When selecting a mechanical limit switch the lifetime cycle count of the switch is important. Optical or inductive don't have this concern. Limit switch circuits should use normally closed wiring so if a cable breaks or is disconnected the limit is hit. You might consider four switches, the two inside would cause the direction to reverse, the outer two would cause the drive to halt. The later two would protect against a crash if the table were to go past the reversing switches
I concur completely. Those limit switches are going to endure a tremendous amount of cycling, so while the click-click and the visual actuation is indeed pretty neat, I think the inductive switches are by far the better way to go. If that grinder gets much use at all, those mechanical switches will have to get replaced a lot, and probably the stops, as well, unless James remakes them of steel or at least Aluminum.
He explained that there is a vinyl coated wire which is wrapped around a shaft which then moves the table. The cable can and does slip on the shaft, so deterministic positioning of the table by rotating the shaft a given amount is not possible.
@@leslierhorer1412 A) I have these type of switches click clacking all day long on decades old machines B) Its a home shop C) as noted by Patrick one would use these not as hard stops but insurance to know the table hasnt slipped on the rope and goes too far
Mechanical life is 30,000,000 operations, so at 2 seconds a direction (one operation every 4 seconds) you’d get almost 4 years 24/7 operation. I suspect a lot of other stuff will break or wear out before that.
Clicky sounds neat when you're doing it by hand a few times; I think it will get pretty annoying when it's clicking thousands of times during a grinding run...
No when on a long job the ending of 'flik-flak' of mechanical reversing is cue to return to the grinder and set it for another pass. Of course you have to be able to hear the machine stepping over.
@@alan-sk7kyit’s going to be a CNC grinder, it will run by its self, if you need something to tell you it’s the end of cycle, just needs to be an alarm or light you can see across the shop floor, not click clack all day coming to an end 😅
I have a REID 618 grinder. The bed is left and right chain driven. The front and back is done with a shiftable ratchet and screw. A large city water company bought it in 1948. Soon afterwards someone engaged the front and back lever after the stop and broke the nut assembly. They did a half fix that broke again. They sat it in the corner and painted it many ties. The two motions are driven by a 400 rpm three phase motor with a reeves drive for speed control. The machine was delivered as a 2 phase machine, interesting wiring. They converted it to 3 phase in the 1960. It was sold at auction about 2010, still broken. I installed VFDs on the movement and spindle. The ways are like new. The left and right reversal is done by a see-saw switch maintains position for current motion. It will also trip if it gets to the travel limit. A switch like that makes programing simple, no single shots, latches, and shift registers.
Hi just my two cents. Inductive sensors react to all metals not just ferromagnetic, but they don't have the same sensitivity. For example if you use aluminium instead of steel the air gap needs to smaller but it would still work. I'd go with the inductive sensors, no moving parts and they look sleeker and you have a visual indicator and they don't need to be debounced. If you go for the clicky ones, remember you need to debounce the signal in software later. In our production facility we had a lot of the roller switches fail after 1-2 years. The rollers wore out started to wobble and could jam the whole system so keep that in mind since they're probably exposed to the grinding dust. Greetings from Germany, love your channel continue the good work!
You could always sense the current of the motor to do the same when the end has been reached the motor current will spike and use that as a sensor, but you know what you are doing and I don't know if this idea will help you in the future, you probably knew this anyway. I love your videos, and I just like you.
07:50 it's hard to see but it looks like the screws have the tell-tail radial ticks of PZ/Pozidriv screws, which might be why you're having problems with your PH/Phillips driver :)
Yup, I was going to say the same thing James - it LOOKS like you're using a Pozidrive screwdriver, whereas, though my experience is MUCH less than yours, I have NEVER found any electrical/onic product from Asia which doesn't use Philips. It seems that Pozidrive is "unknown" over there.
I also did a servo drive conversion to my cheap manual surface grinder. Like you, I also finally settled on a switch assembly for change of table travel after looking at both inductive and capacitive switching. I was concerned about possible desensitivation of the inductive/capacitive switches due to metalic dust. For me, going with a mechanical switch meant relying on a questionable component for absolutely stopping my rack driven table. My solution was using the capacitive switches I had ordered previously and mounting them in protected spaces under the apron to act as failsafe table stops. I then cobbled out a small interface board to tie my travel switching, timer and servo controller to play together. I won't go CNC as the grinder is not worthy of the expense and I don't have the workload necessary to justify the expenditure. What I didn't take into account were the stresses on the flimsy base cabinet of the grinder from the sudden chages of direction generated by the servo, something I need to address. I have enjoyed following along on your conversion project and look forward to more episodes. Your videos are outstanding. Thanks for sharing your journey!!
And here I was thinking of something along the line of a scale or string tape measure mounted out of the way, and then just programming the left and right limits in software on the touch screen. Jog the table left, hit the 'left limit' button, jog right, do the same for the right limit, done. You have an absolute position measure, so don't have to worry about stepper slip. And no unsightly bulge and finger-pinchers on the front of the table!
Nice job James. Very interesting to watch. Those factory bumpers are for relocating to the center set position of a fixture on the grinder. Something like a Harig spin fixture/indexing head or a St Mary's fixture.
A few notes about the mechanical switches. As previously mentioned, use the normally closed contact to detect wire breakage. Also check the lifetime of those, if they industrial, they are a lot, but not infinite. And don't forget the de-bounce in software or hardware. The inductive switches have less issues with lifetime and bounce less, but they are not that position precise to trigger if the metal comes in from the side. They are usually designed to have the metal come in from the front. Precision is not a problem here, so sideways will be fine. Since you have both types, I would use the mechanical ones on the end for emergency stops and the inductive one for direction switch. The clicky ones will annoy you, I'm 99% sure ;)
the prox switches have a sensing range similar to a candle flame - so it is best to have a flat surface for them to sense( like key stock) rather than the round dowel surface.
