Having reviewed many of the other projects CNC around. They all came to the same conclusion, that Servo motors were best but also the most expensive. As my budget did not run to Servos, I decided on using Stepper Motors. Over the years stepper Motors have also become very much more powerful, smaller and cheaper. 

 

However, this then opened up some questions that need consideration.

 

·         What size motors do I need?

·         What happens if I lose a step when machining?

 

With Steppers the basic rules seemed to be: - use the biggest motor you can afford, this avoids loosing steps, if not powerful enough.

This may be fine for commercial builders , but on a limited budget this is not good.

 

      Also, most commercial machines use direct drive onto the lead screws, which not only means they need large motors , but they take up extra space on the work bench.

 

After some research, looking at commercial retrofits. 

I opted for 4 Nm (560 oz. load Capacity) stepper motors, with

Toothed belt reduction drives to further increase their load capacity.