which will increase the height on that side.

I am looking for a solution to fix the problem. What do you suggest that I do to fix my problem?

[Gerald D]

You havn't really told us what the problem is.....something is out of line between the rack & pinion, but which part is doing what, and why?

Suggest you go around with a torpedo level (http://images.google.co.za/images?sourceid=navclient&rlz=1T4IRFA_enZA279ZA280&q=torpedo%20level&um=1&ie=UTF-8&sa=N&hl=en&tab=wi) and see if the table is horizontal, if the rail bottom is horizontal, if the rack teeth are horizontal, if the motor is horizontal, if the motor carrier plate is vertical, if the gantry end is vertical, etc. This will tell where the problem might lie and then we can figure a fix.

[sailfl]

I will look at checking the various things you suggested.

Currently I know that the rack is not horizontal to the pinon gears. I don't remember how far it is off. You can look at how the gear engages the rack and it is not perpendicular to each other. The plate is 90 degrees.

[sailfl]

Gerald,

The X Rails are not horizontal. The aluminum needs to be raised about 1/8" on the outside edge of the C Channel to make them horizontal. The X Motors are slightly off towards the X Rail.


The attached word doc has a small not to scale drawing.

Does that help?

[Gerald D]

It is always better to treat the cause rather then the symptom. Therefore the best thing to do is to get the rails sitting level first. This will also get your V-rollers to seat down firmer onto the V-rail, with a possible improvement in cut quality. Come to think of it, this mismatch between rail and wheel could also be contributing to the noise you hear.

[sailfl]

Gerald,

I believe this problem is the cause of the noise also but it is also causing rack and pinons to wear, correct?

What do you suggest I do to fix this problem?

[Gerald D]

I wouldn't be too worried about the rack & pinion wear - I have seen far worse mismatches still lasting a long time.

Afraid that the levelling of the rails is going to be a big job. The gantry & racks will need to be removed, and then the shimming process must be repeated. A long narrow (about 0.25") strip, 1/8" thick can be inserted on the edge of the c-channel. Maybe run some alu through the table saw?

But I definitely won't try to angle the rack relative to the rail. This will be very difficult to get right, and needs repeating in maybe 5 years' time when the rack is worn out.

[sailfl]

Gerald,

Thanks.

[javeria]

On my machine noise was due to the pinion not meshing with the rack entirely - the reason was that as I use a gearbox there was little space for a large washer and I had used one - this caused the spring not pull the assy completely up.

today I removed that washer and just left the spring washer on and that meant the spring pulled it all the way up!

and voila - so less noise!

I donno if this will help - but I thought i will just mention.

RGDS
Irfan

[Gerald D]

If the spring does not pull the pinion tight into the rack, it makes quite a noise, for sure.

[sailfl]

I am sure that the noise I am getting is because the pinon gears and the racks are not 90 degrees to each other.

[smreish]

...and as soon as I get more than 10 minutes free, I am off to Nils workshop to "tune" up the MM. His C channel has little to much camber and the rack is off just about 1.5 to 2 degrees due to the internal torque of the structural shape. I am making some long narrow shims to bring his racks in line and get a little quieter. The cut quality is not affected...just not whisper quiet.

...soon Nils - soon.

Sean