Homing switch's not working correctly

[Barefootboy4]

Now that I have all three axis working smoothly I started the homing process on the limits
Following the manual of Mach 3 and watching the dianogics screen when I hit any limit (all wired in series NC) the three M1 lights flash on and off and not a steady yellow light. What can cause that? It will not ref all home but just tries to move the z axis beyond it's limit of travel. Thank god I was fast on the E-stop!!

[ilya]

Are you sure that MACH sees your limit switches? Have you set up the ports and pins for them correctly?

To check if your switches actually work, trip the switch manually. MACH should go to emergency mode (red EStop flashing) and tell you that you tripped the limit switch. You can also check the Diagnostics screen and see if your breakout board sends the correct signals to LPT port when you trip the switch.

After that you can set up your limit switches for homing. Sorry, I'm not at the CNC computer right now, can't guide you through the MACH settings. Hope this helps.

My CNC machine plans at www.8020CNC.com

[ger21]

Start with one switch at a time. When you're sure it works, add another. Repeat.

Far, far easier to troubleshoot.

[Barefootboy4]

OK, I found the problem with the limit switch. Electrial interfearance from the 120VAC incoming right next to the limit wires causing bad signal. Re-routed the wires and all is good. Now I have a new issue:

When trying to hit the REF ALL HOME button on the Program run screen the Z axis will only move a small amount and then the Y axis will move a small amount and then the x axis will move to the Limit and home. What could be causing this to happen. In config I only have the X, Y,Z home box's enabled and the correct port and Pins. Any ideas
Steve

[ger21]

What could be causing this to happen?

More noise. Check the diagnostic page when homing, and you'll probably see the LED's lighting up.

[ilya]

Check the diagnostic screen while REFing the axes. It should move the axis until it trips the switch. Make sure that the diagnostics shows you that the switch is tripped. If you see this, but the physical swich isn't tripped, this indicates that you have some problems with hardware part (interference or the like). If you don't see any activity in diagnostic screen, something's funky with the software.

And remember - NEVER bundle together mains AC and high power control wires with low-voltage signals. Also use a star grounding scheme with the star point being your PSU. This is VERY important!

My CNC machine plans at www.8020CNC.com

[Barefootboy4]

I just checked the diagnostic screen and the m1 light is flashing and not on study. I have all six limits wired in a one continueous NC loop right next to the 49VDC to all the motors so it has to be causing the problem. I'll have to re-route the limit wires somehow.
Could you explain what you mean by a star connection?? what is a PSU??

[ilya]

Ok. Try to move the high voltage wires away and see if it'll be any better. This may well be the noise from the motors that couples to the limit switches wiring.

PSU is Power Supply Unit. And I've made up a simple picture that will explain you what star ground is. Basically, you don't want to connect your grounds in daisy chain. Connect the ground from each device with a separate wire to your star ground point at the PSU.

My CNC machine plans at www.8020CNC.com

[Phife]

I had a little interferance with my switches too, I used DeBounce in the Mach3 config screen and entered 700 into the box. It helps alot!

When referencing make sure the machine is moving slow, I have mine set to 30% If its moving too fast the axis could crash through the switch before it has a chance to trigger a stop.

[Barefootboy4]

Hey guys,
Just wanted to say thanks for all your help. had to rewire the limits in a Star format and jumped the Debounce to 800 but now it will "REF ALL" sweet. have my Home off set to 1.0 and it moves off home 1.0 perfect. Thank god for this forum.
Again thank you for the help

[ilya]

Glad to hear it worked!

Wiring is really important. Although it may look like a small thing, these small things often make big difference in performance.

My CNC machine plans at www.8020CNC.com