Board Lenght Measuring Error

[MetalCutter]

Hello Folks,

I was having a problem with my machine measuring incorrectly. I read a few posts and found some of you are having a problem with this also. If you are sure it's not the encoder roller wheel, tracking on a bad board edge, your encoder is probably dirty. Have no fear, it's fairly easy to fix.

Please read this step by step and if you don't feel comfortable doing it call LHR Tech. support for assistance. This may violate your warranty. I am not responsible for any damage to your machine or any thing else that may happen during this process.

Y Axis Encoder R&R:
1. Remove the two small screws at each end of the Squaring Plate. See Fig.
2. Lift Squaring Plate up and gently unplug connector plug from back of encoder.
3. Clean any saw dust you might find on Squaring Plate and Encoder Assembly.

NOTE:
Find a clean place to do the next step. Encoders discs are delicate and don't like dust, hair or scratches. Also, using any liguid or solvent may remove or damage the radial bars on the disc, requiring replacement of th encoder.


4. Remove the two screws on the encoder back cover, clean and set aside.
5. Gently blow out any dust or debris on the encoder disc. Don't touch it as you may scratch it.
6. When you have cleaned it thoroughly, put a thin bead of RTV silicone sealant around the mating edge of the cover.
7 Replace cover and screws. Don't over tighten the screws or you may crack the cover.
8. Reconnect the encoder plug and use some electrical tape to seal the gaps around the plug and wires.
9. Reinstall the assembly into the machine.
10. Put a board in and have the machine measure the length several times to be sure it's working as it should.
11. Be sure to make an end cut and check for square before running a project.


Good luck and happy carving.

Rick

[Jeff_Birt]

Thanks for the great tip Rick. :D

One small correction though; it is the X-axis you are referring to, not Y.

[MetalCutter]

Jeff,

I stand corrected.

[Mike]

I have done that but still am not getting the correct measurement. I put in a clean 20 1/2" board and it reads 20 1/8". Also on cut path I am getting a Step cut on each pass. It is like it is moving the cut 1/8" over each time. The pressure on the rollers is 80-90lbs. Carving text and pictures I am having no problem but cut path is getting bad. I never had this problem before. Any other ideas?

[MetalCutter]

Hey Mike,
I was still having a measurement problem after I posted the first thread.
This is what I've done since.
There are actually 2 encoders for the X axis. The other one is in the tractor drive motor and wasn't sealed properly. This one is difficult to get to and I don't suggest doing it without contacting LHR first. Mine had wood dust in it but this didn't fix it either, but it helped.
Also, on my machine, the board tracking roller O-ring (on the brass wheel) was positioned so when I put a board in the machine the O-ring rubbed on the drive belt and was worn so it wasn't the right diameter any more. The roller was measuring a shorter distance per revolution than it was supposed to. I called LHR to get a part number for the O-ring to see if I could find one locally. The number I was given is a LHR number and didn't help. I bought 2 sizes that I thought were close at OSH. Neither one corrected the error. LHR sent me one and the machine still isn't right. It makes good cuts but it stretches (like scaling) the X axis. This doesn't cause a problem unless I'm cutting both sides of a project or a precision fit is required.

This probably doesn't help you but I hope it saves you some troubleshooting time. If you find something else post it so I can check my machine.

Good Luck,

Rick

[Digitalwoodshop]

To fix Stepping try this.

Masking tape along the underside edge of the board where it touches the brass roller.

Replace sand paper belts. Worn smooth / dirty / streached belts cause stepping.

Good Luck,

AL

[Jeff_Birt]

Out of curiosity, have either of you guys calibrated your machine? There is a procedure to do so in the manual. This will probably not do a thing to help with stair stepping though.

I was cutting out some parts the ranged from 3" long to 25.5" long out of 3/4" MDF this past weekend. The longer parts had some noticeable stair stepping, but were still perfectly usable. I noticed that the machine tends to 'push' the board some in the Y-axis (or its walking as it is being fed L-R). This could cause a bit of 'slippage' throwing off the X-axis reading. As the rear guide cannot be tight against the board, I don't see a way around it. It could also be that the o-ring is slipping on the brass roller.

[Mike]

Thanks guys,
I will be able to try some other things before I call LHR. I did put new sandpaper on not long ago and my cw is extremely clean since I tore it completely apart to clean it. I did have some dust in the bottom but not too bad. Jeff, I looked in the manual and did not see anything about calibrating. Is that in the Beta manual?

