I have limit switches but I dont normally have any use for them. They're there only as a safety feature to prevent damage. As stated a stepper cant burn out in a stall situation but the stresses on a lead screw setup with some serious steppers could be big enough to knock something loose or strip out an anti-backlash nut. X and Y have them at both ends of the travel and Z only max up. If you want them theyre not all that expensive, probably less than 5 bux an axis counting the wire. If you can use them or not depends on your controller hardware. As an example Mach 3 can actually support 3 of then on 4 separate Axis but you also have to have the pinouts on the controller board also. While a limit switch setup would give you a known repeatable zero point as far as the cnc goes the only use I see for that is in some industrial setup where you must have both zero point systems available, the zero the machine uses and the zero point you define on your stock in your cam software. Mach 3 actually supports BOTH the table limit switch zero point coordinate system and a coordinate system based on the zero point set on the stock by your cam program. Other controllers may or may not do that. Why? Simple, the only zero that really matters for non-production stuff is the one on the stock. Even doing production stuff without limit switches is easy to do also. Just create some sort of locating jig and that can be nothing more than an L shaped piece located and clamped down so it will locate each piece of stock in the same spot and orientation. Just set the zero to a corner and surface of the stock on the first piece of stock after its in place in the jig. After you do one simply stick the next stock in the jig and start the g-code over.... You can jog anywhere on the table to get the router out of the way and it will just go back to the first cut point on the next part automatically. The controller will always know where it is referenced from that set zero point. Harder to type this out than to actually do it.. :) Bottom line --- ignore around 50% of what you read on some commercial made production CNC such as one to make crankshafts.. Never seen a hobby CNC with safety doors with interlock switches on it yet.. :) Im not saying a hobby CNC wont mangle fingers, It will if you're stupid enough to go poking around the bit with the router going. It is also not likely a hobby cnc can crush an arm or finger if its in the way either. They just dont have the drive power to do it. Safety should still apply though.
For the most part I agree with your philosophy about limit switches and software limits. I do use limit switches to home my machine but only because I often use a vise that I have parked in one position. When Mach ends it asks if I want to save the fixture. That allows me to know that my zero for the vise is already set up at the rear jaw and right end (where I keep the stop). So, they are handy for things like that but otherwise? Not so much. Good video!
I like to set my zero by homing it to the limit switches. And I don't like to smash the machine against its hard limits (running on leadscrews). Even if it cost me 50€, I'd still go for limit switches 🙂
Good job as always. You always give me food for thought. Feeling silly with my homing switches. But hey, they do serve as a bell and whistle sought of thing when showing off the machine to those unaware types. Thanks Peter for your efforts. Looking forward to the next one.
+Ted Kreeger Maybe I should feel silly for not having them. It is only my personal opinion. I like the idea of the parking function that others have mentioned which I didn't know about . As I said in the video, they aren't for me but don't let my opinion discourage anyone from adding them. If it makes life easier then do it. I'm learning more from the comments posted here. Who knows, the next video might be " why I added limit switches."
Well, my DIY (home made) desktop cnc do not have limit switch too, What I always do whenever I am milling or engraving something. I always point the bit on a drilled hole on my waste board....by jogging them towards it, zero in x and y..then on my material, I place a piece of paper on top lower down my Z axis by jogging again. then all is set.. I just can't just pull it since I am using lead screw. so I have to use the jog function of the software. Great tip CNCnutz.
I would disagree with the soft limits being useless. I have hard limits on the Y-axis, and will bump the unit to them to verify it is square as you do; but then I also have magnetic sensors to detect HOME. I click the HOME button (Running LinuxCNC) and the machine goes through the process. Now the machine knows exactly where it's limitations are with a 5mm safety margin from the edge. (Why bang up the machine and cause additional wear?) Why do it? Because I have certain index points on the machine... (screw points) once homed, I can install a jig that I used months ago, load my setup G-Code, and it will set the G54 (P1) perfectly. Now I can mill my parts very repeatably without needing to fiddle with jogging the X/Y positions or needing to worry about running out too far. I'm holding an accuracy of about 0.0007 inch (0.01778mm) repeatability. The homing function is fast... on average about 8 seconds. Much more simple and faster than me playing with the JOG buttons trying to get it reset after a couple of months. Another thing that I like... is by using the HOME switches, I always start with the spindle at a known position... at any time I can command a G53 X0Y0Z0 to go exactly there... or to some other known offset point. So I may have a jig with X53.6 Y72.4 written on it... and I can type G53 G0 X53.6 Y72.4 to have the machine go EXACTLY where I last had the zero point. Then touch off (Reset the G54) with G10L20X0Y0Z0 and begin. (I've made custom buttons on my LinuxCNC pyVCP panel for this purpose.) I'm certain Mach3 also supports that functionality. Explained: th-cam.com/video/hfEhMILDB6s/w-d-xo.html
Thanks for the explanation. A good point about the jig position. The jigs I use have the zero point built into them and their position is set by the router bit. This makes setting the jig very easy and I can put it anywhere on the table accurately and quickly. For Jigs that need to be screwed down to a certain location as yours are, then my method won't work and the limit switch method is the best. Your jig is the equivalent of the zero plate or the tool changer. something on the table at a fixed point that the machine needs to know about. I don't have them so I come up with ways to do things without them. You have them and use them the the fullest. Offsets are something I haven't got into. I will have to have a bit of a read up on them but I'm sure Mach3 will have all the same functionality as LinuxCNC. Cheers Peter PS Watched your workshop tour, I like the lady router.
