CNC Information and Projects

Stepper motors are affected by resonance. The resonance can become so severe that the stepper will stall and lose position. Stalling can also damage the stepper.

Resonance sounds like a grinding or rattling noise. This is usually followed by a high pitched whine as the stepper stalls while still receiving step signals.

Resonance is caused by parts vibrating in concert with each other. It can be lessened by altering a variety of factors including micro-stepping, acceleration rates, speed, looser or tighter mounting hardware, thicker or thinner stepper mounts, longer or shorter mounting bolts, and a myriad of other variables.

A damper attached to the stepper's shaft can reduce resonance. It is essentially a wheel that turns with the stepper; however, it is not simply a flywheel.

This damper is straightforward, and all of its parts are from Lowes. It is made from a 2-1/2 inch caster, which performs better than a 1-3/4 inch caster.

The caster has a 5/16 inch bore. An axle is made by drilling a 1/4 inch hole in the head end of a 5/16 inch bolt. This hole accepts the stepper's shaft.

A hole is drilled and tapped for a #8-32 or similar set screw in the side of the bolt head. The hole in the bolt for the stepper shaft can be drilled by tightening the bolt in a power drill's chuck, and clamping the drill bit in a vise.
A small bit is used to drill a centered pilot hole. The hole is incrementally enlarged with larger bits.
A drill press makes this easier, but the hole can be drilled with a hand held drill with Vise Grips holding the bit. Two short screws with nuts are tightened into holes in a fender washer. The fender washer is epoxied or soldered against the bolt head.

The caster is sandwiched between a spring and washer. A lock-nut adjusts the spring's tension against the caster. This is a trial and error adjustment.
The caster does not easily freewheel, but it will turn on the axle bolt.

A damper made from a thrift store roller blade wheel also worked well, but the parts may be more challenging to find.

Two notches are cut in the wheel's bore to hold a stud that prevents freewheeling. Image below.
The axle is made of 1/4 inch ID and 5/16 inch OD copper pipe. Right image.

The bearings do not turn; they are used as bushings to hold the axle in the wheel.

A hole for a cut nail is drilled through the copper pipe. The fit should be tight.

The nail rests in the notches in the plastic wheel. The fit should be fairly tight. A little play is okay, but too much will allow the wheel to coast too far, which will cause the stepper to stall on deceleration.

The damper is held onto the stepper's shaft with a set screw that is tapped into a 3/8 inch nut.