CNC Lathe Scratch Build

Wow !!

... I can say no more.

MichaelG.

Not sure if I should start splitting the posts - would like to keep the build history in one place, but as I am visually vociferous the post becomes rather large...Will do what is suggested...

The Lathe bed turned out well, and the base framework is also started - The exercise now being to get the spindle motor positioned with regard to the drive belt, spindle, and motor tilt mechanism. The latter required as the motor will be fitted with a dual sheave pulley, one of 120mm OD and the step below , 80mm OD, giving max spindle RPM of 4000RPM and 2700RPM resp. I am hoping ( torque calcs indicate it is possible) that I will get away with just the 120mm pulley, and still have enough torque at low RPM's - sort of around 20RPM for some 'heavy' cuts.

the Motor specs 1PH and 3PH:

In the event that the smaller pulley is needed, the motor needs to be able to pivot to take up the belt slack, and the motor must slide back 20mm, to line the 80mm pulley up with the spindle pulley - this all to be a one lever movement exercise...

The motor is big for the lathe - 1.7KW @ 220VAC 1PH, and 2.9KW @ 230VAC 3PH.

It is a rather special motor - permanent Magnet rotor, and is actually a very high power closed loop 'stepper motor' dead silent in operation, no noise, no step feeling, etc. It is in essence a AC servo motor, driven by step and direction input. It is a closed loop control, with a 32000 count encoder.

The reason for using this motor is that it has full torque from 0 RPM and maintains the torque well up the RPM curve, esp if fed with 3Phase. In addition to driving the spindle for conventional turning, it serves as the lathe's C axis, with rotational position control capability to within 0.08 degrees, allowing use of live-tooling in the lathe to 'mill' the workpiece in the chuck ( Hex heads, High pitch 'threads' and anything else...) Holding torque is very high, so medium milling should be possible, and low speed toque is high, allowing full 'power' at low rpm's.

Below - The bed trial fitted to the base framework -

lots of effort went into straightening out the base frame after welding, all checked on a granite table..

The Lathe bed is as flat as the proverbial pancake, and once the base frame was straight, the lathe bed side supports were bolted to the bed, and then the side supports tacked onto the base frame. The welds were then tackled in short steps, alternating left/right and obliquely to help prevent the base frame from distorting. It Worked!

See how nice the bed shaped up!

The slides are 25mm square - nice and beefy..

Lots to do before the next post, so that may be in a good few weeks time!

Joe

Edited By Joseph Noci 1 on 24/12/2020 13:44:09

Are you using any wavy bearing springs in your spindle pack at all? Or any spacers between the bearings?

A very nice project. Be interesting to watch the progress. Thanks for sharing what you are doing.

But you should, Michael! At least criticise a little - How else do I know where I am deluded in my doings??

Joe

Neil, no springs, etc in the pack, I am not sure what you mean by tween' spacers - If you peruse the (many..!!) photos the assembly may make sense - the bearing cups fit snugly into the rebated bore of the headstock, and are separated by the rebate ( the boring of which in the mill can be seen in some of the photos). The bearing cones , on the spindle, then fit into opposite cups in the conventional manner, with the combined sheave pulley/pre-load nut holding the assembly together. All running in oil. There are oil spinner/flingers at each outer end, with O-ring seals in the outer headstock flanges, also seen in the photos..

I hope I have not missed something obvious in my 'design' here!

Joe

The idea of the wavy springs is to put a preloaded amount of tension onto the bearings, but does leave a small amount of movement with a large load. This is to allow for expansion if something gets hot or cold, the assembly does not jam up. The inner sleeve idea is that the pre tension load is determined by the sleeve length. So you can do up the rear nut holding the pully etc, but are not effecting the bearing preloaded state. Quite often the spindle bearings will come with information on the amount of preload that they should be, and the amount not to exceed. I can't remember what the N value of the springs are, but they use them in a lot of electric motor bearing installations.