I love the look and sound of those switches! However, I think I would have chosen the boring inductive ones anyway. I'm worried about what grinding dust and coolant is going to do to the mechanical switches, but maybe I'm being too paranoid. If it does become a problem, it looks pretty easy to switch to the other switches. (You already have the necessary parts!)
Another great video. If it were me, I'd use the mag sensors. You won't here those mechanical switches while the grinder is grinding, AND... they will never wear out. The mechanical switches have an MTBF measured in switch-cycles. Plus, "waterproof" or not, the mag sensors will tolerate a cooling bath better and longer. Just sayin'.
My surface grinder had a very similar X axis drive mechanism. It was too much trouble because the wire that wraps end up stretching over the years. Mine came with adjustments to keep snugging it up until the wire breaks, then you replace it and start over. I got too annoyed with this, so ended up replacing the wire drive with a lead screw and lead nut. My first attempt went well, but only lasted a year before the nut wore out. Despite the load rating on the nut being roughly 2x higher than the actual load, it seemed that the inertia of the surface grinder bed was too much and causing too high of a load at a move stop and start. So I replaced the 3/8 lead screw with a 3/4 lead screw and it has been fine ever since. Been working now 4-5 years without anything needing replacing or maintenance on the new drive mechanism. Got the lead parts from Roton. Very interesting to see you do this whole project and the parts you used. My retrofit was done with very similar parts and from Automation Direct as well. Instead of ClearPath motors I used AD Stepper motors though. ClearPath would be a much better choice, and if I ever need to replace one of my motors I will likely change them over. For my sensors on the bed I used four inductive sensors, two NO models and two NC models. The NO ones trigger a change direction on the X axis motor, and the NC ones are my overtravel sensors. Not sure how you plan to feed those sensors into the control scheme with the motors, but I used a little P1000 PLC from Automation Direct to write all my logic and make it all automate for me. They are VERY easy to learn and use, and pair extremely well with AD's HMI products. I originally had mechanical switches, but switched them to inductive because what happened over a year or two was there ended up being gunk buildup on the pivot sections of the mechanical switch from using the surface grinder with coolant. If you use mechanical ones you will have to clean off the switches really well after every use otherwise the same will happen to you. I swapped mine to inductives and haven't had the problem since because they don't care about any gunk residue buildup.
in high cycle applications you only use the clicky switches as dead stops (because each click = wear on the internal components) or where you cant use induction, magnetic, laser sensors as the switch has limited cycles it can run the induction sensor only has to be protected from debris of a metal nature but as long as no damage happens to the end of the switch it will lat until the coil inside fails also you should never design automatically controlled devices to there limits always have a buffer because if a sensor fails you will damage the device if you want to build a dead stop with the induction sensor just put a piece of metal at the back of the adjustable stop that triggers both the upper and lower induction sensor and code it to E-STOP the machine when both are active and in auto mode
I used to work for a company that did concrete conversions on all kinds of old machinery (mainly grinding machines) on surface grinders we had the endstops for the table on a rail so that the travel could be adjusted while the machine is running… those grinders were quite big as well with over 2 meters of table travel on a few of them
One thing to consider is adding a fine adjustment into the bumpers. Still using the single screw to mount to the sled is probably Ok, but 2 would be better. You wouldn't want them to move at all, and having a fine adjustment there would let you keep them mounted, but adjusting the travel after this wears in. Not sure how long it will take before they get worn.
From someone who deals with these style switches in a industrial setting. The cam style will suit your needs the best. The plunger style works best in the load is applied more in a straight down style, vs a ramp. Also with it being on a surface grinder you have less risk of buildup on the switch and it sticking closed. Just my .02
I liked the clicky sound. But for this application I think the proxy sensors will be superior. That click will get annoying real fast , and the mechanical switches are just another thing that will wear out, as far as I can tell there's nothing that will wear in the proxy arrangement, plus it's a much lower profile setup. Cool either way!
I love the clicky switches but the impending mechanical failure of said switches gives me anxiety. I'm sure you'll get a couple million cycles out of these before that happens and for a hobbyist level implementation that's probably more than you'll need! Denouncing may need to be addressed but I love this!
That is nearly identical to the actual setup on actual grinders that I used to actually sell, in terms of outward appearance. Some of the ones we sold had purely mechanical control, and if you wanted clicking, well, you got clunking.
Proximity switches are the way to go...no moving parts, not contact, so they wont wear. I really can't think of a reason to use the mechanical switches at all.
As much as i understand and agree that clicky is so tantalizingly nice; i wouldn't want to hear CLICK CLICK every hecking time it would make ONE pass for hours at a time xD I'd much prefer the induction probes for their silence and reliability, solid state tends to last longer.
you might want to put a cover on the switch - you are going to have a lot of grinding dust, that may interefere with the rollers and gum them up in the long term - probably removable so you can shop vac / air blast them. just to give you something else to print :D
If you decide to use mechanical limit switches, a often overlooked detail is that switches have both maximum and minimum current specs. The maximum spec requires no explanation. The minimum spec is often overlooked and if not met the switch can be mechanically in the closed position but be electrically open due to a thin film of oxide on the switch contacts. An intermittent limit switch is something a good designer wants to eliminate. I checked for this minimum current spec on the mechanical switch you used and it was not given. You may want to reach out for this info from the manufacturer so you can get reliable operation should you decide to use mechanical switches.
