Hi,
I think the frame is a 'standard' size, just what standard...its the great thing about standards is that there is so many to choose from!
You are right, 3000 rpm is a common rated speed for servos in this power output. There are a number of manufacturers who regularly produce
fast servos, Baldor comes to mind. They tend to be expensive tho. While Baldor servos can be had on Ebay pretty cheap the drives are
eye-wateringly expensive, Baldor is owned by ABB and they traditionally are really expensive, I avoid ABB on principle!
The Allen Bradley servo I bought is rated to 3500 rpm. Its listed max is 5000 rpm but without trying to hoodwink the servodrive software I cant
get it to go beyond 3500 rpm. The extra speed would be nice for 1/4 inch tools but I'm not stressing, this is a hobby machine, if a job takes an extra
5 min then so be it.
I would suggest that you consider the price of a replacement spindle motor be the cost of the combined motor and drive. Depending on the
sophistication of a DC drive it may tip the total cost to be more than an AC servo and drive. An asynchronous AC motor (ie induction motor) and
matching VFD will be cheaper than any servo but probably 50% bigger for the same power.
As far as servos go... there are servos and servos! Some brands like Fanuc and Seimens are just over the top price wise and then there are brands like
Baldor and Allen Bradley and many other US or European brands which are just expensive. Delta servos from Taiwan have a good reputation and are
well priced, not bargain basement but not bad. There are cheaper Chinese brands and a lot of those have been rebranded to sound US/European and
for hobbyists probably good enough.
The further you get from known brands the more online research you should do BEFORE you stump up your cash, once they've got your money
its too late for you to decide that the unit is not good enuf!
The range of control strategies is so broad that its hard to specify beforehand. I personally have found that very simple speed control is adequate.
I will at some stage use position control for indexable operations like rigid tapping, that capability is built in and just waiting to be used.
I note that in your original post that you have a USS. At the current time the ESS has a Mach4 plugin but the USS does not. Warp9 are working on
producing a Mach4 plugin for the USS but you may be frustrated waiting. I use an ESS/Mach4 and VERY happy with it.
Craig