Open Source Stepper Motor
Overview
The Global Village Construction Set (GVCS) has a need for stepper motors for linear and rotational motion control. The CNC Multi-machine, torch table, circuit board miller, and others all call for precise motion controlled by a computer or dedicated control device. While the early prototyping stages of these projects will use off-the-shelf stepper motors like the Xylotex Stepper Motor or NEMA. Eventually, we'd like to be able to fabricate stepper motors using the GVCS. This page is used to collect information on the fabrication of stepper motors.
Theory
A stepper motor uses controlled electrical pulses applied to a winding that generates a temporary magnetic field that causes a toothed rotor to move a small amount. Pulses applied sequentially to a set of winding poles is used to create motion. There is a very good animation of this from the wikipedia article on stepper motors. This article also covers all of the basic theory, more characteristics, types of motors, waveforms, forces, etc.
A [http://www.zaber.com/wiki/Tutorials/Microstepping%7C microstepping tutorial at Zaber Wiki goes into the electrical aspects stepper motors.
Parts
Some of the following is taken from the Engineer's Garage.
Depending on the kind of stepper motor being built, the following parts need to be created:
- Toothed rotor
- Shaft
- Shaft bearings
- Stator poles (also toothed)
- Stator cores
- Windings
- Case
Fabrication
| Part | Technique |
|---|---|
| Rotor | Lathed and index milled |
| Shaft | Lathed |
| Shaft Bearings | (separate fab) |
| Stator Poles | Milled |
| Stator Cores | Milled ? |
| Windings | Winder (multi-machine?) |
| Case | Cast? Milled? |
Most of the fabrication needed can be accomplished by a multi-machine (lathe/mill). Bearings present a special problem that should be considered in a separate fabrication process. Roller bearings may be sufficient for this purposes. Winding the cores is also a special task since insulated wire (lacquer?) must be carefully wound around a core. This might be accomplished by a source of rotary motion (the multi-machine) and a linear feeder that moves back and forth across the rotating pole.
The case will also require some thought. Milling it would be quite wasteful. It might be cast out of aluminum, then bored and milled inside to receive the stator poles. This view shows the inside of a commercial motor. Note the inner case to which the stator poles are mounted. Separate end pieces would aid assembly, disassembly and repair.
Assembly
Assembling the motor might consist of (roughly) the following steps:
- Mount the rotor on the shaft.
- Slip bearings over shaft.
- Wire up the stators.
- Mount stators inside the case.
- Slide the shaft assembly into the enter of the mounted stators.
- Attache front and back pieces of the case.
Other Sites
These are links to other sites that discuss how to build a stepper motor: