Machsupport Forum
Third party software and hardware support forums. => SmoothStepper USB => Topic started by: cyberhawkv on September 13, 2012, 02:20:22 PM
-
Hello hopefully someone can help,
I installed the SS on my machine hooked it up to Hobby CNC board, and machine everything works fine except for homing. I checked the switches to see if they work in mach and they do, they light up. Problem is that when I home any axis the system hits the switch (the switch lights) but mach keeps on going ignoring the switch. I have tried 1 axis at a time and it still does the same. This was working fine before I installed the SS board. I do have all the latest updates for the SS installed, and the latest mach 3 installed. I am running the machine on a windows 7 64 Bit computer, with 4 gigs of ram and a quad core CPU. Your help is greatly appreciated thanks again
-
Cant think what could be the problem there but if you attach your xml I will see if there is an issue with your config.
Hood
-
Thanks for your prompt reply,
I fixed the problem -- I had to go into the SS config and set the noise filtering for home at 20.0. Apparentlly there is to much noise with the limit switches.
-
I find this interesting, I'm having the same problem on a brigeport conversion and it does the same thing on my Z axis, 2 switches it runs past the home switch and ignors the limit switch and finally the travel ends and the motor stalls, not a pleasant experiance at all.
It doesn't do this every time just once in a month or so, to often.
Another person on the forum suggested that I use the second switch (limit switch) and use it to disable the drive instead of using it as a limit and add a momentary contact switch so I can re-enable the drive to jog off the homing limit.
I didn't know there was a noise filter for homing can you tell me were it is please so I can try it out on my machine.
Thank you,
Ted
-
cyberhawkv
Usually with noise you will get the switch being seen falsly, ie it will see a false trigger before the switch is actually seen. Cant really see how noise could cause the switch to not be seen but if its working then suppose thats all that matters. I would however be careful with the amount you have as 20 is quite high for the SS filtering and you may well be getting a delay before it is seen.
sqweeker
The reason it is going past the limits is Mach ignores home switches when homing so if your home is not seen for some reason the limits will be ignored even if they are seen. This was made that way as most used the same switches for limits and home as the parallel port had limited inputs. Now with external devices inputs are much more in numbers so often people have seperate home switches (like your Z) sadly there is no way to make the Limits active when homing, hopefully Rev4 of Mach will address this issue.
The filtering is from Plugin Control menu the SS Config, as mentioned above dont put it too high, try 1.43 and step up in these increments until it solves the problem if it does but dont go too high or you will get a huge delay.
Personally I cant see how it will help unless there are issues with the plugin as previously mentioned noise should cause an early trigger rather than none at all.
Hood
-
Thanks for the info, this is very helpful.
-
Hello Hood thank you for the reply,
I don't think I explained the problem very well.
When doing homing or tool changes the z axis does stop on the home switch, during tool changes it also rises up to the home switch and stops.
When you hit the stop button during a program run the Z moves very rapidly up to the home position (safe Z setting) and over shoots the switch them goes right past the limit and jams the ball screw.
Your explaination of Mach not recognizing the limit maybe my problem and I may have to change the safe Z setting.
Thanks again,
Ted
-
I think the SS's soft limits work a bit differently from the parallel ports soft limits but been a while since I have messed with them. Try setting a larger slow zone in Homing and limits page and see if that helps.
Also you may or may not want the X to raise on Stop, prefer it not to, if you dont want it to do that you can disable on the Safe Z page, I prefer to use machine coords for safe Z and just set that accordingly, that way I know it will always go to a set position, mine is -2mm so it is just 2mm before the axis extent. I however have servos with fast acceleration/decelleration so I can be close, if your acceleration/decelleration is slower you may need to set a larger amount.
Hood
-
Thanks Hood,
I'm going to change the safe Z and see if that helps, It's intersting that during the homing operation the Z runs at the speed set in motor tuning,... If I change the speed setting the Quill moves with the new settings.
