Human Interface Upgrade for my PM3520B

[Dan Case LR]

I received a brand new Powermatic 3520B a few days after Black Friday 2015. It's a great lathe for the money, but IMHO it falls short in terms of operator interface. I've designed and built more than a few control/operator interface panels in my 40 years as a Broadcast Engineer, and two of the primary goals of every design are:



An intuitive interface that doesn't require excessive training (particularly when interfacing with non-technical types).
Operator Safety, if applicable.


As I see it, Powermatic's operator interface falls short in both areas:



Big red mushroom-head switches should do only one thing: STOP. Pulling out on the STOP button to start the lathe is counter-intuitive, at least for me--and since I'm the only operator using this machine, my vote is the one that counts.
Controls on the headstock require the operator to reach across the "Line of Fire" to start, stop, and adjust speed. As I see it, operators should NEVER be required to cross the Line of Fire to perform routine operations.
One other thing that bugs me, but admittedly isn't a serious safety problem: turning the speed control fully clockwise should, IMHO, take the lathe to its minimum speed, not a dead stop.


Feel free to disagree with me on any or all of these points--you have the right to do so. The behaviors and control issues I've cited are no doubt more important to me than to some because both of the lathes I've turned on in recent years (Jet 1221VS and Robust American Beauty) had controls either located on the right-hand end of the lathe or on a movable pendant. The movable pendant is the option that makes the most sense to me, so I decided to design and build an operator interface that emulates the best I've ever seen--the Robust American Beauty. The result is shown in the attached photos.

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A small plastic box houses the necessary circuitry to interface with the PM3520B. I've mounted it on the rear of the headstock using holes drilled and tapped to #8-32. I chose the location to avoid any interference with the inverter's cooling air flow or operator controls. This box connects to the PM with a single cable that connects to the wires normally running to the control panel. I considered wiring directly to the inverter, but wanted to leave the option to easily restore the original controls. The only switch on the control panel that is still active is the big red mushroom-head that serves as an emergency stop switch. Next time I place an order with a vendor that has them, I'll replace that with a turn-to-unlock emergency stop switch, and if I'm feeling particularly spunky that day I may replace the controller plate with one that holds only the emergency stop switch (and put the original in a box in case I ever want to change back).

The pendant connects to the control box with a standard 8-pin CPC connector and 7 conductor shielded cable. The pendant end is a standard box made to hold three 22mm switches. The knob at the top controls speed, and the little screwdriver adjustment (trimpot) is adjusted so that the motor just begins to turn with the speed pot fully counter-clockwise. The switch in the middle is a center-off momentary that controls the motor to the right (clockwise) for normal (forward) operation and left (counter-clockwise) for reverse. The red button is a momentary pushbutton that is the stop switch.

The pendant has two rare-earth magnets on the rear that allow it to be placed almost anywhere. The only problem with this is the curved surface on the front of the ways. Because of the curve, only one magnet can grab at a time. I've used magnets rated for holding 70 lbs, which may be slightly overkill, but holds in situations where lesser magnets wouldn't do the job.

I know there are those who believe it is either stupid or sacrilegious to rework the Powermatic's controls like this--we've had that discussion already. I'm posting this for the benefit of others who might want to upgrade their lathe controls like I have, or might be looking for different ideas and alternatives.

Questions? Ask!



D.

[Glen Blanchard]

Dan - That pendant looks awesome! Just like my AB. Well done.






One other thing that bugs me, but admittedly isn't a serious safety problem: turning the speed control fully clockwise should, IMHO, take the lathe to its minimum speed, not a dead stop.





Did you mean to say 'COUNTERclockwise'?

[Dale Bonertz]

Much better than what comes on the powermatic. All lathes should have a remote box. The box I think is the best out there is Vicmarc's. There is a separate switch for forward and reverse which eliminates accidentally hitting the wrong direction like yours and Robusts. It also has the stop bar for quick or emergency stopping. Having said that what you made is so much better and user friendly.

[Brad Adams]

I like it. I have been pondering doing this same thing on my 3520. Where did you source the parts?

[Bill Adamsen]

Very clever idea. I've been getting the rare earth magnets and components from Lee Valley and using them for all sorts of things including putting removable panels in kitchens. I'm guessing counterclockwise as well.

