Milling Machine Autopsy!

[Music] oh this lockdown is just getting to be too much and it's especially hard on the kids it's lord of the flies here now last week they flipped over and set fire to the lathe then they blamed the router for the pandemic and this year's crop failure so they buried it alive just the z-axis sticking out now they've dismembered and are eating the maho me personally i'm still fine with mom's hamburgers and grilled cheeses i guess kids will be kids today i thought we could do a bit of a milling machine autopsy old german iron see how they did what they did you know in the good old days think of it like one of those ancient tech shows most of you know i've been tearing down the maho for a cnc conversion and frankly i'm impressed with what i'm seeing i'm even starting to feel a little bit guilty about tearing it to pieces i figure if nothing else it deserves a good eulogy i'm not quite down to the atomic level just yet but this is my progress so far though given the half-butt effort i've been putting into this i'm quite happy with where it is recall this whole mess started out as a fully assembled milling machine candy coated in 30 years of its own filth i've got it broken down enough that i've been able to figure out what i want to do how i want to do it take measurements in fact i've even started ordering parts for the cnc conversion exciting times we'll take a closer look at these parts but for now this is the machine base how do people do this on camera pointing thing trying to control my hand through the viewfinder is hurting my brain i think i can smell burning this is the z-axis dovetail or what i'm calling the z-axis it's a little bit weird on this machine because it's born as a horizontal mill so the axis naming is a little screwy the x-axis would move perpendicular to this that's the x-axis there that's the x-axis there that's what the horizontal table would attach to the work surface the vice that sort of stuff immediately behind it is the y-axis hold on let me just that's the y-axis and that rides on top of this column that's a tool holder you might see sticking out the front and where the vertical head attaches and that right there is my sitting slash thinking stump invaluable for cnc conversions i'm sure you can get one of these from lee valley or rockler or something but usually they'd be pine for a cnc conversion of this magnitude i'd recommend oak or something harder lots of heavy thinking happens on that thing for anyone who may have been wondering what the weak link literally was in my scissor lift well it turns out it's that crossbar there with the drive nut in it the whole thing bent into a v-shaped and cracked through the middle probably started somewhere on that weld and made its way back when it failed it looked a lot worse than this that whole cross member became sort of a v-shaped and started to pull out of the pins on each end i stuffed some 2x4 packing in there drove it in reverse with the impact gun straightened it out as best i could remember when i told you the big slowdown in taking the maho apart was just the weight of all the components and then i was probably going to get an engine hoist or build some sort of an a-frame well i did neither of those i did most of the assembly with brute force and a lot of lifting with my back i slid the y-axis of the machine forward and onto the z-axis and use the table to lower it as far as i could and transferred it onto the scissor lift the scissor lift did absolutely perfect until i lowered this to the ground the lower this scissor lift goes the more the mechanical advantage just falls through the floor it becomes a mechanical disadvantage now when i've got a motorbike on here i can only lower it so far before the wheels hit the ground and then they start to share some of the load with the scissor lift it became second nature just zipping stuff up and down with the impact driver or the drill what i failed to keep in mind though is that the y-axis of milling machines well they don't have wheels the top of the lift came down to within i don't know two inches of the bottom of the lift and it just gave way live and learn huh i'm gonna do that again not now but sooner or later i'm gonna pack it again drive it so it's preloaded the other way and weld it in place like fix it in the scissor stand luckily i built this thing in such a way that i can't take it apart and here's the y-axis that did in my scissor lift or maybe the z-axis again this is sort of horizontal format the spindle runs through here the tooling is on the end you can't see it but i'm turning the spindle nose now this thing's got to weigh 100 pounds 120 pounds these parts with the aztec glyphs etched into the side are the keys the gibbs that tighten up the dovetail fits we'll get into that later speaking of which an amazing fact number one after all these years this machine still moves like a dream a good dream like the ones i used to have as a kid not the ones that torment me now you remember that hundred pound head that broke my scissor lift i hope you do we literally just by the time that's installed on here that rides on these dovetails by the time that's