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Converting A 13x40 Manual Lathe To Cnc With Servos And Mach3

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gt40

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I wanted to start a new thread to document conversion of my Jet 13x40 lathe. Most of this should translate to similar size lathes like the PM lathes etc. and I hope it will be of help to anyone considering it. I am basically building off of the lessons learned from successfully converting my PM45M mill to CNC.

I have gotten pretty good with Mach 3 software to control the mill and they have a suite of tools for the lathe that includes threading, drilling profiling and I am really looking forward to this even more than the mill.

My Jet mill suffered another crash last year and completely lost threading capabilities on what was a decent machine. Instead, I am converting it to a gang or turret style cnc lathe with vfd and controlled by Mach 3.

I started by taking off the lead screws, x axis compound etc off. All of this goes away with a cnc conversion and I will use a pendant to control it. There is no reason to have cranks and they just get in the way.
Initial mockup. Note the compound goes away:
mockup.jpg
The servo will go underneath with timing gears to run it.

I was able to pick up a 2.5"x 10" x 13" piece of 7075 tooling plate from the scrap pile at industrial metal supply. It will replace the compound and shelter the ballscrew from shards etc and be a rigid platform for a turret or gang setup.

Next I had to machine the saddle to make where I would mount the ballscrew perfectly parallel to the surface on the dovetail. This setup took several hours to get it aligned but I was able to use it to flatten the saddle and also drill the holes to mount the ballscrew:
ballscewdrillingsetup.jpg
I made ballnut mount via cnc on the mill:
ballnutmountcut.jpg

I was a little concerned whether having the ballscrew mounted offset would cause binding but after everything was mounted, a small cordless drill easily moves the x axis really well. I can't even begin to describe how much more rigid everything is with no compound and a giant piece of 7075 on the x axis.

Pic of the ballscrew mounted:
ballscrewmounted.jpg

BTW, I cut the 7075 aluminum 13" tall with my Agazzani vertical bandsaw. the new carbide blade didn't flinch cutting a 5" deep cut 13" tall. I just used beeswax based lube.


Next up, I have timing pulleys coming and a 3 hp extreme duty motor already to go:

motor-tag.jpg

I am putting together a comprehensive list but here is the broad strokes:

1. CNC axis motors- I am going with DMM-Tech 2 axis servo motor setup. They are quiet, extremely smooth and very strong. I have 3 on my PM45m and have run it for 8-10 hours continuously without issues cutting stuff. The .75kw servos are overkill and can snap a 1/2" carbide end mill or move my head on the mill(250+lbs) without issue.


They have 2 axis kits that have everything from the servos, cables, drives, emergency stop switch, limit switches(to stop the machine from crashing and set zero) etc. kit:

DMM TECH LINK: http://www.dmm-tech.com/Files/dmmmaxs14a_p.pdf

I am getting the 400watt 2 axis kit but not getting their power supply modules. For that, I am getting an antec power supply. It is more elegant to me having one high quality overbuilt power supply to run all the servos and drives and simplifies wiring.

http://http://www.antekinc.com/ps-10n56-1000w-56v-power-supply/

It really isn't bad to hook up and I found they had really outstanding techs over at dmm the helped me set up the antek ps and that spent the necessary time to walk me through things and answer my silly questions.

Here is a really good diagram that shows exactly what you have to hook up. Keep in mind for a lathe, you will only need to do 2 drives, servos etc and the "spindle" connection will just go to your vfd and 3 phase motor:

http://mccomsey.net/cnclathe/breakoutboard.pdf

For the ballscrews, you need 2, one for the x and one for the z axis. Ebay is your friend and ground ballscrews can sometimes be found for silly cheap.

Being patient on ebay, I spent $300 total for both axis and I got a THK and Hi-Win ground ballscrews. Ground ballscrews are definitely better but my mill used rolled ballscrews and it is accurate to 2 tenths over 16".

Keep in mind your lead tpi controls your resolution. For my purposes, I am going with 0.2" lead.

