Z axis G1 moves get shorter with reduced feed rate

[spannerman]

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?

[Hood]

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

[spannerman]

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.

[Hood]

Can you attach your xml and I will see if I can replicate your problem here.
Hood

[spannerman]

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.

[Hood]

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

[spannerman]

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.

[ger21]

Sounds like a mechanical issue.

[RICH]

What is "short" amount?
Is it consistant in the amount?

RICH

[spannerman]

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"