[Dan Case LR]

Dan - That pendant looks awesome! Just like my AB. Well done.



Did you mean to say 'COUNTERclockwise'?


Oops. Yes, COUNTERclockwise. Duh!

D.

[John K Jordan]

Nice job!

Do you have a circuit diagram to share? I see something in the middle of the photos that says "Attachment..." but it does nothing when clicked.

JKJ

[Reed Gray]

Having learned on a 3520A, and now on a Beauty, if I had started out with a different set up rather than what is stock on them, and had a set up like what you have, it might seem strange. Mostly I have learned to deal with it. If I have the remote box on the bed of my Robust, I have to bend over to reach it, which can put my head into the line of fire. If the remote is on the tailstock, well, it is on the bed for maybe half of the turning I do, so I would be having to move it a lot. If it is on an arm like Oneway has, every time I would want to hit the stop button, instead of just reaching straight across with my left hand, I would have to transfer my gouge or scraper to my left hand, and then hit the off button with my right, which to me is an extra movement. When considering the 'reaching across the line of fire' point, well, I have had a few blow ups, but the flying pieces are gone before I can hit the off button. If the on/off set up could be configured into the banjo, that is always up on the lathe, but the cord would be in the way. I do like the Robust twist knob for forward and reverse, and don't often start it in the wrong direction. For now, the control box stays on the headstock, right where it was on my PM...

robo hippy

[Bill Boehme]

Reed, have you thought about the foot operated stop switch for the Robust?

[Bill Boehme]

... Feel free to disagree with me on any or all of these points ...

Another EE here and I wholeheartedly agree with your assessments and I like your solutions. However, I feel the need to rag on you for posting sideways images. :p We engineers need to show that we don't let technology get the best of us despite the best efforts of Apple. Besides, my 27" monitor is too big and heavy to turn it on end to view pictures.:D

[Steve Mawson]

Besides, my 27" monitor is too big and heavy to turn it on end to view pictures.:D

That gave me a laugh to start the day. I guess from Texas you have to have a BIG monitor. I do like Dan's set up but probably don't know how to wire it up.
Merry Christmas

[allen thunem]

so did you disconnect the original controls on the headstock???
or can they be used in conjunction with the secondary controls.
i did this to my 3520b some 5 yrs ago based on a previous thread from either sawmill creek or on the mustard monster site.
i just repurposed my original switches and used a double gang box instead of a single gang.
in total agreement that powermatic fell short in this area of their design.

[Bob Bergstrom]

Having learned on a 3520A, and now on a Beauty, if I had started out with a different set up rather than what is stock on them, and had a set up like what you have, it might seem strange. Mostly I have learned to deal with it. If I have the remote box on the bed of my Robust, I have to bend over to reach it, which can put my head into the line of fire. If the remote is on the tailstock, well, it is on the bed for maybe half of the turning I do, so I would be having to move it a lot. If it is on an arm like Oneway has, every time I would want to hit the stop button, instead of just reaching straight across with my left hand, I would have to transfer my gouge or scraper to my left hand, and then hit the off button with my right, which to me is an extra movement. When considering the 'reaching across the line of fire' point, well, I have had a few blow ups, but the flying pieces are gone before I can hit the off button. If the on/off set up could be configured into the banjo, that is always up on the lathe, but the cord would be in the way. I do like the Robust twist knob for forward and reverse, and don't often start it in the wrong direction. For now, the control box stays on the headstock, right where it was on my PM...

robo hippy

i also have gone from a 3520 to AB. With the AB the ways are stainless magnets won't stick. I'm so use to having it on the headstock that I lose track of the switches if I stick them somewhere else. I've had blow ups and reached to the headstock only to find it was not there. By the time I got to the switch it was over anyway.

[Dick Strauss]

Dan,
I've got a similar control setup but with the "twist to release" stop button on all my lathes and DP that uses old speaker magnets. I can't tell if you used a 3 position directional switch or not. It is a good idea to have one extra way to make sure the lathe doesn't start unintentionally (or one more check to make sure you are mindful when turning). After a while it becomes habit.

