Machsupport Forum
Mach Discussion => General Mach Discussion => Topic started by: diyengineer on March 08, 2011, 10:09:03 PM
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Attached is a pictorial i made of how to envision the homing/limit system. I would like for someone to verify if this is "usually" general practice to how things are done.
Lines of defense, from inside to outside:
1. The slow zone- I assume this distance in X units starts at each min and max soft limit and extends inward X units.
2. Min/Max Soft limits- I assume these come after the slow zone. These act as a digital limit switch, for double the safety.
3. Limit/home- These come after the slow zone, and the min/max soft limits.
4. Mechanical Hard stop- Something you never want to hit.
Am i correct about there order?
when using the "home off" function. Does that move the machine "x" units away from the home switch once it has tripped?
Thanks for the help. Trying to clear this all up. :)
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Home Off sets the position of the home switch to the Home Offset value. It doesn't do any movement.
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in addition to Ger.......
When homing, the axis travels at the specified speed until it MAKES the limit/Home switch.
Then it reverses and runs until it Clears, or un-makes the switch. At this point the axis is homed. Note that the axis would have to travel a bit to re-make the switch so the home position is well clear of the limit switch activation.
Soft limits are ignored during the Homing sequence so you can leave them on.
Soft Limit min and max would be from the HOME pos to just shy of tripping the other limit on that axis.
The Slow Zone is to give a fast / heavy axis time to decel to prevent overrunning the setting and tripping the limit switch.
The Home Off is to enter a value that you would like to show in the DRO when AT the Home pos. For instance if you were to home in the bass ackwards direction on an axis that is say 12" long. You would enter 12.0000 (Y as an example).
HTH,
Russ
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One other thing to mention, you can have 2 limits on each axis ALL connected in series to 1 input pin.
When Homing, they are treated as Home switches, otherwise, they are treated as limit switches.
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Thanks Ger and Overloaded!
Few more questions:
"Soft Limit min and max would be from the HOME pos to just shy of tripping the other limit on that axis."
So imagine my X axis homed and the DRO is now @ zero. All movements from zero (home) are in inches and are in a positive direction. What would i set my Y axis MIN soft limit to? Zero?
"The Slow Zone is to give a fast / heavy axis time to decel to prevent overrunning the setting and tripping the limit switch."
I have a heavy gantry and would like to use the Slow zone to make sure it does not come full speed at a limit. My gantry can go upwards of 500ipm and is probably close to 240 pounds.
If my Y axis goes from 0" (home) to 139" (Y Max) would a value of 6" give me a slow zone from 0"-6", and from 133"-136"?
"Home Off sets the position of the home switch to the Home Offset value. It doesn't do any movement."
"The Home Off is to enter a value that you would like to show in the DRO when AT the Home pos. For instance if you were to home in the bass ackwards direction on an axis that is say 12" long. You would enter 12.0000 (Y as an example)."
Throw me another example. I still don't understand haha. (sorry)
One other thing to mention, you can have 2 limits on each axis ALL connected in series to 1 input pin.
When Homing, they are treated as Home switches, otherwise, they are treated as limit switches.
So i can use 1 port and 1 pin for all my home/limits as long as i tell the machine which way to home (+,-) (i home in the negative direction) correct?
I have been using 3 pins!!! :( i didn't know that!
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Thanks Ger and Overloaded!
Few more questions:
"Soft Limit min and max would be from the HOME pos to just shy of tripping the other limit on that axis."
So imagine my X axis homed and the DRO is now @ zero. All movements from zero (home) are in inches and are in a positive direction. What would i set my Y axis MIN soft limit to? Zero?
Yes (assuming you meant "X axis min") Then you jog pos and hit the limit switch at 32.555, set MAX to 32.450 or so.
"The Slow Zone is to give a fast / heavy axis time to decel to prevent overrunning the setting and tripping the limit switch."
I have a heavy gantry and would like to use the Slow zone to make sure it does not come full speed at a limit. My gantry can go upwards of 500ipm and is probably close to 240 pounds.
