Machsupport Forum
Mach Discussion => General Mach Discussion => Topic started by: DAlgie on April 29, 2006, 09:35:31 PM
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I looked through other posts, but, is the home position, where you reference your machine from, always at the end of the axis? What I'm asking is, can a home position be located in the middle of a travel, or somewhere along it? My lathe has a reasonably long bed, and with a low pitch ballscrew it is a ways to go to get a reference point, if the home position was able to be set closer to the work area it might be a nice feature.
DaveA.
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Yes you can set your home switch at any point in the machine travel.
While I dont know the exact procedeure for doing this, I think it is done using a macro.
But it can be done, that much I can definately tell you.
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Hi Dave,
You can have the home position where you want, one of my mills at work has the home position on the X and Y table centre line.
The home position is only really a starting point for the control, so it knows where to start counting from.
Graham.
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Very cool, thanks. I went back to it late last night and understand how it works now. I would imagine that you need to make sure the saddle is on the same side before homing so the home direction setting sends it that way, if you were on the opposite side the control would run it away from the trip point to never never land, or the end of it's travel, whichever came first....
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Well, got the home switches installed, and the trip points. This is a lathe, set the X axis switch at the max X position, and the Z axis switch at about the middle of it's travel. Two questions now, how do I send the machine to find the home switches? I made sure the motors were active, they jogged fine, then pushed the home buttons, I tried the x home, then the z home, then the all home, nothing happened, no movement. Second question, when I jogged to find the home switch, it shut off the motor as it should, but then I couldn't reverse off the switch, the Estop remained on, and I couldn't go anywhere. I had to go into the diagnostic screen and hit limit override to get it off the switch. I seem to remember Art saying something in one of the videos about this, but I can't find it for the life of me.
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It should just start moving.. Do you have the home pins turned on under the ports and pins?
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Yes, have the home pins turned on, tried all directions and settings I can find that seem to be applicable to homing. The home switches work, they stop the motors, so this has me confused a bit. I have the correct pins set for this also. Maybe something strange with the lathe side of Mach, I don't know.
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Can you press the switch and see the state change on the Diagnostics page?
Also what do you have for inputs that are active?
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Yes, pressing either home switch lights up the home light on the diagnostic page ok. No abnormal lights seem to be lit, I am having spindle feedback problems or something like that though, the spindle speed goes haywire a lot, sometimes it settles down and reads the correct speed when running, and it's light on the diagnostic page flicks on and off randomly, but I figured that this was inductive feedback. Didn't think that would be doing anything to the home switch settings though. Thing that has me confused is that the home switches work as limits ok, so I imagined that they are doing what they are supposed to.
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Try setting your debouce to 2000 (20us)
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OK, got it to work, I had home switches set only, needed to have limits set as well, thanks for the help with all this, you guys are cool! One thing, the soft limits don't seem to be working. As I understand it, you set one end, or a mid position with the home/ limit switch, then the soft limit(s) set the other end(s) of the travel, correct? As it is now, I only have the X axis working, the stepper for the Z axis is too small and stalls constantly, have a large one coming. So, I don't know about the Z axis soft limits, but the X seems to overshoot it's number. I'll try messing with negative numbers, etc, maybe I have to double the number as it's a lathe set in diameters, not radius. Also, if I click on 'set home' it goes to it's home switch using the set home speed percentage, but if I click on 'Home' or 'Home all' it runs at full rapid, and the home speed doesen't have any effect for some reason.
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Please post your XML and i will have a look at it :)
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Brian, I posted my lathe XML here. Tried again tonight, nothing I do will make the soft limits work, so I'm hoping you will see something in the XML. if you could, while you're in there, could you look at the spindle feedback, see if anything looks odd? As I said before, it's probably inductive feedback, but the spindle readout has gotten worse, it now bounces around 40,000 rpm or so, and if I start the spindle it never settles down as it used to. Thanks again!
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I added a bit more debounce and I added a button so you could turn on the softlimits. the Button is on the diagnostics page
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Very nice Brian, thank you for that! The soft limits work great now. I still got spindle feedback going crazy, so I messed with the feedback debounce as well, didn't get anywhere with it, I'll have to shield the spindle indexing sensor then. Thanks again.
Dave.
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I think a little shielding should fix you up :)