Machsupport Forum
Mach Discussion => General Mach Discussion => Topic started by: oskie on June 10, 2008, 10:45:14 PM
-
I am sure this has been covered in the past, but I couldn't find anyone having the problems I am having. I have the three switches wired in series and when I go to the diagnostics page the led lights are lit without the switches being reached so the machine tells me the homing is active and I need to fix the problem once I reset the estop button, I unchecked the active low in the pin tab and this fixed that problem, butwhen the axis hits the limit switch it doesn't reverse it's movement, it continues trying to drive the axis ( I have broke 2 switches already). I started testing without the power to the servos( helps with breaking parts) and I notice that when I depress the homing switch it continues to drive and when I release the switch it then moves to the next axis. Any suggestion on what I have set wrong.
Thanks
-
Hi, Oskie
When your Homing are the DROs decreasing in value for X, Y, & Z DRO increasing.
The spindle should be moving, - X left, - Y towards you & +Z up for Home.
When you push the switch "the axis keep moving in the same direction", It Should Stop and Change Directions, When you release the switch axis should stop.
That axis should zero, Then Mach should move to the next axis and home it the same way..
In Config, Home & Limits, Theres a "Home Neg" Check Box and a "Reversed" Box to change Axis direction if needed.
Hope this Helps, Chip
-
If you are using three switches in series (no problem) ALL THREE switches must be shown on Ports and Pins identically.i.e. Xhome YHome and ZHome should all be enabled, all Port 1, all the same pin, and all active hign or low.
If you test these manually, then each switch when pressed should light up ALL THREE led's in the Diagnostices page simultaneously. Mach 3 will sort out which one it wants to look at.
As Chip says - when homing, the axis do not stop immediately, they carry on past the switch slightly, then back off.
I was going to say try just wiring one - but if your diagnostics show all the switches coming in simultaneously, there is not much point.
Have you wired these switches on Make or Break - if you have wired them on Make, then if there is a break elsewhere all three will become inactive.
Running over switches is a hazard - would you try and stop a car by standing in front of it. My switches are now lasers, shining on detectors, to allow for any over-run.
-
The DRO's are moving and continue to move once the switch it hit. With the power turned off to the servo's and a finger on the limit switch I noticed that once I depressed the switch the DRO's showed it to continue to drive in the same direction until I released the switch with my finger. Could the switches need more current than is being provided by the parallel port to function properly. In the diagnostic screen, the LED lite up immediately when any of the switch are depressed and go out once the switch is released. The switches are wired Normally closed ( I have check about 3 times)
Thanks
-
Please attach your xml. You will need to copy it to different location n your drive and rename it before the forum will accept it as an attachment.
Hood
-
Here is *.XML file,. hopefully this file will spill the beans
-
I will let Hood confirm it, becasue I am not experienced at reading XML files - but your configuration does not appear correct. You do not appear to have any home or limit switches active.
-
Your xml seems correct here, what I have noticed however is your motors acceleration is very low, especially on the X and Y, this will mean it will take a while for your axis to slow down, stop then reverse, could that be your problem?
For a test home an axis from mid travel then press that axis switch manually and keep it pressed and see if your motors slow down then reverse. Doing this from mid travel and pressing the switch while close to mid travel will allow you to let the motor run a while without being worried about it crashing into the ends.
Let us know if that is your problem, if not I will look further at your xml and see if I can find anything else.
Hood
-
OK, I will give this a try. Thanks
-
Sorry for the long delay, I am still having issues with homing once I increased the acceleration. It doesn't seem to notice when a switch is hit. I do see on the diagnostic screen that the buttons light once any of the switches are hit. The switches should be NC right? Does the cable need to be shielded that goes to the switches? I am at a loss for what could be happening.
Thanks
Oskie
-
I also forgot to mention another problem duriing homing. I have a gantry that is driven with two servo's one is slaved onto the other. When I attempt to home the X axis the slave doesn't move, causing a nice twisting action on the gantry arm. I have them slaved together as it moves fine, but not when homing. Any help here would be appriciated.
-
Hi, Oskie
In config, General Configuration, Is this box checked "Home Slave With Master".
You may need to change the config, Ports & Pins, "Inputs", Active Low State hear for your home/Limit SW's
Chip
-
Yes cables are best to be shielded. Now when your switches get hit does Mach just stop? If you try and home again directly after that do you get an error in the ticker saying that switches already active?
If yes to these then try going to Config then General config and set the Debounnce up to 2000, if it works then try dropping down step at a time until it stops working and then step up slightly again.
Sounds to me like you are homing, the switch gets hit and Mach reverses but the signal from the switch is not great and it bounces, Mach sees the signal go off for a split second so thinks the homing is complete even though the switch has not really shut.
Hood
-
I changed the breakout board to an optically isolated board and guess what, my servos are now homing like a champ- Thanks for all the help
-
Hi, oskie
Good to hear you got it working.
Chip
-
Thanks, nice to see it finally homing.