I wonder how many clicks the limit switches are specified for. With small parts and a few hundred hours you may end up with quite a few clicks. Having ground material all around can also make them wear faster. Proximity sensors on the other hand will not wear mechanically.
I dont know if its issue for your or not, I tend to just make adapter pigtail and have it on the item (switch in this case) I want to adapter, I dont put it at controller side. Btw, clicky sounds are the #1 reason to choose a limit switch :)
I would use an interface box with two different input connectors, one for the inductive and one for the mechanical. Make up two different sets of pigtails. That way the two could be very easily switched back and forth for testing or in case of a failure, etc.
This project can only be described as: How a MAUPe NERD tries to convert a machine into something it was not designed for. And the result is a machine that nobody would want.
You need to lock up that Hardinge collet chuck, or one day I am liable to sneak in and steal it! 🙂 You might consider a chip shield running the length of the stop channel just because. 'Probably not terribly necessary with a grinder, especially since the dust ejects to the side, but it wouldn't hurt.
Clicky switch is better for one other reason: It's in a machine shop. The odds of a chip or whatever interfering with the proximity switch is not zero. Pretty low because it's a surface grinder, but it would be a particularly lame way to scrap a part.
All good until grit gets into the mechanical bits of the switches and starts to wear things out, the chip/grit issue with the prox sensors is fixed by a wipe with a cloth. Or set up a wiper.
Personally I would go with inductive for the working limits and clicky for overtravel/safety limits in case the inductive sensors fail. I would assume the motors also have current measurement/limits so abnormal current from a crash could also trigger a stop?
Kind of shocked the travel pulley would slip, with 3 wraps around the pulley with slippy(0.2µ) material you still have ~43x more holding force than the tension of the cord from the slack side, while a less slippy material is in the tens of thousands of times more holding. Has the cord even got any tension on it? For further see: capstan equation or belt friction equation.
he could probably just put a fourth or fifth wrap around the spool, it looked like there was plenty of leeway. that'd make it exponentially less likely to slip
Looks like the lifetime issue of the mechanical switches has been addressed with comments below. While the cost of failure is not real high traveling in one direction, (cable just screws off the end of the drive screw) going to other night result in the cable being pulled on to itself and the vinyl coating being damaged. Yes the "click" "click" is cool but doesn't have to come from the switches. Why not add a speaker to produce a click clack to the system. A second solution is to have the software "learn" during the first N cycles about how long the travel is and then shut everything down if all of a sudden the "learned" travel is significantly exceeded.
It's Renzetti's fault. 🙂 As much I like the clicks, and I'm sure those are quality parts, the inductive sensors feel more trustworthy. You can modify that wire rope drive for slipless operation. Two cables, one end of each connected to the roller. You should do a little research, because capstan drives are awesome.
Clicky switches are just so satisfying, I think they are less prone to temperature fluctuations which makes them ideal for CNC. I’m really curious to see what controller system you go with. I’ve been playing with grblHAL and FluidNC recently for my little CNC router, and settled on the former for my DLC32 board. It’s definitely a budget solution with compromises to match. That said, I run external TMC2160 stepper drivers with my LDO stepper motors, so I get some good results.
Watching this I thought at one point you were going to implement both sets of limit switches. I.e. mechanical for setting limits on "stroke" for a particular job, and inductive for absolute limits at the end of table travel in case something goes catastrophically wrong. Or even the other way around depending on which makes more sense for getting the different limit stops to not interfere with each other.
I like the design of the ‘clicky’ switches too, but I can see that noise all day everyday quickly becoming a nuisance and you may in time come to appreciate to silence of the proximity switches
Just a little warning about the sensors: don't rely on the lights too much (shouldnt be a problem in this application, but you never know), because I've had sensors trigger the light a good 1 or 2 mm before the actual sensor triggered. The first time was quite confusing to troubleshoot.
Microswitches are nice but decent linit switches are on while different level. For this specific project though there are some previous designes to take note of or just order the kit and be done with it. I took part of an open source f-ng machine design project some time ago. Called OSSM and sold by Researxh and Desire. Its a servo based open linear actuator. Back and forth if thats your need. Due to nature of the open source and whole world of different available linear rail lengts available, they took the effort to make it auto calibrate in the start. It slowly moves to one end until it detects change in voltage (i guess). Than reads its steps in other direction until the other end stop. Than it sets itself programmed amount short from those endstops. Than itsbspeed and length according to remote dials (in its simple form). First versions were with limit switching with micro switches. But testing showed that any wrong move in the programming it tended to destroy the switch. Later it was redesigned to auto limit to whatever linear rail length was available. Anyway, its a 100-180w servo kit with sensorless homing for whatever lenght back and fourth movement is needed. It can do some other sort of grazy stuff as well in its not so simple mode, but i would assume your automated grinder doesnt need depth searhing robo stomping...
Clearpath servos also offer sensorless homing, but in this case, there's slippage in the drive system, so driving to coordinates is itself unreliable. Replacing the whole drive system with a belt might be a possibility, though.
What about drilling holes through the mount just tangent to where the indicator lights on the switches are and pressing in an acrylic rod? That would give you the visual indication as well!
Does it matter that it's plastic? I almost always "quarter turn" backward to find the start of the threads, if only for fear of crossthreading. Steel, aluminum, plastic, or whichever material.
