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Absolute Encoder position Lost After Power Off

Created by: Muthukumar at: 8/24/2012 8:47 AM (6 Replies)

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8/24/2012 8:47 AM	Rate (0)
Muthukumar Posts: 15 Rating: (0)	Hi.... I am doing a retrofitting work of machine with 840D. The machine is having 7 axes. the configuration is as follows. 1.E/R Module - 36/47 KW 2.NCU 3.Single Motor Module - 108A 4.Double Motor Module - 250A 5.Double Motor Module - 250A 6.Monitering Module - 6SN1112-1AC01-0AA1 7.Double Motor Module - 28A 8.HLA Module. In the second axis of first double motor module and both the axes of 28A double motor modulei am using External Absolute rotary encoder(Siemens make). Encoder Details: Part Number - 6FX2001-5HE13(Resolution 13bit, pulse-512,Single Turn,8192 steps/rev,Endat) Control card Details: Part Number - 6SN1118-0DM33-0AA2(for all the three axes) NUC version - NCU573.5. HMI Version - 07.05.03.00 pl find the attached NC backup also. i have enabled the additional encoder in Axis no 3. Note: the additional encoder is mounted on the motor shaft itself. the lead screw pitch is 5mm. My problem is everytime i power off and on, the encoder is showing different values. but the ref point is not getting lost and the value of parameter 34210- ENC_REF_POINT_STATE is 2 only. pl give me a solution to solve this problem. thanks, muthukumar k. Attachment 1234.pdf (395 Downloads)
Muthukumar Posts: 15 Rating: (0)
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8/27/2012 4:27 PM	Rate (0)
Ekalavya Posts: 2964 Rating: (484)	Muthukumar Hi.... I am doing a retrofitting work of machine with 840D. The machine is having 7 axes. the configuration is as follows. 1.E/R Module - 36/47 KW 2.NCU 3.Single Motor Module - 108A 4.Double Motor Module - 250A 5.Double Motor Module - 250A 6.Monitering Module - 6SN1112-1AC01-0AA1 7.Double Motor Module - 28A 8.HLA Module. In the second axis of first double motor module and both the axes of 28A double motor modulei am using External Absolute rotary encoder(Siemens make). Encoder Details: Part Number - 6FX2001-5HE13(Resolution 13bit, pulse-512,Single Turn,8192 steps/rev,Endat) Control card Details: Part Number - 6SN1118-0DM33-0AA2(for all the three axes) NUC version - NCU573.5. HMI Version - 07.05.03.00 pl find the attached NC backup also. i have enabled the additional encoder in Axis no 3. Note: the additional encoder is mounted on the motor shaft itself. the lead screw pitch is 5mm. My problem is everytime i power off and on, the encoder is showing different values. but the ref point is not getting lost and the value of parameter 34210- ENC_REF_POINT_STATE is 2 only. pl give me a solution to solve this problem. thanks, muthukumar k. Hello.... Could you check the parameter 30230(0)=1 30230(1)=1(2) change to 2 and check Regards, Prakash
Ekalavya Posts: 2964 Rating: (484)
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8/27/2012 7:36 PM	Rate (0)
David_Wiens Posts: 25 Rating: (2)	If the problem is what I experienced a month or so ago, every time you power up you should be somewhere around 0, and the magnitude of your position will be something less than the distance the axis travels in one motor revolution. Is this the case?
David_Wiens Posts: 25 Rating: (2)
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8/28/2012 7:18 PM	Rate (0)
Muthukumar Posts: 15 Rating: (0)	Hi David, you are right. every time i switch off and on the power the encoder is showing a value below 10mm. if i didnt move the axis the value remains the same after the power off/on also. pl help me to solve this problem. thanks Muthukumar
Muthukumar Posts: 15 Rating: (0)
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8/28/2012 7:44 PM	Rate (0)
Muthukumar Posts: 15 Rating: (0)	Dear Prakash, the value of 30230[1] is 2 only. after every power off&on the encoder is showing below 5mm(which is the actual displacement of axis per one revolution of motor) every time after the power off&on.if i didn't move the axis and i do power off&on the value remains the same. thanks, muthukumar
Muthukumar Posts: 15 Rating: (0)
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8/28/2012 8:03 PM	Rate (0)
SteveA Posts: 297 Rating: (41)	I think you need a different encoder. Since the one you have is a single turn absolute encoder, it cannot tell if the machine moves more than 1/2 a motor revolution when the control is off. You need a multi-turn absolute encoder. The last two numbers should be 25 instead of 13. This encoder tracks up to 4096 revolutions, so you could move up to 10 meters while powered off, and it could still retain the correct position. HTH, SteveA
SteveA Posts: 297 Rating: (41)
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9/24/2012 1:52 AM	Rate (0)
Jason. Experienced Member Joined: 7/13/2008 Last visit: 9/20/2024 Posts: 107 Rating: (9)	Yes... SteveA is correct. This is an application error. You selected the wrong type of encoder for your application. Do the engineering better. The system must insert an offset in axis md 34090 everytime that the absolute limit is reached (Regardless of control type). This cannot happen while the system is off, so your position will be wrong in those cases. Single turn absolute encoders are great for inline with rotary axes, but even in these cases, multiturn are more handy to avoid passing the absolute limit of the encoder. I only recommend single turn absolue encoders on a rotary that has a limited range, and I would ensure that I point the zero of the encoder into a position that cannot be reached. (To avoid alignement headache when the axis gets moved while the system is off.) Good luck...easy fix.

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