CNC Lathe From Old Lathe Headstock

I'm not sure if this is the right forum section or not or if there's a way to cross-post in multiple sections as appropriate. If not the right section, please let me know and I'll move it (possible?) or repost elsewhere.

I am thinking about using a lathe headstock as the headstock for a CNC lathe project to work on with my kids.
I can get a Hardinge Super Precision headstock for a reasonable amount. I'd rather have a 2"+ spindle bore if I can swing it (no pun intended).
What I want to do:

-use a 3+ horsepower digital AC/brushless servo motor for the spindle motor to allow it to be a C axis
-linear ways, ground ballscrews with AC/brushless servo motors on X and Z
-tailstock on linear ways
-gang tooling unless I can find an affordable turret solution
-2+ live tooling spindles using something like ER16 or ER20 collets
-coolant
-[full?] chip enclosure?

My software options would be either LinuxCNC which I have never used (but I am very familiar with Linux itself) or Mach 3, which I have used.

I don't have any motion control controllers, but I do have a couple of Axxus DB1 parallel port breakout boards lying around and a couple of old computers with parallel ports.

Let's say I want to get 300+ IPM rapids



My questions:

Are parallel ports inadequate "nowadays" for what I want to do?
What is a decent, inexpensive motion controller that can handle 4+ axes, including a C axis?
I would love to [re]use an old computer with a parallel port if I could, rather than sending it to the scrap heap and not have to spend money on a new PC.

Any motion controllers that work with either LinuxCNC and Mach 3?
Suggestions on motion controllers, other hardware and all the ancillary things that would be needed?

Suggestions on chip enclosures?
Coolants? Sumps and pumps?
Chip augers?


Thanks in advance!

Sounds like a good project in my opinion so go for it.

Thanks. I forgot to ask for suggestions in my original post
And I forgot to mention in my that my software options would be either LinuxCNC which I have never used (but I am very familiar with Linux itself) or Mach 3, which I have used.

I don't have any motion control controllers, but I do have a couple of Axxus DB1 parallel port breakout boards lying around and a couple of old computers with parallel ports.

Let's say I want to get 300+ IPM rapids

Are parallel ports inadequate "nowadays" for what I want to do?
What is a decent, inexpensive motion controller that can handle 4+ axes, including a C axis?
I would love to [re]use an old computer with a parallel port if I could, rather than sending it to the scrap heap and not have to spend money on a new PC.

Any motion controllers that work with both LinuxCNC and Mach 3?
Suggestions on motion controllers, other hardware and all the ancillary things that would be needed?

Linuxcnc IS a motion controller, and doesn't play well with external motion controllers like are often used with Mach3. There are external hardware step-generators that work well with Linuxcnc (such as several cards from Mesa), but I don't know of any that work with both Linuxcnc and Mach.

Old computers, anything much older than a newer P4 with less than 1g of ram probably isn't worth messing with.

Parallel ports are perfectly acceptable ways of controlling simple stepper machines. I have 3 machines running off of them now, and I'm working on a 4th.

Todd wrote:

Linuxcnc IS a motion controller, and doesn't play well with external motion controllers like are often used with Mach3. There are external hardware step-generators that work well with Linuxcnc (such as several cards from Mesa), but I don't know of any that work with both Linuxcnc and Mach.

Old computers, anything much older than a newer P4 with less than 1g of ram probably isn't worth messing with.

Parallel ports are perfectly acceptable ways of controlling simple stepper machines. I have 3 machines running off of them now, and I'm working on a 4th.

What sort of pulse rate can LinuxCNC generate on a P4?
...
i3?
i5?
i7?

I use the mesa hardware and recommend it if you're going the linux route. Talk to PCW here when you know more about the motors and drives you plan on using. That will determine what boards to get from him.
I have Mach3 on a smaller mill that has worked well for me and was a good intro to retrofitting as it got me up and running rather quickly . However, I really like linuxcnc as its extremely user configurable and makes a robust control system coupled with the mesa components. Another key element is, when you hit pause the machine actually stops and continues when commanded. This saved a few parts and cutters so far. In mach I always had a delay in the pause and sometimes lost position when starting again. I'm not up to date on Mach4 so I don't know if that has been fixed and how good the lathe version is.
For me, the learning curve with linuxcnc was steep as I was not used to hal . I needed the forum here to get me started. The members here are great with help.

As far as building a lathe from scratch that is an ambitious project. I speak from experience here as my machine is a converted Hardinge hydraulic lathe that didn't have ball screws and was a major project. It took me several years to get it running. In fact I'm still adding things to it. Not trying to discourage anyone, just want to be realistic.

Not knowing your skill set or the precision you're after, a few things you will have to look into is making a rigid enough base to mount everything on, making the slide mounts accurate so they don't bind, adding the ball screw mounts so they align and don't bind, then mounting the spindle so everything aligns correctly.
In my case I already had a solid base , z axis and spindle to work off but needed to add ball screws and a totally custom x axis. I had a t-slot table that I modified and eventually got flat within .0002" by hand scraping for endless hours. Final alignment was a PITA.

If you're good at welding/fabricating that can go a long way. You can post machine a lot of your components if you have a mill and fine tune with a surface grinder and or hand scraping. You will need some reference masters for verifying flatness and help with alignment. Such as a surface plate, granite angle block and granite parallels. Also, a dial indicator that reads to .0001".
Those items alone can cost more than an old machine with a blown electronics.

