Rubber Belt Calibration Accuracy

[liquidguitars]

MT, I would just make the sled tails over 4" like Kenm810' and Al and "me for that matter", then load the sled under the wide tail and your good to go..

[Fardoche]

What is the version of the installation instructions did you get with you rubber belt ?

I installed the rubber belts over the past few days and went through the belt calibration routines (firmware 1.153). Below are my results after calibration (fractions of an inch represented in decimal for easy comparison to CW values):

By tape measure:
Board1: 23.9375 L x 3.515625 W x 0.750 D
Board2: 48.03125 L x 3.50 W x 0.750 D
Board3: 35.00 L x 3.46875 W x 0.734 D

CW measurements:
Board1: 24.040 L x 3.521 W x 0.750 D
Board2: 48.045 L x 3.524 W x 0.755 D
Board3: 35.186 L x 3.497 W x 0.745 D


The width seems to be the most consistent measurement from run to run and the depth usually works pretty well too. The length will vary a bit (+/- 1/32 - 1/16") from run to run.

I calculate the length measurement error as:
Board1: 0.43%
Board2: 0.03%
Board3: 0.53%

Board2 was the calibration board, so no surprise it's the closest. I can't say I'm satisfied with the overall results though, particularly where Board3 is off in measurement by 1/8"+.

So I really have three questions:

1) Anyone with sandpaper belts out there which can do some similar tests on measurement to see how much it varies from the rubber belts.

2) Are these within the tolerances expected (i.e., should I be happy with the results)?

3) What's the overall impact of the length measurement being incorrect in this kind of an instance. Does one assume that it's off by a similarly small fraction across the entire board and distort the carving by extremely small amounts?


Thoughts on this and any similar data is much appreciated.

[mtylerfl]

What is the version of the installation instructions did you get with you rubber belt ?

Hello,

This one...

http://www.carvewright.com/images/se...alibration.pdf

I'm pretty sure this is still the most current one, until the next update of the software (1.160) is released (which will be very soon, I'm told).

[wacoustics]

Thanks everyone for your insight. I'm a bit confused as to how anything to do with the X measurements could possible affect the Y measurements.

I loaded the calibration boards both ways (centered and off-center) with essentially the exact same results. I was able to get the machine to generally with 1/32" of the correct measurement by doing the following:

1) Cut a calibration board to an exact inch measurement (in my case 36")

2) Measured the machine cut marks but calibration was still off by about 1/16". I went back and lied to the machine and said it was 1/64" shorter than the measurement and now all the boards that I run through are generally within about 1/32".


In retrospect I wish I would have run some measurements with the sandpaper belts. The projects I've run through this though since the belts (one small sign and one guitar neck) seem to be done well. Overall regardless of this the combination of rubber belts and rock chuck seem to be a massive improvement in the machine.

[Gerald Bennett]

The tips and tricks said it is especially an issue with boards over 3 feet in length if you load the board off-center. I would suspect that is mainly true if you don't provide good support for the board, if it is hanging out of the end of the machine it could have enough leverage with its weight to make the head pressure think it is all the way down before it actually is which could lead to the tracking issue, with the board centered that leverage is eliminated so the head pressure should be more accurate, with a shorter board or proper support it probably wouldn't matter. Just my wild guess

[Paul McGrath]

I have a similar problem using the sandpaper belt.

History:
When a longer (36") the board was being measured it threw a "check tracking roller error". Initially I though it was the board lifting off the tracking roller and fiddled with the board support and adding tape. Unfortunately this didn't eliminate the error.

Observations:
a) However, I did find out if I changed the calibration (ver1.162) using a longer board this error disappeared, but showed up with measuring the shorter boards.

b) When I calibrate using a short board the measurements on the longest board that doesn't trigger the error is off by around 1". When I calibrate using the longer board the shorter board is also off by one inch.

Findings:

It looks like the machine compares the belt movement (after the compression roller is free), with the tracking roller data. If these don't match within a set limit the error is triggered.

Could it be that the tracking roller sensor is broken?
Can this tracking board error also occur due to incorrect belt movement?

[mtylerfl]

Hi Paul,

Some other things to check...

...Head Pressure

...the O-ring (check if it is in the groove and not damaged/scuffed/flattened at all)

...verify the rubber O-ring is not contacting the traction belt

...edge of sandpaper belt nearest the keypad (verify it's not rolled under itself)

... the spring damper under the tracking sensor assembly (verify it is there - it's simply a short length of rubber tubing standing on end on top of a screw head...you can't see it without removing the tracking assembly)

[Paul McGrath]

Thanks mtylerfl

I checked the O-ring and took off the squaring plate and checked the spring damper. Both looked good.

In the next couple of days I will check the head pressure and double check the belt.

[mtylerfl]

Thanks mtylerfl

I checked the O-ring and took off the squaring plate and checked the spring damper. Both looked good.

In the next couple of days I will check the head pressure and double check the belt.

Great! Hope you get the problem nailed down tomorrow and get back up and running!

One other thing I forgot to mention before...the machine likes a warm shop environment - you should be ok if the shop is 55 degrees F, or above. Lower temps can cause strange issues.

[Paul McGrath]

Last night I had some success. I checked the head pressure and it was down at 45 (room temp was 20_C).

Ended up doing the following.
-aligned the vertical posts.
-wd-40 the post and screw to strip any old grease off. The white lithium grease feels too thick for the purpose.
-inspected the belt and found a small tare on the far side of the belt. Cut the rip's edges clean.

This brought the head pressure to 65. Still low but better. I will phone carvewright support to see if I can get it up further.

Reset the factory x-calibration factor default and measured a 36" piece of wood. SUCESS!! It was within 1/32".

What would everyone recommend as a lubrication on the post and lead screw? Unfortunately my carvewright's area is not adequately temperature controlled so I need it from 15_C(59_F) to + 50_C(122_F; It's in a muffle box).