installed in here with the rest of its castings and the motor and the variator it's got to weigh 200 pounds and check this out here i'd remove the ball screw head and even pump the dovetails full of oil it was just the oil that was there last time i fired this thing up and it's absolutely weightless again there are no roller bearings in here linear guides it's just a piece of cast iron on another piece of cast iron with a little bit of oil which consequently happens to be my favorite breakfast sandwich except for the last two inches on each end the ways still have their flaking i think that's called flaking that little fish scale looking pattern i hope you see let me try to get you in close this casting i assume was milled flat then ground and flaking put in the flaking is put in to help hold that oil film it's not much but it creates little quote-unquote micro pockets little cavities that help retain oil if it were completely flat if those imperfections weren't intentionally introduced the weight of the head would eventually just push that oil out the sides i'm not sure why it'd be more worn on the two ends perhaps this machine was run a bit without the gib sort of cinched up properly that and i suppose it worked a lot at its extremes all the way in and all the way out while we're here looking at the base slash column the foundation that the rest of this machine is built on i'd like to take a moment to appreciate just how well designed this part is let's stop and smell the 30 year old oil grease and coolant soaked flowers granted i haven't checked the z direction but much to my surprise this machine base has been designed to remain rigorously geosynchronous you see that indicator it's been there since i started this teardown and the machine hasn't budged an inch incredible so if you'd stop you're screwing around for just one minute you'd realize we're now talking about the machine motion and motion control although this is was a cnc mill it's not what you might think i'd consider it cnc on a technicality although there was a computer involved and the computer could move the machine to the best of my knowledge anyway it could only move one axis at a time it's basically a milling machine that let power feed get to its head get it all right fine that was stupid i'll take it out ned so what does that mean one axis at a time and more importantly why am i filming this on the floor of my garage staring into the spindle hi-low selector well first and foremost this machine couldn't mill a circle or arcs or curves or crescents or any other synonym for a circle or partial circle consequently it also couldn't cut at an angle unless the work slipped in your vise i guess but it could face stock off cut rectangular or stepwise contours it could cut and clear pockets basically it could cut any shape where all of the included angles were 90 degrees i think the cnc part comes from the fact that it had feedback for each axis in the form of a dro reading so where power feed is just well power feed it moves until you stop it this could move any given axis a programmable distance it could for example power feed z exactly 2.54321 inches up and heck probably even down the motor and the controller would move any of the three axes via the transmission inside we'll get a look at that in just a moment one at a time until a programmed distance was reached it would keep doing that until the program was finished what i think is cool though is how it moved all three axes with just one motor i mean i think it's fair to say that modern cnc machines have a dedicated motor for each axis motors you could run simultaneously to make all the funny shapes we've come to know and love single motor power feed isn't anything new or particularly exciting here we're looking at the bottom half of a shaolin 13 this is my manual milling machine you don't usually see this part in videos because i do most of my milling up on the machine table but this thing runs x and z on one motor i have no y power feed on this thing there's a motor in the base that sends power up into an apron what i'm calling the apron it stops there because the machine is effectively in neutral and i convert that power either to x or to z in either directions and the machine will keep running either of those axes until i either stop it myself putting it back in neutral or it reaches a limit switch this machine also has a rapid override in the form of a giant pedal on the floor when you see those quick moves and you hear the buzzing in some of my videos while i'm milling it's because i've hit that rapid override it'll power feed at a feed rate i set in the gearbox on the back and when i stomp the pedal it'll override that and run at max speed usually for repositioning or getting in and out of trouble really fast also perfect for breaking end mills but let's get back to the maho and see how it does all of that auto magically clutches right angle gearboxes hydraulic brakes dual input helical bevel gearboxes spline shafts bearing supports this thing is a gold mine of all right maybe just maybe the heidenhain controller electrical cabinet all that nonsense had something to do with how this