Synchronous Motion Linear Motor Questions - Page 2
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  1. #21
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    Quote Originally Posted by Johnny SolidWorks View Post
    Hey Motion - do the motors you guys are using having built-in e-stop functionality/programming? The vendor it was decided for me to work with has essentially told us that in the event of an e-stop, their drives will just drop power, meaning the linear motor motions will either drop (vertical) or 'coast' to a hardstop (horizontal.) This seems kind of unacceptable to me.

    And in the event of a total system power drop (i.e. plant power outage) do you guys have brakes built it? Linear rail brakes maybe? The problem with our application is the linear rail brakes don't have nearly enough braking force to stop the motion, so I'm essentially looking at building a custom e-stop/power-drop brake that can stop our system and still be manually overridden for maintenance, etc.
    Great question -

    Generally, we use a Siemens Line module and all drives are common bussed - we fit a VSM (Voltage Sense Module) to the system and program it such that if the VSM detects a power loss condition then we take the highest inertia load that is presently in motion and allowed to continue moving and that immediately becomes the "Generator" and we program it to decelerate at a relatively aggressive rate that is sufficient to keep the system alive as kinetic energy is converted to electrical energy.

    The electrical energy is then used to withdraw the cutting tool / grinding head / whatever from the part being machined and brought to a controlled stop then brakes are set and the system dies.

    We recently designed a Herkules Grinder retrofit that did cylindrical grinding of rolls to 30 tons . . . the grinding head and motor had enough stored energy when running at speed that we could keep the system alive for 30 second which allowed us to retract the grinding head and park it and bring the machine to an orderly stop. It was a lot of fun during testing to throw the disconnect and watch how the machine responded - the grinding head immediately retracted and parked while the spindle decelerated. The HMI had a Power Loss Alarm message and then stepped through the state logic messages before it finally went blank. Our 24VDC power supply was also fed from the common bus so we could keep the PLC, Motion Controller, and HMI all up during this shut down period.

    We typically rely on dynamic regenerative braking in all of our systems and any holding brakes are for after the system is stopped. In an E-Stop condition, we typically will command an immediate decel to stop (controlled) followed by a safe torque off. (all systems we do have safety rated stop modes that are designed in accordance with whatever stop mode is required through the HIRA study)

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  3. #22
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    Quote Originally Posted by Johnny SolidWorks View Post
    Hey Motion - do the motors you guys are using having built-in e-stop functionality/programming? The vendor it was decided for me to work with has essentially told us that in the event of an e-stop, their drives will just drop power, meaning the linear motor motions will either drop (vertical) or 'coast' to a hardstop (horizontal.) This seems kind of unacceptable to me.
    Can you integrate gas springs or similar as counterbalances to vertical loads? If the motion profiles are not so energetic that they overheat or wear out the springs it would make the system much safer in the even of power loss or an E-stop override.

  4. #23
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    Quote Originally Posted by motion guru View Post
    Great question -

    Generally, we use a Siemens Line module and all drives are common bussed - we fit a VSM (Voltage Sense Module) to the system and program it such that if the VSM detects a power loss condition then we take the highest inertia load that is presently in motion and allowed to continue moving and that immediately becomes the "Generator" and we program it to decelerate at a relatively aggressive rate that is sufficient to keep the system alive as kinetic energy is converted to electrical energy.

    The electrical energy is then used to withdraw the cutting tool / grinding head / whatever from the part being machined and brought to a controlled stop then brakes are set and the system dies.

    We recently designed a Herkules Grinder retrofit that did cylindrical grinding of rolls to 30 tons . . . the grinding head and motor had enough stored energy when running at speed that we could keep the system alive for 30 second which allowed us to retract the grinding head and park it and bring the machine to an orderly stop. It was a lot of fun during testing to throw the disconnect and watch how the machine responded - the grinding head immediately retracted and parked while the spindle decelerated. The HMI had a Power Loss Alarm message and then stepped through the state logic messages before it finally went blank. Our 24VDC power supply was also fed from the common bus so we could keep the PLC, Motion Controller, and HMI all up during this shut down period.

    We typically rely on dynamic regenerative braking in all of our systems and any holding brakes are for after the system is stopped. In an E-Stop condition, we typically will command an immediate decel to stop (controlled) followed by a safe torque off. (all systems we do have safety rated stop modes that are designed in accordance with whatever stop mode is required through the HIRA study)
    That's very slick.

    Do you use the Siemens fail-safe I/O modules where you can run e-stop buttons and other safety I/O through the CNC I/O instead of needing a hardware e-stop loop, relays, etc.? This always looked like something that could simplify the wiring immensely.

    The Siemens gear always seemed to have a lot of powerful functionality. Unfortunately, the only Siemens projects I ever worked on were driven by Technology PLCs. That bit of hardware is god-awful; I'm very glad it's discontinued now so no one else has to suffer through it.

  5. #24
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    Quote Originally Posted by motion guru View Post
    Great question -

    Generally, we use a Siemens Line module and all drives are common bussed - we fit a VSM (Voltage Sense Module) to the system and program it such that if the VSM detects a power loss condition then we take the highest inertia load that is presently in motion and allowed to continue moving and that immediately becomes the "Generator" and we program it to decelerate at a relatively aggressive rate that is sufficient to keep the system alive as kinetic energy is converted to electrical energy.

    The electrical energy is then used to withdraw the cutting tool / grinding head / whatever from the part being machined and brought to a controlled stop then brakes are set and the system dies.

    We recently designed a Herkules Grinder retrofit that did cylindrical grinding of rolls to 30 tons . . . the grinding head and motor had enough stored energy when running at speed that we could keep the system alive for 30 second which allowed us to retract the grinding head and park it and bring the machine to an orderly stop. It was a lot of fun during testing to throw the disconnect and watch how the machine responded - the grinding head immediately retracted and parked while the spindle decelerated. The HMI had a Power Loss Alarm message and then stepped through the state logic messages before it finally went blank. Our 24VDC power supply was also fed from the common bus so we could keep the PLC, Motion Controller, and HMI all up during this shut down period.

    We typically rely on dynamic regenerative braking in all of our systems and any holding brakes are for after the system is stopped. In an E-Stop condition, we typically will command an immediate decel to stop (controlled) followed by a safe torque off. (all systems we do have safety rated stop modes that are designed in accordance with whatever stop mode is required through the HIRA study)
    That is very, very clever. I'm going to send you an email to discuss some things offline, but thanks for being willing to share this approach!


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