Those are "screws designed for plastics" with deep threads and low TPI; I used to make the mistake of not finding the start of the tread when reinstalling this type of screw and while you can get away with it once, many times the screws won't hold that well and you're, well, screwed.
The lever switches need 2 switches but why 2 for the other sensors? If your stepping right and see the sensor its obvious its the right limit, conversely stepping left triggers the same sensor then its again obvious that's the left limit. I don't like to use multiple cables unless absolutely necessary.
He demonstrated the why, in the case where the limit trigger bars overlap, and you are actually working within the limits provided. i.e. the left end trigger is the release of the right trigger, and vice versa. It's not a situation most of us encounter, but it does have some good effect. The other thing to remember is that the drive mechanism is not fixed to the element being driven. Just because a sensor is triggered doesn't mean that the condition expected is what triggered the sensor. If two distinct conditions can cause the same triggered event, 999999 times out of 1000000, it probably will be what you are expecting, but the 1 time in a million that it isn't, is probably going to be the job that sent a part through the wall and dragged the bed the wrong way, and you don't have any way to detect that with a single sensor. 2 sensors is not simply overkill, it's the way to be able to detect problems in the first place.
I'd think in that case you'd actually want to use an LVDT, my understanding is the DRO Scales use a contact type scale where the LVDT uses a non contact Magnetic type of scale.
@@draconis437 I'm not sure I would want to use a magnetic scale on a surface grinder. Perhaps a glass scale. But with James' technical chops, I'm sure he could adapt something like that. I've seen this before. I plan on implementing something with one on my horizontal mill.
I liked your explanation of how and why to position the parts for 3D printing. After 5 minutes of switch clicking I would be tired of listening to the switches. Hope it is fine for you.
Mr James, but why don't you use a linear scale to detect the position of the table since you are planning to use a controller? This would give you much better control of the table (stretching of the rope wouldn't be an issue) not mention that you could change distance of movement on fly? You did use a rotary scale in your electronic screw in lather, remember?
Your project is very much like one designed and built by Pragmatic Lee. They seem to work well. I would suggest that you check with Pragmatic Lee about the programming. I think he has a working program that works well. I was wondering whether you considered using a tachometer approach to the problem? KOKO!
16:52 Is James just leveraging a storytelling technique to build up Anticipation OR Just plain being a Tease? … I’m Paul Harvey and this is the rest of the story.
Why abs/gf-abs over cf-pa? I see this a lot and I'm a nylon fan but if everyone is using abs over nylon it would be good know why. I really appreciate your videos. I learn a lot!
Looks like you were using the wrong sized Phillips bit, that biggest problem with them is that it can be hard to tell if you are using the correct size
I mean you want one to trigger before the other to indicate to the controller which direction ... sure it should already know but its a belt and suspenders kind of thing
The sound of mechanical switches may be satisfying but no self respecting automation engineer would consider them over non-contact magnetic or optical devices due to the potential for mechanical failure. For simplicity I think I might have mounted threaded body sensors horizontally and with spacers under the locking bolts detected the heads of the bolts.
![ILLSLICK - KILLSHOT REMIX [FULL VERSION]](http://i.ytimg.com/vi/RIK8RrqIAzE/mqdefault.jpg)
When selecting a mechanical limit switch the lifetime cycle count of the switch is important. Optical or inductive don't have this concern. Limit switch circuits should use normally closed wiring so if a cable breaks or is disconnected the limit is hit. You might consider four switches, the two inside would cause the direction to reverse, the outer two would cause the drive to halt. The later two would protect against a crash if the table were to go past the reversing switches
I concur completely. Those limit switches are going to endure a tremendous amount of cycling, so while the click-click and the visual actuation is indeed pretty neat, I think the inductive switches are by far the better way to go. If that grinder gets much use at all, those mechanical switches will have to get replaced a lot, and probably the stops, as well, unless James remakes them of steel or at least Aluminum.
Maybe the mechanical switches are going to just be over travel limits and the code will have soft travel limits for use when grinding?
He explained that there is a vinyl coated wire which is wrapped around a shaft which then moves the table. The cable can and does slip on the shaft, so deterministic positioning of the table by rotating the shaft a given amount is not possible.
@@leslierhorer1412
A) I have these type of switches click clacking all day long on decades old machines
B) Its a home shop
C) as noted by Patrick one would use these not as hard stops but insurance to know the table hasnt slipped on the rope and goes too far
Mechanical life is 30,000,000 operations, so at 2 seconds a direction (one operation every 4 seconds) you’d get almost 4 years 24/7 operation. I suspect a lot of other stuff will break or wear out before that.
Cherry MX switch fans everywhere agree: clickyness of a switch is totally valid.
I think these are a little closer to buckling spring keyboards,and still awesome.
any blue switch gang members here?
@@friedrichgotze3264 All blue here
Clicky sounds neat when you're doing it by hand a few times; I think it will get pretty annoying when it's clicking thousands of times during a grinding run...
That, too, but I would say reliability is a much bigger concern.
No when on a long job the ending of 'flik-flak' of mechanical reversing is cue to return to the grinder and set it for another pass. Of course you have to be able to hear the machine stepping over.
@@alan-sk7kyit’s going to be a CNC grinder, it will run by its self, if you need something to tell you it’s the end of cycle, just needs to be an alarm or light you can see across the shop floor, not click clack all day coming to an end 😅
Never heard a surface grindwr before? You aint hearing a switch over it.
Thanks Robin for getting James to go down this rabbit hole!
Clicky sound is a completely valid reason to choose a switch.
