How does acceleration work in the centroid control system?

[carboncymbal]

I recently saw a post referencing acceleration and am a bit confused about how centroid handles acceleration and how setting acceleration time actually works.

The setup manual states that the acceleration time sets the time to achieve maximum velocity. Let’s say I have a machine that can go up to 100ipm. With an accel time if .5 sec.

I assume this means that if I do a move at 100 ipm, the machine will accelerate to 100 ipm in .5 sec, or a rate of 200ipm/sec.

If I do a move at 50 ipm, I assume that the acceleration rate of the machine is still 200 ipm/sec, and that it reached the target velocity in .25 sec. Is this correct?

I saw a post recently where it seemed to
Imply that all accelerations would take .5 sec, so an acceleration to 10 ipm would still take .5 seconds. It seems this approach would leave a lot of performance in the table because the acceleration would need to be set based on the limitation of the motor and machine frame during rapid moves, and be performing at a fraction of available acceleration at lower velocities. Based on that, I’m thinking I may have misunderstood that post.

Thanks.

[cncsnw]

It works the way you expected it to work: the accel time and max rate settings establish the acceleration rate.

That acceleration rate applies to all moves, regardless of the final speed.

[carboncymbal]

It works the way you expected it to work: the accel time and max rate settings establish the acceleration rate.

That acceleration rate applies to all moves, regardless of the final speed.

Fantastic, Thank you!

[suntravel]

look also for Deadstart in the manual:

Deadstart: Determines the speed that an axis will decelerate to before stopping or reversing direction. A low setting
will cause a large slowdown before a reverse in direction, causing your machine to be more accurate. A high
setting will cause less slowdown before reversals, but this may cause your machine to “bang”, which may cause
a decrease in accuracy. This parameter should not be changed

15.3.120 Parameter 165 – Acceleration/Deceleration Options
This is a bit field parameter which modifies certain details of axis acceleration and deceleration when an axis stops
moving, changes direction, or starts moving. The Jog Parameters screen in Machine Configuration sets the original
DeadStart values for each axis. This parameter allows you to modify these DeadStart settings under certain
conditions. Note that if both bit 0 and 1 are turned on (value = 1+2 = 3), then the effect is cumulative, i.e. the net effect
will be that 1/2 of the DeadStart value will be used when a slave axis stops or starts up from a stop. Likewise, if both
bit 2 and 3 are turned ON, the effect will also be cumulative. Note that this feature has no effect for movement
commands handled by Smoothing (P220=1).

Uwe