If my Y axis goes from 0" (home) to 139" (Y Max) would a value of 6" give me a slow zone from 0"-6", and from 133"-136"?
YES. You can experiment with this, my knee mill runs at about 140 ipm and a slow zone of 0.5" is adequate, 1" is more than enough.
"Home Off sets the position of the home switch to the Home Offset value. It doesn't do any movement."
"The Home Off is to enter a value that you would like to show in the DRO when AT the Home pos. For instance if you were to home in the bass ackwards direction on an axis that is say 12" long. You would enter 12.0000 (Y as an example)."
Throw me another example. I still don't understand haha. (sorry)
Normally home the Y in the neg direction so all coords the are Y pos. I have to home my 12" y in the Pos direction. When it hits home, it automatically puts 12.000 in the dro indicating that I am home and at +12". (conventional setup)
One other thing to mention, you can have 2 limits on each axis ALL connected in series to 1 input pin.
When Homing, they are treated as Home switches, otherwise, they are treated as limit switches.
So i can use 1 port and 1 pin for all my home/limits as long as i tell the machine which way to home (+,-) (i home in the negative direction) correct?
YUP. The axis's will home one at a time (normally)
I have been using 3 pins!!! :( i didn't know that!
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It all makes sense now!!!!!! Thank you VERY much!!!!!!!!
I found out that for some reason the mach 3 plugin file for the smooth stepper was not allowing me to use, slow, or soft limts at all!!
----->SmoothStepper_Beta2_v015ogx2.m3p This file, the "stable" version works for me (even though it says beta, its the older version).
----->SmoothStepper_v17bd.zip This version, the newer version did not allow me to use any kind of soft limits, or slow.
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:)
Excellent !
Wish I could help with the SS.
Been to the Warp9 forum ?
I have one but haven't used it yet.
Best wishes,
Russ
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They are pretty sweet! Super powerful little boards. I have 3000rpm servos, Viper100 drivers, 1000CPR us digital encoders and my y axis flies around at 500ipm and the x at 700ipm super smooth. :)
It just needs a few more bugs fixed and it will be amazing! :D
I was unaware of the forum!!!!
I will join asap!
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hello,
I have one question regarding the slow zone setting.
So, the speed is reduced in slow zone only when jogging but when I homing (ref all home) the speed is not reduced in the slow zone and the switches are reached at "Speed %" setting. In fact, all homing procedure is made ar "Speed %" value.
This is normal?
Thanks,
Seb
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Yes that is normal. There is no way Mach can know where it is until a Home has been done so there would be no way to know where to slow down.
Hood
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thank for your fast reply Hood
yes indeed, it's true Mach don't know where is it until a home but in this case the slow zone is a little bit useless because when manually jogging the machine the operator should keep he's eyes there and see where the machine is moving
I'm thinking now for a procedure to have rapid movement for homing, something like zeroing the tool height in big-tex's blue probing screen set, in 2 steps.
first step at a higher speed, until home and then, after a short retract, the second step with slow speed for getting a higher accuracy.
I think an improvement like this will be useful at least for large machines with heavy gantries. If I'll have time and "inspiration" I'll give a try and post here the results. Hope will be positive. :)
Best regards,
Seb
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This will home at the homing speed in Config>Homing/Limits, then home again at 1/10 the speed.
So if you set the Homing speed at 50%, it will home at 50% first, then 5%.
DoButton(24)
DoButton(23)
DoButton(22)
While IsMoving()
Wend
SetParam("XRefPer", GetParam("XRefPer")/10)
SetParam("YRefPer", GetParam("YRefPer")/10)
SetParam("ZRefPer", GetParam("ZRefPer")/10)
DoButton(24)
DoButton(23)
DoButton(22)
While IsMoving()
Wend
SetParam("XRefPer", GetParam("XRefPer")*10)
SetParam("YRefPer", GetParam("YRefPer")*10)
SetParam("ZRefPer", GetParam("ZRefPer")*10)
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wonderful! many thanks Gerry!
working perfectly