Amen!
This is the exact reason a 1bill dollar mech keyboard market exists
Not to sure about that. Afraid it will drive you crazy when running a bigger project on it🙈
@@robertwillemsen368 That might happen, but if it does, James already has the inductive sensors to replace them.
Came for the awesome content, stayed for the clicky sound.
You are one of my largest inspirations for making things and learning all the things needed to accurately make things using mills/lathes
I have a REID 618 grinder. The bed is left and right chain driven. The front and back is done with a shiftable ratchet and screw. A large city water company bought it in 1948. Soon afterwards someone engaged the front and back lever after the stop and broke the nut assembly. They did a half fix that broke again. They sat it in the corner and painted it many ties. The two motions are driven by a 400 rpm three phase motor with a reeves drive for speed control. The machine was delivered as a 2 phase machine, interesting wiring. They converted it to 3 phase in the 1960. It was sold at auction about 2010, still broken. I installed VFDs on the movement and spindle. The ways are like new.
The left and right reversal is done by a see-saw switch maintains position for current motion. It will also trip if it gets to the travel limit.
A switch like that makes programing simple, no single shots, latches, and shift registers.
Hi just my two cents. Inductive sensors react to all metals not just ferromagnetic, but they don't have the same sensitivity. For example if you use aluminium instead of steel the air gap needs to smaller but it would still work.
I'd go with the inductive sensors, no moving parts and they look sleeker and you have a visual indicator and they don't need to be debounced.
If you go for the clicky ones, remember you need to debounce the signal in software later.
In our production facility we had a lot of the roller switches fail after 1-2 years. The rollers wore out started to wobble and could jam the whole system so keep that in mind since they're probably exposed to the grinding dust.
Greetings from Germany, love your channel continue the good work!
Yes, but in this use the stops do not need to be all that accurate. If the table stops within a few mm of the same point each time, it will be fine.
The clicky switches are nice but they can have switch bounce and contact wetting issues that need to be considered.
You could always sense the current of the motor to do the same when the end has been reached the motor current will spike and use that as a sensor, but you know what you are doing and I don't know if this idea will help you in the future, you probably knew this anyway. I love your videos, and I just like you.
Use optical or inductive switching elements, and build your own 'clicky' housing for the aural aesthetic!
07:50 it's hard to see but it looks like the screws have the tell-tail radial ticks of PZ/Pozidriv screws, which might be why you're having problems with your PH/Phillips driver :)
Yup, I was going to say the same thing James - it LOOKS like you're using a Pozidrive screwdriver, whereas, though my experience is MUCH less than yours, I have NEVER found any electrical/onic product from Asia which doesn't use Philips. It seems that Pozidrive is "unknown" over there.
Thank you so much for leaving in you riding the struggle bus with those screws. I'm not as incompetent as I thought.
Absolutely! I feel much better, now. OTOH, I don't think I will ever let James handle any valuable glass objects. 😁
I also did a servo drive conversion to my cheap manual surface grinder. Like you, I also finally settled on a switch assembly for change of table travel after looking at both inductive and capacitive switching. I was concerned about possible desensitivation of the inductive/capacitive switches due to metalic dust. For me, going with a mechanical switch meant relying on a questionable component for absolutely stopping my rack driven table. My solution was using the capacitive switches I had ordered previously and mounting them in protected spaces under the apron to act as failsafe table stops. I then cobbled out a small interface board to tie my travel switching, timer and servo controller to play together. I won't go CNC as the grinder is not worthy of the expense and I don't have the workload necessary to justify the expenditure. What I didn't take into account were the stresses on the flimsy base cabinet of the grinder from the sudden chages of direction generated by the servo, something I need to address.
I have enjoyed following along on your conversion project and look forward to more episodes. Your videos are outstanding. Thanks for sharing your journey!!
I watch a lot of engineering pornography and your presentation is hands down the best! Thank you.
Always nice to see your thoughts during the design and creation. Bravo Sir!
And here I was thinking of something along the line of a scale or string tape measure mounted out of the way, and then just programming the left and right limits in software on the touch screen. Jog the table left, hit the 'left limit' button, jog right, do the same for the right limit, done. You have an absolute position measure, so don't have to worry about stepper slip. And no unsightly bulge and finger-pinchers on the front of the table!
I've definitely had "use clicky buttons" as a design constraint in some of my projects.
Nice job James. Very interesting to watch. Those factory bumpers are for relocating to the center set position of a fixture on the grinder. Something like a Harig spin fixture/indexing head or a St Mary's fixture.
I have to say this channel is my favourite by far. The engineering is top rate. Thanks for sharing.
A few notes about the mechanical switches. As previously mentioned, use the normally closed contact to detect wire breakage. Also check the lifetime of those, if they industrial, they are a lot, but not infinite. And don't forget the de-bounce in software or hardware. The inductive switches have less issues with lifetime and bounce less, but they are not that position precise to trigger if the metal comes in from the side. They are usually designed to have the metal come in from the front. Precision is not a problem here, so sideways will be fine. Since you have both types, I would use the mechanical ones on the end for emergency stops and the inductive one for direction switch. The clicky ones will annoy you, I'm 99% sure ;)
the prox switches have a sensing range similar to a candle flame - so it is best to have a flat surface for them to sense( like key stock) rather than the round dowel surface.
I love the look and sound of those switches! However, I think I would have chosen the boring inductive ones anyway. I'm worried about what grinding dust and coolant is going to do to the mechanical switches, but maybe I'm being too paranoid. If it does become a problem, it looks pretty easy to switch to the other switches. (You already have the necessary parts!)
