Background

The machine uses stepper motors — open-loop control motors that are accurate and reliable — to control axis motion. With stepper motors, however, there's a chance of losing steps in axis motion. This is because lost steps occur when the commanded number of steps and the actual number of steps don't match (a risk with open-loop control). A step mismatch results in a loss of motion on the axis. In most cases, when a machine loses steps, it loses many steps all at once — resulting in a visible stutter or a stall in axis motion, and/or an audible noise. Lost steps often occur when a stepper motor is pushed too hard or too fast, and it exceeds its limits. Although this machine uses stepper motors to control axis motion, the entire system is designed to reduce the likelihood of losing steps. In most cases, the machine breaks smaller cutting tools or stalls the spindle with bigger cutting tools before losing steps. Outside variables, like programming, tooling, work holding, and operator error, are sometimes misinterpreted as lost steps.

Table of Contents

Examine the G-code programs for offset values and cutter compensation value

Reason: Improper use of tool offset, work offset, or cutter compensation

The most common cause of a perceived loss of position or lost steps is operator or program error. Always vet your programs first, before moving on.

Check tool holding (Loss of Z-Axis only)

Reason: The spindle tooling isn’t properly clamped

Examine the cutter to verify that it’s not slipping in the holder, or that the tool holder isn’t pulling out of the spindle collet.

Verify that the collet nut is properly tightened on the spindle before you start cutting.

Verify that the spindle taper, collet nut, and collet are properly cleaned.

Examine the motor coupling

Reason: The motor coupling is loose or cracked

A loose or cracked coupler can allow the ball screw to spin in the coupler freely.

Restart PathPilot and generate a log data file

Reason: Controller or PathPilot problem

After restarting PathPilot and generating a log data file, create a support ticket with Tormach Technical Support, and send us your log data.

Check driver dip switches

Reason: Wrong switch settings

See the machine’s electrical schematic, located in the back of the manual, for proper dip switch settings.