For me, starting at zero speed and jumping to 1.5hz based on the speed pot position and VFD programming is not a big deal (13 or 5 rpms on my lathes and 7.5 rpms on the DP).

For a cheaper wiring option, I used 8 conductor 22g solid sprinkler wire available at HD or L.

[Reed Gray]

I do know there are big red knee operated kill switches for some machines, and am pretty sure I would constantly trigger them by accident. I don't know where I could put a foot kill switch. When I am turning bowls, I typically generate a couple of 55 gallon bags full of shavings per day. The area where I stand stays clear because I push the shavings out of the way with my feet as I turn. Every thing else is ankle to knee deep.

If I go away for a bit and come back, I do worry about turning the lathe on while it is at high speed. Habit makes me check the speed first before starting turning again. I have wondered about some kind of switch that would go back to zero when you turn the lathe off. That way, there is no chance of turning the lathe on while it is at high speed. The simple twist on/twist off would work, and a big red kill switch would be for emergency.

robo hippy

[Mike Goetzke]

Dan - looks good. I'm not the first to do this but for others wanting a remote type switch I did this:

http://img.photobucket.com/albums/v212/mbg/My%20Tools/Powermatic%203520B/Remote%20Switch/7a31e127-4cf4-466f-84a7-81fac2e69056_zpssombp4g1.jpg (http://smg.photobucket.com/user/mbg/media/My%20Tools/Powermatic%203520B/Remote%20Switch/7a31e127-4cf4-466f-84a7-81fac2e69056_zpssombp4g1.jpg.html)

I JB-Welded some rare earth magnets to the back but the magnets must be too slick because they have been falling off. I would like to screw it on like you but it was a challenge to squish all that stuff in that box.

Mike

[Edward Weingarden]

You may want to try some epoxy glue to hold the magnets on.

[Jeffrey J Smith]

I'm so use to having it on the headstock that I lose track of the switches if I stick them somewhere else. I've had blow ups and reached to the headstock only to find it was not there. By the time I got to the switch it was over anyway.
I've gotten used to putting the pendant on the banjo - It sits facing me on the angled side of the banjo. Easy to change speeds or hit the stop button if things go sideways. Beware of putting it on the tailstock and trying to use the tilt-away. It's a very effective way to cut the cable if it gets pinched between the static and moving bed ways...luckily I noticed the potential pinch-point before I did any damage.

[Joe Bradshaw]

While I don't have a 3520B, I have turned a lot one the ones at JCC Folk School. I never had a problem with the placement of the controls. My primary lathes in my shop are a Oneway 1224 with the controls on the left end of the bed, a Oneway 2436 with the swing arm which I move around as it suits me and lastly, a Robust Liberty with the movable control box. I have had pieces blow up on all three lathes. On the small lathe, it is no problem to reach around the spinning piece to shut it off. On the big Oneway, if the piece is to much out of balance and the lathe starts to shake really badly(think moving around on the floor)the lathe will shut off. On the Robust, I usually have the control box close to my left side. Not to be a smart a$$, but, you seemed to have a solution in search of a problem. That's why turners are such a fun bunch, we have answers to questions not asked. Tinkering with your lathe is just part of the journey. Enjoy your new lathe and have a Happy Christmas and a merry new year.
Joe

[John K Jordan]

I have wondered about some kind of switch that would go back to zero when you turn the lathe off.

That should not be too hard to wire up, at least keep it from turning on until the speed control is turned to zero. Perhaps just a latch and logic and a little circuit to sense the resistance of the pot. Perhaps it could even be done with a mod to the existing VFD programming.

The power feed for the XY table on my milling machine has that built in. If the speed control is turned to anything but zero when the feed is turned on it turns on a yellow "fault" light and will not move until the speed control is turned all the way down then back up.

I think having two modes in a variable-speed lathe control would be useful, selected with a switch. Normal mode, perhaps more useful for small things. Big mode, for heavy bowl blanks and such which could get dangerous at high speeds. The Big Mode would switch to slower acceleration / deceleration and maximum speed parameters in the VFD and would have the kind of safety feature you mention. I planned to try adding this to the new VFD I bought when the Delta on my Jet 1642 bit the dust - looks possible from the docs. Slower acceleration might also put less stress on things.

