I've been following the OX forums for a while now getting ready to start building one myself, and while I really like the concept, I am wondering about the resolution these machines are capable of. I was thinking of looking at ball-screw or rack-and-pinion setups for the X- and Y- axis, but this looks to add considerable cost - especially for me here in NZ the shipping costs alone become prohibitive. I like the simplicity of the belt drive system (and the double belt setup looks like a winner), so my question is: has anyone looked at using a worm drive reducer like this one from Aliexpress: 90 Degree Worm Reducer RV030 11mm Input Shaft Worm Gearbox Speed Reducer for NEMA 23 Stepper Motor Brushless Motor-in Speed Reducers from Industry & Business on Aliexpress.com | Alibaba Group These seem to be available in a range of gear ratios, so what would be the ideal reduction ratio to get a decent resolution without making the thing ridiculously slow? It also seems like this would be an easy mod without having to redesign the gantry plates. I would like to build a mill predominantly for wood & perspex, but would also like to be have the ability to cut aluminium from time to time.
Depending on the quality of the gear, you do run the risk of introducing backlash into the system. I wouldn't expect the tolerances on $35 reducers to be all that tight. And with the lowest ratio of 7.5:1. you'll be bringing the system down from 60mm/ revolution to 8mm which is quite a drop and may be too slow for working with perspex. (Basically it would be on par with the TR8*8 lead screws.) An alternate suggestion would be a belted reduction solution. Mark just recently introduced belted reducers in the parts store but these were mainly designed for use with the C-beam setup. An alternate suggestion for OX systems was previously presented here. (Note, it's still a work in progress as I have other issues demanding attention.) You should be able to pull something like this off fairly inexpensively using GT2 pulleys and belts from either ebay or Robotdigg. And pulley combinations in the 2:1, 2.5:1 or 3:1 range should be fairly easy with the wide variety of pulley sizes available. These ranges would give you an appreciable increase in resolution without such a significant loss in speed.