The offsets are cool if you have an array of parts set a known distance... you can make your G-Code, run a part, then go to the next offset and run it again. I know about them... but honestly... I only use G54 (P1) and the machine hard home. (G53) Mach3 does support them... LinuxCNC has 9 defined... but it looks like with a little trickery... Mach3 can have 254... Reference: machmotion.com/cnc-info/g-code.html#G54-G59_and_G59_P1-254_Work_Offsets
Thanks Jerry. I could see them being useful if I was mass producing a product that needed to be put into jigs. I could change one while the other is cutting without having to zero between jigs. I will have a closer look at them. Cheers Peter
@@cncnutz Yeah, do install them, you will get used to them very quickly. It is great when something goes wrong with the job to just reset machine and set line where it ended instead of trying to re position against drilled hole... ive been there.. when using more tools even when manually changing them getting right xy is great especially if u start 10mm then 5mm drill bit, the starting hole would be too big and i continue usually next day so machine is off. If you have job which needs to be interrupted and continued next day or loss of power...(i use notebook so i get signal from cnc power was lost, mach3 stops but notebook goes to sleep mode so i know where machine stopped. Also my machine have encoders... so running machine against hard limits would result in positioning error being turned On on drivers. Any way limits can be good fun
@@vladomiklusicak4652 Oddly enough I will be adding limit switches to my machine in the near furure. I was looking at possible mounting spots yesterday. As you said I will probably really like them once I have them installed just like the Automated spindle and my touch off plate. Before I installed them I never gave them a second thought. Cheers Peter
For a powerful machine, limit switches are necessary. For my 6040, I have optical HOMING switches only, which is incredibly useful for setting machine zero with repeatability especially if you lose position. Optical switches have excellent accuracy, and trying to eyeball it is not an option.
I was watching your cam clamp video when this popped up on auto played afterwards. Thought I'd throw in my 5c worth. I have homimg switches on my machine and have found them invaluable. I also have UCCNC configured with soft limits. So the way it works for me is that I home the machine. This sets my machines XYZ 0,0,0 and from then on, UCCNC will use the soft limits to stop the machine from ever running into any end point. It will decelerate as it comes to the end of the travel and stop without a crash. It will stop smoothly before it hits the homing switch and before it hits the + end travel. The only time it will ever hit the ends is if your steppers are loosing steps. I have gone for weeks without having to re-home the machine and because it never crashes the end point, it never looses its position. Even better is if the power goes out, I just re-home the machine again and now the machine know it's limits and location, but UCCNC keeps the offsets and I can restart the job exactly lined up. Ofcourse this emergency recovery only works if your save your offsets in UCCNC. For me, I have a button on my pendant set to save offsets. So I push a button to Zero, then push a button to save offsets. I also have jigs with locating pins so that I know the exact machine coordinate of it's center point, and by going to the exact machine point and zeroing the work coordinates, it is in the perfect position every time.
Thanks John Im sure they are useful and invaluable in some cases. That said I haven't seen a situation in my day to day machining where that would be useful to me. Anything homing switches can do I can do manually and it is just as quick though I admit that it is not as convenient as something automatic. I have nothing against them but I don't Need them. Maybe one day I will turn to the dark side but not today. Mind you I have already moved to an autozero tool setter so anything is possible. 😉 Cheers Peter
+Trevor Burke I won't leave you hanging as to where to get them. They are just Orings. Take your cutter down to an engineering supplier and get ones that are a good tight fit.
+Trevor Burke I won't leave you hanging as to where to get them. They are just Orings. Take your cutter down to an engineering supplier and get ones that are a good tight fit.
Yes if you are a home builder it is procedure to mount them, so why bothering you can go without them. I left cables on machine for them, want to simplify it with just one switch per axes, magnetic ones and at the end of axes metal parts to activate switch. But it is better use my time to do some projects and learn software tips, and later when I found some time mount them.
