Y axis different

[sharkcutup]

Another item to consider is the placement of the model within the material which can also reduce the DOC. I usually place the model .02 from the top of material. This adjustment is done in the material setup.

Just a thought!

Sharkcutup

[martin54]

Ted mentions that he avoids using a roughing cut where possible, following on from that then it might be that you don't have to run the full roughing cut, often the last couple of passes remove very little material so I have seen myself stop a roughing cut before it has finished to save some time. Comes back to what Ted was saying about different techniques & knowing the machine.

[Clockman]

Another item to consider is the placement of the model within the material which can also reduce the DOC. I usually place the model .02 from the top of material. This adjustment is done in the material setup.

Just a thought!

Sharkcutup

Thank's Sharkcutup, good advice, that is something I try as well

[Clockman]

Ted mentions that he avoids using a roughing cut where possible, following on from that then it might be that you don't have to run the full roughing cut, often the last couple of passes remove very little material so I have seen myself stop a roughing cut before it has finished to save some time. Comes back to what Ted was saying about different techniques & knowing the machine.

That is another great idea that I did not think of, I was watching the last roughing cut which took 5-6 passes the first 4 did cut some material but after that, it was just shaving the ridges off, but taking a long time, next time I will stop at 4 passes, the finishing toolpath I can run without any dust extraction as it just shaves the top ridges off, I am getting a lot of good advice here

[wmgeorge]

......
How did I sync? Jogged the Y to one end within digital caliper range and then turned the power off to the stepper drivers, do not unplug the motors!! With the power off turned with my fingers the couplings where needed to align the two. Power back on do a few test moves to make sure they stay in alignment. If they don't you have either binding, motor tuning or stepper driver issues.

That does not exactly set the axis square to the other. Depends on if the end of the rails are in alignment/square to the other axis.

The way I get things square is the old draftsman triangle trick. Only I cut slots in a thin piece of mdf. The idea is to flip it over between cuts and reference the same edge when doing so. Then measure the distance between the end of the slots.

Once I got the axis square I made two "stop" blocks that contact the ends of the drive carriages. That way I can square it up by turning off the power, manually pulling the axis up against the stops and reapplying power. Works like a dream. IIRC CNCNuts does it the same way because he does not use switches. I have a homing switch so it is a little different.

Dual motor axis are interesting. When working in the middle both motors are sharing the load. But when the spindle gets to either end the closer motor is doing most of the work. That is because the further motor has a huge mechanical advantage via the lever effect so it is not working as hard. So it pays to do most of the work in the middle of the machine rather than in a corner.

My Frame is square and the method I use is spot on thank you. Been doing this long enough I should know how.

[Clockman]

I am still having trouble with missing steps, I have tried all the tips I was given on here, I tried putting the material in the centre of the spoil board, reducing feed rate, I have also tried to carve without doing a rough cut, these are the settings I am using, could someone have a look at them for me, thank you
1/4 inch end mill for rough cut
feed rate = 50
plunge rate = 35
pass depth = 0.1
step over = 20%
1/16 inch Tapered Ballnose for finishing
feed rate = 80
plunge rate =60
pass depth =0.0313
stepover =10%
my X and Y acceleration are both set at 200.000

[GEdward]

Your roughing strategy is pretty modest. I would think that if your machine can't handle those parameters there is something wrong with the machine or the machine's electronics. My machine is not very robust but I can still run a 1/4 inch end mill at .2 - .25 per pass at your feed rates. I also run 30 to 45% step over for most of my roughing. The load on your finish tool is negligible. Your acceleration/deceleration values are not out of bounds but it can't hurt to cut them in half just to see if that makes a difference.
You have not said if the machine always ends up off in the same direction ( y+ or - ). If you are loosing steps because of acceleration loads then the discrepancy should be random because Y accelerates and decelerates roughly the same number of times in both directions unless your roughing and finishing strategy that both raster along X with 0° for the finish path.
One thought that comes to mind is if your stepper drivers are properly tuned to the motors and if the dip switches, if there are any, that set the step/micro-step output are appropriate for your setup. Otherwise I am thinking you have a mechanical bind or load issue.
Ed

[TReischl]

.
.
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my X and Y acceleration are both set at 200.000

If that number is inches per second/second it is really steep. If millimeters then it is pretty slow.