mill functioned maybe but to me these parts here are music to my eyes granted this looks a lot more like a train derailment than a milling machine but what you're looking at is the motive power super highway that course through the veins of the mill bringing each axis to life probably the best way to make sense of these works of art is to follow the money this is a pancake motor they call it that for obvious reasons tastes like pancakes mmm maple syrup dc motor and it ran all of the axes geared up there's a timing pulley there let's spun this thing here we're going to use this as our power source from here on out because it's a lot lighter than the motor it doesn't taste as good this will be quick but as we work through this i'd like you to pause your video every 15 frames or so sit in silence for just one moment and let it sink in just how much trouble these zany germans went through to power a three axis machine with just one motor anyway power came in at the base again one dc motor belt it up to this larger pulley this nets us a speed reduction and quite a bit more torque and into its first of many gearboxes this if i'm not mistaken sat about like that you likely can't see them but there's two bevel gears in there power goes straight through and the 90 degree bend sends power through another spline shaft up to the head of the machine in this orientation the milling machine is laying down on the floor installed this would be straight up vertical going to the head on each axis there's a clutch that's this part right here if i power this gearbox the spline shaft moving off the screen to the right isn't turning that wouldn't turn unless this clutch was engaged we'll have a closer look at one of these in a second this is the arrangement that's powering the head the bit on the top that slides back and forth if power is diverted up to this gearbox via that clutch it spins this trapezoidal nut this was mounted on the back side and that nut pushed or pulled the axis in that first or second mahjo video when i couldn't move the top axis of the machine its screw had completely come out of this nut so this was spinning but nothing on the machine was moving all right that lives there now the second input to this gearbox is just the manual hand wheel i can't see what i'm there it is the y-axis could be moved either with power feed or by hand there's no key in there so it's not turning but hopefully you get the idea if we come back down to the bottom into the first gear box when that was powered by the motor and we follow the spline shaft straight through option b maybe in this choose our own adventure we run into you guessed it another gearbox this one unlike the last one we just saw does not spin an axis nut it's got a seat for an axis nut it's actually this one here this is bolted to this gearbox which is bolted to the frame of the machine that heavy base we saw in the beginning this nut does not move instead power is routed up the spline shaft bridged over via set of spur gears and sent back down in the form of a rotating screw when the screw turns inside this fixed nut well it translates the entire table up and down this is what i'm calling the z-axis because the table is moving up and down while we're here this node i don't even know what you'd call this this gearbox this sub-assembly also has another bevel gear snuck in between the two spur gears that diverted the power down into the screw and the screw itself to accept input from a hand wheel this would be the hand wheel that raised and lowered the table if that weren't enough two more electromechanical clutches i'm showing this to you now because in a second you're not going to be able to see this anymore all of that clockwork fit all up inside this apron the gears and clutches fit something like this the spline and the screw translated with the table quick recap so far in the head at the top the nut spun the screw stood still and it just dragged the screw and the whole head back and forth with it these other two axes the nut is fixed and they're spinning the screws see if i can turn this around for you without busting the stitches on the double hernia and there's the fixed nut for the x-axis so when the table would shift left and right on these dovetails the screw was turning inside of this nut maybe in the shot you can still see the flaking on the x-axis that's pretty excited to find that people ask me all the time what to look for when they're buying used equipment what you want to do is show up at the seller's house toolbox break the machine completely down and see what the ways look like if they look like this it's not a guarantee but it's a step in the right direction since this particular machine has spent a long time in a dark damp environment it's started to throw off some shoots these are what new milling machine sprouts look like if they happen to land in a scrap bin they'll take root and you'll have a clone of your milling machine i'm going to bring you into the pocket in the saddle but before i did i wanted to just give you the big picture to orient yourself z-axis screw and the powered spine shaft are coming in from the bottom and the x-axis rides