[ZeroBacklash]

I recently bought a used lathe, and am planning to retrofit it to CNC, this would be by first time, I owned a Emco Unimat benchtop lathe prior to this but I didn't end up converting that to CNC, I think the bigger lathe would be a good place to start.
So What I am planning to do
1. Add a geared stepper for spindle (70kg-cm) for threading and other tasks, Also add a encoder 12bit on the spindle for indexing, threading etc.
2. Add geared steppers (20kg-cm) to Z, and X axis.
3. Add a dremel to the cross slide to I can do some kind of live tooling.

The general idea being to make it a cnc lathe, plus some kind of horizontal mill (will that dremel on the cross slide)

THe lathe already looks rigid enought and I intend to keep the lead screews as is and not change to ball screws.

What I know from reading these forums is I need
1. Some kind of CAD to make the models.
2. CAM to get some kind of machine / gcode from the CAD model.
3. A gcode sender similar to Mach3 for sending gcode to the controller, currently I have a old PC with a parallel port so I will use paralllel instead of USB.
4. A controller like GRBL to controller the stepper motors.
5. And finally stepper drivers and power supply.

What I don't know yet is.

1. In addition to the above what else do I need to mount on the lathe machine. I heard elsewhere that limit switches needed for home position and end stops. ALthough I don't have any clue what these limit switches would do?

2.If I use parallel port from Mach3 how do I connect the GRBL controller, GRBL i guess is USB right?
I already have a UC400ETH motion controller board from CNC drive, is it a good idea to use it or dircetly drive the steppers from the parallel port. I mean If I use the parallel port directly then I wouldn't even need GRBL right?

3. Is Mach3 good to start with for a newbie or LinuxCNC?

4. What CAM software would I need for the machine above with Caxis, X and Z axis. I mostly intend to use it like a mill with a rotating axis. I mean the dremel would be mounted on the cross slide. Fusion 360 would be ok for this?

Many thanks in advance.
Your replies would be highly appreciated.

[skrubol]

What size is the lathe?

1. Limit switches would be for homing and keeping the machine from hard crashing at the ends of travel. They won't stop the machine from crashing the tool into the chuck, but the home switches keep the machine referenced (so it at least knows where the carriage and crosslide are.) At least 1 home/limit switch are necessary per axis.

2. Mach and GRBL aren't used together. They both serve basically the same function, but Mach has a GUI and file functions as well (so doesn't need a G-code sender.) The UC400ETH is a pulse generator, not a full controller. It's instead of the parallel port with Mach, and it'll allow faster, more accurate and more stable pulses to the stepper driver. Smooth Stepper is another common one for Mach.

3. I think Mach 3 is easier, especially for someone who isn't familiar with Linux, but it's basically deprecated, and Mach 4 has a lot of open questions as to whether it's going to get 'there'. LinuxCNC can do anything, but it does take a bit more to get it going. I'm not an expert on either, I've barely touched LinuxCNC, but plan on building my next rig around it. LinuxCNC isn't compatible with the same pulse generator as Mach, so the UC400 wouldn't work with it. It can work with the parallel port though, and from what I've heard works much better with it than Mach can (good enough for most.) If you need more or faster I/O with LinuxCNC Mesa IO hardware is reasonably priced and can do damn near anything.

4. The Dremel will probably work, but not well. It's a hand tool, doesn't have the best accuracy. On a Dremel I tore apart the front spindle bearing was mounted in a rubber bushing. Not the stiffest.
Fusion 360 should work fine. You'd be using it for 'wrapped' 4th axis or turning.

[cyclestart]

So What I am planning to do
1. Add a geared stepper for spindle (70kg-cm) for threading and other tasks, Also add a encoder 12bit on the spindle for indexing, threading etc.
2. Add geared steppers (20kg-cm) to Z, and X axis.

Stepper on spindle is not needed for cutting thread but you will want the encoder or at minimum a spindle index pulse. To index with a stepper an encoder
is not necessary.
I'm not sure how you're defining "geared steppers". Try not to introduce additional backlash, the stock screws will likely have plenty to begin with.