I have to (reluctantly) agree. And I've got a collection of IBM Model M keyboards I use regularly, so I do likes me some clickeys!
grinding dust of cast iron and steel do wonders for inductive switches
Honestly, microswitches are awesome, & they make automation so much easier. What's not to love?
Another great video. If it were me, I'd use the mag sensors. You won't here those mechanical switches while the grinder is grinding, AND... they will never wear out. The mechanical switches have an MTBF measured in switch-cycles. Plus, "waterproof" or not, the mag sensors will tolerate a cooling bath better and longer. Just sayin'.
Hey I'm with you on the clicky switches James! Now you can do some surface grinding, and get your ASMR fix all at the same time. 😂👍👍
I like your design aesthetic. Very functional and confidence inspiring
My surface grinder had a very similar X axis drive mechanism. It was too much trouble because the wire that wraps end up stretching over the years. Mine came with adjustments to keep snugging it up until the wire breaks, then you replace it and start over. I got too annoyed with this, so ended up replacing the wire drive with a lead screw and lead nut. My first attempt went well, but only lasted a year before the nut wore out. Despite the load rating on the nut being roughly 2x higher than the actual load, it seemed that the inertia of the surface grinder bed was too much and causing too high of a load at a move stop and start. So I replaced the 3/8 lead screw with a 3/4 lead screw and it has been fine ever since. Been working now 4-5 years without anything needing replacing or maintenance on the new drive mechanism. Got the lead parts from Roton.
Very interesting to see you do this whole project and the parts you used. My retrofit was done with very similar parts and from Automation Direct as well. Instead of ClearPath motors I used AD Stepper motors though. ClearPath would be a much better choice, and if I ever need to replace one of my motors I will likely change them over.
For my sensors on the bed I used four inductive sensors, two NO models and two NC models. The NO ones trigger a change direction on the X axis motor, and the NC ones are my overtravel sensors. Not sure how you plan to feed those sensors into the control scheme with the motors, but I used a little P1000 PLC from Automation Direct to write all my logic and make it all automate for me. They are VERY easy to learn and use, and pair extremely well with AD's HMI products. I originally had mechanical switches, but switched them to inductive because what happened over a year or two was there ended up being gunk buildup on the pivot sections of the mechanical switch from using the surface grinder with coolant. If you use mechanical ones you will have to clean off the switches really well after every use otherwise the same will happen to you. I swapped mine to inductives and haven't had the problem since because they don't care about any gunk residue buildup.
Now if you could get it to make the Jones & Shimpman step over ratchet noise James... 🙂 Perfect!
Nice work as ever. Maybe a linear scale for the electronic stops and the mechanical limit switches as safety ?
That is a really cool surface grinder now. I wish I had one a little larger than my x,y table.
That clicky sound is intended as a warning that a switch has definitely been toggled.
As satisfying as clicky switches on a fightstick for fighting games.
Who doesn't love clicky clacky ❤
Now if they went click when they made and clack when they released, it would be the best of all worlds with clickity clack.
in high cycle applications you only use the clicky switches as dead stops (because each click = wear on the internal components) or where you cant use induction, magnetic, laser sensors as the switch has limited cycles it can run
the induction sensor only has to be protected from debris of a metal nature but as long as no damage happens to the end of the switch it will lat until the coil inside fails
also you should never design automatically controlled devices to there limits always have a buffer because if a sensor fails you will damage the device
if you want to build a dead stop with the induction sensor just put a piece of metal at the back of the adjustable stop that triggers both the upper and lower induction sensor and code it to E-STOP the machine when both are active and in auto mode
I used to work for a company that did concrete conversions on all kinds of old machinery (mainly grinding machines) on surface grinders we had the endstops for the table on a rail so that the travel could be adjusted while the machine is running… those grinders were quite big as well with over 2 meters of table travel on a few of them
One thing to consider is adding a fine adjustment into the bumpers. Still using the single screw to mount to the sled is probably Ok, but 2 would be better. You wouldn't want them to move at all, and having a fine adjustment there would let you keep them mounted, but adjusting the travel after this wears in. Not sure how long it will take before they get worn.
Dear lord this was satisfying
Next entertaining video… James tries to use ChatGPT to program the surface grinder! 🤗
From someone who deals with these style switches in a industrial setting. The cam style will suit your needs the best. The plunger style works best in the load is applied more in a straight down style, vs a ramp. Also with it being on a surface grinder you have less risk of buildup on the switch and it sticking closed. Just my .02
You must have an IBM Model F if you're a true lover of clicky switches.
I liked the clicky sound.
But for this application I think the proxy sensors will be superior.
That click will get annoying real fast , and the mechanical switches are just another thing that will wear out, as far as I can tell there's nothing that will wear in the proxy arrangement, plus it's a much lower profile setup.
Cool either way!
Looking forward to your video on the mystery printer.
I love the clicky switches but the impending mechanical failure of said switches gives me anxiety. I'm sure you'll get a couple million cycles out of these before that happens and for a hobbyist level implementation that's probably more than you'll need! Denouncing may need to be addressed but I love this!
Sir it’s a pleasure watching you think and work, makes me want to buy a 3D printer 👴🏻👍
Nice job as usual…to limit switches I prefer NC sensors…much safer
14:20 oh no the counterbores intersect with the extruded feature! Clearly the clicky switches are going to be superior.
A project so cool I had to become a Sustainer.
