Wafersaw: Change of shutdown procedure

Elmer Enriquez eenriquez at snf.stanford.edu
Mon Jun 6 12:15:05 PDT 2005


Eric Perozziello wrote:

>Hi Elmer
>
>This is a problem-  it should not hunt for limit switches
>after the "normal" shutdown procedure!  Only after a
>reset.   In fact, after the normal reset with the
>Emergency stop, and then re-starting, everything
>should stay exactly as it was before, including the
>y-offset for the blade.
>
>-Eric
>
>
>
>
>
>On Mon, 6 Jun 2005, Elmer Enriquez wrote:
>
>  
>
>>Eric Perozziello wrote:
>>
>>    
>>
>>>It should be ok to push the Emergency Stop button,
>>>so if it's doing something funny, we need to find out why.
>>>
>>>When you disable, it has the same effect as pushing
>>>the emergency stop button, so I don't think changing the
>>>procedure is going to help.
>>>
>>>I've not seen it do anything strange since the servo repair,
>>>so if it is, we should find out what's causing it (procedures
>>>or hardware problem).
>>>
>>>-Eric
>>>
>>>
>>>
>>>On Fri, 3 Jun 2005, Jia Feng wrote:
>>>
>>>
>>>
>>>      
>>>
>>>>Hi, wafersaw users:
>>>>
>>>>I just noticed this important change of procedure on coral. I am copying it
>>>>FYI. The problem has been occurring repeatedly recently.
>>>>
>>>>Change of procedure:
>>>>
>>>>-- Do not press the "Emergency Stop" button when you're done with the tool.
>>>>This takes the x,y and z axis motors to their limit switches.
>>>>
>>>>-- When shutting down the tool;
>>>>
>>>>     - Push the "Stop" button
>>>>
>>>>     - Turn off the air supply
>>>>
>>>>     - Turn off the pump
>>>>
>>>>     - DO NOT press the "Emergency Stop" button
>>>>
>>>>
>>>>Jia
>>>>
>>>>
>>>>
>>>>
>>>>        
>>>>
>>Eric,
>>     The wafersaw has gone done 3- 4 times since the servo motor was
>>replaced.   The z and y axis motors would drive pass their limit
>>switches.  I had to replace the -28 volt fuse once and the +28 volt
>>once.  As far as pressing the "emergency stop" button and the disabling
>>the tool being the same thing; their not.  If you press the "emergency
>>stop" button, the system would try to rehome (find the limits) upon
>>start-up.  If you DO NOT press the "emergency stop" and just disable the
>>tool,  the motors will start-up from their current position and will not
>>try to find the limit switches.  TRY IT.
>>     As far as finding out why it's behaving funny, we believe its
>>caused by defective limit switches.  We will replace them when the new
>>ones arrive.  I've heard that Len has replaced the switches several
>>times in the past.  Perhaps pressing the "emergency stop" every time the
>>saw is used puts undue stress on them.
>>
>>- Elmer
>>
>>
>>    
>>
Eric,
     Are you suggesting that we keep blowing fuses by pressing the 
emergency stop button until we find the real problem ?  What is the 
actual harm in not pressing the emergency stop when shutting down the tool ?

- Elmer



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