Cutting deeper in areas???

[alboy]

Hi Guys

Well here is a strange problem, having been cutting loads of plaques something seems to have gone somewhat haywire in that my machine is suddenly cutting deeper on the left side of the item being cut, very noticeable in the picture. you can see on the text that it has cut fairly deep from the top left to cutting so shallow towards the bottom right that it barely cuts through the paint mask.
http://www.mycncuk.com/attachment.php?attachmentid=14504&stc=1

The spoil board is nice and level and the material is of equal thickness.
The CNC uses the DSP controller, used vectric to design the plaque. Thought maybe it was a dodgy output file so remade the design with new tool paths etc but problem still there. Any Ideas ?

Cheers

Al

[Boyan Silyavski]

When all options are exhausted usually means Mach3 is broken. Uninstall, restart,fresh install and paste yourbackup.xml,restart again and should be working.

[EddyCurrent]

Skim the bed and/or spoil board.

[routercnc]

Could it be the tool slipping up inside the collet during the engraving? I've had that happen once which was confusing at first.

Alternatively could be missed steps on the Z stepper - can you remind us of the machine you are using?

[alboy]

Cheers Guys

I do not use Mach3 it's a DSP system using the nk105 pendant and NC file formats. Have already reset and reloaded the DSP OS.

The Spoil board has been skimmed and is nice and level. I double checked by lowering a cutter just touching the bed and jogged around the X.Y axis and all fine.

Hmmmmm.....

Al

[EddyCurrent]

If you have a Z probe I would take readings across the work piece to see if the top surface is level. Also in your CAM software is everything flat on the XY plane.

[alboy]

If you have a Z probe I would take readings across the work piece to see if the top surface is level. Also in your CAM software is everything flat on the XY plane.

Hi Eddy,

do not have a probe although I have one on the shopping list (amongst other items lol) although I am not sure the DSP system supports probes, trying to find that out. I redrew the design again making sure all was well on the XY plane and still the same problem, very odd.

I have cut other plaques with almost the same size text with no problem, I even tried changing fonts in case the font was causing problems but still the same.

Al

[Boyan Silyavski]

Then start from scratch, to find where the problem lies. First check if the machine recognizes correctly the Z0 / top surface/ across all 4 corners. Then you will know that the controller functions ok. There are not many possibilities. if the table is surfaced, the controller is ok, then is something mechanical or software. Eliminate the mechanical by revising and pushing around, looking for some play, if not - its software. Search a previous job that you know has OK code and check.

[phill05]

If all has checked out as level and square no lose mechanical's run an older file that you know worked fine if no difference, try to rotate the workpiece 90 degrees in software re-code and try again, have you used Engraving tool path in Vetric? set the start depth to 0, set (all the next advise depends on cutter used) Flat depth to say 0.5 set your tool up with a pass depth of say 0.5, step over say 40% and code up and test, also check the DSP has no off sets setup.

Phill

[alboy]

If all has checked out as level and square no lose mechanical's run an older file that you know worked fine if no difference, try to rotate the workpiece 90 degrees in software re-code and try again, have you used Engraving tool path in Vetric? set the start depth to 0, set (all the next advise depends on cutter used) Flat depth to say 0.5 set your tool up with a pass depth of say 0.5, step over say 40% and code up and test, also check the DSP has no off sets setup.

Phill

Sorry for delay replying. Well I flipped the workpiece 90 degrees and it seemed to cut ok, If i flip it back to the original orientation, the problem still exists. Tried a couple of other jobs and they are fine if flipped 90 degrees (design longest along the Y axis) but the problem is there still on the original orientation. Very odd

Al

[phill05]

Tried a couple of other jobs and they are fine if flipped 90 degrees (design longest along the Y axis) but the problem is there still on the original orientation. Very odd

Al

If flipped and works okay I would be looking at the other axis for something lose.

[alboy]

Hi Phil
Checked out the X axis and all appears to nice and tight. Think I will get a dial gauge and see if anything has got out of alignment, don't know how though, the thing is built like a tank.

Al

[JAZZCNC]

If machine as been working fine then suddenly started happening then Coupling on Z axis motor as probably come loose and is slipping. Does Z axis return to Zero after job is finished.?

Other than that then how machine is setup regards feeds etc could be problem. The DSP software could have gone tits up but I'm guessing at that.?

