Following along the same path as many others, I have sold my router an bought a mill. It is a Zenith knee mill, which is made in the USA funnily enough! The thing is old, probably around 50 years, but it has been owned by a model engineer for a looooong time, and is in reasonable condition due to this.
I have only just managed to put the thing back together since getting from the drive into the garage, and still have to hook up the motor (via 3 phase VFD for variable speed control) and tighten everything down.
I think the next priority will be to give it a good clean up, and a new lick of paint - that green is nasty!

Ah yes, that takes me back to the days of steam driven CNC. :D
Al.

Nice machine. Similar to my Deckel engraver. How are you planning to CNC it. Ball screws?

Yep, I have been busy on ebay over the weekend, just bought 3 ballscrews which are brand new, old stock. Originally made for Denford CNC machines, they are precision ground. I have started to paint the thing, but there is nt really a lot I can do before the screws and bearings turn up :(

that's a classic old machine. kinda a shame to paint & cnc it, a bit like putting nitros and metal flake on a great old healey :)

The paint is not the original colour anyways. There is quite a lot of sivery-grey beneath the pieces I have removed (such as the belt covers) so I am not doing any real damage.
You are right about CNC'ing though, but needs must! It is the largest machine I could fit into the overcrowded garage.

I take it the current Z lead screw is has a stationary nut in the base, and the screw is driven through a crown and pinion gear. (Same as the deckel). Have you given any thought to how you are going to CNC this axis? I would expect the right angle gears to have unacceptable back lash.

What color are you painting it?

Hi Mark, I am paiting it bog-standard goose grey, so it will look nice once it is all done. Just the head and table left to paint, but that will be done once all the "extras" have been addd to them.

Yeah, the knee operated via a crown gear, but I will leave this alone and use the knee just for tool-changes. The mill has a sturdy quill, which the sliding portion is 4" diameter. It is currently operated on a small worm drive via the front handwheel, but this is well worn and will not be any good to CNC.
What I have in mind is the method used by the mill-drill fitters, so I will mount the ballscrew on the side of the head, and attatch to the base of the quill. Then I can spin the nut to move the screw and quill up/down.
The biggest problem I will have is deciding the best place to mount the ballnut in order to minimize any flexing of the screw-quill mounting plate. Should be easy enough to strengthen it though :)

I didn't look hard enough and missed the huge green quill right at the front :)

This will make the conversion much easier.

Look forward to seeing final pictures.

Ok, so my bearings finaly turned up today, and I managed to make a start on the bearing blocks for the X axis. These two cast iron blocks were already on the table, so just required boring to accept a pait of angular bearings on one end, and a pair of deep groove bearings on the other. A quick 5 minute boring job....oh wait, I forgot it took me around an hour to mount the things on the lathe first! Nevermind, just need to make the spacer for the AC bearings, and the bearing-block caps to hold the bearings in place.

I managed to make the little spacers yesterday, and made a start on turning down the ballscrews. Wow, they were hard! Had to grind off all the hard surface before turning in the lathe. I did attempt to take a deep cut to get under the surface first though, but this was impossible with my setup. I suffered worn tips, shuddering and even a couple of sparks! Nevermind, got the x and y screws turned down now.
I made the y-axis bearing block today, using the existing block, I have just bolted a piece onto it, bored for the new bearings, and made a nice hat to keep it all locked up. Next job is to work out the best way to mount the ball nuts.....X is no problem, but the y will be a little more tricky since I have big nuts ;) and not a lot of room under the table.

Here we go, I managed to cut the nuts down a fraction so they fit under the table, and using a slab of cast iron for the connecting block, it is all working nicely. I had to notch the knee slightly to get the full table travel, but I never removed any real "meat". There was a thin section (maybe 1/8" thick) which just seemed to function as a swarf guard, so I drilled a series of holes through, and it came away easily with a soft blow from the persuader.

After the y-axis, it was simple job to hook up the x-axis screw. Unfortunately, I had to butcher the nut-retaining block a bit (it started off as a cuboid) so it would fit under the table, but again, it is still fully functional and holds the nuts securely in place. Could have done with a milling machine here, but the bandsaw and lathe were put to good use. Just got to give it a lick of paint on the table now, then it will be on to the tricky z-axis.

