I'll try to explain this and maybe there is a simple solution....
As you know the 3 in 1 machines like the Shoptask have 3 Axes. The X being left to right along the longest bed. The Y being the table that slides along the X axis and the Z being the overhead R8 spindle that moves up and down.

These are the conventional axes for milling operation and Mach3 works great.

Now to my delima:
If I want to lay out a simple lathe job, I have been using a cad program to draw my object. This is done in the X and Y plane and translates well to the 3 in 1 machine setup and Mach3.
However, conventional CNC (and manual) lathes use Z and X axes. Z being the long, right to left movement and X being toward or away from the center of the object being turned.

What I am trying to do now is to use the CNC lathe of the 3 in 1 machine to cut a radius or ball on the end of a a piece of round stock in the lathe chuck.

I can lay this out in the CAD program with no problem.
and the Gcode is generated via Sheetcam with no problem.

Now, you and I both know that I cannot just plunge my lathe tool in and cut the entire radius in one pass. So now I need to use the multipass function of Mach3, but alas, it only supports multipasses if a Z depth needed.
If I then convert the Gcode for X and Z codes, then the I and J gcode commands are wrong and all is screwed up.

How are you guys using a 3 in 1 machine for CNC lathe operations that involve radius cuts?

I hope that was clearer than mud....

KaptainKarst,

I have a shopmaster, and being used to using the milling machine conventions I also would generate code and treat the latheing activites like I was milling. Until I converted an harbor freight 9 X 20 to full cnc including automated threading. At that point, I discovered the Mach3Turn Wizards which I think will do what you are wanting to do. They were very handing for threading operations and I think will support your efforts.

I hope it works for you,

Ron :banana:

I too have found the turn wizards.
But are you physically switching the leads of your stepper motors to reflect the axis naming convention of lathe operations (ex. switch the x mill axis to the Z lathe axis and the Y mill axis to the X lathe axis).

Thanks,
Jim

Jim,

No, I not changing cables and would not recommend doing it. But after a little thought, One way to do this, you could reassign an axis in the config settings of mach 3. There you could redirect your step and direction pins (each motor is controlled by step and dir pulses ). Mach3, the controller, assigns which of the pins of the parellel port, has the step and direction for each of the X, Y & Z axis. Then you could save it to alternate configuration file that you would load when started mach3 when you wanted to use this altered configuration.

Talk it over with Dan Mauch at camtronics and make sure you have it straight in your head and on paper. I know that you can do it this way. But you don't to mess up your original configurtion settings, so save a copy of it.

Ron

Ron

Ron,
Hey, thats a great idea to try.
I have created seperate profiles already (I have a cnc wood router as well as the cnc 3 in 1 machine). So I will create an alternate profile and will just have to remember what is what.....

thanks, I'll let you know how it works out after the weekend.
Jim

Jim,
I gave it some more thought, you may also have to adjust your motor tuning in your config file (your back lash and the steps per unit) Let me ask you, was your machine cnc straight from shopmaster? What values are you using for backlash for x, y, & z?

I was monitoring a thread on the conversion of a X3 mill using nook ball screws and he had .011 backlash (and on my x axis I have about .017, which I have isolated to the ball nut, so I courous as to this issue as my shopmaster has nook ballnuts)

Thanks,

Ron

I did the CNC conversion myself on the shopmaster.
I am using the normal factory installed acme screws.
I will have to check on the backlash values next time I fire up the shop computer.

I suspect that I will have to do a complete motor tuning process with the new profile for the lathe operation.

Jim,

If I may ask, what size stepper motors did you use and what drivers? And what kind of rapids can you do. The rapids on my machine or set around 30ipm, which I need to use a tapping head.

To be honest I haven't been too happy with the cnc job because of the fairly large backlash and to correct it would take replacing the screws because they welded the ends of the acme screws to them, so you really can't just replace the ball nuts or add a second one to preload the first.

I pocket out a circle (clean out a 1.20 inch circle on a product that I build and I have say a .018 out of roundness issue) . This is one area that the backlash compensation doesn't quite do it.

Thanks,

Ron

I've got .005" on my x and y axis, and .004" in my Z axis. Using double nut ball screws. Since this is my first time with ball screws I didn't know if this was good or not?

Borrisl,
Good hearing from you, were those double nuts capable of preloading. With preloading that backlash should get even closer to zero, if not zero. You showed your machine eariler in a previous post, it's really something. I wish my backlash were as low as yours. My screws had the ends of the original acme screws welded on, and I'm wondering if I could take the balls out of a new ballnut and slip it over the weld and load the balls in it and then preload it.

