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Diagonal Lines not smooth - Router
« on: December 04, 2011, 08:42:35 PM »
Hi Guys,

I'm having a bit of a recurring, yet intermittent problem with our router.

On Diagonal moves, it seems that we are getting uneven X and Y Axis moves.
All the output files LOOK Ok (Outputting G Code from Vectric V Carve), but on SOME diagonals we are getting "steppy" cuts.

This is causing great hassle when engraving in stainless steel and aluminium as we do quite often.

We have played with the "Stop CV on arcs >X degrees" setting previously, It's currently set to 8 Degrees as much less than this sees square corners curved off.

Any ideas on this would be of great help!

The pictures show the problem as it has occurred just now, The job is 1400mm long (X Axis) x 550mm wide (Y Axis) and engraved area is approximately 350mm high (Y Axis) x 835mm long X Axis.

Thanks for your help!

Offline BR549

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Re: Diagonal Lines not smooth - Router
« Reply #1 on: December 04, 2011, 09:41:34 PM »
Do you see this in the Mach toolpath as well??

(;-) TP
Re: Diagonal Lines not smooth - Router
« Reply #2 on: December 04, 2011, 09:47:06 PM »
Can post a little more info about your machine? motors, reduction? step per mm settings in Mach3

My first guess is that your motors aren't capable of holding their position during microstepping. Are you using a new sharp bit with lubricant? What happens if you do another pass but only take of a small amount around the edges? Does it improve?

I used to get line like that on my machine. Adding a belt deduction vastly improved it. Anytime I get lines now, i just do a small final pass around the perimeter to skim the edges.

HTH
Re: Diagonal Lines not smooth - Router
« Reply #3 on: December 04, 2011, 09:54:20 PM »
Gday TP,
Nope!

The tool path looks all Really good,
I've attached the G code file of just those two letters (I Re-Tool pathed the two worst letters)


Matty:
The machine is originally a Multicam machine, That has been Upgraded by CNC Teknix using their servo drives and motors.
With the upgrade came the switch to Mach3.
Pete and the guys from CNC Teknix set up all the motors and step settings, I'm not 100% sure where to find these settings!
The cutter is a sharp Dee bit with micro drop lubrication, We have re-run the same file, and re-programmed the entire fill-file again but it follows exactly the same line/mistakes.

Could you please explain what a belt deduction is and where i could try setting that?
I might try doing a toolpath just for a pass around the edge as well rather than the file that does the whole fill again too!

Thanks for the assistance guys!
Re: Diagonal Lines not smooth - Router
« Reply #4 on: December 04, 2011, 10:14:07 PM »
Can you send me your Mach3 profile .xml file. If you don't know what this is, right click on the icon you use to start Mach3. There should be a link to C:\Mach3\Mach3.exe /p <something>
The <something> is the name of your Mach3 profile. There should be a file in C:\Mach3 called <something>.xml This is the file i'd like to look at.
(if you don't want to post it publicly, you can email it to me mziebarth@gmail.com)

The belt reduction is a mechanical mod I did to my machine (homemade Mechmate) to add a belt reduction between the motor and the pinion to get more torque and resolution. Its not a software mod.

It just seems the cutter is digging in. I might be wrong. What happens if you run the profile in the opposite direction (ie climb vs conventional)?
« Last Edit: December 04, 2011, 10:16:12 PM by Matty Zee »
Re: Diagonal Lines not smooth - Router
« Reply #5 on: December 04, 2011, 10:27:45 PM »
Hi matty,
Thanks again for the reply!

Attached is the .xml file,

There is no Burr on the edge of the stainless, This often happens when the cutter dulls off,
What seems to be happening is the X and Y Axis seem to be "fighting" each other when doing a diagonal move on that part of the bed.

The owner of the company here thinks it's a tightness in the X axis motion rack, so he is releasing the screws and then re-tightening to see if he can "loosen" the tightness at that point down the bed.

It seems ( and i have a feeling he's on the right track - but the rack and pinion arent the problem!) we could have a hardware issue that is causing the drives to require excessive power to move past this tight spot.
It worries me that its intermittent, and not always repeatable!

Thanks again, I'd like to make sure our settings are optimal!

Cheers,
Rob :)
Re: Diagonal Lines not smooth - Router
« Reply #6 on: December 04, 2011, 10:37:33 PM »
One way you might be able to test that is to recut the same file but shift the orign point by say 100mm in X & Y and see if the problem follows the letters or stays in the same location on the table. Does that make sense?
Re: Diagonal Lines not smooth - Router
« Reply #7 on: December 04, 2011, 10:40:21 PM »
It does!

I will try that, i'm hoping to rescue this large piece of stainless and finish this job first!

Thanks Again!
Re: Diagonal Lines not smooth - Router
« Reply #8 on: December 04, 2011, 11:14:23 PM »
We have re-run the same file, and re-programmed the entire fill-file again but it follows exactly the same line/mistakes.

When you said you re-programmed and re-ran the file, was that on a new workpiece or over the same one? If it was the same workpiece, that means it followed that path under effectively no-load. Sounds very much like a mechanical binding...
Re: Diagonal Lines not smooth - Router
« Reply #9 on: December 04, 2011, 11:23:23 PM »
Hi Matty,

Same workpiece! and you are correct it as effectively under no load.
i was concerned you might say that!

Thanks again!