[tony978]

I think a bearing change on your router should not be as bad as a kress motor .but I was looking at this not a router , so please keep that in mind if it is a pain . Porter Cable 7519 Parts List and Diagram : eReplacementParts.com

[mrlttlman]

ok so I tore it apart and inspected the bearings. lower bearing does not turn smoothly . upper bearing turns smoothly but the piece I believe it should be pressed in I can just slide out with finger pressure. I attached a picture of it so you all can judge or if someone has done a bearing replacement on it they could tell me if it should slide in freely and not pressed in. oh yeah cant find that part on the diagram, guess you got to buy the whole housing to get it

[tony978]

They are cheap ! Buy a new one and change it out ! That might not be the problem but it will be later if ya don't replace it .

[mrlttlman]

new update .
while waiting for the service center to open tomorrow I decided to put a new router on it. after running the code for an hour it did the same thing pretty much. I have come to a conclusion that it has to be ghosts in the machine...... do you think it could be that it doesn't have shielded cable on the stepper motors. everything is tight and slides and glides smoothly ..... I am out of ideas.

[tony978]

I ran into so many problems with steppers with the flashcut cnc system I have. I switched to servos but still run there software and have been happy .
don't get me wrong someone will say they love them and haven't had any problems with them . did you build the cnc ? if so what is the current output of your power supply and what is the rating of the motors ?

[davidtye23]

So far, so good.

[mrlttlman]

I will post that info in the morning when I go back to the shop. I bought the machine and had to disassemble and go through it to make it cut right. it had Teflon bearings when I got it but I upgraded it to all thk rails and bearings. that changed everything. I ordered some shielded cable tonight and will put that on when it comes in. just noticed again the all connections are done with butt connectors. when new cable comes in it will get soldered and heat shrinked. thanks for all the help so far.

[mrlttlman]

here is a picture of the power supply ratings the nema 34 are 4a (2 of them ) and the nema 23 is a 2.5

got the new bearings today but didn't get a chance to put them in. maybe tomorrow. still waiting for the shielded cable.

[aminear]

Is your z axis directly coupled to your stepper, and you are using the stepper bearing as the axial thrust component for the Z?

I doubt that noise is the problem, else you would not return to the same cutting height. Noise to the input of your stepper driver could cause a problem but it would not look like that in the middle of your pocket.

[mrlttlman]

Yes the z is coupled directly . The other part of the question I don't quite understand. would you suggest adding a bearing elsewhere or keeping it as it is.

[mrlttlman]

ok tightened up the machine new bearings installed . ran code for the xyz axis at 300 ipm in the air no cutting but spindle on just to check. after doing it 4 times and checking accuracy . they all came out the same .0005 repeated. Ran the program again on acrylic to clean up previous run . 115ipm @.0137 depth of cut and the lines still appeared but not as bad. Still not satisfied.

[aminear]

I would seriously suspect that relying solely on the stepper motor bearing to hold your Z axis from axial movement is the culprit. With the amount of room you have in the block that your stepper is bolted to, I would think it would be easy to mount 2 bearings and preload them to eliminate the thrust movement. To test this you can mount a dial indicator on the Z axis and see how much movement you can do with a small amount of force. That is a nice touch on that enforcer engraving, I can see why that little line just stands out and you are not happy.

[mrlttlman]

Thanks for the compliment on the engraving. how do I preload a bearing and when I mount a dial indicator on the z axis what im I looking for as far as movement. (sise to side, up or down ) forgive me I am not that smart when it comes to this stuff. the line gets produced after the z axis raises and moves to another spot it seems. I tested the z axis for repeatability and its .0005 maybe the part is secure enough and might be lifting.

[aminear]

If there is no other bearing except the bearings inside your stepper motor, that would be the problem. The stepper is not designed to carry a thrust load.

You can check for up and down motion with your dial indicator.

To install additional bearings and preload them would require machining your leadscrew and the base your stepper bolts to. You can preload the bearing by placing a small shim between the inner races then press the outer races together and secure the whole assembly.

[mrlttlman]

in another words press the bearing on the machined shaft and then press it in the block that the motor is mounted to. so then I will have the lead screw going threw the delrin nut at one end and then the lead screw going threw the bearing or bearings at the other end and then coupled to the stepper motor. would that be correct. also thinking about it now I would have to have the bearings pressed in from the bottom so that they wont get pushed out from all the up and down motion.

[tony978]

Have you have any luck fixing the problem ?

[mrlttlman]

Tony
Not at this time. I am waiting on a bearing block and new motor mount for it. After I hook all of it up I will post the results. Thanks guys for all the info.

[mrlttlman]

Ok guys after waiting a while for the bearing block to come in. (it didint get shipped for some reason) i got it installed. i ran a test before i remade the enforcer piece for the motorcycle shop and low and behold there was still a line but not as apparent but still there. i redid the piece anyways but machined out the k into two seperate vectors that overlapped .020 so you couldnt make out the line. It all came out good. But im not satisfied why this is still happening. Any input would help out again.

Thanks
William

[tony978]

try double sided tape on the part and spray the cut area with a very light lube . I did polycarb yesterday with unist coolube 2210, it is for mql systems but I used a spray bottle .

[mrlttlman]

Tony do you have a close up picture of what you did on the acrylic that you could pm me so i could compare with. Also i did switch to double sided tape. never thought of the lube though. the lines keep happening after the z raises and lowers. Could it be the nema 23 Stepper not strong enough?