Dynomotion

Group: DynoMotion Message: 8630 From: Hugh Sontag Date: 11/13/2013
Subject: Z axis mystery
Hi Tom,

I'm using KMotion CNC with a GCode program.

I'm seeing a problem in which the Z axis appears to be commanded to go too fast.

The GCode program moves the Z axis from 0.1 inches to -2.3 inches, and then back again to 0.1 inches.

What happens is that I get a following error because the speed that the Z axis is commanded to go is very much in excess of the max speed it *can* go. It's a ballscrew with a BLDC motor and encoder. The encoder generates ~41,000 counts per inch.

I can run the Z axis at 23,000 counts per second for 2.4 inches without a problem using a C program in KMotion. The Z axis will move at a this rate of 0.55 inches per second without a problem, no following error.

However, when I run a GCode program to move the Z axis from +0.1 inches to -2.3 inches, the Z axis accelerates until I get a following error. The Z axis following error maximum is currently set to 4000 counts.

Here's the GCode program:

G20 G17 (use inches, use X-Y plane)
G0 Z0.10 (start at Z = 0.1 inches)
G0 Z-2.3 (move to Z = -2.3 inches)
M2

I've attached my current settings for the Trajector Planner  in KMotion CNC. I haven't seen any change in the acceleration and eventual axis disable due to following error, even when I set the Velocity for the Z axis in the Trajector Planner to a really small 0.05 inches per second.

The maximum rate of the Z axis movement is obviously much higher than 0.55 inches per second when the following error occurs.

Can you shed some light on what might be happening? I thought that the Velocity number in the Trajectory Planner was a maximum, and that the Z axis would not be asked to move faster than the Velocity setting. This does not seem to be the case.

I'm currently using KMotion 430.

Thanks,
Hugh



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Group: DynoMotion Message: 8631 From: Tom Kerekes Date: 11/13/2013
Subject: Re: Z axis mystery [1 Attachment]
Hi Hugh,

KMotionCNC doesn't use the motion settings in the Tool Setup Parameters for rapid moves (G0).  Rather it uses the settings in KFLOP.  Recall this thread:


When you tested the motion in KMotion are you sure you saved the Velocity, Acceleration, and Jerk into your Initialization C file so those are set properly when running KMotionCNC?

Regards
TK


Group: DynoMotion Message: 8643 From: Hugh Sontag Date: 11/14/2013
Subject: Re: Z axis mystery
Thanks, Tom.

Your reminder about G0 and KMotion feed rates allowed me to understand the problem and correct the parameters.

If I had been using G1, then the KMotion CNC velocity and acceleration parameters would have been used.

Hugh



On Wed, Nov 13, 2013 at 6:55 PM, Tom Kerekes <tk@...> wrote:
 

Hi Hugh,

KMotionCNC doesn't use the motion settings in the Tool Setup Parameters for rapid moves (G0).  Rather it uses the settings in KFLOP.  Recall this thread:


When you tested the motion in KMotion are you sure you saved the Velocity, Acceleration, and Jerk into your Initialization C file so those are set properly when running KMotionCNC?

Regards
TK