G0 velocity limitation

Is it possible to configure system so that on a G0 call the velocity on the moving axis will move at its programmed max velocity instead of being limited to the slowest axis?
For example on my Bridgeport mill Y is the slowest axis because it has the most weight to move. Z has the least mass of the three axes. I would like to Z to not be limited to the max velocity of the Y axis.
I find that jogs do not suffer this limitation. The axis will move at its respective programmed max velocity.

i asked a similar question recently, though i have not gotten to the point my machine is running i wanted information incase i want ot drive the knee. the answer i got is that the axises will always reach the end of the path at the same time so the slowest axis being used or the one with the longest move will effect the velocity of the others. this doesn't actually hurt the cycle time in anyway and it keep you out of trouble on high speed machines where not coordinating the axises and just going as fast as possible can cause non linear moves that can cause unexpected crashes when you change the rapid speeds. (i've experienced this on hass lathes with gang tool tables because the head programmer was lazy)

i was lead to believe that as long as the slow axis move was short or not used it wouldn't negatively effect the other speeds.

what surprises me is that the y has more inertia than the x. i know there is more mass but it also has a lot less leadscrew and if you left the hand wheels installed that's a fair amount of inertia as well. i don't think people take that into account but it makes a difference. and i wouldn't think you'd see a difference between x and y.

what do you use for motors? leadscrews? lube?

My situation is slightly different than yours. you are dealing with a lathe and I a bridgeport mill.
In my case my the Y axis has the most mass and has the lowest velocity. The Z axis (the spindle) has the least mass and consequently should be the fastest is thereby limited in its speed on a G0 call. When one is drilling with pecking for deep holes, it is obvious that with all the rapid calls it moves as fast as achievable. I hope we can find a solution to our problem. I find that on jogs each axis moves at its programmed max rate.

jensor

jensor wrote:

Is it possible to configure system so that on a G0 call the velocity on the moving axis will move at its programmed max velocity instead of being limited to the slowest axis?
For example on my Bridgeport mill Y is the slowest axis because it has the most weight to move. Z has the least mass of the three axes. I would like to Z to not be limited to the max velocity of the Y axis.
I find that jogs do not suffer this limitation. The axis will move at its respective programmed max velocity.

Do you mean when moving only 1 axis at a time?

On my machine I have different MAX_VELOCITY for each axis. a G0X0 will rapid at the speed defined in each [AXIS_N] section
Check your [TRAJ] MAX_LINEAR_VELOCITY, is is set lower than any of the axes? I would guess not, as it should limit all axes to that limit, but worth a shot.

If you were talking about rapid moves that involve more than 1 axis, then It will limit the speed so that all axes reach the end at the same time.

Yes, I mean specifically moving a single axis such as G0 Z-4. I find even though Z max vel is set to 1.5 (90 ipm) it will only move on the g0 call at .6 (36 ipm) which is the max vel programmed in for the Y axis. If I increase the Y axis to 1.5 then the Z axis speed on g0 call is limited to .9 which is what the X axis is programmed to. However when jogging any axis it will travel at its programmed max vel for that particular axis. The limit in the [TRAJ] section limits the multi axis moves only which will always be higher than single axis moves on a G0 call.

I hope I can find a solution to this limitation.

My setup is on a Bridgeport milling macine and I wanted faster movement on z for peck drilling.

jensor

maybe i'm being too literal about what you wrote but i would imagine the behavior of this would be that the trajectory planner will go as fast as the slowest axis will allow that acheives a linear move unless that velocity exceeds MAX_LINEAR_VELOCITY whether or not it is a combined move, though i can't be certain that's how it works it would be logical. if it were me and all 3 axises had the same max velocity i'd make MAX_LINEAR_VELOCITY 1.73x the speed of a single axis, for a machine with different axis speeds i'd go off the time it takes for the axis that takes longest to reach it's limits and the diagonal of a rectangular box that would be created with the travel of all the axises at a bare minimum but may set it as high as the max velocity that could ever be acheive if all 3 axises were moving at full speed at the same time depending on what was effecting cycle times and how much i used certain moves and how much i could deal with the table changing speeds.

if you want to do x,y,z similtanious moves without being limited by the slow axis and z can go 500ipm and the x can go 200ipm and y goes 150 and the z travel is 5in then the x can maybe go 2 inches and y 1.5 in the time it takes for the z to travel its range depending on acceleration.. if you find the diagonal of that rectangular box and you'd have the maximum velocity that could be achieved which is somewhere around 560ipm for this example that the MAX_LINEAR_VELOCITY could never slow the machine. the formula is similar to the Pythagorean theorem. diagonal=sqrt(L^2+W^2+H^2)

also my numbers i ran for figuring my motor requirements suggest the x would have the most inertia despite the y having more mass becasue the rotational inertia of the longer leadscrew and extra handwheel is pretty significant. the y may have more frictional drag but with lubrication it shouldn't be much at all.

Yes, I mean specifically moving a single axis such as G0 Z-4. I find even though Z max vel is set to 1.5 (90 ipm) it will only move on the g0 call at .6 (36 ipm) which is the max vel programmed in for the Y axis.

Well that just seems wrong.

On one of the knee mills we have power to the the table (W axis) it moves quite slow however it only effects the other axis when in combined moves.

A g0 move of only 1 axis should move at it's max speed and not be effected by any other axis.
As pointed out above I would reset the MAX_LINEAR_VELOCITY higher.
Also check your ini for errors / duplicate entries.

Rick G

Is it possible you are editing one INI file, and running another?
I ran into this when I was simulating to see how mine acted, took a few minutes to figure out why my changes weren't working.

My experience is with an old version Axis 2.3.5. So I recently downloaded the latest version 2.5.1 and experimented with Stepper_inch.ini and found that it behaves as the earlier version.
The default values in the downloaded files were all the same, 1.2 (72 ipm). I made the following changes:

[TRAJ] section MAX_VELOCITY = 3 (180 ipm) (Just to be sure that doesn't get in the way and it shouldn't anyway on single axis moves)
[AXIS_0] (X axis) Max vel to .6 (36 ipm)
[AXIS_1] (Y axis) to .4 (24 ipm)
[AXIS_2] (Z axis) to 1.0 (60 ipm)

When running the program each axis jogged at its programmed max rate. However on a G0 single axis command things were quite different:

G0 X2 moved at 36 ipm (same as its programmed rate)
G0 Y2 moved at 24 ipm (same as its programmed rate)
G0 Z2 moved at 36 ipm (limited to X's programmed rate - not the slowest axis)

I then increased the max vel for the X axis in the ini file to 1.2 (72 ipm)
and then found that the Z axis would move at its programmed rate of 60 ipm!
All axes would g0 at their programmed max vel rates!

So a work around for this problem would be to configure the fastest axis (in my case the Z axis) as [AXIS_0].

jensor