@evanh said:
And the motors don't really like it either. The steep slope creates leakage through the bearings, destroying the lubricant.
Wait… say what? I think I’m a about to learn something important here.
Can you explain the bearing issue?
It was an article in a trade rag long time ago when I was contractor. Not sure I read it or just the title but problem will be due to a general capacitive action between the stator's windings and the rotor I guess. The DC bus is earth referenced still so, as the phases are switched, there is steep voltage slopes wrt the earthed motor frame. The bearings become the easiest path for current to flow.
EDIT: Maybe not easiest path but certainly shortest. On that note, I guess an earthed slip-ring hard against both bearings would do a good job of absorbing that current. Not your usual slip-ring application though. It would need to be custom to conduct to the drive shaft like that.
One of our Haas CNC machines was having trouble with encoder readings. We found that the servo drive cable was run in the same wire loom as the encoder feedback cable. We pulled the drive cable out of the loom and it started working correctly. There was apparently inductive coupling from the drive cable into the encoder cable.
On the P2, there are several digital filter settings that can be selected for input pins. They use the HUBSET instruction for configuration. These filter modes could probably help in some cases.
On the P2, there are several digital filter settings that can be selected for input pins. They use the HUBSET instruction for configuration. These filter modes could probably help in some cases.
See #10 and #12 above, it seems that in actual use, the filter modes do not just help, they are important to get a working solution.
Which is curious, as they should not be mandatory ?
It was an article in a trade rag long time ago when I was contractor. Not sure I read it or just the title but problem will be due to a general capacitive action between the stator's windings and the rotor I guess. The DC bus is earth referenced still so, as the phases are switched, there is steep voltage slopes wrt the earthed motor frame. The bearings become the easiest path for current to flow.
EDIT: Maybe not easiest path but certainly shortest. On that note, I guess an earthed slip-ring hard against both bearings would do a good job of absorbing that current. Not your usual slip-ring application though. It would need to be custom to conduct to the drive shaft like that.
On the P2, there are several digital filter settings that can be selected for input pins. They use the HUBSET instruction for configuration. These filter modes could probably help in some cases.
See #10 and #12 above, it seems that in actual use, the filter modes do not just help, they are important to get a working solution.
Which is curious, as they should not be mandatory ?
In theory, it should be not required. We added these digital filter modes because we saw that other motion-control chips had them, too. In practice, they may be kind of necessary.
On the P2, there are several digital filter settings that can be selected for input pins. They use the HUBSET instruction for configuration. These filter modes could probably help in some cases.
See #10 and #12 above, it seems that in actual use, the filter modes do not just help, they are important to get a working solution.
Which is curious, as they should not be mandatory ?
That's just some hokey Chinese contraption...with a switch! How is "Clk" and "Dt" even quadrature? Does it have mechanical indents? Is it even optical?
Actually it was yours-truly who originally suggested the filtering and yes, because dedicated motion chips and quadrature-counting chips have this. I haven't (knowingly) ever used filtering but I might as well, from now on
The base frequency of the 3-phase voltages driving the motor cancel each other out according to Kirchhoffs law. So if you run a motor with perfectly sinusodial waveforms the bearings will see zero current. However, the 3rd, 5th .... overtones of the three motor termnals are in-phase. Together with the stray capacitance of the rotor windings they produce a non-zero voltage accross the bearings. The voltage is usually rather low but as the resistance also is low a considerable current can flow through the contact areas of the balls to the bearing rings. This gets worse the higher the frequency and the dV/dT slope is.
The contact area of a ball to a flat surface is small and it can even skid on the grease or oil layer at higher speeds causing arcing. The arcing can lead to decomposition of the grease altering its chemical properties and cause corrosion.
@cgracey said:
One of our Haas CNC machines was having trouble with encoder readings. We found that the servo drive cable was run in the same wire loom as the encoder feedback cable. We pulled the drive cable out of the loom and it started working correctly. There was apparently inductive coupling from the drive cable into the encoder cable.
Hey Chip
Intuition tells me that the real problem is elsewhere and all you have done is aleviate something.
Haas ships an awful lot of product (I had the first VF-10 in MI and a HL-4) and they are generally rock-solid
Power cables very much can interfere when laid in tidy bundles with data/signal cables. Speculating ... The strong magnetics from high current possibly can impact the shielding of the data cables which, in turn, somehow impacts data integrity. Maybe as simple as creating a ground differential.
@evanh said:
Power cables very much can interfere when laid in tidy bundles with data/signal cables. Speculating ... The strong magnetics from high current possibly can impact the shielding of the data cables which, in turn, somehow impacts data integrity. Maybe as simple as creating a ground differential.
