Quick Tip: IF you have Home/Limit Switches, here is an example and description on setting them up

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Roadstercycle
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Re: Quick Tip: IF you have Home/Limit Switches, here is an example and description on setting them up

Post by Roadstercycle »

cnckeith wrote: Sat Dec 02, 2017 11:08 pm Scoty i think you are confusing Part Zero location with Machine Home Zero location. these are two different zero points!
Machine Home by definition is machine ZERO. But that is NOT the same as Part (WCS Work Coordinate System) Zero.
When the machine is done homing the DRO (Digital Read Out) is displaying the distance the tool is from PART ZERO (WCS). (You can set the part zero location anywhere you want on the machine using the part setup menus F1 setup, F1 Part etc..)

Once the machine is homed out, pressing Alt D will show you that the machine coordinate system is at X0Y0Z0 when the machine is at the home position.
Jogging to the other end of the axis travel and stopping just before the axis hits a hard stop will produce the number on the DRO you need to enter into the software travel limit values in the wizard.

CNC programmers do NOT use the machine coordinate system to program parts. you use the Work Coordinate System to make parts.
so press Alt D again to switch out of machine coordinates back to the WCS and set your part zero position where every you need to on the machine to make parts!

oh.. and there is no such thing as having the home switch on the wrong side:-) you can put it on either end of the axis. no problem.

here in this old video when i had hair.. i talk about homing and part zeros..

https://youtu.be/mA41pUyONJM?t=6m23s
Keith, I just watched that whole video and it should be in a few places for people to watch for many different reasons not just homing. It is a fantastic wealth of knowledge. Anyone coming from Mach 3 or any other PC controlled controller that never used a industrial type controller would do themselves a great service to watch this. Yes it's old and no touch screen but it is great. I've been using Mach for years and now going to change over both my machines to Acorn and I am so glad I watched it. Answered tons of questions. Make it more available.
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Re: Quick Tip: IF you have Home/Limit Switches, here is an example and description on setting them up

Post by muibubbles »

Can someone explain the homing sequence (for a router table) for me?
The last controller I attempted was linuxcnc and the sequence was rapid to home switch, back off, then slowly index back to the home switch at a slower rate for better accuracy.

I've also read someone with limit + home switches has the sequence set up to rapid to limit switches then slowly back off to homing sensors.

Is this the standard sequence and is this how acorn handles it? or does it simply just stop once the sensors are triggered and sets it as home?
How do you change the speed at which the machine searches for home?
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Re: Quick Tip: IF you have Home/Limit Switches, here is an example and description on setting them up

Post by cnckeith »

what type of router? moving table? moving gantry? paired motor axis gantry or single motor?
homing a router is no different than homing a milling machine.
you have several options when homing any machine tool.
Simple Home and Home to Switch are the two big ones.
Simple Home just sets home where ever the machine is sitting. and is a reliable and simple way to do things , setup hard stops or marks and jog the machine to hard stop and then set home at that position.
"Home to Switch" is controlled by a G&M code program (called cncm.hom) so you have LOTS of choices on how you want the auto homing procedure to occur. Its does what ever the program tells it to do. cncm.hom is a text file so you simply edit the file with the commands you want to achieve the homing you desire.
Homing speed occurs at the slow jog rate for consistent homing results. if that's too slow for a large format machine, simply fast jog each axis close to the switch before homing and then start the home program, now the home program only has a short distance to go to hit the switch. you can also "park" the machine automatically at the end of the day close to the switches so that when homing out the next morning the machine is very close to the switches and you wont have to manually jog the machine close to the home switches everyday.

check out the operator manual on page 13-7 M91, M92, G92, M26, M105, M106 are all common M and G codes used in a cncm.hom. you can use them to build a cncm.hom program specifically for your machine.
Need support? READ THIS POST first. http://centroidcncforum.com/viewtopic.php?f=60&t=1043
All Acorn Documentation is located here: viewtopic.php?f=60&t=3397
Answers to common questions: viewforum.php?f=63
and here viewforum.php?f=61
Gear we use but don't sell. https://www.centroidcnc.com/centroid_di ... _gear.html
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Re: Quick Tip: IF you have Home/Limit Switches, here is an example and description on setting them up

Post by muibubbles »

Thank you Keith that was very helpful I have a moving gantry router, 5'x14' so I will have to fast jog close to zero then home it from there.