front and back the way it's sitting here to and fro when power is diverted to this lower bevel gear via those clutches we saw earlier this gear set spins and if i can get it into view i want to show you that key in the inside bore of the bevel gear that key down there is what turns the x-axis screw and this is the x-axis this is what the table mounts to where the vise would sit and this x-axis screw has a slot milled along its entire length i mean what are the odds the little key we saw on the inside of that bevel gear drives this screw and turning this screw inside of the fixed nut is what moves this table left and right the key can turn this and still slide in this slot so we're done at this point we have power to x y and z though you might be asking yourself rightly so where on earth does the spark plug go on these old german milling machines well it goes right here before we call this a wrap there are three things we should really talk about electromechanical clutches hydraulic brakes and i do realize you've been in lockdown you're probably not seeing too many people these days but you really got to get out of that old shirt you've been wearing have you considered this might more accurately be called an electromagnetic clutch and to better understand what this does let's put it back on one of the gear boxes this happens to have a female end another spline shaft fits in here if i turn this spline the output doesn't move so in this case the motor would be sending power straight through this side is free to rotate mechanical connections only made when this ring gear or face gear is brought in contact with the mating ring gear you see that spring-loaded action and the face gear mating this way no torque is transmitted no mechanical power is transmitted until those are engaged and then it becomes one piece and rotates together i've got a little power supply hooked up ground attached to the gearbox gonna hit this ring the silver ring with 24 volts now i wasn't sure what the operating voltage was i tried 6 10 12 didn't come to life until i hit 24. so that's not engaged now it's engaged and here are all three clutches x y and z that spark plug looking thing we saw earlier is actually a brush the spring-loaded copper plunger threads into the castings through the castings and coincides with the slip rings i guess these are what get power to the coils that actuate the clutches this sub assembly in the apron that we saw before is a bit trippy mechanical power comes up the spline shaft and dead ends in these clutches we actuate the lower clutch that power is sent through the spur gears and the screw turns which raises and lowers the table if electrical power is sent to the upper clutch mechanical power comes straight through doesn't spin the spur gears and instead spins that keyed bevel gear we saw a moment ago that turns the x-axis screw pretty neat huh and by neat i mean insane there you have it ladies and gentlemen electromagnetic clutches these in particular are known as tooth or toothed clutches but no one really knows why you might not see these all the time but they aren't particularly exotic machine components they're pretty much everywhere if you're in a pickle and you need one fast your neighbor has one in their car where it's used to engage the air conditioning but of course you can buy these in all shapes and sizes like you might add gear or bearing and use them where you need what they're not however is cheap especially ones like these hydraulic brakes or maybe this is a hydraulic lock just like the clutches the milling machine has three of these one for each axis not exactly sure how this one does its thing but end result if you send in hydraulic pressure it'll put a kung fu death grip on whatever is inside when this is mounted on something and you send it hydraulic juice it'll squeeze the ever living life out of it these only have a certain range this is too small but this fits around the lead screws in the machine these are used by the mill to lock the screws dead in place we'll open this one up just for kicks but i expect it to be a hydraulic version of what you might know as a posi lock or a keyless hub lock a keyless hub lock lets you install pulley or a gear or whatever onto a shaft without having to use a key lift them in place torque the screws it expands on both its id and its od to lock the two components together it's like two nesting tapers when you drive them together they expand this is the lock from the z-axis which i had trouble moving when i first got the mill the z-axis hand wheel was extremely tight i assume at some point it's life this started to have problems this doesn't look like oem goop to me it was probably leaking and someone tried to fix it with shugu that's one piece that's pretty cool the entire cylinder body is all one piece but i think i see what this thing is doing there's a plastic bushing down in there it appears to work sort of like a blood pressure cuff you know those things that doctors pump up full of air until your arm turns blue bushing feels like it's pressed in there i could probably pull it out if i really put my mind to it but i foresee myself covered in