ZRI repeatability Issue

[Obsidian]

I set up ZRI on our lathe that has two dyn4 drives. It seems to be finding the reference signal during the homing sequence on both axis. I can easily verify this by unplugging the ZRI signal from the drive and watching the homing sequence move indefinitely. The issue is when homing the machine again it does not hold the same zero. We can run a program to do a skim cut, rehome the machine and run the program again and it will be significantly off in X by nearly 0.2". I checked if there were lost steps in both axis and found nothing. The homing speed is set to 40ipm on both axis @ 8000 steps/rev. Anyone have an idea of what could be causing this?

Code: Select all

M92/X L1
M105 /X P-3 F3 ;Move X plus at 3ipm until input 3 closes
M26/X
M92/Z L1
;G0 Z 2
M105 /Z P-4 F3 ;Move Z minus at 3ipm until input 4 closes
M26/Z
M35                               ;Open Turret
G4 P0.5                          ;Pause
M92/A L1
M26/A
;G0 A -.3                      ; Disengage fom worm gear for Turret Lock, Worm Gear has deadspace between tools to prevent turret lock from pushing on the gear.
M26/A
M27                               ; Turn on Turret Lock

[Obsidian]

So after some testing and logging I am find that the repeatability significantly increases at lower homing speeds. At 3 IPM the repeatability rate is fairly low. I can get it to zero at the same home location 2 out of 10 times. At 0.8 IPM ZRI homing the repeatability is at zero 10 out of 10 times. I'm tempted to lower the steps/rev and test.

[slodat]

I had similar results. This is how I'm doing it. Seems to work well.

Relavent section per axis:

Code: Select all

M106 /Z P3 F10      ;Move Z plus at 10 in/m until input 3 opens
M105 /Z P-3 F.5     ;Back Z off switch slowly
M105 /Z P-4 F.5     ;Move Z minus at .5 in/m until ZRI input 4 closes
M26 /Z              ;Set Z home here

Entire homing routine:

Code: Select all

N100 ;Check for an open home switch
;First axis minus and plus
IF #21301 == 0 THEN #111 = 9 ELSE #111 = #21301
IF #21401 == 0 THEN #112 = 9 ELSE #112 = #21401
IF [#20101 != 78] && [#21301 != 0] && !#[50000 + [#111]] THEN M225 #100 "Home switch tripped!!!\nPlease clear before Homing.\n\nPress Cycle Cancel to end Homing";
IF [#20101 != 78] && [#21401 != 0] && !#[50000 + [#112]] THEN M225 #100 "Home switch tripped!!!\nPlease clear before Homing.\n\nPress Cycle Cancel to end Homing"
IF [#20101 != 78] && [#21301 != 0] && !#[50000 + [#111]] THEN #101 = #101 + 1
IF [#20101 != 78] && [#21401 != 0] && !#[50000 + [#112]] THEN #101 = #101 + 1

;Second axis minus and plus
IF #21302 == 0 THEN #111 = 9 ELSE #111 = #21302
IF #21402 == 0 THEN #112 = 9 ELSE #112 = #21402
IF [#20102 != 78] && [#21302 != 0] && !#[50000 + [#111]] THEN M225 #100 "Home switch tripped!!!\nPlease clear before Homing.\n\nPress Cycle Cancel to end Homing"
IF [#20102 != 78] && [#21402 != 0] && !#[50000 + [#112]] THEN M225 #100 "Home switch tripped!!!\nPlease clear before Homing.\n\nPress Cycle Cancel to end Homing"
IF [#20102 != 78] && [#21302 != 0] && !#[50000 + [#111]] THEN #101 = #101 + 1
IF [#20102 != 78] && [#21402 != 0] && !#[50000 + [#112]] THEN #101 = #101 + 1

;Third axis minus and plus
IF #21303 == 0 THEN #111 = 9 ELSE #111 = #21303
IF #21403 == 0 THEN #112 = 9 ELSE #112 = #21403
IF [#20103 != 78] && [#21303 != 0] && !#[50000 + [#111]] THEN M225 #100 "Home switch tripped!!!\nPlease clear before Homing.\n\nPress Cycle Cancel to end Homing"
IF [#20103 != 78] && [#21403 != 0] && !#[50000 + [#112]] THEN M225 #100 "Home switch tripped!!!\nPlease clear before Homing.\n\nPress Cycle Cancel to end Homing"
IF [#20103 != 78] && [#21303 != 0] && !#[50000 + [#111]] THEN #101 = #101 + 1
IF [#20103 != 78] && [#21403 != 0] && !#[50000 + [#112]] THEN #101 = #101 + 1

;Fourth axis minus and plus
;IF #21304 == 0 THEN #111 = 9 ELSE #111 = #21304
;IF #21404 == 0 THEN #112 = 9 ELSE #112 = #21404
;IF [#20104 != 78] && [#21304 != 0] && !#[50000 + [#111]] THEN M225 #100 "Home switch tripped!!!\nPlease clear before Homing.\n\nPress Cycle Cancel to end Homing"
;IF [#20104 != 78] && [#21404 != 0] && !#[50000 + [#112]] THEN M225 #100 "Home switch tripped!!!\nPlease clear before Homing.\n\nPress Cycle Cancel to end Homing"
;IF [#20104 != 78] && [#21304 != 0] && !#[50000 + [#111]] THEN #101 = #101 + 1
;IF [#20104 != 78] && [#21404 != 0] && !#[50000 + [#112]] THEN #101 = #101 + 1
;IF #101 != 0 THEN GOTO 100

M106 /Z P3 F10      ;Move Z plus at 10 in/m until input 3 opens
M105 /Z P-3 F.5     ;Back Z off switch slowly
M105 /Z P-4 F.5     ;Move Z minus at .5 in/m until ZRI input 4 closes
M26 /Z              ;Set Z home here

M105 /Y P2 F10      
M106 /Y P-2 F.5         
M106 /Y P-4 F.5
M26 /Y

M105 /X P1 F10  
M106 /X P-1 F.5   
M106 /X P-4 F.5    
M26 /X      

g53 x15 y14.5 f50

N1000           ;END

[Obsidian]

@Slodat

Thanks for the tip its working much better now. Looks like if you have the homing speed set to high it overtravel's the switch and causes issues finding the same ZRI reference every time. Slowing it down lets you hit the switch and the same ZRI reference point more accurately.

[slodat]

I think the trick is to hit the switch, slowly back off the switch so it’s clear (I use them as homeLimit), THEN slowly seek to switch for the ZRI.

I’m not into soft limits only. I want + and - limit switches.

[martyscncgarage]

If your switch is too close to the marker pulse that may be contributing to the problem. The solution is to rotate the motor shaft 180 degrees or so and reconnect to the machine (assuming direct drive) if belt drive similar. Or move the switch.

Marty

[Obsidian]

@Martyscncgarage

I actually had to do this on the X switch. I moved switch stop just slightly to fix it. It was bouncing back and forth between two different markers. Moved the stop slightly and its hitting the same marker every time now.

[slodat]

I had forgotten the line to move of the ZRI pulse so it’s off for the next axis in my code above.