[alboy]

Hi Jazz

How are you doing. I haven't tried to cut anything with such a fine text before although I have cut smallish text in a different font which seemed ok but can't say for certain if the problem had been there before, the signs etc I had been doing were fairly big, min 1" text. I had notice a couple of times when cutting templates out of 6mm ply that sometimes it wouldn't cut all the way through in parts but put that down to the material initially. I will check the Z axis coupling again. I reloaded the DSP software just in case but it didn't make any difference. Thought I had another problem as well but it just the tip broke off the V bit Doh. All axis return to home position at the end of a job. If I rerun the job on the same workpiece it does the same, so I suppose it's repeat accuracy is good lol.

Cheers

Alan

[JAZZCNC]

No you need to set a Zero work position and return to that not Home position. Reason being that home position is referencing a switch so it will and should always return to that position.
Returning to Zero work position will tell you if you have lost position thru missed steps or slipping couplings etc.

But before all this have you Surfaced the Bed.? . . . . With fine engraving you can't have any error in the bed.!

[alboy]

No you need to set a Zero work position and return to that not Home position. Reason being that home position is referencing a switch so it will and should always return to that position.
Returning to Zero work position will tell you if you have lost position thru missed steps or slipping couplings etc.

But before all this have you Surfaced the Bed.? . . . . With fine engraving you can't have any error in the bed.!

Sorry, was on another plane there. Confusing my MCS with WCS, don't know if that is a common phrasing but that is what DSP refers to as the machine home position and the Work home/zero position. Yes I have returned it to the zero work position after homing and then drilled down with a 2mm drill bit, did this 10 times and was spot on each time??

Al

[Clive S]

Sorry, was on another plane there. Confusing my MCS with WCS, don't know if that is a common phrasing but that is what DSP refers to as the machine home position and the Work home/zero position. Yes I have returned it to the zero work position after homing and then drilled down with a 2mm drill bit, did this 10 times and was spot on each time??

AlSo if I understand you, you are saying that it comes back to the zero work spot in X and Y as you are going down the same hole. But how are you testing the Z zero, is that coming back to the same spot. You could test this by setting work Z to say 10mm above the bed and checking it with a 10mm round rod or a spacer exact. Then run the machine and come back to work Z zero and see if the spacing is exactly the same. ..Clive

[alboy]

The machine is set to have a safe distance of 10mm above home position so when you home to the workspace the end of the bit will be 10mm from the workpiece surface. I set the machine to go from home position to work position and it seems to be accurate each time. I tested the gap with a piece of 10mm thick aly.
I set up a job to drill 10 6mm holes 0.2mm deep in a line across the x axis over a distance of 600mm. and as the holes are being drilled left to right, the far left hole seems correct but the holes get gradually shallower along the right of the axis. Machine bed spoil board seems nice and flat.

Al

[JAZZCNC]

Ok well if your sure it's returning to WC-Zero (forget MC-Z) after the job as finished and no steps are being lost then it must be the table or machine frame. (provided tool is secure in spindle)

The bed may look flat but if it's not exactly parallel to the cutter across the whole area then you'll get this issue. That's why you should surface the bed to be sure.
If you still have issues after surfacing then I'd be looking at the machine frame and if it's twisted etc.!

[Clive S]

The machine is set to have a safe distance of 10mm above home position so when you home to the workspace the end of the bit will be 10mm from the workpiece surface. I set the machine to go from home position to work position and it seems to be accurate each time. I tested the gap with a piece of 10mm thick aly.
I set up a job to drill 10 6mm holes 0.2mm deep in a line across the x axis over a distance of 600mm. and as the holes are being drilled left to right, the far left hole seems correct but the holes get gradually shallower along the right of the axis. Machine bed spoil board seems nice and flat.

AlOk first drill holes are not ideal as they will have a tapered bottom an end mill would be better as it will leave you with a flat bottom and you can could measure it better. Now you say the spoil board is flat, have you checked that with a 10mm spacer across the bed where the holes are drilled? If you have a DTI check to see if you have any end float in the Z axis. ..Clive

[alboy]

Cheers Guys

I will surface the spoil board again just to be sure but it does seem flat when i test the difference between the end of the bit and the surface using the 10mm block. I do not have a DTI but I have ordere one today so hopefully will be able to check things with better accuracy. Will let you know how it goes.

Al