To answer some of your other questions, I think 300 ipm is not a problem with the mesa hardware and the correct motors and screws.
For C axis you may need a brake. I need to add one. Spindle does not stay locked with my vfd.
You forgot to mention a way to actuate the spindle. 2", I assume 16c collets? Do you have a collet closer that comes with it? If it's the big round aluminum air cylinder vari-grip type, be aware that you probably will need to re-build it and they leak air by design and need an aux oiler.
I would spend a good amount of time thinking/designing out the screw covers (way covers) and a good enclosure. You will need coolant if you're cutting metal and that will go everywhere! Covers and enclosure is something I still need to add to my machine.
BTW, I don't think a tail stock will work on a gang setup unless you're only using one tool!

The Mesa boards (I use the 7i76e Ethernet board) generate their step pulses on the hardware. I am achieving about 825 in/min with 20x microsteps and a 5:1 belt reduction on a rack and pinion drive. The 7i76e can control up to 5 stepper motors.

So how it works, is Linuxcnc tells the mesa card to generate steps at a given frequency (up to 10 MHz) and every millisecond, LinuxCNC can vary the commanded Mesa stepgen frequency. This means there is much less requirement on the PC hardware. Personally, given your project, I would skip the parallel port and go with Mesa. Which one you use is up to you and the motors you choose.

I have gone with ethernet and a USFF PC attached to the back of a touch screen in a noisy plasma environment. The other way is to buy a small PC motherboard that runs on 12 volts and treat it as just another component to wire into your control box. Add a Mesa PCI/PCIe card and say the 7i76 and you will achieve an almost identical environment as I have.

OT-CNC wrote:

I use the mesa hardware and recommend it if you're going the linux route. Talk to PCW here when you know more about the motors and drives you plan on using. That will determine what boards to get from him.
...
For me, the learning curve with linuxcnc was steep as I was not used to hal . I needed the forum here to get me started. The members here are great with help.

I'm sure the learning curve will be steep for me. I'm assuming/guessing HAL means hardware abstraction layer.

OT-CNC wrote:

As far as building a lathe from scratch that is an ambitious project. I speak from experience here as my machine is a converted Hardinge hydraulic lathe that didn't have ball screws and was a major project. It took me several years to get it running. In fact I'm still adding things to it. Not trying to discourage anyone, just want to be realistic.

An AHC huh? Going from hydraulic seems like a lot of work.
I have an HC Super Precision, but I'm not going to convert it, as it is too nice of a manual lathe.

OT-CNC wrote:

In my case I already had a solid base , z axis and spindle to work off but needed to add ball screws and a totally custom x axis. I had a t-slot table that I modified and eventually got flat within .0002" by hand scraping for endless hours. Final alignment was a PITA.

I'm pretty sure there's a good reason why so many Hardinge chuckers/HC and other of their machines got retrofitted to be gang tool.

OT-CNC wrote:

If you're good at welding/fabricating that can go a long way. You can post machine a lot of your components if you have a mill and fine tune with a surface grinder and or hand scraping. You will need some reference masters for verifying flatness and help with alignment. Such as a surface plate, granite angle block and granite parallels. Also, a dial indicator that reads to .0001".
Those items alone can cost more than an old machine with a blown electronics.

I have all that. One thing that could be good to use as a base would actually be a heavy granite plate. I see them around, sometimes for free. Trouble is that they are so big and heavy and not easy to machine.
I really wish I were good at welding.

OT-CNC wrote:

To answer some of your other questions, I think 300 ipm is not a problem with the mesa hardware and the correct motors and screws.
For C axis you may need a brake. I need to add one. Spindle does not stay locked with my vfd.

I'm thinking of continuous contouring/milling with live tooling, not just indexing.

OT-CNC wrote:

You forgot to mention a way to actuate the spindle. 2", I assume 16c collets? Do you have a collet closer that comes with it? If it's the big round aluminum air cylinder vari-grip type, be aware that you probably will need to re-build it and they leak air by design and need an aux oiler.

Well, if I go with an existing headstock, it'll probably be 5C and I would use the existing lever action collet closer.
Many of the CHNCs are 16C, but then I would just retrofit the whole machine
I used to have a CHNC. I actually prefer lever collet closers over air.
If I had money, I'd buy a full on CNC lathe with a bar feeder.
I am eyeing a small footprint Nakamura Tome and a small footprint VMC.

OT-CNC wrote:

I would spend a good amount of time thinking/designing out the screw covers (way covers) and a good enclosure. You will need coolant if you're cutting metal and that will go everywhere! Covers and enclosure is something I still need to add to my machine.
BTW, I don't think a tail stock will work on a gang setup unless you're only using one tool!

Yep.

My intention is to use brushless/AC servo motors and drives for all the axes and to have the spindle be a step/direction C axis as well, with a 3+ horsepower AC servo.
I know that I will probably use some accuracy that way.

Anybody have recommendations for reliable AC servo motors + drives?
Discounts for kits?

I'm using the 750w DMM servos and drives on my lathe. So far they work well for the price. I did have some config issues trying them as steppers with encoder feedback. You can use them as steppers or with +-10v input.
Tecos look similar and there's Yaskawas etc...
You can do C axis with VFD and encoder using a closed loop vector drive. I'm lacking a brake at the moment to get that to work beyond temporary positioning. I did tinker with a special config but I'm not up to date with what the current C axis control methods are. In normal lathe mode you can read in the spindle encoder to linuxcnc for rpm and direction control. This allows threading and rigid tapping. Beyond that you are looking at a custom /advanced config.