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beegee

JUNMA Servo and safety

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Has anyone used Junma Servos on a system? The problem is you have a Estop input, but there is no info whether it is consistent with any safety class. If you just cut the power (what we used to do with a Sigma II) the controller of the servo looses power too. So you loose your position at E-stop. This is in certain case not that interesting taking into account that in my applications different axes can interfere, so startup/origin search has to be done with help of the operator (step by step). If I keep my positions in the controller I only have to do this after a power up. anyone any suggestions/experience how to solve this? Beegee

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You can use servo motor model with brake. one you cut the power to the driver the motor stop in his last position. J.bmp

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That gives you an approximate position: the brake is only a static brake and the motor first stops using dynamic braking, which isn't controlled. so yo can know it (depending on the application) probably within 10 mm. I will still have to do an origin search afterwards. (we move on an 400mm axis with more than 2 m/sec) I'm stiil waiting for an answer about the safety class from Omron, but I fear I will have to be very creative.

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I don't think the estop input is actually 'emergency stop'. It's only single channel. I think this is one of the 'features' of a cheap servo system. Are you using the pulse or ML2 version?

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Yes I am, together with a Trajexia....

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The E-stop has no safety category because it is done in software. A sollution can be to use a contactor between drive and motor and use a safety relay with delayed contacts. You then use the E-stop to stop the motor (goes into baseblock) and then you can cut the power between Drive and motor at reset you will have to perform a clear drive and clear the following error (datum(0) in Trajexia) to eliminate the errors. I still have to check what's happening with power cuts but this could be a solution for Junma end safety issues while still having your encoder values

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Junma Drives have one input called E-Stop. However according to manual the drive is not certified for STO (Stop Category 0), according EN standards. If you are targeting an EN-954 CAT 3 or higher, STO, you will need additional contactors (TWO) between Amplifier and Motor. (I assume you have Safety Relay in your machine). If you don't want to use Additional contactors, you have the chance to use Sigma II (-F) which is compliant with STO according to NE standards. (2 Emergency inputs and EDM Outputs). According to the web (google), the next generation of OMRON-YASKAWA drives (SIGMA V) has embedded safety for all sizes.

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What you're telling is true but the price implication of changing over to Sigma-II are quite big for a machine builder. The additional problem you have by cutting power between Junma drive and motor are that you have to take special precautions for power interruptions during operation. You could cut the current before the drive goes into base block

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It is clear that Sigma II is more expensive than Junma series, therefore has more features, in this specific topic EN-954 certification for Safe Stop. (-F series) The principle of safety is to achieve Safe systems. I've seen a lot of machines where power is CUT before the Amplifier, of course in the past it was cheapper and easier than putting a well dimensioned 2 contactors between Drive and Motor. But in this case, machine designe MUST ensure that Actuator (Motor) is not receiving power from motor before operator is allowed to enter into hazarous area. I'm quite PRO Junma, since this is the 1st really PLUG'n'PLAY servo that I've ever seen (tuningless algorithm). Also performance/price is really GOOD.

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