What I know from reading these forums is I need
1. Some kind of CAD to make the models.
2. CAM to get some kind of machine / gcode from the CAD model.

Fusion360 is working fine for me

I heard elsewhere that limit switches needed for home position and end stops.

This can all be done in software without physical switches. Of course physical switches add convenience and some safety margin.

3. Is Mach3 good to start with for a newbie or LinuxCNC?

If you want to use the UC400ETH linuxcnc isn't an option. If you're open to other hardware give linuxcnc a good look, it's not Windows but it's not user unfriendly.

[ZeroBacklash]

What size is the lathe?

1. Limit switches would be for homing and keeping the machine from hard crashing at the ends of travel. They won't stop the machine from crashing the tool into the chuck, but the home switches keep the machine referenced (so it at least knows where the carriage and crosslide are.) At least 1 home/limit switch are necessary per axis.

2. Mach and GRBL aren't used together. They both serve basically the same function, but Mach has a GUI and file functions as well (so doesn't need a G-code sender.) The UC400ETH is a pulse generator, not a full controller. It's instead of the parallel port with Mach, and it'll allow faster, more accurate and more stable pulses to the stepper driver. Smooth Stepper is another common one for Mach.

3. I think Mach 3 is easier, especially for someone who isn't familiar with Linux, but it's basically deprecated, and Mach 4 has a lot of open questions as to whether it's going to get 'there'. LinuxCNC can do anything, but it does take a bit more to get it going. I'm not an expert on either, I've barely touched LinuxCNC, but plan on building my next rig around it. LinuxCNC isn't compatible with the same pulse generator as Mach, so the UC400 wouldn't work with it. It can work with the parallel port though, and from what I've heard works much better with it than Mach can (good enough for most.) If you need more or faster I/O with LinuxCNC Mesa IO hardware is reasonably priced and can do damn near anything.

4. The Dremel will probably work, but not well. It's a hand tool, doesn't have the best accuracy. On a Dremel I tore apart the front spindle bearing was mounted in a rubber bushing. Not the stiffest.
Fusion 360 should work fine. You'd be using it for 'wrapped' 4th axis or turning.

Sorry for the delay in replying, I generally don't login to my email frequently enought to see notifications that I had received for my post here. I just happend to open my email and saw a couple of answers to my post over here.
Apologies again!

Size of the lathe is around 4 feet long. Distance between centers maybe around 2.5 to 3 feet.
1. So you are saying that I need to connect one home limit switch per axis, this is where the cross slide will go and rest when idle? Is this correct?
2.Ok got that, currently I have wired the UC400ETH to a breakout board, I have not yet wired it to the machine. Just tested in on a table, things are looking good on the table at least. not yet wired any inputs or outputs just wired the steppers and kept them on the table and jogged them via the UC400ETH controlled by Mach3.
3.Currently I will check out Mach3, although I'm keeping my options open on LinuxCNC, thanks for the tip.
4. So what is this wrapped 4th axis? Any ideas of mouting a milling chuck attachment, a sort of DIY, or use a collet and a high speed BLDC motor. I saw a few posts where users had modified a bldc and mount a ER-?? collet on it.

Thanks for all your inputs and time. They are truly awesome! :violin:

[ZeroBacklash]

Stepper on spindle is not needed for cutting thread but you will want the encoder or at minimum a spindle index pulse. To index with a stepper an encoder
is not necessary.
I'm not sure how you're defining "geared steppers". Try not to introduce additional backlash, the stock screws will likely have plenty to begin with.

Fusion360 is working fine for me

This can all be done in software without physical switches. Of course physical switches add convenience and some safety margin.

If you want to use the UC400ETH linuxcnc isn't an option. If you're open to other hardware give linuxcnc a good look, it's not Windows but it's not user unfriendly.

