CNC'ing a mini-lathe

Why re-invent the wheel? The motion control software is the hard part. Have you seen Mach-3 or LinuxCNC? They do the hard part, getting G-code into smooth motion. LinuxCNC even does rigid tapping, although you need the spindle controlled in both directions by the control program for that. I do a lot of tapping on the mill, so this was a big development for me.

There's no need to control the compound rest, in fact most CNC lathes take that off, it is not needed when the control can do all the non-orthogonal motions you need.

Jon

I agree programming is the hard part. I'm re-learning C after about 15 years... I'll look the suggestions up and see what's practical. Total cost so far is

LinuxCNC is free, Mach3 isn't free, but it's cheap (free if you can use the code size limited demo version). Neither require any programming, just configuration of appropriate I/O, limits, scaling, accel/decel rates, etc. You need to look at G code since essentially all CNC controls work from G code.

CNCing my 7x10-14 is on my todo list. I do not see any good reason to CNC the compound or even keep it. I can cut any angles I need just by programming them.

Mach 3 does have a basic lathe setup, and there are definitely lathe setups for LinuxCNC.

After getting some feedback here, and watching some videos on YouTube I think I can setup gang tooling to do 90% of any work I want to do on it without ever changing anything but inserts.

I recently found that one can get almost any component for CNC at very reasonable prices. And decided that I ought to get up to speed on CNC and build a couple of little projects. So far about all I have done is buy a break out board for the printer port of a PC and some PIC module boards. The PIC boards are shown at ebay item 320917531143 You can also get the bare boards on ebay . In fact at this time the only boards listed on ebay are the bare board. But looking at this item number you can get a better idea of what the board is .

Anyway I am at the point of getting either LinuxCNC or Mach3. In your opinion is it worth the money for Mach3. I am already using Ubuntu so Linux or Windows no big deal.

Dan

Leaving the compound in place is only going to make the machine less = rigid.

--suggest pull it off and mount a sturdy tool post or a slot type gang = slide directly to the cross slide.

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If you're already familiar with linux, go for LinuxCNC for sure. If you want to do some things not provided for by the planners (Say a

16-axis machine or something of the sort)j, LinuxCNC is easy to modify -- with the full source code supplied with it, and a variety of languages to write special features in. Mach3 I believe to be proprietary code, so getting the source to modify things.

Also -- if you opt to use servo motors instead of steppers. Servos give smoother operation and potentially much faster "rapid" moves (non cutting positioning moves). There are lots of places where you want the rapid moves -- things like positioning the cutter for the next pass on threading -- where you never even explicitly ask for the rapid move -- it is simply a part of the "canned cycle" which does the threading. But those positioning moves can eat up a lot of time on a slower machine. My stepper based Emco-Maier Compact-5/CNC certainly suffers from the limited stepper speed during the rapid moves. Some of these days, I'll replace the steppers with servos, and make a linux based controller for it.

Enjoy, DoN.

Mach3 is proprietary though based on the original EMC. It does have a substantial amount of customizability and background scripting capabilities if you need them. It is also free for the demo version which is complete with only a 2000 line g-code limitation, and Art is on record saying if you can live with that limitation enjoy at no charge. Mach3 will be easier to configure and maintain than LinuxCNC if you are not already familiar with Linux.

Mach3 can run servos using one of the step/dir servo drives. They give you most of the benefits of servos at a lower cost than a closed-to-the-control-loop servo setup.

Gretings Bob, Gang tooling is a great way to get the most productivity from a lathe. Many CNC machinists I know get locked into using only the turret positions for tools. The time it takes for the turret to move away from the work, index, and return to the work, can be huge compared to the time it takes to actually cut the part. If standard insert tools are used and the tool positions fixed then changing one tool for another is fast and programming is easy because you know where the tool tips are. Eric

Gang tools are nice but oftentimes (especially with swiss type machines ) you can also use holders in the turret that hold several tools at each position (depending on chuck diameter, distance between tools and so forth )...

If you already know your way around Linux, then go with LinuxCNC. It is more flexible and configurable that Mach. The only thing that Mach has is their "screensets" which allow you to configure your screen so it looks like a pinball machine. I have never understood the point of this. Totally baffled. The Axis screen does all I need, makes perfect sense, and all I have added is a spindle RPM display to the side.

Mach has a slight advantage to higher step pulse rates with software step generation, which I don't really like, anyway, it is putting a horrible burden on the CPU when there are much better ways to make step pulses. LinuxCNC has the ability to use servos in a number of ways, rigid tapping and non-cartesian machines.

Jon

Mach3 has plenty of flexibility and scripting capability to handle such custom things as ATCs and most anything else you can think of. Mach3 is also free to try out and free to use if you can live with the 2,000 lines of G code at a time which is the only limitation in the demo version.

With today's multi-core CPUs and microwave level clock rates, the burden is pretty negligible.

Yep. Rigid tapping is nice, and I believe people have successfully used it in Mach3 (I've not tried) as well since the key requirement for rigid tapping is a spindle encoder, not servos. Non-cartesian machines are neat to read about, but few people actually build or use them.

Amen!

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Assuming that you really must use stepper motors. My preference is for servo motors and servo amps.

Non-Cartesian? -- You mean like the hexapod? I believe that was one of the early experiments built around EMC (what LinuxCNC used to be called.)

Enjoy, DoN.

There's hexapods (Stewart platforms) and hexaglides, and 4- and 5-axis machines, as well as robots and SCARA arms. There are also other schemes that can be assembled from a combination of rotary and linear axes.

LinuxCNC can control all of these, although the more unusual ones require writing some code. Also, this flexibility allows you to correct for inaccuracies in the machine construction, as Stuart Stevenson at MPM demonstrated with a 5-axis Cincinnatti mill in his shop.

The big difference between Mach and LinuxCNC in this are is LinuxCNC can control all of these machines in Cartesian space, with standard XYZ G-code, and let the kinematics routines figure out what crazy angles the joints need to be in to reach each position. So, you can even JOG a robot in Cartesian coords. Mach just treats all axes as numbers, so you'd have to program all axes of a robot numerically.

Jon

Mach3 supports traditional 4th-6th axes just fine. No hexapods though.

Yes. I'll worry about that when I try to run a hexapod. Not holding my breath on that one though, I expect I'll remain in the traditional cartesian space for the foreseeable future.

That's correct. In fact, I'm going to be making soon some gang toolholders for drills and boring bars because the stock toolholders only hold two tools. Eric

Axes 4,5,6 are typically rotary axes. I've only used a 4th axis a few times and when I did I cheated and configured it as a linear axis based on the circumference of what I was machining to simplify the CAD/CAM work.

I was thinking of milling a keying slot directly into the cross slide, and then making all other components to drop into it and bolt solidly to the slide.