Looks awesome great design
That is nearly identical to the actual setup on actual grinders that I used to actually sell, in terms of outward appearance. Some of the ones we sold had purely mechanical control, and if you wanted clicking, well, you got clunking.
and the step over ratchet... ;-)
Proximity switches are the way to go...no moving parts, not contact, so they wont wear. I really can't think of a reason to use the mechanical switches at all.
Clicky for the win!
Sound is a very legit reason for using a tool or another. That's the reason why i have whips..hehehehe.
As much as i understand and agree that clicky is so tantalizingly nice; i wouldn't want to hear CLICK CLICK every hecking time it would make ONE pass for hours at a time xD
I'd much prefer the induction probes for their silence and reliability, solid state tends to last longer.
you might want to put a cover on the switch - you are going to have a lot of grinding dust, that may interefere with the rollers and gum them up in the long term - probably removable so you can shop vac / air blast them.
just to give you something else to print :D
If you decide to use mechanical limit switches, a often overlooked detail is that switches have both maximum and minimum current specs. The maximum spec requires no explanation. The minimum spec is often overlooked and if not met the switch can be mechanically in the closed position but be electrically open due to a thin film of oxide on the switch contacts. An intermittent limit switch is something a good designer wants to eliminate. I checked for this minimum current spec on the mechanical switch you used and it was not given. You may want to reach out for this info from the manufacturer so you can get reliable operation should you decide to use mechanical switches.
Who else wants a 2hrs "ASMR" video of those switches clicking and clacking?
I wonder how many clicks the limit switches are specified for. With small parts and a few hundred hours you may end up with quite a few clicks. Having ground material all around can also make them wear faster. Proximity sensors on the other hand will not wear mechanically.
I'm also on team proximity switches.
Thank you!
I dont know if its issue for your or not, I tend to just make adapter pigtail and have it on the item (switch in this case) I want to adapter, I dont put it at controller side. Btw, clicky sounds are the #1 reason to choose a limit switch :)
I would use an interface box with two different input connectors, one for the inductive and one for the mechanical. Make up two different sets of pigtails. That way the two could be very easily switched back and forth for testing or in case of a failure, etc.
Looks good i think the clicking would get really annoying after a while. but maybe thats just me lol.
This project can only be described as: How a MAUPe NERD tries to convert a machine into something it was not designed for. And the result is a machine that nobody would want.
So Robin renzetti is who we can blame, got it, nice excuse for fun.
I'm probably stating the obvious,. It might be a good idea if possible to back them up with stops in the software too.
Nice job.
You need to lock up that Hardinge collet chuck, or one day I am liable to sneak in and steal it! 🙂
You might consider a chip shield running the length of the stop channel just because. 'Probably not terribly necessary with a grinder, especially since the dust ejects to the side, but it wouldn't hurt.
Amazing stuff 😎
I hope you add one of those traffic light indicators to the grinder, so you can easily see when it is done or there is a fault.
Clicky switch is better for one other reason: It's in a machine shop. The odds of a chip or whatever interfering with the proximity switch is not zero. Pretty low because it's a surface grinder, but it would be a particularly lame way to scrap a part.
All good until grit gets into the mechanical bits of the switches and starts to wear things out, the chip/grit issue with the prox sensors is fixed by a wipe with a cloth. Or set up a wiper.
The table knows where it is because it knows where it isn't
Personally I would go with inductive for the working limits and clicky for overtravel/safety limits in case the inductive sensors fail. I would assume the motors also have current measurement/limits so abnormal current from a crash could also trigger a stop?
Kind of shocked the travel pulley would slip, with 3 wraps around the pulley with slippy(0.2µ) material you still have ~43x more holding force than the tension of the cord from the slack side, while a less slippy material is in the tens of thousands of times more holding.
Has the cord even got any tension on it?
For further see: capstan equation or belt friction equation.
he could probably just put a fourth or fifth wrap around the spool, it looked like there was plenty of leeway. that'd make it exponentially less likely to slip
Is there a reason you want the stops so close together that you have an overlap?
Interesting project.
Thanks for the taking us through the process.
really small parts
Maybe Quinn could send you some Robertson screws 😅
Looks like the lifetime issue of the mechanical switches has been addressed with comments below. While the cost of failure is not real high traveling in one direction, (cable just screws off the end of the drive screw) going to other night result in the cable being pulled on to itself and the vinyl coating being damaged. Yes the "click" "click" is cool but doesn't have to come from the switches. Why not add a speaker to produce a click clack to the system. A second solution is to have the software "learn" during the first N cycles about how long the travel is and then shut everything down if all of a sudden the "learned" travel is significantly exceeded.
screwdriver magnetizer/de-magnetizer would be handy
It's Renzetti's fault. 🙂
As much I like the clicks, and I'm sure those are quality parts, the inductive sensors feel more trustworthy.
You can modify that wire rope drive for slipless operation. Two cables, one end of each connected to the roller. You should do a little research, because capstan drives are awesome.
Clicky switches are just so satisfying, I think they are less prone to temperature fluctuations which makes them ideal for CNC.
I’m really curious to see what controller system you go with. I’ve been playing with grblHAL and FluidNC recently for my little CNC router, and settled on the former for my DLC32 board. It’s definitely a budget solution with compromises to match. That said, I run external TMC2160 stepper drivers with my LDO stepper motors, so I get some good results.
Watching this I thought at one point you were going to implement both sets of limit switches. I.e. mechanical for setting limits on "stroke" for a particular job, and inductive for absolute limits at the end of table travel in case something goes catastrophically wrong. Or even the other way around depending on which makes more sense for getting the different limit stops to not interfere with each other.