Oh! Currently I already mounted the 3 motors on the lathe, I bought some overpowerd geared stepper motors.
1. Spindle - 30Nm 15:1 gear ratio
2, X axis (carriage) - 7Nm
3. Z axis (cross slide) - 2.2Nm
All the above motors are geared and they have play in them, its mentioned in the datasheet.
4. Yet to decide upon what cutting tool / collet to fix on the cross slide, whether to use a dremel or a BLDC motor?

Thanks for the info on Fusion 360 and the limit switches.

Again, thanks for all your valuable inputs, truly appreciated :cheers:

[skrubol]

If you're only going to have one switch per axis, It should be near the safe (away from the chuck) end of the travel. It would be the home switch and also the limit switch for that direction. The limit for the other direction would be a 'soft' limit, but on a lathe I don't know how much the limits toward the chuck matter, as it's still easy to crash the tool into the part or chuck.

Wrapped 4th axis is using the rotary axis in place of one of the linear axes (on a mill,) so if you were engraving, rather than engraving on a flat plate, you would be wrapping that around a cylinder. I guess on a lathe you might have the accessory spindle oriented on the same axis (the wrapped toolpath would need the accessory spindle mounted perpendicular to the main spindle, parallel to the cross slide axis.) as the main spindle, for things like drilling off-axis holes or cutting flats. I guess this setup would just be lathe with live tooling.

Another option would be a high speed spindle or maybe a good trim router if the budget was tight. You would need something small enough in diameter that you could mount it with its centerline at the same height as the main spindle centerline.
Normal motors are not suitable as spindles, spindles have special bearings (paired angular contact or tapered roller bearings.) The basic ball bearings in a motor can't handle much thrust and probably aren't preloaded much, so will have a lot of runout. Some cheap ebay spindles are just that. It's a giveaway of that if the shaft out of the 'spindle' body is narrow, then has a larger diameter ER chuck on it. A dremel would probably be better than one of those.

[islaww]

I know that you have purchased some of the components already, but you may want to look into Centroid Acorn Lathe version. Along with tooling approach and specific controls designed for lathes, Centroids control software includes "Intercon", which is a lathe specific conversational CAM product. Acorn is DIY priced and has a DIY support forum. If you compare them side by side, in either lathe or mill version, Acorn is light years ahead of Mach or UCCNC, which would be the options of your controller.

[ZeroBacklash]

I know that you have purchased some of the components already, but you may want to look into Centroid Acorn Lathe version. Along with tooling approach and specific controls designed for lathes, Centroids control software includes "Intercon", which is a lathe specific conversational CAM product. Acorn is DIY priced and has a DIY support forum. If you compare them side by side, in either lathe or mill version, Acorn is light years ahead of Mach or UCCNC, which would be the options of your controller.

Just saw a sneak preview of Acorn Intercon conversational programming on you tube and it seems pretty good.
I don't know how I missed this! How much would a whole Acorn system cont along with Intercon?
Can intercon be used standalone too along with other systems or is it tied to Acorns system only?

[asuratman]

If you use UC400ETH then you will use CNCDRIVE which afaik does not support lathe yet. Then it is much better to use acorn or maybe mach3 but without uc400eth/cncdrive.

[ZeroBacklash]

Yes, you are correct, the UC400ETH is somewhat redundant in this sytem, the system could have been run directly with something like Mach3, however currently I don't have a system that had a parallel port, probably I could have used a parallel port card.

[Stigoe]

Another option would be LinuxCNC, preferably with a Mesa-card instead of parallel port.

[skrubol]

If you use UC400ETH then you will use CNCDRIVE which afaik does not support lathe yet. Then it is much better to use acorn or maybe mach3 but without uc400eth/cncdrive.

UC400eth supports mach as well.
Not sure how the UC400eth is, but generally pulse generators are better than the parallel port with Mach, (but often have some caveat's depending on their drivers, etc.)

[kawazuki]

This can all be done in software without physical switches. Of course physical switches add convenience and some safety margin.