Another thing I think would add to lathe safety for people who turn big things: an out-of-balance detector. This would shut down the motor when severe vibration was detected. This would need a knob to adjust the threshold so it wouldn't kick off for minor vibration. A circuit with a simple accelerometer mounted inside the headstock could do this; it could trigger a deceleration/stop before the piece could complete even one out-of-balance revolution. (Accelerometers are used to detect and measure motion and vibration in machines, bridges, etc. There is probably one in your cell phone.)

Someone who enjoyed playing with an Arduino could whip up all of these and more in short order.

JKJ

[Geoff Whaling]

Dan,

I agree with you that the operator interface’s on many of our hobby machines and placement of Emergency Stops (E-stops) fall well short of what is industry best practice. Good to see that you are addressing some of those issues on your machine – well done!

Operators should NEVER be placed in a dangerous position to operate a control or an E-stop.

The fixed placement of E-stops on the headstock of lathes capable of turning larger bowls, platters etc is contrary to machinery codes of practice. A turner using a “hobby machine” in a work place or a teaching facility should seek advice on compliance.

Industry machinery codes of practice mandate the fitting and placement of E-stops generally including a clause such as "the stop control is prominent, clearly and durably marked and immediately accessible to each operator of the plant."

IMO all machines in our hobby shops should be fitted with


“no volt” switches, that return the switch/circuit breaker to the off position if for any reason powers fails or is interrupted and must be deliberately reset before the motor / circuit is operational again – engineering out the potential for dangerous restarts.
an emergency stop that disengages power to the motor and stops the machine AND remains off until deliberately reset.
an on / off switch which may also incorporate forward / reverse controls AND can operate as an emergency stop i.e. push button & not a toggle switch with a shroud, & not a flip centre/left /right rotary style switch.
a means of isolating power to the whole of a single machine – including the VFD components, switch panels etc. i.e. a switched outlet.
a master switch/isolator/circuit breaker that isolates power to all power circuits other than lighting.


I also firmly believe that speed control pots should NEVER be used as “off switches” it is a very poor practice wrt safety and preventing dangerous restarts.

Utopian perhaps, but it is what we should be striving for if we have the financial means to do so.

Some manufacturers incorporate these features into a single combination E-stop / ON / OFF control which is why they also incorporate the “pull out to reset” feature to meet the “must remain off until deliberately reset” requirement.

Vicmarc have a very good human interface panel on their current lathes which I believe meets our Australian industry plant code of practice. However the placement of the control panel is not ideal on some machines such as my VL150. Vicmarc to their credit have already addressed some of the issues with the VL150 design and I believe their hazard / risk assessment / engineering controls process is a model for small independent manufacturers.

Sadly Michelle DuFault died in a Yale Uni laboratory operating a lathe in 2011 because the hazard / risk assessment procedure failed to identify the lack of guarding and lack of an E-stop “immediately accessible to each operator of the plant" and failed to rectify the omission/s.

We all should take safety issues (guarding, placement & design of controls etc) more seriously and lobby manufactures / importers / suppliers to improve the designs so that “hobby machines” at least comply with basic industry machinery codes of practice for E-stops etc.

[Reed Gray]

Hmm, wondering about the 'out of balance' turn off thing.... Given some chainsawn blanks and how rough the outside is, you could register some heavy 'out of balance' signals just from standard roughing cuts.

I did hear a story about Dave Ellsworth sending a blank through a wall at one of the early Symposiums at UC Davis.

Using the variable speed knob for turning the lathe off and on does work, and I think that is one way that some compensate for making sure the start up speed is zero. Maybe not ideal, and it confused me when I turned on some one's lathe that did that, but it isn't dangerous.

Interesting safety discussion!!!

robo hippy

[John K Jordan]

you could register some heavy 'out of balance' signals just from standard roughing cuts.

That's the reason for the "threshold" sensitivity control. If normal roughing imbalance triggers the circuit, the user would adjust the threshold control as needed. A sudden and severe balance problem, say from an accidental high speed, would still trigger the cut off since it would be much higher force.

A monster lathe encased in concrete and bolted to the bedrock could require finer tuning since it might not shake as violently but it should still be possible to sense the imbalance. I understand these sensors are used on massive industrial equipment.