+Majsta Ć. I bought my switches determined I would install them this build. Got it moving and thought I would do it later. 8 years later I still have the switches sitting under the table. I'm sure they will still be there in another 8 years. No point rushing these little jobs. 😁
I've just ordered a bag of microswitches on Ebay to install limits on my machine - then I see this video, and I panic a little. But it's all OK. My machine is not like yours and I will be using the switches for homing and position finding. I know a stepper can happily go clunk into an end stop, but I can't happily watch it. And of course a stalled stepper has lost its position, whereas one that trips a limit switch still knows exactly where it is.
No need to panic Don. I said I don't NEED the switches. I didn't say that you shouldn't use them or that they are a waste of time. I think you will find them useful and will enjoy having them. I have some on order at the moment and will be adding them to my machine in the future as part of an upcoming project I undertaken. Cheers Peter
If you move into hobby cnc from a lathe, with auto-feed and powered carriage leadscrew etc, then the destructive forces are something difficult to forget. What I am baffled by is how a sloppy microswitch is supposed to provide a precision end-point? They are used on factory machinery safety guards (and microwave oven doors) because they are a last resort to cut off all power instead of a hand, not twinkle a light or do something in software. I have had enough industrial copiers apart (and CD ROM drives etc) to know that a slotted IR opto-detector is the standard way to detect a travel end-point accurately.
The power of a worm drive is phenomenal as you say. I think the answer to the micro switch question is they are cheap and many years ago they were all that was really available so have probably what people think of when you say switch. These days optical and proximity switches are off the shelf items and are far superior for sure. cheers Peter
Deffo needed for beginners, I trashed 3 ball screws snapped 2 couplers in one move, and if I had them fitted it couldn’t have done any damage. It still bugs me now that I trashed it. I stop there. good videos, thanks for uploading.
+theDaftman Sorry to hear that. I have never heard of anyone breaking ballscrews or couplers with a stepper motor let alone 5 items in a single move. Stepper motors usually stall and slip when they reach a hard limit. It implies a serious mismatch of components. Either your ballscrews and couplers are too small or your steppers are way too big. The biggest worry for me is that sooner or later one of your limit switches will fail and you will break another coupler and ballscrew. It would bug me as well. Cheers Peter
It's not just for beginners mate. everyone should have limit switches. Not only as a safety measure against crashing into the ends of travel, but because if there's a communication error, power outage, or you need to stop / re-position the machine... Using limit switches, and set G28.1, then even in the event of power failure, when you bring the machine back online, you can simply home the machine, and send the G28 command, and you'll be back to the start position of your last operation.
They are on all industrial machines because they are essential not just usefull. I have seen them fail a few times, once on an SCM Routomat Twin Bed, bearing in mind industrial machines often rapid at over 10 meters per minute and weight a LOT, there was a massive bang, the ground shook and people came ruunning out of the office to see what had happened but the machine held together, although the X axis screw had dents from the nut bearings so had to be replaced. The second time, on a Multicam 8000 (rapids at over 15 meters p/m), one of the two Y axis motors ripped of it's mounting and the linear rail had bearing dents in it, when the operator jogged the machines Y axis off the limits not realising only one side of the gantry was powered and that the other was jammed we ended up with twisted bent gantry, permently. I've started using small hobby machines after 17 years with industrial machines and have tried without switches, but it's extremly slow and inacurate when it comes to referencing the machine and it also hurts to see it crash, there is stress on the motors and machine that are just not necessary. It's an almost free upgrade with massive benefits. Yes they are not essential on small hobby machines but the only reason you should not fit them is if you have tried and just can't figure it out, which is fair enough, it's not the end of the world.
I'm back trying to set up my machine after an absence and I can get Y and Z to perform correctly in Mach3. Yet the X-axis always tries to sail right on through the limits that I've set for it. I first go into Machine Co-Ordinates and SoftMax is 33" on the X-Axis, the SoftMin is 0 and it's SoftMax 14 and SoftMin 0 on the Y-Axis with SoftMax of 0 and SoftMin of 9.5 on the Z-Axis. After I've made my settings whenever I hit REF ALL it goes to the above settings and tries to continue on and on on the X-Axis. It doesn't matter if I enable Soft Limits or not. Any insight that you can provide would be greatly appreciated.
I'm sorry Ronald but I can't really help as I don't have switches or limits setup on my machine. Hopefully someone else will be help you out. Maybe one day someone will show me folly of my ways but until then I will keep on using my machine without them. Cheers Peter
Thanks anyway Peter, CorvetteGuy50 gave me a rundown on the subject with a new video that he just posted. I myself didn't want to run Limit Switches as we both know, that they're not infallible. I was intending on not Running them. But couldn't find an exact method of setting up my machine that was in Plain English.
