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  #1  
Old Mon 18 June 2007, 10:30
Marc Shlaes
Just call me: Marc
 
Cleveland, OH
United States of America
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Copied from elsewhere:

. . . . The limit switches are also somewhat obvious - designed to prevent 'over-travel' of movable components. What I really don't understand is how a specific job is actually started. That translates to a non-understanding of the function of the home switches. Are the axes manually jogged until the home switch is triggered and then the router knows where it is at all times? . . . . .
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  #2  
Old Mon 18 June 2007, 11:15
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
Marc, would it help you if you realise that we havn't ever used a home or limit switch?

An example; we mostly cut parts out of sheets. An early decision was that we will ignore the edges of the sheets - ie. all edges of finished components will be re-cut. A result of this approach is that precision homing is very seldom required. Therefore, if we have cut 500 pizza platters, we manually jog the router (with the keyboard cursor keys) until the center of the bit is over bottom left corner of the sheet of plywood, give or take 1/8", then press "Start". The next sheet gets laid at the same corner of the table and Start is pushed again (without any jogging of the router). Cheap labour does this all day. "Homing" within 1/8" was done only once.
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  #3  
Old Mon 18 June 2007, 12:38
Marc Shlaes
Just call me: Marc
 
Cleveland, OH
United States of America
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That did help. I thought that the home switch(es) were used all the time to "calibrate" the router. I also cut things out of sheets and the exact size of the sheet isn't important all the time but - once in a while - it is. Like for instance if you are cutting / carving something on the other side of a piece where the first side is finished.

Like I said, I have never even seen one.

Maybe there happens to be another builder within, say, 3 hours drive from Cleveland, OH, US?

Anyone?
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  #4  
Old Mon 18 June 2007, 13:01
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
The trick for lining up front & back is to drill "registration" holes through the center of the workpiece (at the scrap edges) into the spoilboard, flip over and drive dowels through the holes.

Hang around the ShopBot forum for this sort of stuff.

Where a homing position is very useful, is when you have a power failure during a long cut and you need to find the original reference point again.

With Mach3, the limit switch and the home switch can be one and the same switch. If you are doing normal cutting the switch behaves as a limit switch - it trips the movement. However, when you are in Homing mode, then Mach3 finds the switch, zero's itself, and moves away from the switch again.
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  #5  
Old Mon 18 June 2007, 15:11
Marc Shlaes
Just call me: Marc
 
Cleveland, OH
United States of America
Send a message via Skype™ to Marc Shlaes
This little bit was a gem. "With Mach3, the limit switch and the home switch can be one and the same switch." I didn't realized that. I was guessing but never asked.

Shows that there are no dumb questions.
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  #6  
Old Mon 18 June 2007, 21:17
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
Realise that all the limit/home switches are wired in series, and therefore Mach3 does not know which specific switch has been hit. However, Mach3 is clever enough to know what it was doing just before hitting a switch and can figure out which switch was hit. If you hear a bang while reversing your car, you know it is at the back.
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  #7  
Old Tue 19 June 2007, 07:46
Marc Shlaes
Just call me: Marc
 
Cleveland, OH
United States of America
Send a message via Skype™ to Marc Shlaes
Gerald,

I thought I picked this up on some drawing earlier: "all the limit/home switches are wired in series". I thought I was nuts and just couldn't figure out the drawing. These little tidbits help a lot.

From your earlier post on "a backwards way of looking at things"... I actually am not the slightest bit worried about learning to drive the MM, nor building the mechanical parts correctly. I know I can get it done. I just don't understand any of the control aspects. Therefore, building the control / operational components just don't seem so "step-by-step" as the other aspects.
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