Ok, I understand - I have basically followed the same construction as in the headstock on my Emco V10P lathe - and as is, I suppose, in most minilathes with taper roller bearings. The headstock body is a large chunk of aluminium and should help conduct heat away reasonably fast - in any case, the lathe won't be production standard..!

Joe

A lot of work, this 'little' lathe..

The Base frame as proto'ed in CAD

Fair progress made on the base frame and its cladding - base frame became a priority so that I can have it painted and then mount the lathe bed and start on the X and Y axis structures. The lathe bed needs to be in-situ to begin fitting Axis drive motors, etc.

The base frame is made such that fore and aft of the lathe bed are two sluice cavities down which swarf and suds can spill, into a full frame sized tray under the lathe. The tray has a belly pan, leading the suds to an outlet pipe, into the suds tank - all that still to follow in coming months!

The render shows two trays, but that has changed to one big one.

The top aluminium cladding fitment:

Cladding in place - Sluice cavities can be seen below.

Lathe bed trial placement:

rear View of Bed and base frame.

The frame sides cladding is also complete. Will be fitting and drill all the pop-rivet holes on the weekend. Then a clean up, de-burr and off to the powder coaters..

Joe

Lathe Frame and cladding back from powder coating, and part assembled.

Front View:

Lathe bed and headstock fitted.

The Grey horizontal part with the two horizontal handles is the Swarf drawer / coolant drain . The Swarf would be persuaded to go down the forward and rear swarf slots, seen in photos below as does eventual full flood coolant. The drawer has a shaped base to lead coolant to a drain hole, back to the reservoir and pump.

Left side view shows the front swarf slot - about 150mm at the mouth.

The Rear swarf slot, 80mm at the mouth.

View under rear slant cover showing the Brushless 2KW motor - driven by step/direction pulses, with a 12000 step/rev resolution - will serve as the C axis as well eventually.

View of the rear wall, ( cladding to be fitted still) - shows the swarf drawer and its slope.

Lots to do still - On the cabinets - coolant drain, reservoir, pump, Electrical box and wiring, Upper cabinet sliding enclosure for splash guard,.

Then the lathe itself, at least it now sits on the cabinet, itself on sturdy casters, so I can get to all sides of the lathe and continue with the carriage and cross slide and associated ball screws, etc.

Have got together all the electronic modules (MESA Cards) and a suitable 64Bit mini-PC, with LinuxCNC installed, starting the great adventure with HAL, and the .ini files...Have got that all running and driving my CNC Router as a test bed - LinuxCNC is a whole new game!

Joe

Edited By Joseph Noci 1 on 30/01/2021 13:36:02

Next Installment on the lathe build..

Most of the major part manufacture for the lathe proper is done - some small items left to do - ballscrew to ballnut mating seals, pulley keyway broaching, etc..

Doing the counterbores on the X axis slide plate / carriage -

Made an under-pin fitting into the mill slot, over which the thru-hole in the carriage plate slips, and then the plate is clamped to the mill table. The endmill, used to counterbore for the capscrew head, is centered over the pin. So, plunge, unscrew clamps, lift plate and slip next hole over pin, clamp and plunge.

The X and Z axis limit switches where a bit of an issue - all the readily available sensors are rather large - mostly the tubular/cylinder style, and make an unsightly fit - so made up some Hall sensors which work very well, and fit cleanly. - these to be encapsulated in epoxy resin.

The headstock is all done - pulled the cheap Indian test bearings out and cleaned all parts, inc the final Timken bearings, oiled and assembled - feels soooo smooth!

19mm collet fitted with a 19mm ground test bar fitted to check runout. Bar is 300mm long, 0.005mm runout at collet, .012 at bar end - need to investigate that...

The small square plate at the base of the headstock, below, is the Z axis hard-stop for homing Z.

Manual collet closer wheel and drive pulley sheeve. Rotary encoder below

Brass button is oil filler with breather hole

Brass button is oil drain.

Headstock alignment:

The whole lathe alignment is quite a daunting task.

Headstock nod - to bed in Y and Z = using test bar, with an accurate square ( 70mm diameter x 160mm tall Aly bar, squared off at ends) with feeler gauge to test height to bar at collet and test bar end.

