X-Axis shift problem

[billybehr]

Hey ya'll- long-time-no-been-here. I just got back from Honduras a couple of months ago (thanks to Uncle Sam) and finally got to see my CW again. I would like to say it was a touching reunion, but unfortunately it restarted my love/hate relationship with it. I had a problem with it not measuring correctly in the x-axis and hence did not cut properly. My first carve was a disaster; I made some great designer firewood. It carved it and then when it went to cut it, it went into the carved region with the cutout bit. I spent days on the phone with CW and tried everything I think of. They sent me custom configuration files, talked me through measuring and checking the x-axis calibration and finally told me I had to send it in. I went off to Honduras and by the time I got back, my warranty with CW had run out, so I sent it to Sears. They told me I had a bad board sensor and replaced it and sent it back. As soon as I got it back I ran the x-axis board measurement and it was well over 7/8ths of an inch off. I ran a small project and it seemed to do alright. Then I made a custom project that needed to be cut out and since I was doing it in 3/4" red oak I did 1/8th inch passes for the cuts and this is what I got. See the picture below. I am going to call Sears tomorrow and talk to the technician that said my machine was "good to go" and see if maybe I need to send it back to her. Unfortunately I cannot adjust my x-axis calibration far enough to make it measure correctly. The board I put in is 36". When it is measured, the machine gives me 35.083" and I can't shift the calibration any farther to the lengthening side. Any help would be great. Maybe ya'll can give me some ideas to present to Sears before I send it back in.
41828

[liquidguitars]

some quick things to check..

1. make sure the o ring is on the AUX roller " small brass wheel".
2. check to see if the sandpaper or rubber belts is not making intermediate contact with the AUX " best time to see this is when the the board clears the front roller during a measurement.
3.check table pressure, load your woods front edge under the out feed roller, crank it down then lift gently on the board to check for excessive play. When the pressure is correct you should be able to lit the wood about a 1/16" of a inch " like when your checking your motorcycle's suspension or a old truck full of fire wood, a little play in the springs is fine to much and it will slip.
4. use tape on the bottom of the stock.

[Ike]

One other note, if the O-ring is missing or needs replaced you need to replace it with the correct size 5/16" ID X 7/16" OD. I used the wrong size and it did not measure correctly!

Ike

[Digitalwoodshop]

LG and IKE are right on in there posts.

Time to stand on my soap box and talk about this stair stepping issues..... "In the end.... It is ALL ABOUT the BRASS ROLLER"

We don't have the whole story here about what your project looks like as a .mpc and how you are doing this project. Ask Bud will be along shortly and ask you to post the .mpc.

I would love to have seen a picture of the board right out of the machine with the scrap wood attached. It would have answered some questions I have about your setup. Looking for Pilot Errors that can be tripping you up.

Questions?

Did you use a sled? With a project like this, I would.... A Dedicated Sled.... or Carrier Board...

Did you have 3.5 to 4 inches of wood at the head end of your project? Or did the wood pop out from under 1 roller with every pass.... AND when the edge of the board bumped into the roller to go under it again, the board slipped slightly on the sand paper belts and this is the error you are seeing... While the board is only being held by one roller it can tip UP and loose contact with the brass roller causing this error.

So here are some rules that I play by and get excellent results.....

Oak is a hard and slippery wood that is hard to cut on the machine.

1. First off.... If no sled, then you need to run a strip of masking tape along the edge of the board that the brass roller makes contact with. This will give the Brass Roller something to sink it's teeth into and make sort of a Rack and Pinion between the board and the brass roller. The Brass Roller is the slight weakness with the machine that machines like the Shop Bot don't need to deal with. Since our board moves, then there needs to be a exact feedback between what the X Axis is being told to do and what the actual board is doing since it is free to move. The Brass Roller is that feedback.

ANYTHING that lets the Brass Roller slip in contact with the board will cause a error that will never be recovered from. On YOUR project you had a ERROR with EACH PASS of the machne.... It could have been as simple as the PILOT ERROR of letting the board pop out from under the roller and while not being held flat to the table, the brass roller lost contact for a second and the machine was still moving the X waiting for the correct Brass Roller reading.... That LOST CONTACT MOVEMENT TIME is the ERROR you see in your stair stepping. OR the bottom of the board edge at the Brass Roller is MISSING SOME WOOD.... OR a DENT or notch.

So one end of the wood is stair stepping and the other end your bit cutting the board shorter with each pass.... The final pass, the bit was making a FULL CONTACT DEPTH cutting the whole thickness of the board with that last pass... Must have made quite a racket.... SEE my Oval Clock Picture..... This is BM.... Before Masking Tape.....

2. Second is FEED Rate... You set the depth of cut to multi passes and that was GOOD.... BUT did you lock the machine into a feed rate of 1st gear? Most likely NOT..... Normal cut like you doing the cut feed rate will be 2 different speeds.... 1st gear on curves and detail and 2nd gear on long runs....

I actually had clicking in the Y Axis cutting plastic tags when my bit dulled and the spinning cutting was not fast enough and the Y was pushing tooooooooo fast...... The result was clicking of Y teeth slipping..... I needed new Y Gear Box Bearings too at the time. But the feed rate in 2nd gear was too fast for the bit to cut....

SO how do you lock the feed rate into 1st gear you ask.... Well it is as simple as changing the bit selection to a 1/4 inch ball nose.... That locks the feed rate to 1st gear.... But use the 1/8 or 1/16th bit....

This does NOT work for a CUT PATH with TABS....... I do my cut path without tabs as I use double stick tape to hold the cut plastic tags in place. You could do this project without tabs but leave a skin of wood at the bottom to hold the pieces in place..... But know if one broke loose, it would more than likely snap the bit.

So say we skip the locking into 1st gear with this project and use tabs like I do for ALL my other Wood Projects... This is my next GREAT DESIRE for a future change to designer...... We Got the Depth of Cut.... NOW we want a FEED RATE SELECTOR.... Normal..... 1st gear and 2nd gear Cut Path.... Want "Locked Feed Rate".... A selector in the Depth of Cut Menu to LOCK the FEED RATE to 1st GEAR......

3. The 3rd thing I would do is since the Oak is so hard and smooth and likely to slip on the sand paper belts, then you place 4 strips of additional masking tape on the bottom of your smooth oak to give the sand paper something to bite into....

4. The 4th thing I would do is design into your project 4 inches of dead wood to keep the project under both rollers at all times. This would keep it flat to the bed.

I always use "place on end" rather than center and all the extra measuring.... I design into designer the 4 inch dead area and either waste the 4 inch OR tape a piece of scrap wood on the end.... OR use a SLED with 4 inches already built in like my TAG BOARD.

5. Design a SLED with ends to always stay under the rollers and tape the wood blank into the sled.

SO following most of that you will END the stepping problem.....

Off Soap Box...

AL

[liquidguitars]

Thanks Al!

centering.. It adds one more measurement in the mix that could go wrong when carvings. Using " place on end" or "place on corner" my work is spot on even if I have a bad infeed sensor!!!