[rbraeking]

You don't seem to be running too fast for your steppers, In fact, you could probably run a lot faster. I'm not familiar with the G540 but check motor heating. You may be trying to push too much amperage and overheating the driver. Or you are microstepping too much and overrunning your kernel speed.

Bob
SS CNC Router - Home

[ger21]

Make sure the G540 isn't overheating. It may need a fan or heatsink on it.

[Catmandu13]

I finally got the Z-Axis finished an mounted. Pics to follow soon. Everything seemed to be jogging fine until I noticed Mach3 recording the steps wrong. I set those via the Axis Calibration section of the Settings tab. Now everything seems to be moving the right distances and whatnot. The odd thing is, now when I click on Goto Zero or at the end of a tool path, when it returns to zero, Mach3 reports it moving at a rate of 120-340-ish IPM depending on the distance from zero. And it does seems to be moving a great deal faster, so I believe it! So fast in fact when it dead stops, I think skips steps. My feed rate for the project and for jogging has been set to 30IPM. So I'm not sure where it's getting overwritten.

Oh and as for the faulting of the G540, it was either not having my Z-Axis connected, or my parallel port cable was slightly askew. Seems fine now.

[rbraeking]

What are your motor settings in speed/acceleration? Your motors should ramp up and down at the beginning and end of the gotoZero move. All three axes should arrive at zero simultaneously.

Bob

[Catmandu13]

That did it! It seems like every time I correct one setting something else comes undone. While resting at zero, after I set the ramp velocity to limit to 250ipm, It threw in some 90" offset from my current position. The same thing happened when I calibrated the axis yesterday. I was going to mess around with it using just soft limits...but now I'm thinking wait the two more days and install the end of stroke limit switches.

Honestly it all makes sense if the default were for another table with different pitched screws or r&p, and when calibrated to my smaller table, it was still using the same higher speeds, but at half the distance scaled down. So what I originally thought was a decent speed(though having never set the motor ramp speeds previously) the control thought was going 2x as fast, and when calibrated to be half the distance, it went the full speed it was originally set for. Which explains why my Z didn't really seem affected as much, that length doesn't get very long for any machine, so scaling it down isn't as great of leap.

Either way, I think I'm going to play it safe and install switches.

[rbraeking]

You can actually zero the machine coordinates without limit switches. Go to Config/Ports & Pins/Input Signals and uncheck x, y, and z home. Jog machine to your desired x,y,z zero position and reference all axes. That will reset your machine coordinates to 0,0,0.

[rbraeking]

You are definitely skipping steps or slipping mechanically. Your table could be moving or your workpiece could be climbing out of its clamping device. A test in the air may not indicate the problem. You may be skipping from the pressure on the bit. Or your router/spindle clamp may be slipping. 35 thou is quite a bit of slip/skip/warp. You may also be pushing the bit too hard based on your spindle speed. Your bit could be slipping in the collet.

Mechanical is first to look at then electronic.
Bob

[Catmandu13]

So i did find that my router cable was running very closely parallel with the z axis cable. So separated that out, ran a test, same drift.

Checked the clamping and it's in there solid.

I ran the 0.5 to 1.0 test 500 times at the 100in/min @20 accel, and it zero'ed fine, no drift.

I routed my project in a piece of plywood at 18000rpm max depth of 0.05" with the z axis slowed down to 10in/min @ 5 accel, and it also drifted about the same amount. Not sure if the depth here is enough to cause significant pressure on the bit. I also made sure to push the bit into the collet fully. I rezero every time, and at the end of the run, I tell it to go to zero and it always seems to be off about the same amount start to finish.

I even ran the project once with the router on, rezero'd turned the router off, and just let it retrace it's steps...drifted.

The thing I have burning in the back of my mind now is I'm using a 10amp powersupply for 4 3.5v steppers. If i recall the math right, it's 4steppers x 3.5amps x 0.68 = 9.5 Minimum required amperage of the powersupply. So i should be good, but every similar kit out there seems to supply a 12.5amp power supply. So i wonder if I have enough overhead for all the 3D movement. With that in mind I may be drifting on all axis while moving, but not noticing it as much on x and y. I guess I could scan my generated g-code, and separate out the Z move commands from the x/y movement...That might help if this is the case.

[rbraeking]

" I guess I could scan my generated g-code, and separate out the Z move commands from the x/y movement..."
That won't work for the project. All three need to move together for v-carving.

Bottoming out the bit in the collet is incorrect. The collet pulls the bit in as it tightens. If not allowed to do so it does not get tight and centered. Is your bit climbing out of the collet?

Try running the g-code without material and see if there is a change. Also run it with your spindle running and a second test with your spindle off. That will eliminate electrical interference from the router.

Are you planing off the workpiece with the router before v-carving? That will eliminate table variation.

My thought is that if you are attempting to get such fine resolution out of a machine made of wood/MDF you will be continuously frustrated. Wood moves too much and is not rigid enough.

I just had a thought. Your spindle shaft may be growing due to heat. (likewise your bit shank) Try and preheat the spindle. 35 thou is not that much. If you are using an electric air cooled router that may well be the problem.

Bob

[Catmandu13]

The bit doesnt appear to be climbing out out of the collet. In fact I have hard time getting it out of there at all, so much so that I purchased another collet for the planing bit.

I havent planed the table yet. I know there's a low area, but the small section of the workspace of the table I'm currently using is decently level. Leveling the table out fully is a near future project. I have been zeroing to the same space each time. So when it returns to the same spot level table or not, it should still be the same vertical distance.

Last night, I zero'd above the piece with a 3/4" block inbetween. Then removed the 3/4" block. I sent it to zero and it very very lightly scratches the surface.

Ran the code with the router turned off and with the 3/4" Z offset and when finished the 3/4" block would not fit under the bit when told to goto Zero. Using my fingernail to mark how far down the bit was, it was off by 0.12.

I checked my DC amp draw to the G540 while running and it never even reached 4 amps.

I rechecked for binding and I think that's where my issue is I powered it all down and hand rotated the Y-Axis and noticed it was significantly easier to move than my Z even with pushing up on the Z assembly. So i loosened the outer shaft collar on motor mount and it now moves a bit more freely, like the Y.

While looking around I noticed the stepper was also off kilter a bit from my sad excuse for motor mounts. (I'll post a pic of it for laughs later tonight). On side was 0.05 off from the other. Leveled it out.

So with that I reran the project in air, rezero'd to the same offset. Afterwards it let the 3/4" block slide back under just lightly scratching the surface. So needs more testing, but it was around 3am last night so I didn't do a followup pass, but presumably it looks like it was just simply binding after all. Tomorrow I'll carve some wood and see how it fares.