**RESOLVED** Limit Switch Wiring 101 - DC3IOB

[diycncscott]

Before getting started with wiring your limit switches, it is important to understand that the DC3IOB electrically disables motor rotation in one direction when a limit input is open. When the "-" input for an axis is open, motor rotation is disabled in the CW direction. When the "+" input for an axis is open, motor rotation is disabled in the CCW direction. This behavior is hardwired on the DC3IOB in the drive and can't be modified via the PLC program, direction reversal or any other software setting.

Therefore:

1. Limit switches MUST wired as normally closed.

2. A single limit switch can NOT be wired into both limit switch input directions of an axis. As discussed above, wiring a single switch into both directions on an axis will disable BOTH directions at once preventing all motion on that axis until the switch is manually cleared.

3. ALL unused limit switch inputs MUST be defeated. Limit switch inputs can be defeated either by jumpering the input to input common or by using the limit DIP switches on the DC3IOB. Click here to see how to defeat a limit input.

4. If direction reversal is turned on in software for an axis, the limit switch input wiring for that axis will need to be reversed. Click here to see how.

... to be continued

[Centroid_Tech]

Question: Do I need to use the existing deceleration switch for the z-axis on my Bridgeport Series II mill?

Answer: No you do not need to use the decel. switch because the machine only moves at the slow jog rate during homing. Which by default is 24 ipm. Once the machine is homed the Z-axis cannot go past the home position.

[mrdttr]

My limit switchs seem to react to slowly for the controller to be able to home the machine ? Is that possible or have I missed something else. I did have to reverse the motor travels inthe config on my X & Y axis. The Z seems to work OK. I'm updating a Bport Boss 5 machine

[diycncscott]

Mrddtr,

I'm not sure what you mean when you say "My limit switchs seem to react to slowly for the controller to be able to home the machine"

The limit switches should be wired directly into the DC3IOB servo amplifier - when a limit switch opens, the axis will stop instantaneously. The amplifier is hard wired to electrically disable motor motion as soon as the switch opens.

First, go into the Diagnostics screen and confirm that no limits are tripped.

Next, confirm that your limits are wired into the drive correctly first jogging to the middle of travel for each axis, disable the "Ajax Limit Handling" & "Ajax Limit Inputs" Brains in Mach using Operator->Brain Control and unchecking the box next to the Brain and then "click reload all brains". Now, trip a limit on an axis -if you tripped the + limit, it should only let you move the opposite (minus). If it lets you move positive while the plus limit is tripped - your limit is incorrectly wired, switch the + and - limit wires for that axis to correct.

Do this for all axes and all directions.

Once you have your switches wired correctly, re enable the above Brains.

Scott

[mrdttr]

I'm running CNC11 so I dont think I have the diag screen you mention. Upon further investigation I realize that when I trip a - or a + switch the control locks out both directions for that axis on both X & Y. The circuit looks correct other than I carried the common from the DC310B out to only one switch common and then jumped from that common to the other switch common. The returns are dedicated + or _ . The display tells me which limit is tripped when it stops ie X+ limit tripped. Yet it seems to lock out both directions.
Thanks

[diycncscott]

Mrdttr,

You have your software limit switch settings and hardware limit switch settings in conflict.

In CNC11 software:

F1 -Setup -> F3 Config (pw = 137) ->F2- Mach F2 - Motor

1. Change all your software home and limit switch settings to zeros
2. Press F10 to accept/save
3. Go to the mauin screen
4. Jog all axes tot he middle of travel
5. Now, trip a limit on an axis -if you tripped the + limit, it should only let you move the opposite (minus).
If it lets you move positive while the plus limit is tripped - your limit is incorrectly wired, switch the +
and - limit wires for that axis to correct.
6. When you done this for all axes in both directions, press the "alt" and "i" keys simultaneously, this will bring up the I/O display screen
Trip each input and make a note of what PLC input the X+ trips, the X- etc....
7. Go back to the motor setup screen as described above and enter the appropriate input numbers for home and limit for each axis and direction. If a direction does not have a switch wired - leave it at zero.

8. Press F10 accept/save.

Regards

[mrdttr]

Problem solved. And yes I did have both X & Y + - reversed for there respective axis. Now the machine will home it's self & allow me to back off a limit trip when I jog to far.
Again Thank You
I'm fairly sure I'll have more questions but for now you have relieved some real frustration.