Almost finnished the z-axis nut carrier now, so here it is so far. Essentially it is a spindle with the two ballnuts trapped inside so when it is spun, the ballscrew will move, hopefully taking the milling spindle with it. The first few pictures show the insides - a bored cylinder to trap the nuts and hold the bearings on. I managed to drill the clearance holes for the ball-returns on the rotary table. If I never had that, I guess it would have been a file job since the piece was too big to offset in the lathe. This part is made from 2.5" dia 2024 aluminium since that was what I had on hand.

The last two shots in the previous post show the bearing holder. 4" aluminium bored to just clear the spindle, then bored each end to hold the bearings. A hat on each end keeps everything locked together, and there is just enough room on the end to get that pulley on!

Last job for this part will be to turn a flat section on the whole assembly and mount it to the miller on the round plate shown in the last photo. i ahve really had enough for one day though, so it wil have to wait!
Oh yeah, don't be scared to comment guys, it is nice to know there are people interested in this!

Hi Kong
I'm watching with interest!

Keep going! nice so far!

Amazing. What sort of propulsion will be employed?

Eric

Thanks guys, always nice to know what people think :)

Eric, I have 2 servo motors so far, almost the same as yours. All I know about them is they are 48v, but are similar in size to the ones you used so hopefully they will be ok. The thrid motor is proving difficult to find, we just don't have the suppliers over here unless you want to pay top dollar. There is one on ebay I am watching at the moment - http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&category=92083&item=7523322804&rd=1&ssPageName=WDVW which looks like it should be suitable. Otherwise I am constantly watching ebay, and ebay.de too. The geckos are on order and should be here shortly.
I am gonna go to the metal shop tomorrow and pick up a steel plate to connect the z ballscrew to the spindle. I am thinking somewhere around 3/4" thick should be acceptable, but there will be around 4-6" between the spindle and screw, so I must be certain it won't flex under a heavy cut.

There is one on ebay I am watching at the moment - http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&category=92083&item=7523322804&rd=1&ssPageName=WDVW

Are you are aware that motor has a wound field? and as such will require a Field supply and open-circuit field monitoring.
Al.

Nope, it didn't even click! Not to worry, I haven't bid on it so nothing is lost. Just gotta kep searching. Thanks Al.

What about this one then - http://www.distel.co.uk/asps/details1.asp?ID=TE18
Althiugh I only have a 48v power supply, so I guess I will lose some speed, the spec states 1485 rpm at 48v. How will this effect the torque of the motor? I guess I really should take some time to learn this stuff eh?!

I am not sure how that armature is connected with three wires for fwd/rev, unless they have some odd armature configuration? I would think that would limit it somewhat compared to a DC servo amp that will do the reversing automatically. I would get alot more information before picking that up.
Al.

Thanks Al, I phoned the guy today, and he assures me it will work with Gecko drives, as long as I use diodes on the lines. Bottom line is, I have little choice at present, so I will go with it. As soon as the geckos turn up, I will give it a go. If it doesn't work, he will be getting it back.....watch this space!

On with the z-axis. I managed to get a flat milled on the cylinder, unfortunately it was too big to turn on the lathe, but luckily my father has just taken delivery of a Sieg X3 mill, so I shot over there and used his mill. Thanks dad ;)
The steel plate was a bigger problem, since it was also too big for the lathe, and I needed to cut a 4" diameter hole. I ended up drilling a series of holes around the circumference which let the centre slug drop out (well, with a couple of blows from the persuader of course).
The other problem was mounting onto the spindle - If I used a clamping method, I would have lost 20mm of travel, and since I only have 4" anyways, I had to drill/tap holes in the underside of the quill and bolt it on that way.
All mocked up for now, I will take it apart again tomorrow now I know it all works, and tidy up the plate a bit on the bandsaw. Here what I got for now...

Well sorry guys, I have been working so hard on this thing, I simply ran out of energy for photos! Anyhow here we go.....got the motors mounted, check out the size of the z-axis servo! I still reckon it may cause some problems, but I will try it anyway. Just started work on the wiring box today, shouldn't be too long before it is up and running.

I think you definitely get the award for OLDEST retrofit to date.

Faster, faster!

Looks like you are progressing quite nicely!

I am just kicked back, watching the speedy progress so far, but since I first saw this thread a few weeks ago, I couldn't help but notice that it looks like you are using white lithium for the ways (post #8, left photo)...please tell me this isn't true.

