After spending some time browsing the
web and looking at how other people have built these machines I ended up
with the following specifications:
- At least 8' by 4' as this is a standard sheet size.
- Stepper motor drive - Servos are faster and not prone to lost
steps but they are also much more expensive.
- PC control. Why buy a dedicated controller when modern PCs are so
- Positional accuracy +/- 0.5mm. There is no point going
better than that because heat distortion will ensure nothing comes out
exactly to size anyway.
- Due to a lack of space in my workshop it must be possible to pack
the machine away somehow.
- It must be constructed from low cost and easily available
- The rails and drive mechanism must be resistant to the vast
amount of abrasive black dust that plasma cutters generate.
After haunting the CAD CAM EDM DRO
mailing list for a while I started drawing out some plans. There were
three main design problems to overcome.
- How to control motors to get accurate
- How to convert the motor rotary
motion to linear motion
- Positioning the cutter with minimum backlash
This is the cutter table. The work is supported with lengths of
25mm angle iron with the points upwards. After a lot of use the angle
gets quite messy and has to be replaced.
This is a pic of the setup with monitor, control box
After one motherboard died, presumably due to dust inhalation I turned
the power supply fan around so thet the case is slightly pressurised to
keep out the dust. The intake is covered with a large foam filter to
catch the worst of the dust. The black mark on the filter is after one
The end result is well worth the effort. The machine will cut 2mm plate
at 1.3 metres (51") a minute. The cut out parts are usually within +/-
0.5mm unless I am cutting very thin material which tends to distort
badly. My next project will be a good test for the machine. (see the FrankenRover
section for more