Love your channel and usually your advice but I have to disagree with how helpful I have found limit switches to be. I only have a small hobby Chinese 3020 to play with and for me, learning the CAD, CAM, material choice, bit choice, feeds and speeds and a whole lot more has been fun but hard! They have been a great help with easily maximising my table area, repeatable finding zero or specific coordination for 2 sided machining and from stopping my machine slamming itself apart if I get something wrong! I would say they are MORE important for hobby DIYers!
No Worries Shaun, I am expecting people to agree and disagree on this subject, with people from both sides of the fence joining in. I have not been disappointed and learned a couple of other functions that limit switches can be used for. While they are not things that would cause me to rush out and install them they are worth noting. I do enjoy learning new things. Thanks for sharing your thoughts, I do appreciate it. Cheers Peter
I tried them at the beginning. They are notoriously unreliable. When homing you think they will stop the machine, but if not for what ever reason, they break. First themselves and then the machine.
all makes sense to me... I would like limit switches to home the gantry that way when your machine finishes a job it will park itself out of the way automatically. Probably more convenient for a lead screw type machine not one you can just push around easily when the motors are off.
Never though of the ability to home the machine to an out of the way location at the press of a button. That could be handy but then as you say I can just push the gantry out of the way if it is a problem. Thanks for the info. Cheers Peter
yea you can give it a button or add G28 to the end of your gcode .... just add homing to the end of every job you run threw your cam program.... voila no buttons needed. take care
Limit switches and soft limits go hand-in-hand. Homing a machine that size would take, what? 45 seconds? Seems like 45 seconds per power cycle would be worth never slamming the machine into a hard limit, unless it somehow doesn't have enough power to damage itself.
+Hirudin Running my machine into the hard limits won't damage it. It very rarely hits a hard limit by accident. I see what you mean about the soft limits. I was thinking of them used as a limit in their own right but can see how they would work in conjunction with the limit switches to define a working area. Thanks.
Thanks again Peter. You've found, what I think, is an important nitch (where I live). IE, most instructions in CNC are like the Mach3 instruction manual, not a lot of detail, and too many unrecognizable spaces between one point and another. So the novice, and or, person who hasn't lived long in this world becomes easily lost. And for some reason, the big boys are unable to communicate to people like me. THANKS for bridging the gap.
If i Run my machine in hard stop I will destroy coupler and might damage ball screw!! Limits must to have. Soft limits are fantastic every time start your router just Home it and you have fantastic protection also wit give you warning straight away when you load Goode that it might be outside your limits. As I really enjoy your channel must very strongly disagree on this one .
Thanks Marek. I understand why you like your limit switches and they are necessary to your machine. I am concerned that the machines designer has constructed it such that it will damage itself if and when one of the limit switches fails which will happen sooner or later. Cheers Peter
There's no need to run the gantry into the hard limits at full speed. Also hard limits are there it is a safety feature to stop the gantry from running off the end. If they break under normal circumstances then they have not been engineered correctly. Cheers Peter
I have limit switches, but the only thing I use them for is one click parking... I just hit Home all and away it goes without me having to park it manually. Still have to turn off the PC once it's parked though ;-) Call me lazy....
You have no idea what your talking about, limit switches help Protect your cnc by Not constantly Smashing into the end of the Screw or bed. As for Finding Machine Zero, Limit Switches are much Quicker than Finding a Hole, then entering the Coordinates.
Ive never seen an Industrial CNC (Haas, Mazak, Mori, OKK, etc) without limit switches, softlimits, or both, slamming a 2 ton moving head into a hardlimit at 1000 IPM because you miss a decimal point or a negative number is a real pucker moment, not to mention potentially pricey. and thank you youtube for showing me this and making me necro a thread.
I have limit switches but I dont normally have any use for them. They're there only as a safety feature to prevent damage. As stated a stepper cant burn out in a stall situation but the stresses on a lead screw setup with some serious steppers could be big enough to knock something loose or strip out an anti-backlash nut. X and Y have them at both ends of the travel and Z only max up.
If you want them theyre not all that expensive, probably less than 5 bux an axis counting the wire. If you can use them or not depends on your controller hardware. As an example Mach 3 can actually support 3 of then on 4 separate Axis but you also have to have the pinouts on the controller board also.
While a limit switch setup would give you a known repeatable zero point as far as the cnc goes the only use I see for that is in some industrial setup where you must have both zero point systems available, the zero the machine uses and the zero point you define on your stock in your cam software. Mach 3 actually supports BOTH the table limit switch zero point coordinate system and a coordinate system based on the zero point set on the stock by your cam program. Other controllers may or may not do that.