If inches, try changing that number to something like about 25-30.

[citrusguy]

I am still having trouble with missing steps,

What is your grbl $1= value? If not set to 255, you could be "losing steps" whenever grbl "unlocks" the steppers.
EDIT: Never mind. See you are using a screw drive.

EDIT #2: What stepper drivers are you using. I have seen reports that some Chinese drivers can be problematic.

[GEdward]

If that number is inches per second/second it is really steep
Good call. Brain fart on my part. I'm reading acceleration and thinking rapid feed rate.
Ed

[Clockman]

I am still having trouble with missing steps,

What is your grbl $1= value? If not set to 255, you could be "losing steps" whenever grbl "unlocks" the steppers.
EDIT: Never mind. See you are using a screw drive.

EDIT #2: What stepper drivers are you using. I have seen reports that some Chinese drivers can be problematic.

I am using an X controller from Inventables so the stepper drivers are built in

[Clockman]

Your roughing strategy is pretty modest. I would think that if your machine can't handle those parameters there is something wrong with the machine or the machine's electronics. My machine is not very robust but I can still run a 1/4 inch end mill at .2 - .25 per pass at your feed rates. I also run 30 to 45% step over for most of my roughing. The load on your finish tool is negligible. Your acceleration/deceleration values are not out of bounds but it can't hurt to cut them in half just to see if that makes a difference.
You have not said if the machine always ends up off in the same direction ( y+ or - ). If you are loosing steps because of acceleration loads then the discrepancy should be random because Y accelerates and decelerates roughly the same number of times in both directions unless your roughing and finishing strategy that both raster along X with 0° for the finish path.
One thought that comes to mind is if your stepper drivers are properly tuned to the motors and if the dip switches, if there are any, that set the step/micro-step output are appropriate for your setup. Otherwise I am thinking you have a mechanical bind or load issue.
Ed

I will reduce the acceleration by half and try it again, it seems to be off in the same direction all the time (Y-) meaning when it finishes a carve and returns to work zero it is off by 1/4 inch or more, and when I then home the machine it should hit the limit/homing switch on the left-hand side and stop, but the right-hand side crashes into the end of the rail stop first before the switch is reached, as it is off square , I hope I am explaining this properly
I do raster in Y at 90 degrees to go with the grain
I don't know if the stepper drivers are properly tuned to the motors, but everything was working well, I am hoping it is acceleration, I will test again on Monday
I did cut some test circles today about 1/4 inch deep in 3 passes and that went well and returned to zero as it should, it seems to be only when it is under a little pressure

[TReischl]

Hopefully you are squaring up the machine in between these crashes?

Yanno, it could be something as simple as a defective stepper motor or a bad component on the control board.

I think you said it was running just fine and then this started happening IIRC. So if you did not make any changes and then it started acting up that would sort of lead me to think what I wrote above.

[Clockman]

Hopefully you are squaring up the machine in between these crashes?

Yanno, it could be something as simple as a defective stepper motor or a bad component on the control board.

I think you said it was running just fine and then this started happening IIRC. So if you did not make any changes and then it started acting up that would sort of lead me to think what I wrote above.

Yes, I do square the machine at the start of each cut, I did think of swapping the 2 stepper motors on thr Y axis to see if the problem shifts to the other side, or just replace the one on the right, I have no idea how to find out if the control board is faulty other than replacing it, that is an expensive item, and it may be okay, I will start with half the acceleration first and see how that goes

[Clockman]

I reduced the acceleration by half and then tried the same file again this time doing an air carve (as it's Sunday) and I had exactly the same problem, I am not sure what that tells me
I will run a different file now to see if that makes any difference
it is the right hand Y-axis only Y- finishes about 3/8 inch forward of work zero, when I switch off the power and move Y back by hand it is all aligned again at work zero