I know this machine was likely one of the first machines built after the wheel was discovered, but I would steer away from the grease for the ways.

Other than that - as you were....carry on.

Scott

Lol, it is just some cleaning cream I used whilst cleaning up the machine. The ways are actaully dry at present. Everything needs tightening, adjusting and oiling before I fire up the machine. Thanks for the insults though guys ;)

Lol, it is just some cleaning cream I used whilst cleaning up the machine.
Oil of Olay? Does that stuff work on machines, too?

Thanks for the insults though guys ;)
No insults - just having fun! :stickpoke

Keep up the progress reports, huh? Seriously - I love seeing retro-fits like this.

Scott

Erm, slight technical hitch guys, I crashed the y-axis at full speed :(

I got the thing fired up today, and noticed a bit of binding in the y-axis at one extent of its's travel. So I spent a couple of hours taking it apart and tweaking the nut-holder, got it all back together, but didn't notice the encoder cable become detatched from the encoder. So as soon as I engaged the drive, the y-axis flew at full speed around 6" and crashed straight into the main column. Needles to say there is some damage, but it is late now over here so I will leave it until tomorrow to investigate.
At least I know the motors can run the machine fast! I never managed to hit the e-stop until it was too late.

Sorry to hear about that unfortunate 'crash'. Can you fix the damage without too much hassle?

I'm just busy busy with a Sieg X1 retrofit and a bigger machine would always be nice. Maybe when I'm finished, I'll also start looking around for an old machine to do my own 'antique' retrofit. It seems like an excellent idea. Why cut up a new machine when you cut up an old one??? :)

Regards
Warren

Ohhh no!
I've been quiet here...watching, as I too love seeing retros with lots of updates. I would have lost a lot of sleep, if not all of it.
I too hope the damage is minor compared to what could 've happened.

SOOOooo sorry :(

Let us know when you're back at it!

Bloy

Hey, all back together again, with a new set of angular contact bearings. I guess when the table hit, the full force of the thing fired straight into the bearings :( At least it all works again, and I can jog the x and y axis at over 100 IPM.
Not so good on the Z though, I can only hit 50 IPM before it faults the drive. Acceleration is high though, which is a real bonus on that heavy axis. Perhaps a set of springs to aid the upwards travel would be a good idea eh? I will have a go at tuning up the drivers tomorrow, then I guess I will have to try and cut something!

Just noticed another problem now!
If I have the z and x axis on together, when I jog the z, the x-axis will stutter. Only a fraction, but it does jump. Doesn't with the y axis, only with the z and x. Any ideas?

noise. Make sure encoder cables are shielded.

Eric

Encoder cables are shielded, and grounded at the gecko end only. I recall you had a similar problem on your router, I better go find that thread!
edit - nope, that was your limit switches :(

Problem solved (well, fingers crossed anyhow!)
There seemed to be some noise due to the use of the err/res detection circuit. So unplugging the wires from the gecko's to this circuit cured the problem. I just hope thee are no more issues when I start the motor!

There may be some that still remember this thread, so I thought I'd give an update:

I'm the new owner of this project.

Since getting the machine, I have:

Gutted and rewired the control box.
Modified the Z-axis ball nut housing with more heavy duty grub screws.
Found the source of the 'noise'

The 'Noise'

The noise was nothing to do with the control box as I initially suspected. I had rewired it, paying attention to good practices to reduce crosstalk and capacitive coupling. The 'noise' was still present.

It turns out it was a far more simple problem. The Z-axis motor employs some sort of diode configuration to ensure its correct operation. There was a ground lead to this, crucial to its correct operation and this ground lead was connected to the chassis of the Mill.

HMM! I thought. The chassis of the Mill was actually floating with respect to earth. So... to my eternal relief, I simply reattached the wire to Mains Earth... and the machine works perfectly.

Let this be a lesson to you all to ground properly :)

Comments appreciated.

Macaba

I need some help.

I am thinking of counter-balancing the weight of the quill with a cable and pulley system (simplicity wanted!), and I would like some good suggestions as to what the likely weight of the quill of this zenith knee mill is. All I can guess is HEAVY!
Once I have an idea of the weight, I can then look at cable guage, pulley sizes and what it is going to be supported by.

Thanks for any help you can give