Why? Simple, the only zero that really matters for non-production stuff is the one on the stock. Even doing production stuff without limit switches is easy to do also. Just create some sort of locating jig and that can be nothing more than an L shaped piece located and clamped down so it will locate each piece of stock in the same spot and orientation. Just set the zero to a corner and surface of the stock on the first piece of stock after its in place in the jig. After you do one simply stick the next stock in the jig and start the g-code over.... You can jog anywhere on the table to get the router out of the way and it will just go back to the first cut point on the next part automatically. The controller will always know where it is referenced from that set zero point. Harder to type this out than to actually do it.. :)
Bottom line --- ignore around 50% of what you read on some commercial made production CNC such as one to make crankshafts.. Never seen a hobby CNC with safety doors with interlock switches on it yet.. :) Im not saying a hobby CNC wont mangle fingers, It will if you're stupid enough to go poking around the bit with the router going. It is also not likely a hobby cnc can crush an arm or finger if its in the way either. They just dont have the drive power to do it. Safety should still apply though.
For the most part I agree with your philosophy about limit switches and software limits. I do use limit switches to home my machine but only because I often use a vise that I have parked in one position. When Mach ends it asks if I want to save the fixture. That allows me to know that my zero for the vise is already set up at the rear jaw and right end (where I keep the stop). So, they are handy for things like that but otherwise? Not so much. Good video!
Thanks.
I'm with you. I Don't use them, in the past 9 years.
Thanks Jim
I like to set my zero by homing it to the limit switches.
And I don't like to smash the machine against its hard limits (running on leadscrews). Even if it cost me 50€, I'd still go for limit switches 🙂
What I learned from this is I definitely want limit switches haha
Good job as always. You always give me food for thought. Feeling silly with my homing switches. But hey, they do serve as a bell and whistle sought of thing when showing off the machine to those unaware types. Thanks Peter for your efforts. Looking forward to the next one.
+Ted Kreeger
Maybe I should feel silly for not having them. It is only my personal opinion. I like the idea of the parking function that others have mentioned which I didn't know about . As I said in the video, they aren't for me but don't let my opinion discourage anyone from adding them. If it makes life easier then do it. I'm learning more from the comments posted here. Who knows, the next video might be " why I added limit switches."
Well, my DIY (home made) desktop cnc do not have limit switch too, What I always do whenever I am milling or engraving something. I always point the bit on a drilled hole on my waste board....by jogging them towards it, zero in x and y..then on my material, I place a piece of paper on top lower down my Z axis by jogging again. then all is set.. I just can't just pull it since I am using lead screw. so I have to use the jog function of the software.
Great tip CNCnutz.
I would disagree with the soft limits being useless. I have hard limits on the Y-axis, and will bump the unit to them to verify it is square as you do; but then I also have magnetic sensors to detect HOME. I click the HOME button (Running LinuxCNC) and the machine goes through the process. Now the machine knows exactly where it's limitations are with a 5mm safety margin from the edge. (Why bang up the machine and cause additional wear?)
Why do it? Because I have certain index points on the machine... (screw points) once homed, I can install a jig that I used months ago, load my setup G-Code, and it will set the G54 (P1) perfectly. Now I can mill my parts very repeatably without needing to fiddle with jogging the X/Y positions or needing to worry about running out too far. I'm holding an accuracy of about 0.0007 inch (0.01778mm) repeatability. The homing function is fast... on average about 8 seconds. Much more simple and faster than me playing with the JOG buttons trying to get it reset after a couple of months.
Another thing that I like... is by using the HOME switches, I always start with the spindle at a known position... at any time I can command a G53 X0Y0Z0 to go exactly there... or to some other known offset point. So I may have a jig with X53.6 Y72.4 written on it... and I can type G53 G0 X53.6 Y72.4 to have the machine go EXACTLY where I last had the zero point. Then touch off (Reset the G54) with G10L20X0Y0Z0 and begin. (I've made custom buttons on my LinuxCNC pyVCP panel for this purpose.) I'm certain Mach3 also supports that functionality.
Explained: th-cam.com/video/hfEhMILDB6s/w-d-xo.html
Thanks for the explanation. A good point about the jig position.
The jigs I use have the zero point built into them and their position is set by the router bit. This makes setting the jig very easy and I can put it anywhere on the table accurately and quickly. For Jigs that need to be screwed down to a certain location as yours are, then my method won't work and the limit switch method is the best.
Your jig is the equivalent of the zero plate or the tool changer. something on the table at a fixed point that the machine needs to know about.
I don't have them so I come up with ways to do things without them. You have them and use them the the fullest.
Offsets are something I haven't got into. I will have to have a bit of a read up on them but I'm sure Mach3 will have all the same functionality as LinuxCNC.
Cheers
Peter
PS Watched your workshop tour, I like the lady router.
