Thread: Home switches in EMC2...DRIVING ME INSANE

1. Home switches in EMC2...DRIVING ME INSANE

I've posted about this before, and although everyone's advice is sound and makes sense, and makes sense to me, I'm going NUTS because it won't work !!!!

I understand that the table travel should *look* opposite to what EMC2 shows in it's little window (that the cutter moves opposite the table).

I understand that my 0,0,0, should be TABLE full to the right, back to the column, and head at the top.

My Z works perfectly. Awesome!

X and Y are making me mad though.

For each axis, EMC2 has two settings to invert. That would be "Direction" and "Step"

Maybe I need a better explanation of this because I'm just not sure what is what.

It boils down to this: When I home my machine, it hits the limit switch, backs off, taps it again, and then acts like it is the OPPOSITE limit. No matter what combination of inverting I try!

In my axis settings it also has a home, a Blank to Blank limit of travel, a home switch location.

Am I wrong by putting in (for example for x) home is at 0, travel is 0 to 6 (this is sieg X2 I am being conservative so I won't hit a hard stop which I have down more than I like to think about now!!! And put the home switch at 0.

So I do that, it goes to home, hits switch backs off, completes homing, and then it will ONLY travel in the direction opposite the home switch!!! Do I need to put in negatives or something? If I completely jack up these settings, I'll never get any G code to run!

What am I doing wrong??????? If anybody can explain this to me and solve it I swear I will cut out your name in aluminum and hang it above the machine!!!

2. What does the machine show if:

- You move to the MIDDLE of the table and zero everything, and move the TOOL to the left? Number on the DRO positive or negative? Does the LEFT arrow produce LEFT tool movement?

- Now back at 0,0.... Does the up arrow move the tool towards the back of the table? What does the DRO show, positive or negative?

Inverting the signals may not be what you need but I used inverting only to get the axis moving in the direction that agreed with the arrow keys for left/right and front/back. That is independent of where the switches are located. You config tells the machine what coordinate is applied when you home against the switch. I'd suggest seeing if you can get it to behave as expected without the switches configured.

Get it moving correctly and make sure that when you manually move the tool to the left front of the table and set that as home that it zeros the machine coordinates (switch the DRO to machine not relative) and that from there, moving to the back right produces positive X and Y values. Until that is right your going to go insane trying to fight with the homing procedure.

3. Take another look at how your Z is setup and then just copy that to start.

i.e Z travels to the MIN and hits the limit switch, goes positive a bit then travels negative again till it hits the switch again - correct?

Get the direction going the proper way for you. i.e the table moves to the left for a positive motion. If you centered your table and then moved it to the left you would be going positive. So your limit switch is on which end of the travel? To be the same as the Z axis that you know works it would need to be catching the table going all the way to the right. So make sure you set-up the limit as a MIN + HOME in stepconfig.

Remember you have to match up the limit configuration with where the limit switch is - the behavior your describing sound like the limit is configured as a MAX not MIN.

Mike

PS - if you can't get it you can try asking for help in the Linuxcnc forum here LinuxCNC (formerly EMC2) - CNCzone.com-The Largest Machinist Community on the net! or go to the linuxcnc home page and find the links to help there.

4. remember - you need to think of your machine in regards to the tool tip.

lets say you stuck a piece of graph papar on the table. So if you set the cutter above the lower left of the graph paper it will be x0,y0. Positve x is the cutter going right on the graph paper. Positive y is the cutter going to the top of the sheet of graph paper. When Z is going negative - the tool is going towards the paper/table.

Clear as mud?

5. Originally Posted by samco
remember - you need to think of your machine in regards to the tool tip.

lets say you stuck a piece of graph papar on the table. So if you set the cutter above the lower left of the graph paper it will be x0,y0. Positve x is the cutter going right on the graph paper. Positive y is the cutter going to the top of the sheet of graph paper. When Z is going negative - the tool is going towards the paper/table.

Clear as mud?
Ive got a good understanding of this concept. Took me a couple days at first (back when i was wrangling mach3) but i get it. Travel is relative to the tool head. When i jog right, the table should move left. When i jog back, table should move forward. Im moving the cutter, not the table.

I cant test until i get off real work but my jog keys and display were matched to the table movement and as the previous poster said until i make my jog keys relative to the cutter, i will be driving myself nuts setting limits.
I will let you guys know how it goes tonight after work.
Thank you all so much!
Just need to figure out the difference between inverting "x step" and "x direction" in emc2 now....

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6. Don't invert the X Step unless the driver requires it. This pertains to if the driver considers a step pulse to be L ---- H ---- L or if it uses negative logic H ---- L ---- H. The direction signal is just that H rotates the motor shaft in one direction and L rotates it in another. Inverting that changes the direction the table moves at a hardware level.

The other way to do that is to change the 'steps per' value to a negative number. It will have the exact same effect in reversing the movement of the table.

7. Originally Posted by photomankc
Don't invert the X Step unless the driver requires it. This pertains to if the driver considers a step pulse to be L ---- H ---- L or if it uses negative logic H ---- L ---- H. The direction signal is just that H rotates the motor shaft in one direction and L rotates it in another. Inverting that changes the direction the table moves at a hardware level.

The other way to do that is to change the 'steps per' value to a negative number. It will have the exact same effect in reversing the movement of the table.
Thank you for clearing this up for me. It didnt seem to affect my g540 anyway. But at the time i started messing with that setting i had so many things inverted it felt like australia.
Making the steps per negative... Sounds like this might solve my problems maybe...we will find out tonight.

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8. IT WORKS! THANK YOU ALL

As I learn more on CAM i'm putting names in aluminum

9. Originally Posted by photomankc
Don't invert the X Step unless the driver requires it. This pertains to if the driver considers a step pulse to be L ---- H ---- L or if it uses negative logic H ---- L ---- H. The direction signal is just that H rotates the motor shaft in one direction and L rotates it in another. Inverting that changes the direction the table moves at a hardware level.

The other way to do that is to change the 'steps per' value to a negative number. It will have the exact same effect in reversing the movement of the table.
This just saved me a bunch of headache, THANK YOU! My Y was reversed for some reason & the negative sign was the trick.

Thanks again!

Mike
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10. Glad my meager knowledge could assist a couple folks!