Just don't let some marketing guy put a SawStop mechanism on a lathe. I'll bet that would spin your cowboy hat blank off the lathe and out the door.

JKJ

[Dan Case LR]

I can't tell if you used a 3 position directional switch or not.

Center-off with momentary (spring-return) on each side of center.




For a cheaper wiring option, I used 8 conductor 22g solid sprinkler wire available at HD or L.

This is a mistake on two fronts.

First, you shouldn't use solid wire in an application where it will be flexed around. The wire will fail after repeated flexing.

Second, cable used to extend the control wiring should be shielded (either foil shielding with a drain wire or braided overall shield) with the shield firmly grounded on ONE end (the other end floating), and the shield should not be used as a current-carrying conductor (a separate ground conductor should be used instead). The wires you are extending all connect directly to the VFD, and the extra length of unshielded wiring can make the VFD susceptible to false commands and cause interference with other devices.


D.

[Dan Case LR]

Another EE here and I wholeheartedly agree with your assessments and I like your solutions. However, I feel the need to rag on you for posting sideways images. :p We engineers need to show that we don't let technology get the best of us despite the best efforts of Apple. Besides, my 27" monitor is too big and heavy to turn it on end to view pictures.:D

Okay, I've got that rag coming--I saw the rotation issue when uploading and hoped there would be an option to rotate them while posting. I intended to rotate them but my wife came to pick me up for a little shopping trip and, well, you know... :)

D.

[Dan Case LR]

You may want to try some epoxy glue to hold the magnets on.



JB Weld IS epoxy.

D.

[John K Jordan]

JB Weld IS epoxy.

I discovered something interesting about gluing magnets with JB Weld when making a magnetic fence stapling tool. I drilled a shallow hole in steel, filled it with JB Weld, pressed the end of a small supermagnet into the hole, then added a fillet of JB Weld around the magnet. As I watched, the JB Weld mixture began to ooze up out of the hole and mound up on the top of the magnet! I pushed it down and it did it again. I suspect it was because of the fine iron particles they put in JB Weld.

I was able to make a good fillet and bond by repeatedly pushing the epoxy back into place until it started to set up.

Perhaps something like this messed up the bond on the magnets discussed here.

BTW, I like to use the magnets with countersunk holes. I drill and tap and fasten with a machine screw. I have also used superglue to hold magnets.

JKJ

[Dan Case LR]

Thanks all for your comments and compliments. I've had several requests for circuit details, so here's the scoop.

The switches and boxes are all pretty standard stuff available from vendors who supply industrial automation components. The speed control pot was the most challenging to find at a reasonable price.

The item at the heart of the controller (inside the black box) is a little circuit board I made and isn't available as an off-the-shelf assembly. If you know what you're doing around a piece of Vectorboard and are capable of fine detail electronic soldering work, you can build one without much problem. I spent a lot of time minimizing the size of that board so I could keep the black box as small as possible.

The circuit is built around a CD4013 CMOS Dual D Flip-Flop. One flip-flop controls the forward direction, the other controls reverse. The flip-flops are used in S/R mode (Set/Reset). Using steering diodes, the forward switch sets the forward flip-flop and resets the reverse flip-flop. Similarly, the reverse switch sets the reverse flip-flop and simultaneously resets the forward flip-flop. The stop switch resets both flip-flops. The Q outputs operate relays via garden-variety NPN transistors. The 12VDC source is a board-mount encapsulated switching supply fed by the same 240VAC feed used by the RPM display.

If there is enough interest to justify a short run of printed circuit boards, I'd consider building a few more of these to sell. I won't discuss that further here, lest I be found advertising--but if you'd be interested, drop me a PM.

Questions?

D.

[Geoff Whaling]

Just don't let some marketing guy put a SawStop mechanism on a lathe. I'll bet that would spin your cowboy hat blank off the lathe and out the door.

JKJ

So true! We see a few mishaps from electronic braking systems that are set a little to aggressively and chucks / face plates not set up correctly.