As feedback signals that are critical to functioning are to be transmitted with the new trend in
single-cable connection technology, increasing importance is placed in the issue of shielding
and compensation with this installation technology. Powercables that have been established
to date are therefore not to be taken into consideration. Instead, specially shielded cables
with modified impedances are used.
Smart Feedback Device developed around ten years ago, the inexpensive yet robust technology becomes a digital feedback system with 24Bit resolution on the motor and regulator. The main task of the digital resolver (SFD interface) is to convert the analog encoder information internally into an interference resistant, purely digital RS-485 signal.
The problem that I have with this stuff is that you are tied to them. I recently had a customer with a dead encoder. Now a regular incremental unit, I can have the next day but this was a Profibus device and the machine was down for six weeks waiting for a replacement.
The problem that I have with this stuff is that you are tied to them. I recently had a customer with a dead encoder. Now a regular incremental unit, I can have the next day but this was a Profibus device and the machine was down for six weeks waiting for a replacement.
Craig
The industry has a long time solution for this. It's called a spare parts package. It also involves the customer not abusing their OEM relationships. I stocked long lead parts best I could, despite constant threats from management and overzealous inventory sweeps from accounting.
I agree, you don't just wave a magic wand or go down to the local hardware store to get any of this automation stuff. The customers that don't get this, don't deserve to be this business. As you can surmise, I'm more than calloused about lack of preparation and a victim mentality.
As feedback signals that are critical to functioning are to be transmitted with the new trend in single-cable connection technology, increasing importance is placed in the issue of shielding and compensation with this installation technology. Powercables that have been established to date are therefore not to be taken into consideration. Instead, specially shielded cables with modified impedances are used.
Smart Feedback Device developed around ten years ago, the inexpensive yet robust technology becomes a digital feedback system with 24Bit resolution on the motor and regulator. The main task of the digital resolver (SFD interface) is to convert the analog encoder information internally into an interference resistant, purely digital RS-485 signal.
Impressive. Looks like they are employing every technique to achieve it. Including full balanced electrical isolation using a DC/DC converter.
I sense that this is more to do with the Kollmorgen marketing guys than engineering.
There is a never-ending debate, out there, regarding common-ground/no common-ground between RS485 devices.
The only thing different here is the "special Kollmorgen hybrid cable".
They haven't depicted the terminating resistor but that's probably too much detail for this illustration, anyway.
Craig> @whicker said:
@Mickster said:
The problem that I have with this stuff is that you are tied to them. I recently had a customer with a dead encoder. Now a regular incremental unit, I can have the next day but this was a Profibus device and the machine was down for six weeks waiting for a replacement.
Craig
The industry has a long time solution for this. It's called a spare parts package. It also involves the customer not abusing their OEM relationships. I stocked long lead parts best I could,
Doesn't work.
Going off of 1988 numbers, a line going down at GM cost $1M/hour. In this context, define "long lead". At some point, replicating the whole production line as a backup would make sense.
Not much is fixable any more. How many times did Radio Shack help bail me out on a Sunday morning when a line went down...plenty
Those were the days
My customers receive a "care-package" without even knowing it because if I made it a "spares option", they wouldn't go for it. It's no big deal in the grand scheme of things. The spare P2-Edge module is the priciest item. I don't use surface-mount I/O buffers because socketed devices are easily swappable.
I can just imagine it:
Kollmorgen marketing: Guys, no-one understands what a watchdog relay is...the key word here needs to be "safety" and so we're gonna rename it to a "SIL3 Safety Technology Module"
Yup, and electrical isolation make that work best by allowing the common mode volts to swing much further. That's how come Ethernet can tolerate so much. The high frequency transformers are a natural fit.
I just want to run a DC bus throughout the machine, period. Drivers can be very compact and can be situated on or near each motor....along with a P2 (bit criminal to dedicate a P2 to just one axis).
Commands to be a wireless mesh network.
The big name (sheep) can continue with their ETHERCAT nonsense.
Comments
It was an article in a trade rag long time ago when I was contractor. Not sure I read it or just the title but problem will be due to a general capacitive action between the stator's windings and the rotor I guess. The DC bus is earth referenced still so, as the phases are switched, there is steep voltage slopes wrt the earthed motor frame. The bearings become the easiest path for current to flow.
EDIT: Maybe not easiest path but certainly shortest. On that note, I guess an earthed slip-ring hard against both bearings would do a good job of absorbing that current. Not your usual slip-ring application though. It would need to be custom to conduct to the drive shaft like that.
One of our Haas CNC machines was having trouble with encoder readings. We found that the servo drive cable was run in the same wire loom as the encoder feedback cable. We pulled the drive cable out of the loom and it started working correctly. There was apparently inductive coupling from the drive cable into the encoder cable.
On the P2, there are several digital filter settings that can be selected for input pins. They use the HUBSET instruction for configuration. These filter modes could probably help in some cases.
