Probably, many who are viewing the “DIY or DIY” section faced with the need to find / select a suitable pair of gears or a finished gear for your project. And also faced with the difficulties of this search.

The ability to manufacture gears on my own has long interested me. Factory methods of cutting gear with modular cutters, etc., by industrial methods are of little use at home. And to make to order costs a lot of money for one piece or they want a batch of 1000 pcs.

Various attempts to cast gears made of epoxy resin and plastics ended in nothing.

• For molding, you still need a sample, and this is not always possible.
• Casting requires "file completion".
• The resulting gears are fragile and often have defects.

At the gear made on a 3D printer, no tears can not watch. Although some of the tasks they cover.

The idea that the correct gear can be done on a 3-coordinate CNC machine without additional accessories came to my mind not immediately. But, experiments have shown that the idea is working.
Oddly enough, but no one uses this method. All are cut out with a modular cutter and on the DIY thematic forums are full of questions “what about the gear to make / order / find”.
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After many experiments I stopped at the option of plug - ins for inkscape .

Plugin for inkscape “gears_evolvente.py” (Copyright © 2011 Dave Web), slightly modified for the formation of additional elements (center mark, hole, additional circle - pitch diameter, etc.)



Plugin for creating rack rack_gear.py (Copyright © 2013 Brett Graham). Also worked on the little things.




Module 1mm, as the minimum module, which cutter 1mm cuts without serious deviations from the required shape. As the material is ideal textolite or glass fiber. Additional processing of finished gears and rails is not required.

The gears cut by this method are also used in various projects. Gears withstand a decent load and wear until noticed.

Characteristics of tested rake-gear drives

Backlash rack and gear

Experiments have shown that the backlash in a pair of “rack-gear” micrometer with a clock scale is 0.05–0.07 mm with a load on the rail within 0.5–1 kg.

This gap was at an exposed gap in the pair sufficient to move easily and without jamming. The gap is set with a hard clamping of the rack with screws (oval hole on the rail). Gear on the axis of the stepper motor. Engine tightly bolted to the base.
Backlash in gearing gear is subjectively no worse than a pair of factory metal gears with a 2mm module.

Reline nonlinearity

Unfortunately, I don’t have the exact tool to measure the linearity of movement. Using a caliper remove only determine that the linear displacement error at 50mm (in steps of a stepper motor) does not exceed 0.5mm (it is more difficult to determine more accurately).

Some conclusions

Using homemade gears and rails for homemade designs is a good idea.
Production cost is minimal for small batches and single copies.
The main disadvantage of drives on a pair of gear-rail: More noisy work than when using a belt or ball screw. However, this was to be expected.