The offsets are cool if you have an array of parts set a known distance... you can make your G-Code, run a part, then go to the next offset and run it again. I know about them... but honestly... I only use G54 (P1) and the machine hard home. (G53) Mach3 does support them... LinuxCNC has 9 defined... but it looks like with a little trickery... Mach3 can have 254...
Reference: machmotion.com/cnc-info/g-code.html#G54-G59_and_G59_P1-254_Work_Offsets
Thanks Jerry.
I could see them being useful if I was mass producing a product that needed to be put into jigs. I could change one while the other is cutting without having to zero between jigs.
I will have a closer look at them.
Cheers
Peter
@@cncnutz Yeah, do install them, you will get used to them very quickly. It is great when something goes wrong with the job to just reset machine and set line where it ended instead of trying to re position against drilled hole... ive been there.. when using more tools even when manually changing them getting right xy is great especially if u start 10mm then 5mm drill bit, the starting hole would be too big and i continue usually next day so machine is off. If you have job which needs to be interrupted and continued next day or loss of power...(i use notebook so i get signal from cnc power was lost, mach3 stops but notebook goes to sleep mode so i know where machine stopped. Also my machine have encoders... so running machine against hard limits would result in positioning error being turned On on drivers. Any way limits can be good fun
@@vladomiklusicak4652
Oddly enough I will be adding limit switches to my machine in the near furure. I was looking at possible mounting spots yesterday. As you said I will probably really like them once I have them installed just like the Automated spindle and my touch off plate. Before I installed them I never gave them a second thought.
Cheers
Peter
For a powerful machine, limit switches are necessary. For my 6040, I have optical HOMING switches only, which is incredibly useful for setting machine zero with repeatability especially if you lose position. Optical switches have excellent accuracy, and trying to eyeball it is not an option.
thanks for your advice
I dont use them either... been giving it some thought thou. You been putting out alot of content...thats awesome! thanks for sharing peter!.
+Gcodeonedesign
Thanks Juan.
That is the way I have also run my machines. Limit switches cause more problems than they are worth.
I was watching your cam clamp video when this popped up on auto played afterwards. Thought I'd throw in my 5c worth.
I have homimg switches on my machine and have found them invaluable. I also have UCCNC configured with soft limits. So the way it works for me is that I home the machine. This sets my machines XYZ 0,0,0 and from then on, UCCNC will use the soft limits to stop the machine from ever running into any end point. It will decelerate as it comes to the end of the travel and stop without a crash. It will stop smoothly before it hits the homing switch and before it hits the + end travel. The only time it will ever hit the ends is if your steppers are loosing steps.
I have gone for weeks without having to re-home the machine and because it never crashes the end point, it never looses its position. Even better is if the power goes out, I just re-home the machine again and now the machine know it's limits and location, but UCCNC keeps the offsets and I can restart the job exactly lined up. Ofcourse this emergency recovery only works if your save your offsets in UCCNC. For me, I have a button on my pendant set to save offsets. So I push a button to Zero, then push a button to save offsets.
I also have jigs with locating pins so that I know the exact machine coordinate of it's center point, and by going to the exact machine point and zeroing the work coordinates, it is in the perfect position every time.
Thanks John
Im sure they are useful and invaluable in some cases. That said I haven't seen a situation in my day to day machining where that would be useful to me. Anything homing switches can do I can do manually and it is just as quick though I admit that it is not as convenient as something automatic.
I have nothing against them but I don't Need them. Maybe one day I will turn to the dark side but not today. Mind you I have already moved to an autozero tool setter so anything is possible. 😉
Cheers
Peter
Thanks for sharing. Great video as always. Just a quick question, is that a collet stop on the larger cutter you hold up? Thanks.
Yes it is, well spotted.
I will be doing a video on that shortly.
Cheers
Peter
+CNCnutz (Peter Passuello) Fantastic, I've been looking for a place that sells them. Eagerly awaiting your video. Thanks
+Trevor Burke
I won't leave you hanging as to where to get them. They are just Orings. Take your cutter down to an engineering supplier and get ones that are a good tight fit.
+Trevor Burke
I won't leave you hanging as to where to get them. They are just Orings. Take your cutter down to an engineering supplier and get ones that are a good tight fit.
Very clear, thank you.
Yes if you are a home builder it is procedure to mount them, so why bothering you can go without them. I left cables on machine for them, want to simplify it with just one switch per axes, magnetic ones and at the end of axes metal parts to activate switch. But it is better use my time to do some projects and learn software tips, and later when I found some time mount them.
+Majsta Ć.
I bought my switches determined I would install them this build. Got it moving and thought I would do it later. 8 years later I still have the switches sitting under the table. I'm sure they will still be there in another 8 years.
