Z axis drift

breezy

breezy

Moderator
I had a machine crash today when the Z axis machine zero shifted down by about 25mm.

I was air cutting the attached .nc file when suddenly the spindle dived into the table. Fortunately I didn't have a cutter, just a sharpen dowel installed. The WCS was set to X0, Y0, Z-25 this set the point of dowel about 5mm above the true WCS, which is about 18mm above the table. The dowel was driven about 5mm into the table. When the crash occurred I hit the hard wired program stop button, which stopped the program at line 26245, but the crash had occurred in the previous 2D contour. I don't know which line of code drove the spindle into the table.

The job is clearing a 2D adaptive 45mm wide a cross a piece of timber 46mm wide then running a 2D contour down each side of the cleared area, repeated 22 times. The pieces are packed together to form a continuous cut of 1012mm. I am trying out different cutting methods to reduce machining time.

When I jogged the spindle up until it stop at what MASSO thought was the machine Z zero the Z DRO was reading 40mm and the spindle was about 25mm below the limit switch.

MASSO S/N 1801

Running v3.40

Job created in Fusion 360 running MASSO post processor Version: 42267 Changed: 4 days ago.

Regards,

Arie.

For the Bicton Men's Shed.
 

Attachments

  • Cross-vertical.nc
    708.6 KB · Views: 42
breezy

breezy

Moderator
I wasn't watching it the whole time, didn't notice any drift down.

It just dived into the table and then dragged along the table, then raised up moved across to the other side of the cut and dived into the table again. At this point I was able to stop further movement and shutdown the spindle.

Looking at the g-code and the position that the spindle dived into the table, it was in this portion of code.

(2D CONTOUR3)
N30850 G0 X130.4 Y312.8 This is the point spindle dived into table.
N30855 Z17.
N30860 Z7.
N30865 G1 Z3. F5000.
N30870 Z-6.2
N30875 G18 G3 X129.6 Z-7. I-0.8 K0.
N30880 G1 X128.8
N30885 G17 G3 X128. Y312. I0. J-0.8
N30890 G1 Y267. F10000.
N30895 G3 X128.8 Y266.2 I0.8 J0. F5000. And travelled to here.
N30900 G1 X129.6
N30905 G18 G2 X130.4 Z-6.2 I0. K0.8
N30910 G0 Z7.
N30915 X162.6
N30920 G1 Z3. F5000.
N30925 Z-6.2
N30930 G2 X163.4 Z-7. I0.8 K0. Stopped machine on this line of code with spindle buried in table.
N30935 G1 X164.2
N30940 G17 G3 X165. Y267. I0. J0.8
N30945 G1 Y312. F10000.
N30950 G3 X164.2 Y312.8 I-0.8 J0. F5000.
N30955 G1 X163.4
N30960 G18 G3 X162.6 Z-6.2 I0. K0.8
N30965 G0 Z17.
N30970 G17

The physical travel through the table was not the full 46mm so I have to assume that the Y axis lost steps, but I didn't check that.

I don't understand what Fusion is trying to do with the G18, G17, G3 codes, but in the CAM I was requesting a finishing cut with a downcut cutter to remove the 1mm left on the wall of the adaptive clearing that was done with an upcut cutter.



If you want the settings file I can obtain it next Monday when I attend the again.

Regards,

Arie.
 
breezy

breezy

Moderator
Quote from MASSO Support on March 13, 2019, 6:59 am

In case of Z axis we have seen that as the Z axis has to work against the gravity, there is more load and it can miss steps, so please first check the mechanical setup. you could also try to reduce the acceleration and max feedrate settings of the Z axis if you are missing steps.
Click to expand...

We were having instances of the pulley moving on Z acme thread, that has been fixed, filed a flat on the acme rod to enable the grub screws to better engage the rod and added a locknut on top of the pulley.

Will check acceleration and feedrate of Z axis. But I don't think we are missing steps because when we first setup the machine the Z axis was behaving badly, so we adjusted the acceleration and feedrate to a fairly moderate rate.

Also for the crash we had it would have been a massive amount of missed steps, the Z axis dropped about 25mm from the previous 2D contour operation a few seconds earlier.

