retrofit on EMCO PC turn 55
17 Jun 2012 15:30 #21041
by chuck1024
Replied by chuck1024 on topic Re:retrofit on EMCO PC turn 55
I really do not understand the obsession with reusing the original motors. Most likely it will lead to a lot of wasted time and expense buying and experimenting with hardware that may never be used in the end. Best case ending is OEM performance of 30 IPM which isn't all that great.
Replacing the steppers and using a G540 is a very well defined solution that is very straight forward and easy to implement. The cost is known and the results are predictable and the performance will be double the OEM speeds.
Replacing the steppers and using a G540 is a very well defined solution that is very straight forward and easy to implement. The cost is known and the results are predictable and the performance will be double the OEM speeds.
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17 Jun 2012 15:35 #21042
by andypugh
Replied by andypugh on topic Re:retrofit on EMCO PC turn 55
chuck1024 wrote:
A good point, well argued. The only reason I am suggesting it is that you said that the flange and shaft sizes were not actually NEMA23, and that modifications would be needed.
The three-phase steppers sound like they might be rather nice though.
If I was converting one of these machines (and one was rather tempting me on eBay last week) I think I might look at a servo conversion, rather than swap the steppers. Mainly because I have the servos, though.
I really do not understand the obsession with reusing the original motors.
A good point, well argued. The only reason I am suggesting it is that you said that the flange and shaft sizes were not actually NEMA23, and that modifications would be needed.
The three-phase steppers sound like they might be rather nice though.
If I was converting one of these machines (and one was rather tempting me on eBay last week) I think I might look at a servo conversion, rather than swap the steppers. Mainly because I have the servos, though.
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17 Jun 2012 16:11 #21044
by chuck1024
Replied by chuck1024 on topic Re:retrofit on EMCO PC turn 55
The PC Turn 55 that I converted used 5 wire steppers that looked like NEMA 23 motors but in reality the bolt pattern was slightly different and the shaft size was a little bit smaller. I managed to modify the mounting plates and ream out the pulleys to fit new motors without too much trouble. Jason states that his machine actually has NEMA 23 motor so he won't have to deal with any mods other than drilling a hole in the motor shaft to pin the pulley.
I chose the Keling Inc motors because they can be wired in bipolar parallel for very low inductance which is desireable for driving from the original 24V supply. I kept the original supply because I needed 24V for the tool turret. Without that requirement I would have chosen a higher voltage to insure high speeds. As it turns out, the steppers operate well on 24 v.
It is also important to keep in mind that while 185 oz motors might seem small, I am pretty sure they are substantially stronger than the original motors and there is no reason to push things much further and risk damaging other components such as the lead screws.
I chose the Keling Inc motors because they can be wired in bipolar parallel for very low inductance which is desireable for driving from the original 24V supply. I kept the original supply because I needed 24V for the tool turret. Without that requirement I would have chosen a higher voltage to insure high speeds. As it turns out, the steppers operate well on 24 v.
It is also important to keep in mind that while 185 oz motors might seem small, I am pretty sure they are substantially stronger than the original motors and there is no reason to push things much further and risk damaging other components such as the lead screws.
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19 Jun 2012 04:19 #21079
by jrkeat
Replied by jrkeat on topic Re:retrofit on EMCO PC turn 55
So I went through the stepper board. There are 3 slots for driver cards, two of which are filled (for the X and Z axes).
Of the 16 connections, there are 6 pairs of inputs (2 pairs per axis) that are each differenced, amplified, and sent to the 3 motor cards slots. So persumably these are direction and step.
That leaves 4 connections.
One wire that is directly connected to the same pin on each of the cards--zero ohms. It does not appear to be connected to the power supply. The 3 other lines appear to be buffered outputs, one from each motor card.
Does anyone have a guess about what these 3 outputs and one shared connection would be for?
Of the 16 connections, there are 6 pairs of inputs (2 pairs per axis) that are each differenced, amplified, and sent to the 3 motor cards slots. So persumably these are direction and step.
That leaves 4 connections.
One wire that is directly connected to the same pin on each of the cards--zero ohms. It does not appear to be connected to the power supply. The 3 other lines appear to be buffered outputs, one from each motor card.
Does anyone have a guess about what these 3 outputs and one shared connection would be for?
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19 Jun 2012 05:19 #21082
by PCW
Replied by PCW on topic Re:retrofit on EMCO PC turn 55
enable and fault would be my guess (with one of the two commoned)
(this assumes these signals use a common signal VCC or gnd)
another possibility is that there is just an enable in or fault out per drive
and its isolated, so the signal common is brought out to connect to gnd or +5 or some such
(this assumes these signals use a common signal VCC or gnd)
another possibility is that there is just an enable in or fault out per drive
and its isolated, so the signal common is brought out to connect to gnd or +5 or some such
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19 Jun 2012 14:53 #21103
by jrkeat
Replied by jrkeat on topic Re:retrofit on EMCO PC turn 55
Andy-
Why do you advocate using the Mesa board rather than parallel ports? One parallel port come for free, and extras can be had for about $25, while the Mesa pair 5i25 7i76 cost $200. I suppose that doesn't take care of the VFD control.
