Hi Azalin,
I think the harmonic drive or strain wave has too greater reduction. If you look on-line you'll find 50: and 100:1 are common with only a few of 30:1.
If you have a rotating axis like mine that would mean then even with a 3000rpm servo the best you could get is 100rpm at the chuck. I can promise you that many rotary toolpaths
require some thousands of rotations and it will take an age at only 100rpm.
My fourth axis has a reduction of 19.5:1 for an output speed of 150rpm, and its useful but I sure as hell do not want it to go any slower.
For a rotary axis I would guess around 10:1 is the sweet spot, that would give me an output speed of 300rpm, and that would make my cycle times
less.
In the next few weeks my rotating fourth axis will become a trunnion table, and then 50:1 or 100:1 would be fine as the axis only rotates +90 to -90 degrees.
New Zealand has a Goods and Services tax that should and usually does apply to all imports of 15%. Some low value items (<$400NZD) come in without GST
but most other items do. For instance I had to pay GST on the servo reducer I pictured. The cost was $180USD, but the shipping cost was nearly the same and with GST
it cost me $635NZD landed at my door. So $180USD sounds pretty good, but the reality is not quite so attractive, but still I'm happy, it is a truly superb piece of
engineering and will serve me well, and that's what I paid for.
Just as a matter of interest while my fourth axis will become a trunnion my C axis will be a B axis if the trunnion is rotated 90 degrees, and that would mean I have
a 6.75:1 reduction between the 'B axis' servo and the chuck for a rotational output speed of 444 rpm, a useful increase which I look forward to to reduce the cycle times
of my 4 axis rotary toolpaths.
Craig