Then Z axis slide rails ( front and rear) height to test bar with dial indicator ( as below).

The headstock rotation - using dial indicator on side of test bar and rotate headstock til parallel.

Z slides are parallel to each other to 0.005 / 0.008mm, ie the steel bed width is parallel.

X axis will be done by machining a face and verifying for flatness.

X axis assy fitted and initially squared with headstock face.

More in a week or two..

Joe

Edited By Joseph Noci 1 on 14/02/2021 20:49:22

Very impressive Joe, do you have specific tasks for this when it's finished?

Thank You Pete. The build did not start with any major use in mind - the result is limited to what a 5C collet lathe can do and will only work under full CNC, so cannot even be used as a manual lathe - even with electronic handwheels fitted for X and Z. A six station auto-tool changer is in the design stage as well, and the structure is that of a conventional slant bed CNC lathe - the tool approaches the work from behind the work piece so manual operation is a recipe for a crash! Inverting the X infeed direction in the brain, while ignoring the direction in the eye is not easy!

You, and others, will have noticed by now my 'mechanical engineering' pleasure lies not in the building of models, steam (or otherwise) engines, etc - I enjoy building machines, which make more machines!

The lathe is a huge challenge. The build accuracy is not easy to achieve - my mill(s) are a lot smaller than the major parts of the lathe, so a flat lathe bed is not easy to achieve, etc. Since I am trying for better than 0,005mm on machined parts, aligning the lathe axis and headstock is key, and difficult!

Together with the ATC is intended a full C axis and basic live tooling - a milling spindle that can cut in X or Z axis on the work piece, so some additional mechanical challenges ahead.

And then the control software is another mission - there is no commercial controller and software available to control a Lathe with C axis and live tooling - to qualify, there is, but at major prices, for the big CNC names in industry - many thousands of Pounds! Likewise for the CAM software, which will be another interesting exercise.

The intent for the controller side is to use LinuxCNC and 'make' it work - another big journey! That will be the subject of separate topic of posts in due course!

Hope this rather narrow topic is of interest to more folk on the forums and not just taking up server space!

Joe

Definitely not - I guess perhaps like many here, my own workshop practice has it's roots firmly in the century-before-last, and due in part to my own laxity, is anchored there at present due to a lack of detailed understanding of modern control systems & construction methods - so to me, this is essential reading - a guided walk through unfamiliar territory, if you like.

I find myself almost embarrassed at my inability to make informed comment other than bland noises of congratulation, so err too much on the side of that piece of advice that states 'It's better to keep silence and have the world think you a fool than open one's mouth and prove it..', I guess.

Threads like this one, and the 'Adventures with a KX' by JB et al are vitally important if the hobby is to have a widespread appeal and future to those burdened with the increasingly limited space and resources of modern living.

Think it's great, please carry on..

Joe, I completely understand where you're coming from, I enjoy fixing up machinery and old tools as much as I like making stuff, slight ocd forces me to make sure everything is painted and looking nice, some consider the machines and tools a means to an end, and making tools look nice ridiculous, it's a fair point, they are just tools, but I enjoy kitting my workshop out, it's a job in of itself.

I didn't really have much interest in modelling when I joined this forum, but I've convinced myself, when my ocd allows me to stop fixing up old lumps of iron, I might have a go at some modelling, there was a guy building a WW1 artillery gun on this forum, I'm sure you've seen it, sadly he's not posted an update for a while, it's an excellent build, and has inspired me to possibly make something similar in the future.

As with the above post, cnc definitely isn't my area of expertise, your posts are interesting and educational to me also, keep them coming.

Well, I believe in treating my equipment with care and that the machines will then deliver the design performance even after I am gone..

I could never feel comfortable going to make something on a machine that is covered in years of grime, chipped by careless tossing of tools onto it, greasy and messy, etc...I clean most of the gunk off the machine at the end of the day - makes it nice to start again the next day, without trying to dig the machine out the swarf and muck...

