Problems with lathe

[terry1956]

Hi out there. I am hitting a few problems with a lathe I am trying to convert. It all started when I tried to calibrate the lathe in mach3 ( what a total pain that this). Anyway trying to make the stepper motors move .5mm lead to this problem. Ok they would move the distance maybe three times before cutting out and it took turning off the power to the break out board and drivers for a time before the motors would move again, then the same would happen. I am using one of the 100khz breakout boards from Amazon. One of the stepper motors is a 6amp closed loop system using a CL86T driver and a nema 34 motor. The other motor is the motor which came with the lathe which is nema motor but is 8 wires into 4 configuration. The power supply is a 24vdc. So any ideas on the cutting out.
I am also trying to get information on Linux, is this a better system for lathes, if so what board do I need, I am running usb windows 10 64bit. Is calibrating the lathe easier then the nonsense in mach3 turn. I am in the U.K. thanks

[Doddy]

Terry1956,

Background: I've converted a Myford ML7 to CNC. For better or worse.

You have 3 questions which need to be dealt with largely separately.

Your "cutting out". There's a lot of possibilities, and very little info. From the outset I'd look at your NEMA 34s and question the 24V supply voltage - you really should be up at 60 volts or higher. In fact the first hit I had with a CL86T indicates a 30V minimum supply rail. Conversely, I'd question a NEMA 34, but as you've not indicated what lathe you have.... Anyway - you'll need to fault-find a bit more for us. Are the stepper drivers getting hot?, what's the supply voltage doing when the system freezes?, are there any fault indications on the stepper driver? Does the same happen if the steppers are mechanically uncoupled from the axis-drives? Does this happen on one axis, or both? Also, for background - are you using the original trapezoidal screws or have you replaced these? Photos are always welcomed (though you may have a 10 post limit to hit before you can post those?) Please, help us to help you - provide some more detail.

The "100khz breakout boards" most certainly will tie you to Mach3. If you want to consider another motion controller (such as LinuxCNC) then you'll need something different. If you have a parallel port then this is one way forward; the LinuxCNC route also favors/supports the Mesa hardware - good kit, but expensive, and perhaps unobtainium with the current semiconductor crisis. Others will advise on more hardware/software combinations - I've only used LinuxCNC/Mesa.

Linux vs Mach3. By this I expect you mean LinuxCNC - which is what I use (and, I think what most people here use for turning). It's not that it's the best, more than it's the least worst. It's powerful, certainly, and supports the turning functions well. But if I was to assume that you've not used Linux before then my first bit of advice would be to understand that you have a vertical learning curve ahead of you. Others on this forum with far more experience of LinuxCNC would be able to advise further and more accurately. I'd simply say that it's not straightforward. "Calibration" is a funny old word - what are you trying to calibrate? the X/Z axis are much of a muchness regardless of Mach3 Turn or LinuxCNC - both require you to understand the basic mechanics of the CNC conversion (offset / turns, and steps/turn). What both Mach3 and LinuxCNC do require for any basic threading is a form of spindle-encoder - and for this to be calibrated. Have you had a thought for this?

[terry1956]

Thanks for your reply. I think that I am not using enough power for the stepper motors which in turn is leading to the lost of steps. I have ordered a new higher rated power supply. One one thing that puts me off Linuxcnc is going backwards with using a printer cable. I know that the 100khz is not the best breakout board however it’s one good point is it automatically sets the ports and pins. I remember years back pulling my hair out with ports and pins. As to what I am trying to calibrate, we’ll that would be the movement of the axis to match the distance given in mach3. So the motor moves the correct distance to what mach3 thinks it has moved. I will wait until the new power supply turns up and start playing again Thanks for your help.

[Muzzer]

The more recent Mesa boards connect using ethernet, so there's no need for parallel ports / printer cables as such. As for the "pins/ports" business, setting up all the HAL and INI file settings can be quite a challenge in LinuxCNC, even with the config wizards. The LinuxCNC support forum is well intentioned but you are still expected to go on a bit of an adventure with no certainty where it will end up and the software is constantly evolving. If you are wary of getting back into that, you may be better sticking with something else.

My Colchester Bantam runs LinuxCNC and the gmoccapy GUI which sort of works now (although some features don't) but I have to admit when I moved on to my Tree CNC lathe, I wimped out and went with Centroid Acorn which is much more of a known, stable quantity with good support. I know others have had good experiences with UCCNC, so there are other options out there.

