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Messages - chad

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OK, lets start from scratch.

First explain exactly what switches you have, what pins they connect to, and how you have them wired. And what you have set in the ports and pins. and we will try to figure out what is going on.

I just went through all of this on my mill and sorta-kinda have it figured out. It sounds like you are doing the same thing I am doing but there must be one of those "gotchas".


Hi Sid :

You can crank up the debounce some also, Try 1000, or 1500.

AS for the wiring, you should get some shielded cable for the wires. It will help Lots!
You DO want to connect the shield to ground but only at the controller end. It is the reason that a tin-foil hat won't stop the mind control rays, that is why mine has a ground cable ;)

Do you have one wire that connects serially through your limit switches or one pair of wires from each switch and then daisy chained at the controller?

If that still doesn't work put a .1 mfd cap as close to the db25 as you can get it and wire one side to the input to mach and the other side to gnd..


I don't think you should have the limit override pin set to anything, make it 0. If i am interpreting the ports and pins correctly that is only used if you have an external push button to do the same thing as going to the diag screen and hitting it there.

I think that is used if you have tangible- real control panel.

please correct me if i am wrong.


You are correct, if you enable the limit override and hit the estop reset button you should be able to drive off the limit switch,unless you have soft limits enabled also then you would have to enable the soft limit override also.


Hi ,

I think I can see some of the confusion. 

Ok usually the REF ALL AXIS HOME for x and y is 0,0 and in the lower left corner (machine coordinate with home switches). When you go y4 it will move to y +4. If you then go y2 it will move y2, all of these numbers are positive. you would have to to go y-4 to get in to - numbers, but if your home is 0,0 then you couldn't physically move past your home position witch should be the physical limits of your machine. Now all of this is assuming you have home limit switches installed and properly configured. 

else { you don't have any home switches and you are using the zero buttons to set a home position, then depending on how you generate your gcode will dictate where the 0,0,0 position is relative to the 0,0,0 on your part. in this case things could go to - based on how your part g code was made.

OR you do have home switches installed and you are setting a offset relative to the machine coordinate.

This is kind of a confusing aspect of cnc work. The best thing to do is go to the WWW.mcahsupport.com site and look at the coordinate systems video, then the homing and offsets video. It took me a couple of times through the videos and a lot of experimenting to get my head around it.


Oh yea and usually the Z 0 at the up most position, and negative into the work.

Just thought of something else in case you aren't thoroughly confused yet. There are settings for Incremental and absolute positioning. I would recommend looking this up in the mach manual. It will probably do a better job of explaining it than I would.


General Mach Discussion / Re: Relay to Router
« on: May 22, 2006, 03:11:36 PM »
HI, I would recomend NOT to connect like the first diagram by bcromwell.

If you take 5v and connect it directally to the lpt pin when the pin is told to go low (gnd) it will be a direct short between +5v and gnd inside of your lpt chip. The chances are verry good that that will blast at least that output and probally the whole lpt.

Look at the pic below. This will limit the current in the low state from the +5 to about .005 A. the lpt should be able to sink this without a problem and it should give the ssr enough umph to fire the opto-coupler in the relay. Do not add a resistor on the other side of the relay just tie it directally to gnd. If this doesn't work let us know and we will find you a simple ttl buffer that will drive it.

bcromwell, Sorry to disagree. :)

General Mach Discussion / Re: motor tuning
« on: May 14, 2006, 03:06:59 AM »

Ok,first somebody else's numbers won't do much for you. Stepper tuning is very much an individual thing. It is relayted to motor voltage, drivers, full or micro-stepping, and your individual machine characteristics
We can help you get things working but we need more info on the setup ,like:

Motor voltage (the voltage of the power supply)
--->Stepper drivers?<----
are they direct drive or is there a belt or other form of reduction?
What kind of machine is it?
what are the power transmission devices? ( ball screw, acme thread, all thread, belt,) what are the linear slide mechanisms? ( skateboard wheels, nsk slides)
are they making any noise when you try to jog?
do you have the ports and pins set correctly?
is your e- stop flashing?

Start LOW in the motor tuning. velocity 5, accel of 5,  (step pulse 5 , Dir pulse 5, these only will go down to 1 when you have all other things working.)

Unfortunally with this kind of thing there are NO short cuts. You just have to figure this stuff out and learn it. It isn't that hard you just have to devote some time to master it.
I can get pretty much any mach machine (assuming the hardware is working and wired right) in about 5 minutes moving enough to start testing and fine tuning. Besides, unless you really know how it works you will never get optimal performance out of it:)



Show"N"Tell ( Your Machines) / Re: Chads new machine
« on: May 12, 2006, 02:05:44 PM »
That is a great suggestion, i will look into it!

I still have to add in the C and B head. That will add about 130 lbs to the end and that should help as well. Most of the noise was because I was driving the pen tip to the plywood too hard. The other issue was the aluminum bar that I was using could flex in the x and y direction and added a springiness. Basically i made an old stile cnc controlled phonograph. The z and everything it's mounted too are very rigid and hopefully when the BC head is mounted it will squash most of it.

I guess i won't know until i start cutting wood.


General Mach Discussion / Re: New guy needs help!
« on: May 12, 2006, 04:08:11 AM »
sshneider, and others.

Here you go!



Show"N"Tell ( Your Machines) / Re: Got My mill running :)
« on: May 12, 2006, 03:51:19 AM »
Brian That is awesome!!

When the big project is done we ae going to put AD 1k on our BP clone, i can't wait!

how is the g rex treating you? I am just kind of waiting until it is a little more mature but it seems to be running pretty well!

Kudos to ART and MARISS


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