How? Without at least one physical switch per axis the controller will never know where the tool / carriage is at any one time. Switches for a home position are usual and then soft limits may be applied to hopefully prevent excessive movement crashes!

[skrubol]

How? Without at least one physical switch per axis the controller will never know where the tool / carriage is at any one time. Switches for a home position are usual and then soft limits may be applied to hopefully prevent excessive movement crashes!

You can manually home machines. A lathe generally needs to be touched off the end of the workpiece anyway (unless you're doing a batch of parts and have exact cut stock.) Any number of ways to find the center.

[cyclestart]

How? Without at least one physical switch per axis the controller will never know where the tool / carriage is at any one time. Switches for a home position are usual and then soft limits may be applied to hopefully prevent excessive movement crashes!

It was probably reckless to suggest that but it is possible. My 'lathe' is just a lathe headstock on a mill like a poor man's Tormach Duality.
The software doesn't know it's not a real lathe and it runs without switches. The mill also runs without switches.

[Jim Dawson]

How? Without at least one physical switch per axis the controller will never know where the tool / carriage is at any one time. Switches for a home position are usual and then soft limits may be applied to hopefully prevent excessive movement crashes!

I run my mill without home switches, it does have end of travel switches for safety, so a ''floating'' home position. I zero on the work, and have a settable ''parking'' position that is relative to the set zero position. My lathe does have home switches and final home position is set to the index pulses on the axis servos. The tool offsets are measured from that point.

[ZeroBacklash]

Many Thanks for all the inputs!
I'm back again, was busy in the motor assembly of the lathe. The motors are already geared and then I've coupled them to the final shaft with another set of gears.
So I guess there would be some significant backlash in there.
I did watch a few videos on you tube on how to measure backlash on the linear x / z axis with a dial guage.
However I'm still not clear on how to measure the backlash on my rotary spindle axis, do I need some special equipment here or a dial guage would suffice?
Secondly, after I do measure backlash, Would Mach be able to compesate these for all axis including the rotary axis.

Thanks in advance!

[ZeroBacklash]

However I'm still not clear on how to measure the backlash on my rotary spindle axis, do I need some special equipment here or a dial guage would suffice?

I just remembered, that backlash on the rotary axis may not be as import if that axis is just rotating in one direction. There may be a way to home the rotary axis in the same direction for subsequet operations.
Even so it would be interesting to know how to measure backlash on the rotary axis?

[hfjbuis]

I measure backlash the following way:
Use a soft aluminum bar and a sharp HSS turning tool.

Turn the bar 1 mm down over a lenght of 20 mm using a cutting depth of 0.01 mm for the last pass.
Zero the dial at the last pass.

• Turn the bar 0.01 mm down and note the total cutting depth (0.01 mm for the first pass)
• Stop the carriage at the end of the pass
• Reverse the dial back to the zero position
• Return the carriage to the start position. The tool should scratch the surface!
• Repeat the above steps until the tool doesn't scratch the surface any more.
• The backlash is equal to the total cutting depth.

You can use the same procedure for the X-axis. This also works for the C-Axis if you could do a broaching/shaping pass.

[ZeroBacklash]

I measure backlash the following way:
Use a soft aluminum bar and a sharp HSS turning tool.

Turn the bar 1 mm down over a lenght of 20 mm using a cutting depth of 0.01 mm for the last pass.
Zero the dial at the last pass.

• Turn the bar 0.01 mm down and note the total cutting depth (0.01 mm for the first pass)
• Stop the carriage at the end of the pass
• Reverse the dial back to the zero position
• Return the carriage to the start position. The tool should scratch the surface!
• Repeat the above steps until the tool doesn't scratch the surface any more.
• The backlash is equal to the total cutting depth.

You can use the same procedure for the X-axis. This also works for the C-Axis if you could do a broaching/shaping pass.

Thanks for the info, its highly appreciated, I will have to read what to said a few times over for that to sink in. :cheers: