Maybe a Q for greatoldone! But sounds like you're on the road, makes me question the need for a servo. At 36 '' per minute carriage travel, thats not slow!
Btw, What is the overall dia of ur leadscrew?
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electronic lead screw
- Thread starter greenail
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Btw, What is the overall dia of ur leadscrew?
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My lead screw diameter is .792". I'm curious as to why you ask.
My lathe maxes out at 2400 rpm although I seldom operate above 750 rpm. At 2400 rpm and .040"/rev, that's almost 100 ipm. That would be around 2300 rpm from the stepper but it's crazy fast. A more reasonable maximum for me would be 750 rpm and .020"/rev. for 15 ipm and 360 stepper rpm. Even that is probably more than the spindle motor can handle.
With the closed loop hybrid stepper, the servo offers little advantage. It has a flatter torque curve but servos provide less torque for a given size.
Oh, OK, will fit an amt102 encoder to my dual shaft stepper then, cheers!
My leadscrew is 22 mm, or imperial equiv, so ½nut drag / friction overhead greater than yours.
well slightly, i mean!
its a 7/8" shaft but a bit of meat lost when made, so ended up at 22.16mm.
i suppose the angle of attack of the tool for a given material would impact on carriage loading too.
rewatched part 4, Clough's alarm led on, he power cycles to reset. But dunno if he monitors it.
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On my driver, when it lost steps, the lost step led came on but as long as the motor's lost steps had not exceeded the preset(and unknown) threshold ,the feedback loop tries to compensate and the motor continues. When the threshold is exceeded the driver shuts down and presumably sends the alarm to the controller. The driver then has to be power cycled to resume. The controller has no mechanism to shut the driver down having only PUL, DIR, and EN inputs. I haven't tested the enable function but I suspect that it just inhibits the movement of the motor and doesn't shut the driver down.
Since the driver would most likely be buried in a control cabinet, it would be difficult to see the flashing LED. Having an external signal for the user would be a plus. I would guess that the alarm function would just be used to display the the error on the user control panel. Since Clough has no individual LED for alarm, it would have to be displayed on the seven segment display; something like flashing all the decimal points in synchronization with the driver LED or trying to spell out the condition with the display limited alphanumeric capability. The curiosity is that Clough recommended leaving the USE_ALARM_PIN enabled in his video #10. I would think he would have disabled it until he had built in the functionality.
I haven't seen an over current or over voltage alarm yet so I don't know how the driver reacts. According to the manual, the driver shuts down and has to be powered down to resume. On lost steps, it flashes six times, not seven. I counted the three times to be sure that I was counting right. If the threshold is exceeded the driver shuts down. This happened when I changed from forward to reverse at a fairly high leadscrew rpm. Then I have to power down the driver to resume operation.
I think the force presented to the carriage during turning will depend on a lot of factors besides material, depth of cut, and feed/rev. Certainly a dull tool will require much greater force. I am not sure of a good way to assess this quantitatively. A dynamometer on the lead screw or load cell directly driving the carriage. As a rough estimate, the crank on my lathe is on a 3.5" circle so each revolution of the crank travels 3.5 x π" or 11". 18 full turns of the crank moves the carriage 17" so the mechanical advantage of the crank is 11 x 18/17 or 11.6. Neglecting friction, one lb. of force applied to the crank will produce 11.6 lbs. of force at the carriage.
Yes agree with all stated re Alarm situ.
Maybe a word to Clough via his site may prompt a clarification re enabling the alarm status.
I am surprised clough's f/w allows a sudden reversal without a deceleration ramp, then stopping first!
Seeing that U already are set up, is there a need for rigorous measurements? Maybe just find a real world fail threshold, then address it.
Certain jobs I have avoided / wont do so wont need the HP to cut, one being course threading of stainless steel.
(Briney eye will probably gonna do a load cell/ strain gauge test on his carriage, later on.)
Rocketronics video of a vicious cut shows absurdly fast, deep low pitch cutting; you may have seen it. But its in aluminium AFAIK.
Thankyou RJ, for the specifics re 6x flash, lost steps
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I had some question regarding the alarm and enable settings. I left both as they were in the default settings (#define INVERT_ENABLE_PIN true and #define INVERT_ALARM_PIN true).
From the driver manual, I can leave the enable pins unconnected which from their circuit diagram would imply that enabled operation occurs with zero volts across the inputs. Given that Clough has tied all three + pins and assuming that he used the same configuration as in #4 video, and the software settings use negative logic, I should measure 0 volts across the enable pins . I actually measured 3.48 volts. It may be that Clough leaves the driver disabled except when he is sending step and direction. I'll have to check that further. ( Maybe time to pull out the scope.)
I measured 3.29 volts across the alarm pins which is probably acceptable. Just considering my 5.2 volt supply and the two 10K resistors in Clough's drawing, the voltage would be be 2.6 but adding in the LED voltage drop in the optoisolator would bring the voltage near my measured voltage. Allowable tolerances for the resistors could make up the difference. However, from the software settings, 0 volts should be true which is the opposite of what I see. I need to do some further investigating to clear this in my head.
I was hoping to use the enable signal to turn off the driver when I am not using the lead screw. I will probably just cut the power to the driver instead.
From the driver manual, I can leave the enable pins unconnected which from their circuit diagram would imply that enabled operation occurs with zero volts across the inputs. Given that Clough has tied all three + pins and assuming that he used the same configuration as in #4 video, and the software settings use negative logic, I should measure 0 volts across the enable pins . I actually measured 3.48 volts. It may be that Clough leaves the driver disabled except when he is sending step and direction. I'll have to check that further. ( Maybe time to pull out the scope.)
I measured 3.29 volts across the alarm pins which is probably acceptable. Just considering my 5.2 volt supply and the two 10K resistors in Clough's drawing, the voltage would be be 2.6 but adding in the LED voltage drop in the optoisolator would bring the voltage near my measured voltage. Allowable tolerances for the resistors could make up the difference. However, from the software settings, 0 volts should be true which is the opposite of what I see. I need to do some further investigating to clear this in my head.
I was hoping to use the enable signal to turn off the driver when I am not using the lead screw. I will probably just cut the power to the driver instead.
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Am glad U are diving into all this, THANKYOU!! these details are not covered by Clough.
afaik, when enable pin is hi, in this setup, the H bridge is floating, so no stepper coil currents flow,, except, If the stepper is already in motion, & the drive is suddenly not enabled, (or disabled), the stepper back-emf will be dissipated by the bridge (intrinsic fet diodes or better, external fast diodes) & power supply rail protection diodes, as a recirculating current. Whether these diodes exist or not is unknown to me. But, they should be fitted if the manufacturer has scruples!
BTW, and this may not be pertinent to your drive type,
there is a warning i read somewhere re the low cost TB6560 ( https://www.ebay.com.au/itm/TB6560-...ngle-1Axis-Controller-Stepper-Motor-Drive-cw/) and this family of drives,
that the powering up & down sequence should be done in the correct order so as to not have the driver powered up without its inputs from the pc, or other signal source present first, vague memory here, sorry but cant clarify further. But U may know more..
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I'll have to try to deactivate the enable input to see if there really is no stepper current. The manual says nothing about the enable signal other than it must be activated at least 5 µsec before the direction signal or step signal. The controller is sending out a pulse stream whenever the lathe spindle is turning. The simpler approach will be to power down the driver after stopping the spindle. So far, that hasn't caused any problems shutting down either controller or driver first.