Hello,

I am new to TO andmotion, and I am wondering in which situations the actual position could be lost, so that homing is needed?
I suspect that after a power loss, you should home the axis again, but are there other situations as well?

With kind regards,
T.

AutoGen_1093558

Hello,

I am new to TO andmotion, and I am wondering in which situations the actual position could be lost, so that homing is needed?
I suspect that after a power loss, you should home the axis again, but are there other situations as well?

With kind regards,
T.

MC_POWER should always be active. Homing will be needed if the enable is lost. When I started out with motion control, this was my #1 problem. 

qwazee

 

AutoGen_1093558

Hello,

I am new to TO andmotion, and I am wondering in which situations the actual position could be lost, so that homing is needed?
I suspect that after a power loss, you should home the axis again, but are there other situations as well?

With kind regards,
T.

MC_POWER should always be active. Homing will be needed if the enable is lost. When I started out with motion control, this was my #1 problem. 

 sorry, but this reply is just wrong.

Neither should MC_Power be always active, nor is homed-state lost when the eneable is lost.

For information when the homed-status is reset, see here, section "Resetting the "Homed" status": https://support.industry.siemens.com/cs/ww/en/view/109781849/138763785739

And for that statement about MC_Power: just forget about it. Check the manual to see for what the instruction is needed, and in your program ensure you check the requirements that have to be met before activating the TO with MC_Power. Basically this FAQ shows what to check and how to do it: https://support.industry.siemens.com/cs/de/en/view/109750297

Regards,
daviso

@daviso: Thank you for making your reply.
May I demonstrate my perspective and ask your discussion on the matter?

Attached is a small demonstration animation. Open loop motion control (pulse & direction) is installed on a CPU1212C (FW:V4.5). Step7 V17 is used as engineering software.

Thanks in advance for your review.

Hi there,

of course you need to have the axis enabled via MC_Power when you want to execute functions on the TO such as movements and referencing, no doubt about it.

But saying it has always to be active is just too general, and I fear people read it and take it for granted, and then run into problems later on.

There are prerequisites for enabling the axis with MC_Power, these have to be met, otherwise MC_Power.Enable should not be set: https://support.industry.siemens.com/cs/de/en/view/109773400/127243612683

Also there are functions that require the TO to be inactive, such as doing a TO restart with MC_Reset (though I have to say that at the moment this is the only thing I can remember to require an inactive TO).

Regards,
daviso

 If it helps you, you can use this method to overcome incremental position loss at power off and on of the CPU.

You keep on saving actual position of TO in a retain tag onto a DB. When you turn the PLC on, you launch MC_Home to restore the previously saved position.

Be careful, if you save the wrong position value, you will have a referenced axis in the wrong position (or reference)!

BR,

BE

AutoGen_1093558

Hello,

I am new to TO andmotion, and I am wondering in which situations the actual position could be lost, so that homing is needed?
I suspect that after a power loss, you should home the axis again, but are there other situations as well?

With kind regards,
T.