How do I access the G&M code program? Is this simply opening a txt file that I have to manual write scripts? (I think this is similar to where I began to get lost in linuxcnc) Are there any videos on this?

When you say "slow jog rate" this is referring to the speed rate I assign to the "tortoise jog speed" button correct?
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Re: Quick Tip: IF you have Home/Limit Switches, here is an example and description on setting them up

Post by cnckeith »

muibubbles wrote: Tue Jan 02, 2018 10:58 pm

How do I access the G&M code program? Is this simply opening a txt file that I have to manual write scripts? (I think this is similar to where I began to get lost in linuxcnc) Are there any videos on this? << Press "F6 Edit" on the main screen of CNC12 to edit the loaded G code program, or use windows and navigate to any .txt or .cnc or .nc program and right click and Edit the program. I use Notepad ++ (setup for g code editing see TB 294 http://www.centroidcnc.com/dealersuppor ... ds/294.pdf) >>>

When you say "slow jog rate" this is referring to the speed rate I assign to the "tortoise jog speed" button correct? << yes, you set that rate in the Wizard or inside of CNC12>>
Need support? READ THIS POST first. http://centroidcncforum.com/viewtopic.php?f=60&t=1043
All Acorn Documentation is located here: viewtopic.php?f=60&t=3397
Answers to common questions: viewforum.php?f=63
and here viewforum.php?f=61
Gear we use but don't sell. https://www.centroidcnc.com/centroid_di ... _gear.html
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Re: Quick Tip: IF you have Home/Limit Switches, here is an example and description on setting them up

Post by muibubbles »

Thanks Keith, I will look into the file and study it some more!

The other day I was trying to wire up some NPN Proximity switches and got a little confused as the Acorn wiring diagram and other diagrams/info I came across only showed 2 wire connections (while the Proximity sensors have 3) With the help of marty I got them up and running so I just wanted to share how I wired them up for anyone who is more visual like me.

Brown- +24VDC
Blue- Common
Black- Acorn Input
Image

Hope this helps some of you!
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Re: Quick Tip: IF you have Home/Limit Switches, here is an example and description on setting them up

Post by hackish »

I read the entire thread. I was wondering what happens when the acorn tries to home but already has an active home switch signal?

I was thinking of setting up a home signal at the machine origin and using the actual machine limits to trip a hardware fault in the Minas A4 Panasonic servo controllers. This way, the software limits should stop the machine from crashing, but if it doesn't, the servo controllers will stop it. The problem I can forsee is that the machine may not have been parked on the positive side of each origin switch - so can the acorn be told to backup until the home signal clears?

Is this possible, or simply a bad idea?
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Re: Quick Tip: IF you have Home/Limit Switches, here is an example and description on setting them up

Post by Gary Campbell »

You will receive a "LIMIT SWITCH...." message, requiring you to move off the switch. You can always modify the homing file to check the switches and move off. Very few restrictions with the Centroid system
GCnC Control
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https://www.youtube.com/user/Islaww1/videos
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Re: Quick Tip: IF you have Home/Limit Switches, here is an example and description on setting them up

Post by hackish »

Does the homing file allow conditionals? In other words, if switch is X then do Y, otherwise do something else?
Gary Campbell
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Re: Quick Tip: IF you have Home/Limit Switches, here is an example and description on setting them up

Post by Gary Campbell »

If then and if else, among others are available
GCnC Control
CNC Control & Retrofits
https://www.youtube.com/user/Islaww1/videos
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