Just adds to the pleasure of making stuff!

Anyway, thanks both of you for the encouragement - I tend to get lost in the making, and sometimes wonder if the madness is maybe only mine - would rather not foist that on 'conventional' modellers!

Joe

Yikes! Joe strikes again. Most impressive.

All I've done today is sharpen a pencil...

Dave

Super cool - and great progress. Well done.

BEWARE - Very little engineering in this post!

Well, a month later and some more work done - although this has been the mentally taxing part of the project so far..

Most of the mechanical work is done - A little bit of metal bashing was done - enclosures for the LCD and Linux computer, Operator control panel, etc, and that was sent of for powder coating and so I had to start the wiring of the whole system - a task I dislike and have been putting of for as long as possible!

There are three brushless servo drives - X axis, Z axis and the main spindle. The axis servos require a power supply - 70VDC@10amps. The main spindle runs off 220VAC. There is also an 8 station ATC - the next project - and a milling Live Tool - the project after that! An operator control panel sits where one would normally grab a lathe's handwheels, with jog wheels, buttons, spindle and axis controls, etc. A mini PC sits with the LCD. LinuxCNC is loaded as this is the only way to go for a lathe with C_axis and live tooling. None of the multitude of other systems ( PlanetCNC, Centroid, Hico_Vital, Eding CNC, and a small handful of even less capable offerings) can do a lathe with C_axis and live tooling.

LinuxCNC, employs I/O cards that do all the Servo pulse generation/interpolation, as well as monitoring all I/O ( limit,home, control switches, jog controls, etc). These cards are made by MESA Electronics in the USA - they make a huge array of cards and enable the automation via LinuxCNC of almost any type of machine - Robot arms, Hexapods, multi axis lathe/mill, etc.

All this makes for wiring nightmare!

So this last month was mostly spent the wiring, which is 'mostly' complete - I am presently busy buzzing out pin-top-pin against my wiring diagrams.

Also over the last two months I have been trying numerous CAM packages - I covered CAM software needs in an earlier post - Since CAM will make or break the lathe's ability to do anything fancy, I spent a LOT of time evaluating various packages - I will discuss that in a topic previously raised on the subject for those interested.

Somer statistics of time on this project;

Mechanical work so far - 518 Hours (!)

Wiring - 78 Hours

CAM software evaluation - 97 hours.

Some photos of the wiring saga:

Inside the snake is the Loom to the ATC and Live Tooling connectors on the X axis - carries power and all control signals. Also visible, the power supply feeding the servos and live tooling.

The loom itself:

The ATC/Live Tool connectors:

Connectors to the ATC and Live tooling on the X Axis

Start of wiring the main Distribution Box..

The Mini PC fitted to the rear of the LCD - PC is about 166mm square, 2GHz processor, 4GB ram, 128GB Solid state drive. Connects via ethernet to the MESA controller card

Operator Control Panel ( still short of knobs..)

Distribution Box Wiring 'complete'. The MESA control cards are visible in the central section.

Rear of control panel showing wiring and the MESA 7i73 Module - this module manages all the control panel I/O, jog wheels, etc, and sends the data to the main controller in the distribution box, serially, at 1.2megabaud.

Safety related controls - Spindle/tooling ON/OFF, E-Stop, etc, are wired direct to the main control card in the dist box, or to the Servo and or mains cut for E-Stop.

Dist. Box and Control panel connected and checking pin-to-pin wiring..

When the enclosures are back from the coaters I will assemble the display/PC and connect up to the dist box and control panel and then the fun starts trying to understand LinuxCNC and HAL.....

Joe

To add a few more statistics;

There are 42 detailed wiring and looming diagrams, and 18 detailed, wire colour coded, pin to pin wiring tables.

There are also 67 mechanical drawings and I have a very detailed , representative 3D model of the lathe, and a useful 3D model of the lathe stand.

sample of wiring diagrams and connection pin lists:

130 drawings....

I must be nuts...

But I can't stop now..

What an inspiration Joe

Thank you