I like the concept of the "out of balance" control, good in theory, probably quite practical, but how many turners would over ride it so they can turn out of balance work? :confused:

[Dick Strauss]

Dan,
Sprinkler wire is fine for a 10-20 ft total path length. Longer lengths that run in parallel with power cables can have an issue with induced currents if unshielded, but not 10-20 ft. Solid wire is fine for a home build that doesn't see much movement but it is definitely not up to industrial standards that you are used to meeting. The version of wire I bought contains enough conductors to use one as a ground. One could easily buy 8 lengths of THHN and route them through a protective rubber hose as another option for a home build.

[ron david]

guess a fellow just should stick to a treadle lathe and not have to worry about interfacing or whatever. just take your foot off and it's done. one will not have to worry about having to go to university to how to operate a wood lathe; sorry I meant to say how to start and stop it.
ron

[hu lowery]

It would be a tough job to have a motion detector that would shut down when needed and let you go past first harmonic which I am finding handy to do pretty often. My chainsaw whittled blanks usually hit a harmonic somewhere between 450-700RPM. Much less abuse on the machine and the body to get above that first harmonic when it isn't too violent and turn at a speed to get things roughed in a hurry.

It is always a judgment call whether to try to get above that first harmonic or not and the last thing I want is the electronics helping me out with that decision in real time!

Hu

[John K Jordan]

It would be a tough job to have a motion detector that would shut down when needed and let you go past first harmonic which I am finding handy to do pretty often

I agree it would be an interesting challenge but I think it is possible. In fact, it's already been done but not on lathes AFAIK. In the "old days" some associates did analysis and control research, much of it based on monitoring and controlling rapidly spinning things that tended to come apart loudly and destructively at certain harmonic frequencies. Much was learned as much was destroyed! Good fun. I don't know, but I suspect each big smash cost more than the value of my farm, house, barn, shop, tools, and vehicles. (I had my head buried in software at the time.)

I think the key here would be monitoring speed and acceleration along with vibration amplitude and duration. Since the idea for this would be to prevent a disaster from accidentally turning the speed too high, either by bumping the knob or if the control was set too high at start, any harmonic, "when it isn't too violent" as you say, would be traversed fairly rapidly.

The software could ignore a window of vibration as long as it was below a user-defined threshold (or a hard threshold pre-determined to be destructive to the lathe, if, as you imply, it is too violent), sense the smoother transition and then watch for the onset of dangerously destructive vibration. I think the software could also detect whether the speed was being turned up by hand or just spinning towards wide open, knowing the acceleration curves set in the VFD. For a slow advance in RPM it could "assume" the speed control was under the control of the operator and ignore the vibration. It could be programmed to sense increasing violent vibration at a set speed. Note that the microprocessor I am thinking of here is a simple chip and a few components costing only a few dollars in quantity.

BTW, I'm not suggesting this could easily be added or even should be added to a lathe, I just put it out for discussion as an idea. (Thinking up ideas was a fun part of what I got paid for before I retired years ago. Some resulted in patents, more went in the trash.)

Here's another idea: I think a lathe could be built that would cancel vibration dynamically by sensing and controlling integral counter weights. This could theoretically remove all vibration at all harmonics and adjust itself as wood was removed. It probably would not be cheap but might not be unreasonable if produced in quantity. In fact, I know people who might be interested in researching this if they can find the funding. Perhaps this has already been done in industry, I haven't kept up lately. I have llamas and horses to feed.

JKJ

[ron david]

I agree it would be an interesting challenge but I think it is possible. In fact, it's already been done but not on lathes AFAIK. In the "old days" some associates did analysis and control research, much of it based on monitoring and controlling rapidly spinning things that tended to come apart loudly and destructively at certain harmonic frequencies. Much was learned as much was destroyed! Good fun. I don't know, but I suspect each big smash cost more than the value of my farm, house, barn, shop, tools, and vehicles. (I had my head buried in software at the time.)

I think the key here would be monitoring speed and acceleration along with vibration amplitude and duration. Since the idea for this would be to prevent a disaster from accidentally turning the speed too high, either by bumping the knob or if the control was set too high at start, any harmonic, "when it isn't too violent" as you say, would be traversed fairly rapidly.