Why do you advocate using the Mesa board rather than parallel ports? One parallel port come for free, and extras can be had for about $25, while the Mesa pair 5i25 7i76 cost $200. I suppose that doesn't take care of the VFD control.
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19 Jun 2012 15:00 #21104
by BigJohnT
Replied by BigJohnT on topic Re:retrofit on EMCO PC turn 55
Probably the same reason I like and use the 5i25 7i76 combo for a stepper system for anything beyond an etch a sketch or a low powered hobby machine with no I/O. I have ran my plasma on the parallel port and it might make sense to start there depending on the machine and other considerations. As soon as I started adding things like limit and home switches and probe inputs and.... I quickly ran out of I/O. Just as a note I did not run directly from the parallel port but used a BOB from CNC4PC to safeguard my parallel port and then I needed to add some relays but in the end I was still limited by software step generation speeds limits. So in hind sight I would have been better off to skip step one if only the 5i25 was out then...
John
John
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19 Jun 2012 16:18 #21113
by andypugh
Replied by andypugh on topic Re:retrofit on EMCO PC turn 55
jrkeat wrote:
A parallel port is $25 and a 5i25 is $80. Considering that the 5i25 gives you 2 x 25 pin parallel-port equivalents and also has hardware step generation then I think it is a better investment than a second parallel port.
Hardware step generation is not just about higher maximum step rates, you also gain from a much lower granularity at high step rates. This ought to mean that the peak step rate can be higher. (the worst case with software stepping is when you switch from 1 pulse every 2 base threads to one pulse every thread. That demands an instantaneous doubling of motor speed, which clearly won't happen in the real world.
Add to that the fact that the 5i25 is rated at 25mA per pin whereas a plug-in parallel port might be 3.3V and 3mA source / 15mA sink (if you are unlucky).
The 7i76 is optional, but many people do add a BoB to their parallel port system. These typically cost $50. Again, the Mesa 7i76 is about 3x as expensive. But it does give you a lot more IO pins (48), and those are able to switch 32V @ 300mA, so can drive proper big relays and contactors directly.
As already noted, the 7i76 has a built-in fwd-rev and analogue voltage for VFD control.
I agree that it often makes sense to use just the parport, and it can also make sense to buy a BoB for that parport. But I am less convinced that it makes sense to buy a second Parport and BoB because by that stage you are likely to be working on a more serious machine and are likely to see the advantages of a more capbable IO system such as the Pico PPM or Mesa cards/
I am aware that I sound like a Mesa salesman half the time though.
Why do you advocate using the Mesa board rather than parallel ports?
A parallel port is $25 and a 5i25 is $80. Considering that the 5i25 gives you 2 x 25 pin parallel-port equivalents and also has hardware step generation then I think it is a better investment than a second parallel port.
Hardware step generation is not just about higher maximum step rates, you also gain from a much lower granularity at high step rates. This ought to mean that the peak step rate can be higher. (the worst case with software stepping is when you switch from 1 pulse every 2 base threads to one pulse every thread. That demands an instantaneous doubling of motor speed, which clearly won't happen in the real world.
Add to that the fact that the 5i25 is rated at 25mA per pin whereas a plug-in parallel port might be 3.3V and 3mA source / 15mA sink (if you are unlucky).
The 7i76 is optional, but many people do add a BoB to their parallel port system. These typically cost $50. Again, the Mesa 7i76 is about 3x as expensive. But it does give you a lot more IO pins (48), and those are able to switch 32V @ 300mA, so can drive proper big relays and contactors directly.
As already noted, the 7i76 has a built-in fwd-rev and analogue voltage for VFD control.
I agree that it often makes sense to use just the parport, and it can also make sense to buy a BoB for that parport. But I am less convinced that it makes sense to buy a second Parport and BoB because by that stage you are likely to be working on a more serious machine and are likely to see the advantages of a more capbable IO system such as the Pico PPM or Mesa cards/
I am aware that I sound like a Mesa salesman half the time though.
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19 Jun 2012 21:10 #21124
by BigJohnT
Replied by BigJohnT on topic Re:retrofit on EMCO PC turn 55
Does the 7i78 card work with hostmot2? It is only $69...
John
John
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19 Jun 2012 21:15 #21125
by andypugh
Replied by andypugh on topic Re:retrofit on EMCO PC turn 55
BigJohnT wrote:
It certainly ought to. The devices are self-configuring at the hardware-to-5i25 level.
Does the 7i78 card work with hostmot2? It is only $69...
It certainly ought to. The devices are self-configuring at the hardware-to-5i25 level.
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