No point rushing these little jobs. 😁
I've just ordered a bag of microswitches on Ebay to install limits on my machine - then I see this video, and I panic a little. But it's all OK. My machine is not like yours and I will be using the switches for homing and position finding. I know a stepper can happily go clunk into an end stop, but I can't happily watch it. And of course a stalled stepper has lost its position, whereas one that trips a limit switch still knows exactly where it is.
No need to panic Don. I said I don't NEED the switches. I didn't say that you shouldn't use them or that they are a waste of time. I think you will find them useful and will enjoy having them. I have some on order at the moment and will be adding them to my machine in the future as part of an upcoming project I undertaken.
Cheers
Peter
If you move into hobby cnc from a lathe, with auto-feed and powered carriage leadscrew etc, then the destructive forces are something difficult to forget. What I am baffled by is how a sloppy microswitch is supposed to provide a precision end-point? They are used on factory machinery safety guards (and microwave oven doors) because they are a last resort to cut off all power instead of a hand, not twinkle a light or do something in software. I have had enough industrial copiers apart (and CD ROM drives etc) to know that a slotted IR opto-detector is the standard way to detect a travel end-point accurately.
The power of a worm drive is phenomenal as you say.
I think the answer to the micro switch question is they are cheap and many years ago they were all that was really available so have probably what people think of when you say switch.
These days optical and proximity switches are off the shelf items and are far superior for sure.
cheers Peter
Deffo needed for beginners, I trashed 3 ball screws snapped 2 couplers in one move, and if I had them fitted it couldn’t have done any damage. It still bugs me now that I trashed it. I stop there. good videos, thanks for uploading.
+theDaftman
Sorry to hear that.
I have never heard of anyone breaking ballscrews or couplers with a stepper motor let alone 5 items in a single move. Stepper motors usually stall and slip when they reach a hard limit. It implies a serious mismatch of components. Either your ballscrews and couplers are too small or your steppers are way too big.
The biggest worry for me is that sooner or later one of your limit switches will fail and you will break another coupler and ballscrew.
It would bug me as well.
Cheers
Peter
It's not just for beginners mate. everyone should have limit switches. Not only as a safety measure against crashing into the ends of travel, but because if there's a communication error, power outage, or you need to stop / re-position the machine... Using limit switches, and set G28.1, then even in the event of power failure, when you bring the machine back online, you can simply home the machine, and send the G28 command, and you'll be back to the start position of your last operation.
They are on all industrial machines because they are essential not just usefull. I have seen them fail a few times, once on an SCM Routomat Twin Bed, bearing in mind industrial machines often rapid at over 10 meters per minute and weight a LOT, there was a massive bang, the ground shook and people came ruunning out of the office to see what had happened but the machine held together, although the X axis screw had dents from the nut bearings so had to be replaced. The second time, on a Multicam 8000 (rapids at over 15 meters p/m), one of the two Y axis motors ripped of it's mounting and the linear rail had bearing dents in it, when the operator jogged the machines Y axis off the limits not realising only one side of the gantry was powered and that the other was jammed we ended up with twisted bent gantry, permently.
I've started using small hobby machines after 17 years with industrial machines and have tried without switches, but it's extremly slow and inacurate when it comes to referencing the machine and it also hurts to see it crash, there is stress on the motors and machine that are just not necessary. It's an almost free upgrade with massive benefits. Yes they are not essential on small hobby machines but the only reason you should not fit them is if you have tried and just can't figure it out, which is fair enough, it's not the end of the world.
I'm back trying to set up my machine after an absence and I can get Y and Z to perform correctly in Mach3. Yet the X-axis always tries to sail right on through the limits that I've set for it. I first go into Machine Co-Ordinates and SoftMax is 33" on the X-Axis, the SoftMin is 0 and it's SoftMax 14 and SoftMin 0 on the Y-Axis with SoftMax of 0 and SoftMin of 9.5 on the Z-Axis. After I've made my settings whenever I hit REF ALL it goes to the above settings and tries to continue on and on on the X-Axis. It doesn't matter if I enable Soft Limits or not. Any insight that you can provide would be greatly appreciated.
I'm sorry Ronald but I can't really help as I don't have switches or limits setup on my machine. Hopefully someone else will be help you out.
Maybe one day someone will show me folly of my ways but until then I will keep on using my machine without them.
Cheers
Peter
Thanks anyway Peter, CorvetteGuy50 gave me a rundown on the subject with a new video that he just posted. I myself didn't want to run Limit Switches as we both know, that they're not infallible. I was intending on not Running them. But couldn't find an exact method of setting up my machine that was in Plain English.
With only hard limits for your machine are these used to home x and y?
I just used them to square the machine and stop it driving for the end of the gantry.