The software could ignore a window of vibration as long as it was below a user-defined threshold (or a hard threshold pre-determined to be destructive to the lathe, if, as you imply, it is too violent), sense the smoother transition and then watch for the onset of dangerously destructive vibration. I think the software could also detect whether the speed was being turned up by hand or just spinning towards wide open, knowing the acceleration curves set in the VFD. For a slow advance in RPM it could "assume" the speed control was under the control of the operator and ignore the vibration. It could be programmed to sense increasing violent vibration at a set speed. Note that the microprocessor I am thinking of here is a simple chip and a few components costing only a few dollars in quantity.

BTW, I'm not suggesting this could easily be added or even should be added to a lathe, I just put it out for discussion as an idea. (Thinking up ideas was a fun part of what I got paid for before I retired years ago. Some resulted in patents, more went in the trash.)

Here's another idea: I think a lathe could be built that would cancel vibration dynamically by sensing and controlling integral counter weights. This could theoretically remove all vibration at all harmonics and adjust itself as wood was removed. It probably would not be cheap but might not be unreasonable if produced in quantity. In fact, I know people who might be interested in researching this if they can find the funding. Perhaps this has already been done in industry, I haven't kept up lately. I have llamas and horses to feed.

JKJ
are the llamas and horses monitored, fed and controlled by electronics also?
ron

[John K Jordan]

are the llamas and horses monitored, fed and controlled by electronics also?

The are monitored by the dogs, controlled by electrons in the fences, and fed by the old guy.

JKJ

[ron david]

The are monitored by the dogs, controlled by electrons in the fences, and fed by the old guy.

JKJ
that is pretty simple isn't it? Just about as simple as it should be to operate a wood lathe!!
ron

[John K Jordan]

Just about as simple as it should be to operate a wood lathe!!

And perfectly safe too! Unless you are a stray dog. Llamas don't like stray dogs. They upset the balance.

[Fred Belknap]

Some washing machines have a self balancing system on the spin cycle, maybe it could be adapted to a lathe.

[John K Jordan]

Some washing machines have a self balancing system on the spin cycle, maybe it could be adapted to a lathe.

I wondered about that. I suspect, without thinking hard about it, that the spin balance control is simplified by fixed RPM and known expected loads. I know a wad of wet blankets will easily overwhelm the balancer! I've never examined the mechanism but by pushing on the cage it feels like it is spring-based.

[Geoff Whaling]

Having such technology, out of balance compensation, is fine in some respects - but eventually it becomes the turners responsibility to decide "when enough is enough" - what is simply to much to expect from the machine / system and all the add-on technology.

[Bruce McVeety]

Hmm, wondering about the 'out of balance' turn off thing.... Given some chainsawn blanks and how rough the outside is, you could register some heavy 'out of balance' signals just from standard roughing cuts.

I did hear a story about Dave Ellsworth sending a blank through a wall at one of the early Symposiums at UC Davis.


robo hippy

As I'm heading out to David's shop next week for a turning class, a thought this would make for a great dinner table story. I emailed him last night about it and here's his response:

"Ha...close, BUT!!!
I went too thin about 2/5ths down from the top of a hollow form, stilled the lathe, and asked if anyone recognized "that sound." Someone piped up that I'd gone too thin. So I stuck my finger in the hole and pulled the entire top off. Fortunately, I was able to show how the gouge could finish off the interior of a calabash-like shape and saved the demonstration.

I have had a few minor explosions over the years, but never was able to put a piece into a wall...leave that for the folks who do open bowls😏"
Take care, David
PS...you can quote me if needed."

A good story either way!!!

[Dan Case LR]

After re-reading the off-balance portion of the thread, a very basic safety mechanism comes to mind: floor interlock switches.

this will vary by stand design, but for demo purposes assume we have a machine with a 4-legged stand and each leg has a flat plate contacting the floor. Interlock switches are mounted at each leg such that the switch is closed/active when the lathe is at rest. The four switches are connected in series to produce an interlock loop that if opened will stop the lathe.

In a badly unbalanced condition where the lathe's feet lift from the floor, the lathe stops. By using the right switch and adjusting it properly, false stops are minimized or eliminated while anything that causes the lathe's legs to rise causes an emergency stop.

just a thought I needed to het out of my head.

D.