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Author Topic: Jogging and DRO errors  (Read 3210 times)

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Re: Jogging and DRO errors
« Reply #20 on: February 04, 2018, 09:37:13 PM »
Hi Mike,
just had another thought (funnily enough it wasn't that painful either!), just for testing purposes set both
your native and preferred units to millimeters and try the same experiments. I'm wondering if it a rounding
error in the conversion between metric and imperial.

Certainly can't hurt to try.

Craig
My wife left with my best friend...
     and I miss him!
Re: Jogging and DRO errors
« Reply #21 on: February 04, 2018, 11:23:25 PM »
because it converts in whole numbers. I could use either metric or imperial.
I ended up setting the drivers to 1:2 and 2032 steps per inch vel 60 and acc 5
thing is, I gave it a command string instead of jogging and the results at the dro were perfect.
g01 x4 f20 g01 y2 g01 z1
g01 x2 f20 g01 y1 g01 z0 and the readouts finished at 2.0000, 1.0000, and 0.0000
I couldn't ask for more.
Why the jog function is off a bit I don't know, and I'm not caring so much any longer.
Re: Jogging and DRO errors
« Reply #22 on: February 05, 2018, 12:35:49 AM »
Hi,
kool your making progress. It would appear that you jog increments are such that they don't land on whole numbers and therefore subject to rounding errors.

Most importantly Mach will execute Gcode and be able, at least according to the DRO, to drive to the right location. The challenge now is to see to it that the
motion controller and axis drives follow suit.

Craig
My wife left with my best friend...
     and I miss him!
Re: Jogging and DRO errors
« Reply #23 on: February 05, 2018, 10:08:09 AM »
This is a known issue that affects some motion controllers in the current build (3481). It has been addressed in later builds (I tested with 3633 and the issue was gone), which you can download and test here: ftp://ftp.machsupport.com/Mach4/DevlopmentVersions/
When we are ready to release a locked-down version, it will be available on our website and I will update this thread as well. If the issue persists in other versions, there is something else going on that we'll need to tackle.

Happy CNCing!
-Bryanna
Newfangled Solutions Helpdesk: http://support.machsupport.com
YouTube Support Channel: https://www.youtube.com/c/MachSupportOfficial
Re: Jogging and DRO errors
« Reply #24 on: February 12, 2018, 11:41:29 AM »
This is a known issue that affects some motion controllers in the current build (3481). It has been addressed in later builds (I tested with 3633 and the issue was gone), which you can download and test here: ftp://ftp.machsupport.com/Mach4/DevlopmentVersions/
When we are ready to release a locked-down version, it will be available on our website and I will update this thread as well. If the issue persists in other versions, there is something else going on that we'll need to tackle.

Happy CNCing!
-Bryanna

Good news!!!

In fact, I have a similar issue too. I use ESS 216 + Mach4 3481.
Hope to meet the officially upgraded version soon. ;)
Re: Jogging and DRO errors
« Reply #25 on: February 12, 2018, 02:01:30 PM »
I think I know how to fix it.
Send a command for G0 x1.
I know Mach4 is very complex, but it's a little odd anything other than that would happen. Hence my comment about fuzzy math. Giving direct commands to move gives perfect DRO results.
In my testing the DRO result after a jog changed with accelleration settings changes. That should not be. Unless they've got something like Bernoulli's equation providing the result to send. KISS?
Re: Jogging and DRO errors
« Reply #26 on: July 13, 2018, 03:15:26 AM »
I have a similar problem, which is a pain for touching off manually.  Both the DRO's and actual machine movement is less than that commanded by either Gcode from the MDI or jog - so I don't believe it has anything to do with the controller.

Now running version 4.2.0.3804  (but the problem also existed in versions from May and  Sept 2017)
Screenset:  stock wx4 from latest download, and in customized wx6 from ~Sept 2017

As this is bugging me, I've done some more tests today to quantify the problem.  The table below shows the error for 5 separate executes of a line of gcode via the MDI ie G54 G91 G0 Zstep.  For example, if Z0.001 is commanded 5x, the DRO and the machine move in uniform steps to 0.005 (so DRO/5X  = 1.000).  Same for 0.002mm, but not so for increment values from 0.002-0.098mm.  For step sizes above 0.098 mm everything is perfect.  Odd, especially as ridiculously small steps work OK.

step
(mm)         DRO @ 5X      DRO/5X

0.001   0.005   1.00
0.002   0.01           1.00
0.003   0.01           0.67
0.004   0.015   0.75
0.005   0.015   0.60
0.006   0.02           0.67
0.007   0.02           0.57
0.008   0.02           0.50
0.009   0.025   0.56
0.01           0.03           0.60
0.09           0.42           0.93
0.098   0.49           1.00
0.099   0.495   1.00
0.100    0.5            1.00

The jog command will not work at all for step sizes below around 0.05mm, meaning that I always have to use an MDI line of gcode to execute fine jogging.

Note that in all cases DRO changes are accurately reflected in axis movement (using a Z-setter, 0.01mm divisions).

I realise that 0.001mm movements are totally meaningless for machining, but my router/engraver will move 0.001mm on and off the 3D probe repeatedly (Z axis only - so no backlash issues) - despite the use of 1/25th microstepping.

Any ideas please?  This is really bugging me.

Best regards,
Louis

Re: Jogging and DRO errors
« Reply #27 on: July 13, 2018, 04:28:31 AM »
A quick followup note.  Decided to try the above tests at much lower speeds.  Previously used G0 or G1 F100.  I've found that the DRO error disappears for feeds of 75mm/min or slower - so G54 G91 G1 Z-0.05 F75 gives the correct DRO change of -0.05mm, but using F76 gives only 0.03mm.

However still no luck with fine jogging, even with a jog speed down to 1%.

Louis