[Jeff_Birt]

The calibration procedure is on page 39 of the manual (or there abouts), look for 'Calibrating Machine Offsets'.

I was looking a bit at my machine tonight and noticed that the pivot for the board tracking sensor acts as a sort of ledge to guide the board onto the sensor when it is moving back to the right (after it moves completely to the left) during board measurement. I placed a straight edge from belt to belt across this ledge and found that it was actually a bit higher than the belts. Thinking that this might cause some drag on the board and reduce the contact between the board and the o-ring, I added a 0.015" shim between the squaring plate and the sensor. I took some length measurements of the board before and after and it seemed like it might have helped.

Before: board was 28.125" long
1) 28.14
2) 28.14
3) 28.14

After shim:
1) 28.12
2) 28.13
3) 28.12
4) 28.12
5) 28.12

I'll have to do some test cuts to see though.

[liquidguitars]

I calibrated my machines with the 3/8 joining bit yesterday and it seems to the fix for some of probs I was having between readings from 2 units.
Now I am reading around.006". “Thanks go to AL for the idea”

LG

[Mike]

I will try these things in the morning. Thanks for all of the help. We have been in the middle of MAJOR reconstruction and have not been able to get back into this forum for some time. It sure is nice to know you guys are still helping out. Hopefully will be moved into NEW shop in the spring. Its not all that big but it will be mine not rented.

[Mike]

Well, I calibrated my cw. The stepping was reduced. It still will not measure my 20.5" board. It keeps reading around 20.113". Even with masking tape on the bottom. I did another cut path with masking tape on the edge and it just about stopped the stepping. When I took apart the encoder I noticed what appears to be something on it. air would not blow it off and I did not know if I should use my finger. There is a dark mark on the encoder at a diagonal across some of the bars.

[MetalCutter]

Just wanted to let y'all know I talked with LHR today. This problem is a head scratcher. Dave said he will talk with engineering in the AM and let me know what thier diagnosis is. I'll be glad when I stop making custom firewood.:(

[oldjoe]

Mike just a quick question is the small rubber O ring that is on the encoder still in its groove or did it pop and that is what is running crossways on the encoder
Just a thought.

[pkunk]

FWIW, I believe the measurement error is software related. I consistantly get the wrong measurement when I choose 'keep under rollers'. Just yesterday I had a 61" board the if 'keep under rollers' was chosen, measured 58"+ and as soon as I changed to not under rollers it measured correctly. Lest any of you thing I missed something, the letters were centered & I had over a foot to spare at each end. This was the same on 2 different boards, both straight & true, rough sanded to 100 grit on my drum sander so friction was not in the equasion.

[mtylerfl]

Hello Paul,

Interesting observation regarding the measurement difference related to selecting keep under rollers vs. not selecting that option.

Are you experiencing this with the 1.121 firmware version, or a previous version?

[Jeff_Birt]

If you choose 'Stay Under Rollers' when it measures the board it will subtract the extra 7" needed to stay under the rollers. So, a 20" long board will measure as 13" in 'Stay Under Rollers' mode.

[MetalCutter]

I have tried to recalibrate my machine since this problem arose but it stops about half way through. No error messages, it just goes back to the "Calibrate Offsets" command. LHR said there is no way for the end user to reset the calibration data. The machine would need to be sent back to do this.

[MetalCutter]

FWIW, I believe the measurement error is software related.
I initially thought it might be software so when I called LHR yesterday I talked with Software Support first. After explaining the problem I was promptly transfered to Machine Support. I have a feeling it's a combination of both. The machine has a problem and the software isn't set up to deal with it.
Just a guess.

[pkunk]

Hello Paul,

Interesting observation regarding the measurement difference related to selecting keep under rollers vs. not selecting that option.

Are you experiencing this with the 1.121 firmware version, or a previous version?
Both. I have one of each on 2 cards.

[pkunk]

If you choose 'Stay Under Rollers' when it measures the board it will subtract the extra 7" needed to stay under the rollers. So, a 20" long board will measure as 13" in 'Stay Under Rollers' mode.
So how do you explain my under 3" difference? I does it consistantly.

[Mike]

Mike just a quick question is the small rubber O ring that is on the encoder still in its groove or did it pop and that is what is running crossways on the encoder
Just a thought.

The o-ring looks fine. I will take another look at the encoder and maybe take a picture to show you.

[Mike]

I am running 1.121