Testing servos/Drives UPDATE

Since I fully gutted the cabinet and removed all inside wiring (but not wires coming from the outside to the huge terminal block), I was
able to test more stuff.
I did test the X-Y servo motors last night by just applying voltage to their DC leads. They moved nicely. At 30 volts incoming, the X-Y table moved at about 1 inch per second, and the motors consumed appx. 1.3 amps.
What this tells me is that the mill is not "broken" (no surprise here), and also that 80 volts and 20 amps total capacity of my power supply, should be plenty for my light home use hobby purposes.
What I will do, for now, is just make a convenient terminal block on the outside of the mill, so that I could move X,Y,Z by applying DC voltage to these terminals.
I will hopefully get to that tonight. Also tonight, I will start making aluminum adapter plates for the US digital encoders.
The next step would be to connect encoders to Jon's motion controller, apply voltage to DC motors and see encoder data displayed on the PC.
I will try to spend a long time without hooking up servo drives, to wire and program as much as possible of safety related stuff (limits, estop etc). My own hands will be motor controllers, so to speak.
With the encoders working, and hand motor control, this will be actually a fully working semi-manual mill!
i
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Iggy, you're likely to end up like me. I enjoy making old iron better than new so much that this has become my metalworking hobby. Looks like you're headed toward a wonderful machine for less than $1K out of pocket.
Karl
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I think so too.
Now, do you think that I am on the right track with my plan to implement everything except servo drives first, and wait with servo drives until everything else has been debugged? Does that make sense?
i
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Ignoramus3037 wrote:

Not really, being able to move the machine axes under CNC control is pretty integral to testing and debugging everything else. Since it's already a CNC machine, you already have limit switches in the appropriate places already, so the only debugging involved will be configuring the control software to know where to find those inputs. Control of outputs such as coolant and spindle control is similarly easy.
There really isn't that much "everything else", the servos are the bulk of a basic CNC mill beyond the control. The rest is six limit switches, a coolant pump relay, and spindle control which could be a serial connection to the VFD or fwd / rev signals and a speed voltage.
I don't recall your mill having an ATC, but if it does, ignore it until you get the rest working properly.
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On 06/15/2010 10:33 AM, Ignoramus3037 wrote:

If you were an experienced engineering team designing NC mills for a living -- maybe not. You should know enough to do a few preliminary tests, make some claims based on similarity to previous products, and smoke test early. OTOH, even in a commercial setting it's not a bad way to go, and certainly what many teams do after the initial test lets out too much magic smoke.
Since you're an individual, I think you're on a very good track. Maybe not the _best_ track, but certainly a very good one.
--
Tim Wescott
Control system and signal processing consulting
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I am trying to think like a computer programmer. Get a framework in place first and make sure that it is safe. Then add more risky stuff.
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Ignoramus3037 wrote:

The key thing with the servos is to disconnect the motors from the machine when first setting them up so a runaway from a servo loop issue only results in a whirring motor. Once the servo is setup with a stable loop and able to hold position when you manually twist the motor shaft then it's safe to connect the machine and work on the fine tuning.
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Great point.
i
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