Regards,

Arie.
 
breezy

breezy

Moderator
Quote from MASSO Support on March 13, 2019, 6:59 am

G17, 18 are for plane selection, details here: https://www.masso.com.au/masso-documentation/?section=g17-xy-plane-selection
Click to expand...

Figured out what Fusion is doing with the G17, G18, G3 code combinations. They are the vertical & horizontal lead in & lead out curves.

I reworked the Fusion CAM last night to get a single 2D contour cut instead of the linear pattern that I was using that resulted in 22 2D contours.

Regards,

Arie.
 
breezy

breezy

Moderator

Update.​


Tried the new file and the spindle still crashed into the table half way through the program. So I reduced the Z axis accelerance to half it's previous setting and tried again, it didn't crash into the table, but now I'm getting soft limit alarms before it completes the program. Run out of time to investigate, so will continue next week.

I had been getting soft alarms when moving the machine around by commands in the MIDI and had put down to errors that I was making. But now I suspect it maybe a bug in the software.

Also upgraded to 5 axis licence but have not modified the machine to run independent Y axis motors. Will be installing new proximity switches to replace lever action limit switches at the same time.

Regards,

Arie.
 
masso-support

masso-support

MASSO Support
Staff member
soft alarms means that the requested motion command is outside the min and max travel values of your axis travel.
 
breezy

breezy

Moderator
I'm aware of that but in this case the soft alarm coming up was X when the program should be commanding travel on the Y axis. The spindle was sitting 80mm from X0 and Y was at the back of the machine. I'm not sure of which line in the program the alarm occurred on. As I said I was out of time so need to test next week.
 
breezy

breezy

Moderator
Had email discussion with another member of the shed (we attend on different days) and he had an X soft alarm on his project.

Right near the end of the finishing pass, where the roughing pass had no problem, the router threw an x-axis soft limit error. I will see if comparing gcode from the roughing pass to the finishing pass can provide a clue to what caused that problem in this instance.

So I suspect that there is a problem with the MASSO, hope to work out how to reproduce it so @masso-support can fix it.

Regards,

Arie.
 
masso-support

masso-support

MASSO Support
Staff member
Hi Arie,

I would like to run your file on my Masso and see if it triggers a soft limit for me.

Can you let me know what max and min values the soft limits are for your X, Y & Z

Also can you post your MASSO_settings.htg file and I will load it into mine and run it to see if it make a difference. Just save the settings in the F1 screen under 'Save & Load Calibration settings' and copy it from your USB stick. Another useful feature is the print screen. If you want to grab a screen shot you can press the print screen key on your keyboard and it will dump a screen shot to the usb stick.

Cheers

Peter
 
breezy

breezy

Moderator
Peter,

All details in this post https://www.masso.com.au/forums/topic/alarm-soft-x-limit/

Should move this conversation to that topic now as this topic was about Z axis slip which I may have fixed by reducing the acceleration setting.

Not at the shed now, so can't check soft limit settings but we home the machine to the back right corner and set X axis at 1100mm and Y at 1075mm. Due to space restrictions on the left front corner.

Z is homed to top of carriage, travel set to 90mm. Need to reset that as I made changes last week that gave us about an extra 10mm of travel.

For the program start point, X & Y are at 0,0 and Z has been set at a random height as I'm just doing a dry run to test machine setup.

Regards,

Arie.

PS. I use a different login at the shed for members to use.
 
masso-support

masso-support

MASSO Support
Staff member
Thanks Arie,

I will enter your figures and have another look tomorrow night. (Different time zone and it is after 1 am here)

I did run your file and did get X soft limit trip and when I increased it I got a Y Soft limit trip. Not really surprising because it is going way outside the table area as you can see in the screen capture.

At the end it moves to a point well away from the cut in the top right hand corner of the screen. I did see Y at around 2m and X was over 1100 so that might be the reason.

I will move to the other thread but thought I would finish this one here.

Do you have another file you can post that is giving you the soft limit issue?

Cheers

Peter
 

Attachments

  • Print-Screen-001.bmp
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