If one were to use both, the mechanical switches as safety limits would be best, since they will rarely see any use.
I like the design of the ‘clicky’ switches too, but I can see that noise all day everyday quickly becoming a nuisance and you may in time come to appreciate to silence of the proximity switches
I'd agree with the sentiment on clicky switches for tactile human interface but I suspect the clickyness will get old really quickly on a long grind.
Just a little warning about the sensors: don't rely on the lights too much (shouldnt be a problem in this application, but you never know), because I've had sensors trigger the light a good 1 or 2 mm before the actual sensor triggered. The first time was quite confusing to troubleshoot.
Microswitches are nice but decent linit switches are on while different level.
For this specific project though there are some previous designes to take note of or just order the kit and be done with it. I took part of an open source f-ng machine design project some time ago. Called OSSM and sold by Researxh and Desire. Its a servo based open linear actuator. Back and forth if thats your need. Due to nature of the open source and whole world of different available linear rail lengts available, they took the effort to make it auto calibrate in the start. It slowly moves to one end until it detects change in voltage (i guess). Than reads its steps in other direction until the other end stop. Than it sets itself programmed amount short from those endstops. Than itsbspeed and length according to remote dials (in its simple form). First versions were with limit switching with micro switches. But testing showed that any wrong move in the programming it tended to destroy the switch. Later it was redesigned to auto limit to whatever linear rail length was available.
Anyway, its a 100-180w servo kit with sensorless homing for whatever lenght back and fourth movement is needed. It can do some other sort of grazy stuff as well in its not so simple mode, but i would assume your automated grinder doesnt need depth searhing robo stomping...
Clearpath servos also offer sensorless homing, but in this case, there's slippage in the drive system, so driving to coordinates is itself unreliable. Replacing the whole drive system with a belt might be a possibility, though.
Intro: Never underestimate the worth of a good tactile switch.
What about drilling holes through the mount just tangent to where the indicator lights on the switches are and pressing in an acrylic rod? That would give you the visual indication as well!
Does it matter that it's plastic? I almost always "quarter turn" backward to find the start of the threads, if only for fear of crossthreading. Steel, aluminum, plastic, or whichever material.
Those are "screws designed for plastics" with deep threads and low TPI; I used to make the mistake of not finding the start of the tread when reinstalling this type of screw and while you can get away with it once, many times the screws won't hold that well and you're, well, screwed.
The lever switches need 2 switches but why 2 for the other sensors? If your stepping right and see the sensor its obvious its the right limit, conversely stepping left triggers the same sensor then its again obvious that's the left limit.
I don't like to use multiple cables unless absolutely necessary.
He demonstrated the why, in the case where the limit trigger bars overlap, and you are actually working within the limits provided. i.e. the left end trigger is the release of the right trigger, and vice versa. It's not a situation most of us encounter, but it does have some good effect.
The other thing to remember is that the drive mechanism is not fixed to the element being driven. Just because a sensor is triggered doesn't mean that the condition expected is what triggered the sensor. If two distinct conditions can cause the same triggered event, 999999 times out of 1000000, it probably will be what you are expecting, but the 1 time in a million that it isn't, is probably going to be the job that sent a part through the wall and dragged the bed the wrong way, and you don't have any way to detect that with a single sensor. 2 sensors is not simply overkill, it's the way to be able to detect problems in the first place.
i'm surprised you didn't use a DRO scale instead and get absolute positioning. No chance of overshooting a switch.
I'd think in that case you'd actually want to use an LVDT, my understanding is the DRO Scales use a contact type scale where the LVDT uses a non contact Magnetic type of scale.
@@draconis437 I'm not sure I would want to use a magnetic scale on a surface grinder. Perhaps a glass scale. But with James' technical chops, I'm sure he could adapt something like that. I've seen this before. I plan on implementing something with one on my horizontal mill.
@@MyLilMule Ya, i didnt think about that, thats also a good reason not to use those proximity switches
Hey James
Would love to see you working with the new AI features on fusion. Any take?
I liked your explanation of how and why to position the parts for 3D printing. After 5 minutes of switch clicking I would be tired of listening to the switches. Hope it is fine for you.
Mr James,
but why don't you use a linear scale to detect the position of the table since you are planning to use a controller?
This would give you much better control of the table (stretching of the rope wouldn't be an issue) not mention that you could change distance of movement on fly?
You did use a rotary scale in your electronic screw in lather, remember?
Your project is very much like one designed and built by Pragmatic Lee. They seem to work well. I would suggest that you check with Pragmatic Lee about the programming. I think he has a working program that works well.
I was wondering whether you considered using a tachometer approach to the problem? KOKO!
that's great !
16:52 Is James just leveraging a storytelling technique to build up Anticipation OR Just plain being a Tease? … I’m Paul Harvey and this is the rest of the story.
Why abs/gf-abs over cf-pa? I see this a lot and I'm a nylon fan but if everyone is using abs over nylon it would be good know why. I really appreciate your videos. I learn a lot!
Looks like you were using the wrong sized Phillips bit, that biggest problem with them is that it can be hard to tell if you are using the correct size
I mean you want one to trigger before the other to indicate to the controller which direction ... sure it should already know but its a belt and suspenders kind of thing
The sound of mechanical switches may be satisfying but no self respecting automation engineer would consider them over non-contact magnetic or optical devices due to the potential for mechanical failure. For simplicity I think I might have mounted threaded body sensors horizontally and with spacers under the locking bolts detected the heads of the bolts.