hydraulic oil my money is on hydraulic pressure behind that plastic bushing makes it squeeze in sort of into an hourglass shape and inside there is this almost collet looking piece it's very thin metal relief cuts all the way around it that plastic pushes on these squeezing them onto whatever is inside that's pretty neat and pretty simple if that's indeed how it works there's nowhere to get a bite on this okay whatever oil goes in one side and whatever's inside ends up with an atomic wedgie hydraulic breaks everyone judging by that dead look in your eyes i'm guessing this is about the point in the video where you might be sorry you even asked it's the same look my wife not to mention if i keep talking we'll be getting further away from the major and more into the cnc conversion territory but just as a teaser and after much internal struggle for the conversion i've decided to go with separate motors on each axis the pancake party is over folks everybody get your sticky hands out of i'll be going with servos no steppers here and i hope you're all sitting down for this ethercat controls i'm sure you all know this my apologies ethercat stands for ethernet for control automation technology and and i have no idea what that means i hear it's all the rage these days it's the future of cnc and it's pretty powerful stuff suffice it to say i'm getting way out of my comfort zone on this one motors and drives have already shipped we'll talk about those when they get here between me and you i'm more intimidated by the new control system than the actual mechanical conversion speaking of which x and y should be pretty straightforward ball screw conversion famous last words i think i just need to gut out anything that gets in the way do some machining and replace the fixed nuts with ball nuts i'll likely need to make new end caps for each axis to accommodate like the preload bearings or just the bearings maybe just modify these we'll see how much space i have to work with once i get all the hardware in here the major curve ball so far anyway i think is going to be the z-axis this bit right here that we saw earlier this screw here is 30 millimeters maybe 28. it's a trapezoidal screw and is the biggest screw in the machine to retrofit this with the ball screw i'd need to go down one or two sizes 24 25 millimeter i'm not sure what the standard sizes are three quarter inch maybe but all of those seem small the balls in ball screws are freaking tiny and this whole apron x-axis and work table are going away quite a bit to go to a larger ball screw one and a quarter or one and a half i don't know 35 millimeters would require quite a bit of modification to this machine simply to make space and if that weren't enough this is the screw that translates the nut stays still and the screw runs up and down inside of it the easy way out is to make a spinning or driven ball nut which isn't trivial or cheap i'm not 100 just yet but at this point i'm leaning towards leaving the trapezoidal screw in there and working with it as is it's obviously well suited to the load but downside cnc machines like to go up and down like newlyweds on their honeymoon that's a lot of wear and tear with me just a moment i need the thinking stump then there's the backlash thing these screws have backlash though it may not be a big deal here since it's a vertical axis and there's a lot of weight involved it's what i'm telling myself today anyway this is probably one of the very few instances where gravity is on my side all of that weight will always keep the nut on one flank of the screw and maybe backlash wouldn't be a big deal but well i don't know if anyone has any strong feelings either way let me know down in the comments we'll get deeper into the cnc side of things as parts come in and my ideas crystallize but for now that's all i got i hope you enjoyed that thanks for watching it just dawned on me my apologies we did a milling machine autopsy and i haven't even shared my findings for the official cause of death thanks for watching

Channel: This Old Tony

Views: 722,473

Rating: 4.9558182 out of 5

Keywords: maho, milling machine, cnc conversion, clutch, electric clutch, electromagnetic clutch, brake, gearboxes, etherCAT

Id: np72HhAiMc4

Length: 26min 22sec (1582 seconds)

Published: Sun Jun 07 2020

Reddit Comments

[u/jwm3]

Another fantastically funny guy that does CNC and electronics videos is Marco Reps. If you like ToT then I highly recommend him too. Jam packed with dad jokes and a fair bit more in depth technical info. Here is a recent CNC one https://youtu.be/vB_FvkllLPc

[u/doomjuice]

Luckily I built this in such a way it can't be taken apart...

Dead

[u/GeneralSubtitles]

All that filth accumulated. Needs a lesson or two from my_mechanics

[u/[deleted]]

I love ToT. His videos are so well made and it’s great to see the progress he has made from his earlier ones. His technical knowledge is amazing but his jokes really keep me looking forward to new videos :)

[u/slo196]

Used to run Maho and Deckel VMC’s in the days of manually inputting G code on the control panel. Pretty good machines.

[u/jlude90]

Maho Maho mannnn, I've got to be, a Maho man