The Best Steppers/Servos Setup Thread

[Zeeflyboy]

are they actually proper servo's or "Chinese" servos?

the price is great, cheaper than I was expecting to pay for a new setup and if they work well then excellent

http://www.ebay.co.uk/itm/CNC-Leadsh...c=1&rmvSB=true

They aren't servos at all, they are closed loop steppers...

Jazz - all very well saying don't be fooled by that link, but I have yet to see any quantitive testing that shows there is no or very little difference between closed loop and open loop steppers... all the comparisons I have seen have shown them to be superior. Have you come across any evidence to support the assertion that there are open loop systems that can get close to the efficiency of a closed loop system? The 3 phase ones also have a higher resolution at 1.2 degrees per step rather than the 1.8 of most 2 phase steppers, which is about a 30% improvement.

As for being able to use higher voltage, the model he linked to is also rated to 2,000rpm - higher voltage is unlikely to help you get beyond that speed on traditional drives I would say? The closed loop steppers manage to maintain higher torque at high speeds too when compared to open loop which is useful to consider when talking about performance at higher speeds.

As to the playing catch up - it really depends on what you are making and where the problem occurs. Lets say your g-code has a slight blip and you lead out from a contouring cut into a full depth cut of the surrounding stock (it's happened to me!) - were open loop steppers to lose some steps from that they would then go on to ruin your work piece where the closed loop would have caught back up before it even moved to the next operation... also depending on the work and the point that it happens, a small defect may be acceptable (or may not even show on the final piece if it happened while clearing or doing any work away from a final contour or surface) and the rest of the operation would still be dimensionally correct. Lost steps would go on to offset the entire work from then on and completely ruin the whole piece.

As I said, if you just view them as normal steppers I think they are a good choice, and arguably one of the better choices if staying with steppers. They aren't really that much more expensive than good digital drives and decent quality stepper motors but do honestly have some advantages too so if the extra expense isn't an issue then I don't see why you shouldn't consider them among your options. Personally I just consider them as a high end stepper system, and they've fulfilled all my expectations so all I can say is I've been very happy with them