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Setting machine Coordinates
« on: June 23, 2010, 01:26:32 PM »
Hi Ail,

I am having some difficulty with homing and machine coordinates.

When I jog the table so that all home switches are active and in their respective homes, how do I tell Mach that the current position is "HOME"  Currently the machine coordinates show it to be in another arbitrary place and I cannot seem to set the current position to zero.  I want to be able to test out the homing of the table and insure all axis go home properly and position properly.

Any suggestions?

A second question is, when my table moves the DRO's indicate the table has moved twice the actual movement of the table. Is this set up in the motor tuning section?

Thanks

Kevin

Offline Zaae

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Re: Setting machine Coordinates
« Reply #1 on: June 23, 2010, 11:37:14 PM »
Well, you'll need to straighten out problem number 2 first, but we'll need some more info to help, are you running stepper motors or servos? Other info needed is screw TPI, additional gearing, microstepping?
Re: Setting machine Coordinates
« Reply #2 on: June 24, 2010, 09:07:52 AM »
Thanks for the input...here are details on my setup

Using stepper motors all have a 1.8 degree / step

For X & Y axis Ball screw is 1" diameter with a screw lead of 0.5"  Both are direct drive with no gearing.

Z axis has a pitch of .1"

I am not sure how to answer your question on micro stepping. I am using Gecko G203V drives for each axis.

I had run through the calculations on the motor setup, but I am guessing I doubled something by accident.

If you need additional information let me know. I really appreciate you assistance.

Kevin

Offline Zaae

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Re: Setting machine Coordinates
« Reply #3 on: June 24, 2010, 01:36:46 PM »
Forgot to ask, how many starts do your screws have?

I'm no pro with this stuff, I've only done it a few times, but here's my calculation, based on a single start screw:

direct drive motors, so no gear reduction.
1.8 degree motors = 200 steps per rev.
10x microstepping = 2000 steps per rev. (according to gecko's website for the G203V)
5tpi 1 start screws = 10000 steps per unit (inch in this case).

If you want to run metrics, divide 10000 by 25.4 = 393.700787 steps per unit (mm this way)

Someone please correct me if this is wrong.

Offline Zaae

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Re: Setting machine Coordinates
« Reply #4 on: June 24, 2010, 02:55:31 PM »

As for your question about homing, I have a modified screen set, so the wording may be a bit different, but the basic idea is the same. Make sure you've got your steps per unit all figured out before you work on this, or your numbers will be wrong.

First, move your machine manually to somewhere in the middle, well away from any limits, and click reference all home, but be ready to hit stop. Note which direction each axis is moving. If any of them are moving away from the limit switch, click Config->homing & Limits, and check reversed, or home neg to correct it. Also make sure Auto Zero is enabled. Once you have all axes moving towards their respective limit switches, you can start setting up the limits.

Click reference all again, and let each axis hit the switches, but again, be near the e-stop button in case they don't stop like they should. If this all works as it should, this will tell mach3 where 0,0,0 is at, and will reset each machine coordinate to zero.

Next run each axis manually as far as you'd like it to move, and enter the number from the respective DRO into the homing and limits config page.

Last, soft limits must be enabled if you want the machine to actually use these constraints.

The setup is different for each machine depending on its configuration, wiring, LH/RH screws, etc. so you may have to fiddle with the settings in the homing & limits page to get things working as expected.

Hope all this helps :)
Z
Re: Setting machine Coordinates
« Reply #5 on: June 25, 2010, 09:09:00 AM »
Hi Zaaephod,

Thank you for the assistance on this. I entered the motor calculations per your suggestion, moved to the center of the table and clicked on REF ALL HOME  All axis briefly moved, and I believe Mach 3 thinks it is already at home.

My home switches are active low and each input pin is showing high when I reference all to home.

 I have verified when the home switches activate the respective input pin goes low. and operates as I would expect.

ACTIVE LOW is checked on the input settings section.

If I uncheck this, setting it to active high and then reference all to home Mach 3 tells me "Requested Home axis home switch is active, please fix then home." I would expect all this if I am thinking correctly.

For my home switches I am using NPN proximity switches, the respective input has a 2.2K pull up resistor to 5V. When the home switch activates, the pin goes low.

Hmmm What am I overlooking?

Thanks

Kevin

Offline Zaae

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Re: Setting machine Coordinates
« Reply #6 on: June 25, 2010, 09:53:51 AM »
Kevin,

Have you configured the input pins under Ports & Pins?  I guess I didn't go over that. The input signals tab lets you set up what pins are for what signal in mach.

For example, XHome enabled, port 1, pin 11 for me is my X limit switch. I'm betting this is what you're missing.



Re: Setting machine Coordinates
« Reply #7 on: June 25, 2010, 11:21:18 AM »
Actually I have all that set up my home switches are on port 1 pins 15, 13, 12

I can see these indicators toggling on the diagnostics screen when I manually jog the table to each home switch.

Offline Zaae

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Re: Setting machine Coordinates
« Reply #8 on: June 25, 2010, 12:03:37 PM »
It sounds to me like you've got everything set up then. I'm sure we're just missing something simple here, but it's so hard to tell without seeing the configuration. If you'd like, you can post your XML file and I'll take a look at it when I can. Problem is, over the last few months, I've quoted a bunch of jobs and, just as expected, they all showed up at once, with deadlines that are painfully close. I won't be around again until later tonight or tomorrow.

Off to make some chips :)
Re: Setting machine Coordinates
« Reply #9 on: June 25, 2010, 04:55:42 PM »
I agree I am overlooking something simple. Here is the XML file.

One observation I just noticed....I disabled the ESTOP input on the config screen, because I am not using that input. However each time I disable it, save the settings and exit. The next time I go back into the input settings it is enabled. perhaps this is what is shutting me down??