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Author Topic: Z axis G1 moves get shorter with reduced feed rate  (Read 4966 times)

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Z axis G1 moves get shorter with reduced feed rate
« on: June 14, 2010, 09:06:41 AM »
I am having this problem.
If feed rate is set below 6"/min then G1 move of Z axis gets shorter.
G0 move is fine
X axis does not exhibit this problem.
I am using ver 3.041 trial version.
Can anyone help?

Offline Hood

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Re: Z axis G1 moves get shorter with reduced feed rate
« Reply #1 on: June 14, 2010, 01:53:04 PM »
Is this a stepper or servo system?
Can you swap a drive from Z to X and vice versa and see if the Z still is the problem axis.

Hood
Re: Z axis G1 moves get shorter with reduced feed rate
« Reply #2 on: June 15, 2010, 10:17:57 AM »
Hi Hood
this is a stepper system and using Mach 3 turn.
I'll swap the plugs round and see what happens.
It's odd though that the problem only seems to occur on G1 moves but not G0.
For example:-
Z=3
G1Z4 stops short
G1Z3 returns to Z=3
G0Z4 goes to Z=4
G0Z3 returns to Z=3

I'll post again with the result of swapping the axies.

Offline Hood

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Re: Z axis G1 moves get shorter with reduced feed rate
« Reply #3 on: June 16, 2010, 01:26:10 PM »
Can you attach your xml and I will see if I can replicate your problem here.
Hood
Re: Z axis G1 moves get shorter with reduced feed rate
« Reply #4 on: June 16, 2010, 03:35:15 PM »
Hi Hood
A thought has occurred to me. I originally set this system up with a small desktop PC with separate graphics card and everything worked fine. I replaced the pc with an all-in-one unit with touch screen and integrated graphics and the problem appears to be related to this change. I used the same xml file on both units. I have attached it for your perusal anyway. I will see if i can find another PC that I can use to prove this theory. The only other change was to replace the leadscrew with a trapezoidal one.

Offline Hood

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Re: Z axis G1 moves get shorter with reduced feed rate
« Reply #5 on: June 16, 2010, 04:20:08 PM »
Just to clear things a bit, when you command the G1 move to Z4 does the DRO stop short or is it the axis only?
Hood
Re: Z axis G1 moves get shorter with reduced feed rate
« Reply #6 on: June 16, 2010, 07:44:22 PM »
The DRO indicates the correct movement but the axis stops short. Also the amount by which it is short increases with a reduced feed rate.

Offline ger21

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Re: Z axis G1 moves get shorter with reduced feed rate
« Reply #7 on: June 16, 2010, 09:58:05 PM »
Sounds like a mechanical issue.
Gerry

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Offline RICH

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Re: Z axis G1 moves get shorter with reduced feed rate
« Reply #8 on: June 16, 2010, 10:38:51 PM »
What is "short" amount?
Is it consistant in the amount?

RICH
Re: Z axis G1 moves get shorter with reduced feed rate
« Reply #9 on: June 17, 2010, 03:40:20 PM »
Here is a table of results, all commanded movements are 1"
Feed Rate ins/min                Actual movement
1                                        0.45"
2                                        0.62"
3                                        0.76"
4                                        0.84"
5                                        0.90"
6                                        1.00"