Let's see what the shopmaster guys think,

Thanks,

Ron

They do have pre-loading capability, however I've been unsuccessful in getting them to zero. Probably just my lack of knowlege in the matter. I did have the welded ones that came with the Shoptask on at first. I didn't have any problems getting the ballnut off. The welded section was smaller in diameter than the opening.

Borrisl,

Do you think that it is possible to add a second ballnut to the welded ball screw(on my shopmaster). The only way that I see to do it is to dump all the bearing and place the 2nd ballnut on the screw (past the weld) and try to load the bearings. How difficult would that be. Or I guess the question is can it be done.

Thanks,

Ron

Borrisl,
I forgot to ask, what kind of backlash did you have before you added the new ballscrew and ball nuts?

Ron

Before I had about .0012-.0015 backlash with the single ballnuts. .050" on the Z axis.

I think the problem would be having to replace the bearing block on the table with something that was threaded for the second ball nut. I'm sure it probably could be done though. I certainly am not the expert in this matter. I'm frankly having difficulty getting all my backlash out. I really don't like the idea of backlash just because it's a limiting factor in my learning experiance in getting a precision product.

The limit of backlash, precision bearings and upgrading the motors has greatly improved my rate of material removal rate. I can use a 1" end mill in 6061 T6 aluminum taking .125" at 12 ipm. That's about the machines extents. Any more than that it started having a seizure. Lot's of rigidity issues.

About axis orientation on a 3 in 1 machine. I've considered swapping the pin configuration in Mach3 to orient the axis in more traditional arrangments. Then in lathe functions it would be as it is now, mill mode would have the x axis along the table and the y traveling the bed.

Ive pretty much given up using the mach3 turn. Im programming everything on the mill to do my turning. Its working out a lot better now.

Just seems like my back lash changes day to day, or sometimes even by the part. Using lead screws now but will be going to ball screw I think...

I've upgraded my motor to 2HP 3450 rpm and with a fresh (4 flute) (about 1800 rpm )cobalt .500 I can take .070 to .080 at 12ipm and that's about all.

Back to Jim's original concern, I thinking pin reassignment in a Mach3turn config file may do it.

Borris,

I do have to ask, how did you get the .050 backlash out of the Z. without limiting the z axis travel even more? (I know I getting off the subject of the thread.)

Ron

.050" is about standard on the Z axis stock. The worm spline drive on the spindle allows for lots of backlash.

Thanks for all of the replies!

I was able to change the Step/Direction pin assignments in Mach3 turn and produce the desired results.

The old X (right to left) direction of travel in Mill Mode is now the "Z" axis in Lathe mode. The old Y (in and out) direction of travel in Mill Mode is now the "X" axis. I dissabled the old "Z" (up and down) in Mill Mode settings so I only have to deal with the two axes (interesting thing about the English language: axes like in multiple things chopping wood is spelled exactly like axes as in more than one axis but yet pronounced different).

I then calibrated the motor tuning section and set the backlash.
By the way, someone ask about backlash settings. I'm using the factory ACME screws and the backlash for the X (or Z in lathe mode) is .012". The backlash on the Y (or X axis in lathe mode) is .015". Now what I have not done yet is to possition the carrige on opposite ends and the middle of the long axis and measure the backlash to see if it is constant along the entire length of the axis (just happy to be making stuff at this point).

I was however able to make an outside "dome" on the end of a piece of 1" 6061 using the O.D. Wizard in Mach3. It turned out nice (except that I need to center my cutting tool better because I had a very small nipple in the center of the dome).

My next quest will be to learn how to use CAD and SheetCam to design an entire job using arcs and radiuses (not just one operation as the wizards do) and get it posted to G-code that is correct for the axis layout in Mach3 turn.

This is step #413 in my quest for world domination..... :-)

Ron111.
Sorry for forgetting about answering a question you posted earlier.
I am using 640 in/oz NEMA34 steppers. However, at this point I went with a constant current (not chopper like Gecko) type of controller using 3 12 volt power supplies. It works, but my top end rapids are only about 6ipm. which for my small projects has been fine thus far (I'm not using flood coolant either, just a can of SprayOn brand cutting fluid).

The wood CNC router that I built from scratch is using the Gecko drivers, 60 volt power supply and 240 oz. NEMA 23 motors and I get 30ipm rapids. I should be able to do even better than that if I change out my .75" dia. X 10 tpi ACME screw to something smaller in dia. with less pitch......

thanks for your help.
Jim

Kaptain,
Excellent debreifing, glad you have the situation under control. I do like the Mach3 Widzards. They work good for me.

Ron