If you want to read about this stuff, here is a decent primer: http://blog.cnccookbook.com/2014/01/...nc-conversion/

When you convert the mill to cnc, you won't need cranks, and the whole lead screw and threading part of the lathe(the lower box assembly on most gear head lathes) is better removed.

My jet used to look pretty much the same as the PM lathes. Now it is definitely on a "diet":
stripped2.jpg

left overs:
stripped3.jpg

took some time to prep the lathe now that it is all stripped and gave it 2 coats of primer. The original finish was showing it's wear and I think the lathe was just a little jealous of darkzero's spotless finish on his machines. Seriously, I wonder how you keep a lathe that clean and use it :p Simply amazing...

primer.jpg

I ended up having some fun with the paint:
painted1.jpg
painted2.jpg

painted3.jpg
"gap"
gap.jpg

For reference, this is what the lathe looked like when I started with it:

lathe1.jpg

I have a set of THK SHS in the right size. I was going to just machine the whole top of the x axis flat and use them but the current arrangement is tracking tight and true. I am working on an epoxy granite slant bed design with all linear guides but needed to make the Jet work so I could make the spindle:

linearslides.jpg
Finally, I drilled and tapped the timing pulley and mounted it. The axis moves smoothly and without binding using the drill and by hand.

I am using a 15 and 25 tooth "L" timing gear setup. The belts are 3/4" wide and allow you to move without backlash or slippage when you change direction.

pulleys.jpg
FYI, here are the pulleys I actually ordered:

15L075 Aluminum Pulley 15 tooth MPB OD=1.760 inch

http://shop.polybelt.com/15L075-Alum...15L075-6FA.htm
25L075 Aluminum Pulley 25 Tooth, OD=2.954 inch

http://shop.polybelt.com/25L075-Alum...25L075-6FA.htm

With the .2" lead on the ball screw, and the lower gear ratio, this combo increases torque and resolution.

Here is the breakdown to convert the mill to cnc servos, drives, breakout board and cables. I have had awesome results with DMM tech + many hours of support from them schooling me on my builds:

Part Number Part Quantity Total Expense
DYN2-H DYN2-H AC Servo Drive 2 $250.00
60M-DHT-36 0.4kW AC servo motor 2 $394.00
DMB4250-8B Breakout Board 1 $115.00
CA-MO55-1H 1ft Molex 5/5pin Breakout Board to DYN2 ServoDrive 2 $16.00
HW-04-NPS Inductive Proximity Switch 4 $56.00
HE-04-RMS Emergency Stop Switch 1 $12.00
CA-MRS232-6 6ft RS232 to Molex 7 pin drive tuning cable 1 $15.00
Sub Total: $858.00
Shipping: $64.00
Total USD: $922.00

Looking at the rest, you will need to add a power supply for $150, a couple of ballscrews at $300 and some metal costs for mounts.

I expect total costs to convert the lathe to CNC to be less than $1500 dollars.

FYI, the DMM Tech folks are up in Canada and have been around for 20 years. No affiliation but they have tech you can actually talk to when configuring things.

Quick video making the z axis servo motor mount at 7000 rpm with my cnc converted Precision Mathews PM45m mill. I was paranoid and slowed it down to 30 ipm. The mill does fine at 70...


I made a monolithic ballnut block that is 1.8" thick and mounts to the saddle. I also made the two bearing blocks that support each end of the ballscrew. The trick was getting everything square and aligned. I was rewarded by a z axis that moves very smooth without any binding on the full range. The ballnut block has a "L" shaped cutout for my skarf guard I am making to protect the ballscrew. It is so stiff and solid compared with the way the lathe was stock and there is absolutely no perceptible backlash:zaxis1.jpg
zaxis3.jpg

zaxis4.jpg

I re-thought my x axis aluminum platform and converted to a massive 8"x 8" x1.5" steel block that sits on one side of where the aluminum block went. The steel is much heavier at 28 lbs but the main reason was to preserve the max stock capacity of the lathe.