See #10 and #12 above, it seems that in actual use, the filter modes do not just help, they are important to get a working solution.
Which is curious, as they should not be mandatory ?
Something like this?
https://emersonbearing.com/wp-content/uploads/BPK-S-500x414.jpg
P.S. some references says they can't be used in Clean Room applications, but there must be many other solutions for such cases...
In theory, it should be not required. We added these digital filter modes because we saw that other motion-control chips had them, too. In practice, they may be kind of necessary.
That's just some hokey Chinese contraption...with a switch! How is "Clk" and "Dt" even quadrature? Does it have mechanical indents? Is it even optical?
Actually it was yours-truly who originally suggested the filtering and yes, because dedicated motion chips and quadrature-counting chips have this. I haven't (knowingly) ever used filtering but I might as well, from now on
Craig
The base frequency of the 3-phase voltages driving the motor cancel each other out according to Kirchhoffs law. So if you run a motor with perfectly sinusodial waveforms the bearings will see zero current. However, the 3rd, 5th .... overtones of the three motor termnals are in-phase. Together with the stray capacitance of the rotor windings they produce a non-zero voltage accross the bearings. The voltage is usually rather low but as the resistance also is low a considerable current can flow through the contact areas of the balls to the bearing rings. This gets worse the higher the frequency and the dV/dT slope is.
The contact area of a ball to a flat surface is small and it can even skid on the grease or oil layer at higher speeds causing arcing. The arcing can lead to decomposition of the grease altering its chemical properties and cause corrosion.
Hey Chip
Intuition tells me that the real problem is elsewhere and all you have done is aleviate something.
Haas ships an awful lot of product (I had the first VF-10 in MI and a HL-4) and they are generally rock-solid
Craig
Power cables very much can interfere when laid in tidy bundles with data/signal cables. Speculating ... The strong magnetics from high current possibly can impact the shielding of the data cables which, in turn, somehow impacts data integrity. Maybe as simple as creating a ground differential.
Ah-ha...They call it "detent"....There's the reason for needing filtering
Craig
I'm gonna guess that is optical serial.
single-cable connection technology, increasing importance is placed in the issue of shielding
and compensation with this installation technology. Powercables that have been established
to date are therefore not to be taken into consideration. Instead, specially shielded cables
with modified impedances are used.
The problem that I have with this stuff is that you are tied to them. I recently had a customer with a dead encoder. Now a regular incremental unit, I can have the next day but this was a Profibus device and the machine was down for six weeks waiting for a replacement.
Craig
The industry has a long time solution for this. It's called a spare parts package. It also involves the customer not abusing their OEM relationships. I stocked long lead parts best I could, despite constant threats from management and overzealous inventory sweeps from accounting.
I agree, you don't just wave a magic wand or go down to the local hardware store to get any of this automation stuff. The customers that don't get this, don't deserve to be this business. As you can surmise, I'm more than calloused about lack of preparation and a victim mentality.
Impressive. Looks like they are employing every technique to achieve it. Including full balanced electrical isolation using a DC/DC converter.
I sense that this is more to do with the Kollmorgen marketing guys than engineering.
There is a never-ending debate, out there, regarding common-ground/no common-ground between RS485 devices.
The only thing different here is the "special Kollmorgen hybrid cable".
They haven't depicted the terminating resistor but that's probably too much detail for this illustration, anyway.
Craig> @whicker said:
Doesn't work.
Going off of 1988 numbers, a line going down at GM cost $1M/hour. In this context, define "long lead". At some point, replicating the whole production line as a backup would make sense.
Not much is fixable any more. How many times did Radio Shack help bail me out on a Sunday morning when a line went down...plenty
Those were the days
My customers receive a "care-package" without even knowing it because if I made it a "spares option", they wouldn't go for it. It's no big deal in the grand scheme of things. The spare P2-Edge module is the priciest item. I don't use surface-mount I/O buffers because socketed devices are easily swappable.
Craig
I can just imagine it:
Kollmorgen marketing: Guys, no-one understands what a watchdog relay is...the key word here needs to be "safety" and so we're gonna rename it to a "SIL3 Safety Technology Module"
Craig
True. And the data pair shielding is not shown either. And that definitely should be indicated.
If I only saw the top trace, I'd believe that I was in serious trouble:
https://ti.com/lit/an/snla049b/snla049b.pdf
Craig
Yup, and electrical isolation make that work best by allowing the common mode volts to swing much further. That's how come Ethernet can tolerate so much. The high frequency transformers are a natural fit.
I wanna go one better than all of this nonsense
I just want to run a DC bus throughout the machine, period. Drivers can be very compact and can be situated on or near each motor....along with a P2 (bit criminal to dedicate a P2 to just one axis).
Commands to be a wireless mesh network.
The big name (sheep) can continue with their ETHERCAT nonsense.
Craig