Advice on 4th Axis

[m_c]

I think I've probably looked at 4th axis more than most on here, but still never got around to making one.
For woodworking, you do have the benefit that you won't need quite as much holding torque as for my intended metalworking use.

In terms of ready made 4th axis, the options are pretty limited.
There are plenty cheap ones, that are simply a stepper motor connected to a basic chuck/spindle setup. Probably ok for light engraving/cutting on smaller diameters, but lacking torque for anything larger.
There are one or two with Harmonic drives, which greatly increase torque compared with the previous belt option, and would likely be good for your purpose, but they don't have enough torque for what I'd intend to do with one.
Then you're into worm drive options. Provide the most torque, but with the sacrifice of speed.

A good option if it would work for you, is something with a brake. It does mean you end up with a glorified indexer, but for lots of uses it is often enough.

For ready made options, http://www.skyfirecnc.com/Parts.asp do harmonic drives, although I have no idea what their current supply times are like. Komatias on here (owner of Emvio Engineering) is probably the best to ask, if he is still a Skyfire dealer...
Belt drive, the InTurn http://www.theinturn.com/ is probably the most advanced option, and if you're considering building your own, there is a big thread over the mach support forum detailing the original design/build.

Other than that, a search of Alibaba is likely to produce lots of Chinese options of varying levels of complexity/quality. There'll likely be plenty cheap/basic options on AliExpress, but the more industrial/less popular items can be found on Alibaba.


Although, before you commit, I'd suggest working out what your torque requirements are likely to be. If you post up your spindle power, some cutters and the speeds you normally use, I can run some figures for you, so you can get an estimate of what 4th axis torque you're likely to need.

[OMLCNC]

Although, before you commit, I'd suggest working out what your torque requirements are likely to be. If you post up your spindle power, some cutters and the speeds you normally use, I can run some figures for you, so you can get an estimate of what 4th axis torque you're likely to need.

Spindle is this 3kw https://www.ebay.co.uk/itm/EU-CNC-22...QAAOSwfeJgOILv

Cutters: Straight 12.7mm Dia, Speed 18000rpm Feed 40mm/sec , Bull Nose 19mm Dia,Speed 18000rpm, Feed 40mm/sec

Nothing bigger than these I would think

Thanks for info and torque estimates