Bit not touching

[Jcpb321]

Started a project today and it asked for 1/8 cutting bit, loaded it and when it went to the bit plate, the plate came out but bit only went within 1/4" of touching. Also when it tried to touch board it was also 1/4" short.
Then of course it don't think I put the bit in and asks again to load bit!

If I do a depth measurement on a board I never get the right thickness either so I am guessing it is a problem with Z motor control! Any ideas!

[DocWheeler]

John,

Since the machine can not "see" if the bit touches, it relies on sensing more current needed to drive the Z motor.
I think what is happening is that there is something on the Z rails, a bad bearing or two, dust in the belt, or dust in the belt gear. Also check out the motor and that gear assembly.

Something is causing it to sense some resistance.

[Digitalwoodshop]

Ken,

YOU the MAN !!!!! I could not have typed it better.....

And watch that area between the upper and lower bearing, a hard to clean area of the rails....

AL

[Jcpb321]

Ken,
I just pulled the flex cable, took off the 4 bearing covers and found one speck on the bearings, it actually looks real clean. Moved the chuck up and down and I feel no resistance such as a rock in the way. Al, I even looked with my high intensity lamp between the bearings and checked as much of the gear belt as I can see.. I'll blow it out just incase.
Ken which gear assembly are you talking about???

BTW when it is all the way to the keyboard side it does not seem to have a problem going all the way down without hesitation, must have more juice in that position!





John,

Since the machine can not "see" if the bit touches, it relies on sensing more current needed to drive the Z motor.
I think what is happening is that there is something on the Z rails, a bad bearing or two, dust in the belt, or dust in the belt gear. Also check out the motor and that gear assembly.

Something is causing it to sense some resistance.

[Jcpb321]

Ken and AL,

Well I went to blow out everything and removed the board I had in, raised up the head and took out my cutter, Now I have to eat posssum, there is some roughness but it is mostly towards the bottom. there are no chips in the belt or on the bearings so I guess I do have a bad bearing like you said Ken.

Al, do you have a source for replacing these? I was thinking you had posted something about bearings at one time but it would only be the 4th time I was wrong today but thought I would ask anyway!

Thanks for the help gentlemen.

[DocWheeler]

I was thinking about the gear at the motor itself, just behind the top belt sprocket.
Given all that you have inspected, do you have the new 14 conductor or the older 18 conductor flat cable.
The reason I ask is that in the "A" machines there was wiring down the inside of the Z truck that might be acting up.
For the Z axis to work good at the front of the machine but not at the bit-plate or board-touch seems odd.
If you can not detect resistance manually at those points, it sounds electrical somehow.

Looks like we were posting together!

[Jcpb321]

Ken,

I took that apart and it seems to go around smoothly, that plastic gear looks clear cept for the little grease in it, the plastic cover is intact.

I do have the 14 pin connector but I am thinking I still have an A machine so I won't rule nutin out!

Tomorrow I will move the head all the way to the plate and see how it moves.

[TerryT]

Check the side play of the gear. Sometimes, when the bearings in the z or y gear box wear the tension of the belt can pull them sideways and they bindup causing a stall.

[Digitalwoodshop]

My source for the roller bearings for the rails will be LHR. I did find the numbers for the gear box bearings located inside the Z and Y gearbox. It was posted a while back.

AL

[Jcpb321]

Thanks Al, like i said I wasn't sure but I would rather be wrong than not ask!