Cheers
Peter
Love your channel and usually your advice but I have to disagree with how helpful I have found limit switches to be. I only have a small hobby Chinese 3020 to play with and for me, learning the CAD, CAM, material choice, bit choice, feeds and speeds and a whole lot more has been fun but hard! They have been a great help with easily maximising my table area, repeatable finding zero or specific coordination for 2 sided machining and from stopping my machine slamming itself apart if I get something wrong!
I would say they are MORE important for hobby DIYers!
No Worries Shaun,
I am expecting people to agree and disagree on this subject, with people from both sides of the fence joining in.
I have not been disappointed and learned a couple of other functions that limit switches can be used for.
While they are not things that would cause me to rush out and install them they are worth noting.
I do enjoy learning new things.
Thanks for sharing your thoughts, I do appreciate it.
Cheers
Peter
Peter, Lol I love the video ending ouch.
Thanks Lou.
Had to go back and see what the ending was. I forgot I did that. 😁
Cheers
Peter
I dont have them either. Just a pain
I agree Max.
I like to keep things simple then there is less chance of something going wrong.
Cheers
Peter
I tried them at the beginning. They are notoriously unreliable. When homing you think they will stop the machine, but if not for what ever reason, they break. First themselves and then the machine.
all makes sense to me... I would like limit switches to home the gantry that way when your machine finishes a job it will park itself out of the way automatically. Probably more convenient for a lead screw type machine not one you can just push around easily when the motors are off.
Never though of the ability to home the machine to an out of the way location at the press of a button.
That could be handy but then as you say I can just push the gantry out of the way if it is a problem.
Thanks for the info.
Cheers
Peter
yea you can give it a button or add G28 to the end of your gcode
.... just add homing to the end of every job you run threw your cam program.... voila no buttons needed. take care
+builtrodewreckedit
Thanks
Of course you need them i clattered my y axis without them by putting the decimal point in the wrong place
Thanks for your opinion no "Limit switches"
Very interesting point
Thanks Julio
Limit switches and soft limits go hand-in-hand. Homing a machine that size would take, what? 45 seconds? Seems like 45 seconds per power cycle would be worth never slamming the machine into a hard limit, unless it somehow doesn't have enough power to damage itself.
+Hirudin
Running my machine into the hard limits won't damage it. It very rarely hits a hard limit by accident. I see what you mean about the soft limits. I was thinking of them used as a limit in their own right but can see how they would work in conjunction with the limit switches to define a working area. Thanks.
Might be good for new users as well
Thanks again Peter. You've found, what I think, is an important nitch (where I live). IE, most instructions in CNC are like the Mach3 instruction manual, not a lot of detail, and too many unrecognizable spaces between one point and another. So the novice, and or, person who hasn't lived long in this world becomes easily lost. And for some reason, the big boys are unable to communicate to people like me. THANKS for bridging the gap.
+Peter Rouzaud
Thanks Peter.
If i Run my machine in hard stop I will destroy coupler and might damage ball screw!! Limits must to have. Soft limits are fantastic every time start your router just Home it and you have fantastic protection also wit give you warning straight away when you load Goode that it might be outside your limits. As I really enjoy your channel must very strongly disagree on this one .
Thanks Marek.
I understand why you like your limit switches and they are necessary to your machine. I am concerned that the machines designer has constructed it such that it will damage itself if and when one of the limit switches fails which will happen sooner or later.
Cheers
Peter
ya but my gantry weight is over a hundred pounds, if its running full speed and slams at the end, things are going to break
There's no need to run the gantry into the hard limits at full speed. Also hard limits are there it is a safety feature to stop the gantry from running off the end. If they break under normal circumstances then they have not been engineered correctly.
Cheers
Peter
... and ust something else to have to troubleshoot when it doesn't work.
+Feed The Chunk
I would hate to try and trouble shoot one that was tripping for no reason.
I have limit switches, but the only thing I use them for is one click parking... I just hit Home all and away it goes without me having to park it manually. Still have to turn off the PC once it's parked though ;-) Call me lazy....
Parking out of the way is a good Idea I didn't know about.
Personally I am too lazy to to install them just for parking. ;-)
Cheers
Peter
grin
Wink
You have no idea what your talking about, limit switches help Protect your cnc by Not constantly Smashing into the end of the Screw or bed.
As for Finding Machine Zero, Limit Switches are much Quicker than Finding a Hole, then entering the Coordinates.
Ive never seen an Industrial CNC (Haas, Mazak, Mori, OKK, etc) without limit switches, softlimits, or both, slamming a 2 ton moving head into a hardlimit at 1000 IPM because you miss a decimal point or a negative number is a real pucker moment, not to mention potentially pricey. and thank you youtube for showing me this and making me necro a thread.