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Author Topic: Limit switch issues  (Read 19768 times)

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Re: Limit switch issues
« Reply #100 on: December 27, 2015, 12:35:39 PM »
ok see, that's what confuses me...to me, home and origin are one and the same.....

Ok, saving my offsets, instead of making me search through the manual, how would I do that? (btw, this is another piece of terminology that I can't get my head around, why are they called "offsets" when what I am doing is saving my origin....? To me, an offset is the distance from a particular location not THE actual location....

btw: I'm making notes of everything being posted then I'll go to the shop and try again....my CNC computer in my shop doesn't have net access....(just wanted you to know)
« Last Edit: December 27, 2015, 12:38:49 PM by MuskokaMike »
Re: Limit switch issues
« Reply #101 on: December 27, 2015, 12:37:51 PM »
Quote
Now, here is another design flaw in my CNC....the builder, in his infinite wisdom, designed it so that under NO circumstances would you break a tool. He has built into the machine flexibility so that the machine will kick off axis etc instead of damaging a tool

A more flexible machine can break tools easier than a rigid machine, by allowing a tool to pull itself into the workpiece until it snaps.

exactly...and it also causes massive amounts of chatter which puts stress on the tool......see, what I've learned is: the company I bought the machine off of is really just a guy in a garage who builds and sells these machines NOT a real  builder....I mean, who would even consider using plastic racks and pinion gears? I think I broke teeth on my first week of using it.....
Re: Limit switch issues
« Reply #102 on: December 27, 2015, 12:41:59 PM »
just one more thing: my pins should be set to active high.....by doing this will I cause any "magic smoke" lol to come out of my electronics?

Because I can't see the switches being normally open, that would defeat the purpose wouldn't it? meaning they would SUPPLY power to the axis when triggered instead of cutting power to the axis......

Offline bfgstew

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Re: Limit switch issues
« Reply #103 on: December 27, 2015, 12:42:37 PM »
It might be wiser to bite the bullet and get rid of it, start afresh with a more robust and modern machine, there seems to be more and more problems getting uncovered that are going to bite your ass the more you try to improve things.

Offline bfgstew

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Re: Limit switch issues
« Reply #104 on: December 27, 2015, 12:47:45 PM »
N/C or normally closed means just that, in a dormant state the switch is closed, therefore makes the circuit, visa versa N/O or normally open means the exact opposite.
High looks for the signal voltage, in this case +5vdc, Low means the opposite it looks for 0v or in this case a switch going fron N/C to N/O - your limit switch being triggered.

No magic smoke will get out setting them high or low, it is just a way of stating what the pins are looking for.
Re: Limit switch issues
« Reply #105 on: December 27, 2015, 12:57:16 PM »
It might be wiser to bite the bullet and get rid of it, start afresh with a more robust and modern machine, there seems to be more and more problems getting uncovered that are going to bite your ass the more you try to improve things.

well, the electronics all seem to be of reasonable quality and the steppers etc are powerful enough...so since I can't afford to lay out $5000 (or more) for another machine, I'm just going to replace all the flexible crap with aluminum.....from looking at the linear bearing prices and 80/20, I should be able to do it under $500.00.....

Get this: I couldnt' figure out why my signs were "growing" as they got longer....I eventually found the problem: the steel frame that everything mounts too was 1/8" wider at the 48" end than the 0 end lol......I tried to move it into position so the 2 x rails were parallel but couldn't because it is made of 1 1/4" square steel tubing...so I put a pipe clamp on it and cranked it down so the 2 rails are back to being parallel.....that was literally a WHAT THE HELL moment.......
Re: Limit switch issues
« Reply #106 on: December 27, 2015, 12:58:25 PM »
ok, I've got a bunch of notes....

As they say in the movies:

COVER ME, I"M GOING IN! lol

Offline bfgstew

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Re: Limit switch issues
« Reply #107 on: December 27, 2015, 01:13:46 PM »
Agree, electronics look fine, drivers and steppers fine, Mach3 fine but what it is all connected to is garbage, unfortunate but true.
continue to get the electonics and mach3 sorted and you'll be fine with the rest.

Offline stirling

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Re: Limit switch issues
« Reply #108 on: December 27, 2015, 01:26:02 PM »
I see things have moved on a tad but I'll answer some of the questions you posed to my earlier post anyway.

1)that doesn't explain why a user would want to move one or more of their axis past the limit switch where by doing so, they will damage their machine.

I have no idea why a user would WANT to do that - he would have to be a very stupid user indeed. I've explained why Mach3 doesn't PREVENT a user from doing that.

2)but your "home" should be 0,0,0 on the table, not (in my case) 0,48,0. Once zero'd in, you can move the gantry anywhere you like.

There's no "should" about it however much you would like it to be true. Home is a datum - it matters not one jot WHERE it is. It affects NOTHING you can do or can't do.

BTW - this will probably muddy your waters even more but home is very RARELY (if indeed EVER) at 0,0,0. That would mean that your Z is homed toward the BOTTOM of your Z and THAT is plain silly for a variety of reasons.

But look - if you have switches at front left then just set THEM up in the software as your homing switches and call it 0,0 if it makes you happier. (you still really don't want to set Z home to be zero though).

3) funny, mine are wired in parallel and yet home consecutively.....if I understood why you write, they should all home at the same time.....

Read again - I said if they are wired in parallel "you can choose to set up so axes home concurrently".

4) but ftp links are a web address....

They most certainly are NOT.

Offline BR549

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Re: Limit switch issues
« Reply #109 on: December 27, 2015, 04:27:06 PM »
Mike what may be mixing you up is the fact that there are 2 sets of coordinates in play with CNC work. You have machine coordinates and Work(user) coordinates. The machine coords are what the machine uses to establish a point in 3d space as a reference. It can be 0,0,0 or ANY point . Once stabliched teh machine then simply counts units to move where you ask it to move.  Refhome is teh point the machine goes to and establishes the reference. You can use switches or do this manually. You can still do this manually as accurately as any switch. The switches are just conveinant. Once you reference the machine it uses THOSE coordinates until you shut mach3 down. Then mach3 will loose all reference to the table.

The work side is another completely independant set of coords that YOU the operator use to setup work and reference to for machining parts.  Why are they called offsets ? because they are ALL an offset from the original refhome position that the machine uses for reference. The word offset can be either in NOUN form or a VERB. You can "offset" a position or you can use an "offset".

To be able to reset after a work stop ( outage ) all you have to do is Reset teh Work 0,0,0 to what it was originally on the table. To use the centerpoint of the tool is very hard to do. Using the side of the tool is very easy and very accurate. But yo have to realize you are setting it up as an offset so teh centerpoint of the tool will be established.

When you first setup the material i would machine a simple  L corner somewhere on teh material that runs up and down and left and right to the table motion. That will give you a reference point for X and Y axis. Record those positions somewhere in case you need them to set back up after a work stop. To reset the table simply move the tool over and touch off the tool to that spot in X and Y then set the dro for each axis to that value. NOW your machine is set back up to the exact point on the material (part). THAT is just one way of doing it there ARE many ways it can be done.

Another would be to use accurate home switches and Work offsets to setup the part then if needed you can simply refhome and go to the correct offset.

However you do it just pick a method and stick with it. ONCE you have figured it out you can restart a dozen times and it will machine correctly each time.

(;-) TP