[terry1956]

Hi, I looked at the centroid acorn but at nearly £400 it’s a shed load of money for a board. The lathe itself only cost £80.

[Muzzer]

No matter what you do, it'd going to cost you more than £80 - it's really a question of what you fancy. Perhaps a DDCS 3.1 would fit the bill?
https://www.aliexpress.com/item/1005004250543546.html?spm=a2g0o.store_pc_allProduc t.8148356.58.3c89312eco0cQi&pdp_npi=2%40dis%21GBP%21%EF%BF%A1164.69%21%EF%BF%A 1164.69%21%21%21%21%21%402100bdd716611770518524106 ed72d%2112000028540277150%21sh

[JohnHaine]

What lathe is it?

I can't understand the issue with "calibrating" the axes. It's just a matter of doing a straightforward calculation and typing the steps/unit into a Mach3 text box.

I'm not familiar with the "100 kHz breakout board" but I assume that it comes with a Mach3 plugin for the USB port? Do you have this? Many of the USB controller from the Far East have a poor reputation for the quality of the USB implementation. I use CNCDrive UC100s and they work perfectly for me. Does the one you have support threading and probing? These have to be done in the motion controller - threading is mandatory for a lathe to be much use and probing is useful for tool setting. Mach3 is fine for threading on a larger lathe with plenty of spindle power and inertia.

[terry1956]

Hi John, the problem is not the amount of movement in the axis, I have sorted that. The problem is the following. If I input by hand something like z+40, the motor moves 40mm all good. However it only moves at a very slow crawl. If I adjust the acceleration etc in motor tuning, safe etc. and input z+40 the speed is the same just a crawl. However if I jog the motor it moves at a good speed.
I am not interested in threading, as I find just using a die faster. I have the lathe just too make smaller parts for my O gauge locomotives. It maybe the breakout board, but I have used the same type for years on a mini mill.

[JohnHaine]

But do you also enter a feed rate?

[Doddy]

Terry - apologies if I'm asking the blinding obvious - but you are setting the feed-rate in the G-Code? And does a G0 Z40 also crawl? Have you tried a F200 or F20 before moving?

Sorry - it is going back to basics, but a MDI input should be able to match the jog speed.

[JohnHaine]

Right, I've just tried this. Look at the Feedrate DRO just above the MDI. If M3 has just been started it probably says 5 mm/min. So if you type in Z-5 it crawls along. To be frank I've never not typed in a G-code word into the DRO so never seen this behaviour, I would always specify a feedrate. If you type Z-5 F100 it moves MUCH quicker and the default feedrate is now set to 100mm/min until you use another F word to define a new one. Doddy is quite correct.

[terry1956]

Hi, all I was asking the stepper motor to do was move a set distance, so I could measure it and set the steps. Unlike mach3 mill, mach3 turn doesn’t have an automatic calibration system. The only way to set the steps is by asking the motor to move, measure and adjust until you get the right number of steps. I did not know that I had to also input a speed. I just had the idea that the motor would move at the same speed it did when jogging. Is this not correct? I am trying to follow a video on utube by a chap who went through this process. But like many things so much is left out. And the mach3 manual is very grey in this area.

[JohnHaine]

Look, it is quite unnecessary to "calibrate" an axis in the way you describe. All you need to know is the screw pitch, any gearing between the motor and the screw, the motor steps/rev, and any microstepping ratio set in the driver. Then there's a simple formula in the M3 manual for calculating the steps/unit that you type into the appropriate config box. Unless your leadscrew is basically inaccurate that will give you a number as accurate or more accurate than a calibration. If you give us these numbers for your machine we can show you how.

Many G codes are "modal", that is once you execute one the machine stays in that mode until switched out of it. G0 and G1 are such modes. This is useful as for example you can profile cut with a G1 X Y then carry on just by giving a string of Xs and Ys (on new lines) for the rest of the cut. It seems like on install the MDI is in G1 mode and set to a low feed rate - I think 6 mm/min. This makes sense as it means that random coordinates typed in aren't going to make the machine head for the hills. If you type in G0 though it will set the machine to rapid moves so then subsequent coordinates will cause moves at the rapid rate just like a G0 in a program. However using G1 mode is a bit more controlled, but to use it you just need to set a sensible feedrate, and as you've discovered 6mm/min isn't! To set a sensible feed rate just type in say F60 <return> and the feedrate box should show this number and now the axis will move 10x faster - but type in a G1 as well just to make sure it's in the right mode.

In general YouTube videos are no substitute for documentation. The M3 manual (you do have a copy?) is pretty good.