The 13x40 lathe can handle stock 8" in diameter with the right chuck but with the aluminum going the whole width of the cast iron x axis base, I inadvertently cut that in half. I don't normally turn giant stock but definitely want to be able to in the future. Here is my 4" extension on the PM45m mill that is 8" diameter and brings my PM45M mill to 11.5" y travel:
head%20extension2.jpg

Here are the shots for the new steel x axis. There is a noticeable difference in the stiffness. I will add some bellows like these to cover the ballscrew:

http://www.arceurotrade.co.uk/Catalo...achine-Bellows

steel1.jpg


Re-doing the axis wasted a nice giant piece of mic6 but I regained my full stock capacity.

z servo mounting block
z-blocks.jpg

New "saddle". This holds the servo and ball nut in place and allows for a scarf guard:
new-saddle.jpg

saddle2.jpg

x axis servo plate with boss cut for the mount:

xservoplate.jpg

New DMM Tech servos:
dmmservos.jpg

drives:
dmmtechdrives.jpg

back-oofservoplate.jpg

saddle3.jpg

mountedxservo.jpg saddle4.jpg
zservomounted.jpg

An overall shot:
finished1.jpg

FYI, I wanted to take a moment to share the outstanding tech support I have been getting over with servo company I used to do the conversion, DMM Tech. I fried a breakout board by dumping high voltage into it(my fault) and they overnighted a replacement free of charge and free shipping from Canada. They also spent over an hour on the phone while we traced down a random interference issue. You want to keep the servo power cables away from the control ones. I had them touching and the current fields messed with the control. They just walked me through it while we tested some stuff over the phone and everything is just working.

They are also helping me set up a hall sensor to pick up the spindle rpm as I hope to be able to set up constant surface speed as well as for threading. There are boards for sale but the tech walked me through using a cheap hall sensor I had laying around to save money.


I ended up investing in Dolphin Turn for cam. I have been busy learning. I am starting to make sense of things and I was able to design a new 18650 powered xm-l light and... finally was able to thread with my lathe once more. The whole reason for me doing this conversion was I had a bad crash on the lathe a year ago and it was going to cost about the same to fix it as go cnc. I am pleased I can thread again and am starting to make some lights.

After learning how to thread on a manual lathe properly, my first experience threading via cnc was really humbling. less than 90 seconds to face, turn and thread a tube with perfect accuracy. I will post some stills of the threads but they came out beautiful. I also tested cutting various stock out in steel and aluminum and threading to fit nuts I had laying around and well, it just works:

Quick pic of part of a light I am designing. I made these bodies setting up the tool offsets in the mach 3 software that runs the lathe. FYI, the finish is right off the lathe without polishing and with mist coolant I borrowed from my mill. It is about 3 minutes to make a part including facing, profiling, threading both sides and parting off the finished part. I had to get a left and right side threading tools to do this but it works well:
ry%3D480

Thanks for looking...
 

darkzero

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Yup, nice job Mark! Can't wait to see it in action with my own eyes. Did you paint it with rattle cans or a spray gun? I want to repaint my mill someday but I don't want to move it out of the garage.
 

bpratl

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Nice design and machining, looks like a good choice in using servos.
 

gt40

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Yup, nice job Mark! Can't wait to see it in action with my own eyes. Did you paint it with rattle cans or a spray gun? I want to repaint my mill someday but I don't want to move it out of the garage.
I painted with industrial paint rattle cans- 2 coats primer and then 3 coats of the orange. Seems to be holding up at least as well as the stock Jet paint.
 

Uguessedit

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Wonderful Work I hope it has been holding up well for you. Did you ever get to work on your slant bed after this was completed? I like how you substituted a larger ball screw off to the side. I wish I had thought of that for the lathe project here. Maybe still follow suit. I have been thinking about a t slotted Cross table to change out to a grinder or turret easily. It would be nice to have quick swap features. I may have missed it however did you run a pulley off the spindle directly or did you retain all or a portion of the gear head? Again.., very nice build.
 
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