Need help ASAP! Losing travel from stepconf to cnc

and what is the actual TPI or pitch of your lead screw?

cmorley wrote:

looking at your x and y pulley calculation.

Do you really have the motor running faster then the leadscrew?

you specified 18 teeth on the motor and 1 on the leadscrew.
This increases the rpm of the leadscrew - usually people gear down the leadscrew.

Chris M

This is from the setup guide for LinuxCNC for my particular machine:

The cleanest way is to replace "leadscrew" with "belt" in that dialog, and then everything makes sense.

Motor steps per revolution is given by the motor construction: 200 steps for 1.8 degrees per step, 400 for 0.9 degrees per step.

The driver microstepping is given by driver design and configuration. Allegro A4988 drivers (as on the Pololu carrier boards) support 1x, 2x, 4x, 8x and 16x microstepping. They are usually configured using jumpers on the driver board (buildlog stepper shield, RAMPS etc). Texas Instruments DRV8811 drivers (as on the Grblshield) support 1x, 2x, 4x and 8x microstepping. On the unmodified Grblshield, they are configurable only for all drivers at the same time, using a single set of jumpers. The Z-axis microstepping modification allows the Z axis to be set to 2x microstepping while the X and Y axes are set to 8x. Grblshields from full and premium Inventable kits are already modified. Gecko controllers support, if I recall correctly, 10x microstepping. And so on.

Pulley teeth is 18 : 1 (the actual number of teeth on the pulley).

Set the leadscrew pitch to your belt pitch, which is 12.5 teeth per inch for MXL.

The Z axis settings are 1 : 1 motor:leadscrew (direct coupling) and a leadscrew pitch of 20.32 turns per inch (M8 thread). Set the microstepping as discussed above. If you have independently configurable microstepping for your Z axis, 2x is usually fine enough.

By the way, the .69444375 number as shown is correct: it is 12.5 / 18, because they set the pulley ratio to 1 : 1. To move the axis one inch, the motor needs to turn .69444375 turns. It is the same thing, but I think my way is easier to understand.

The 18:1 is pulley to belt. There are 18 teeth on the motor pulley.
The Z lead screw is M8 of 20.32TPI

After much frustration and trial and error, I used the actual driver program to configure it. I also reduced the microstepping to x4 (even though the driver board is set for x16), and eventually in the program itself I was able to get it 1":1" of XYZ travel.

Well I'm glad you figured it out....

But for future reference:

Please give as lots of info, particularly if you are doing something odd.
eg it seems you are not using a leadscrew ,your using a belt - this sounds like a gantry router or something along those lines.
This means we must assume, we kinda hate to assume.

standard stuff we usually need to know:

what version of linuxcnc?
How did you get that version (compiled it, live cd, buildbot)
did you modify it?

How did you make the config?
did you hand edit it?

what's the problem?
what did you do to get the problem?
what did you expect to happen
what actually happened

Information about the machine/interface electronics/ screen your are using.
some times zipping the config and posting it or pastebin ing a particular file is helpful

makes getting a good answer faster.

Even though you got the scaling right you still had some seemingly crazy numbers for axis max velocity and max acceleration
6 inches a minute (which is slow) with 3000 inches per sec per sec acceleration seems very high.

Chris M