But when it runs up from a stop command to safe Z it seems to run up at the fastest speed it can, do you know if the speed is setable for this or is it something in mach that is overriding the motor tuning settings.
Either way If I set safe Z to just above my work coordinates I should be in better shape I'm hoping.
Have a great weekend,
Ted
-
For homing the axis should run at the % of Max velocity that you have set in Homing and limits. For example if your motor tuning had a Velocity of 500 for the Z and the Homing Speed % in Homing and limits was set to 50% then the homing speed would be 250 units per min.
Safe Z will travel at full rapid speed (Velocity that you have set in Motor tuning)
Personally I prefer to have the safe Z set in Machine Coords as then I know exactly where it will go to, if in work coords then it will be different every time with different code. Suppose most of the time that would be ok as it would move above your work but if for example you had safe Z set to 10mm in work coords and you pressed Go To Zeros it may smash into a clamp or something if that was higher than 10mm.
Hood
-
Thanks Hood,
Appreciate the info, the problem I'm having is that when the machine goes to safe Z (as it is set now) it retracts to the home switch or is supposed to go to the home switch, but it occasionally over travels.
I did slow down the rapid rate to 1/2 of what it was set to before so that may help my situation.
Have a good one,
Ted
-
the problem I'm having is that when the machine goes to safe Z (as it is set now) it retracts to the home switch or is supposed to go to the home switch
I'm not aware of a setting in Mach that will make a safe Z go to the Z-axis home switch. There are three basic choices, move to a location is work coordinates, move to a location in machine coordinates, or move a certain distance relative to where the Z now is. None of these care about your home switch.
-
Hi Jeff,
Sorry for the confusion, trying to be precise with a monster head cold is a task.....
When we start up the mill and reference it home 0 Z in machine coordinates is the homing switch.
The Safe Z is set to go to Machine coordinates 0 to it goes up to the home switch position.
This was getting over shot, the 0 position, Hood has said that Mach doesn't support a home and limit, so my assumption is that the mill is over shooting the home position hitting the limit switch but the travel speed maybe to fast and thus it is jamming the ball screw at the top of the travel.
What I'm doing now is slowing the travel down to 1/2 of the prior velocity and also going to set the safe Z to 0.250 above the work coordinates so when someone hits the stop button it doesn't crash again.
Thank you,
Ted
-
The only way I can see that you would have problems with it overshooting Z=0 is if your Z-axis is loosing steps. If your trying to maximize your Z travel and have your home position set just shy of the axis locking up then your Z may be binding just enough as you approach the home position to loose steps. Once you repeat the safe Z move a few times your Z axis will be off enough to over travel and bind. I like to set my home sensors to go off with at least 0.05" (on a small mill) to 0.5" (on a large router) of travel left in the axis. This gives you a bit of wiggle room and helps prevent problems.
-
Hi Jeff,
As far as I can tell the Mill is not losing steps, home is a quarter inch ahead of the limit switch, we also use the Z=0 position for tool changing, can change tools all day and not miss a beat, hits the home and stops every time, only time it screws up is when you hit the stop button and the quill makes a hasty retreat.
The other hassle is that if it did it everytime it would be relatively easy to trouble shoot,... it only does it once in maybe 10 to 20 times so it is not a consistant problem just really annoying when it happens. I had read a post from another user that also converted a bridgeport he was having the same issue and he used his limit switch to trip the error line on the servo drive to stop the over travel he said it was the only way he could fix his problem.
Thank you again,
Ted
-
You have to be really careful with the 'Stop'. When you hit stop Mach just stops outputting pulses, there is no deceleration, it just stops. Chances are you will loose position and your axis could drift on slightly as there will be no deceleration to help slow it. I've not tried to use 'Stop' in combination with Safe Z so I can't say how it works but given how Stop works I can't imagine that the results would be predictable.
If you need to pause the machine while cutting use Feed Hold. The brings things to a controlled stop and keeps you from losing position.