electronic lead screw

[weston1968]

If the system stopped shy of the target position that would generally indicate the available torque was insufficient. Leadscrews have a lot of stiction and friction and thus may require a lot of torque, hence CNC systems generally use ballscrews. Perhaps cleaning and lubrication might be sufficient, or moving to a higher torque stepper or changing belt or gearing ratios. Adjusting the half nuts could also help reduce friction. Converting the Lathe to ballscrews and adding a multidimensional control is more than an ELS, it is really a CNC that uses something other than gcode. Whatever works for the operator is good. Programming is programming, whether gcode or something else.

I'm planning to CNC the mill eventually, but just do an ELS on the lathe. However I find that it generally takes about 3 iterations to finalize a design so that I'm satisfied with it, and in a sense we are in a short production run. I really enjoy the 3d printer's ability to make another copy with changes. The design tools make the gcode so I rarely get into that level of detail. Not being able to easily make another part causes us to either mod the first one or just make do with a less than satisfying design.

I had to loosen the grip of the half nut. It originally was set too tight in order to reduce backlash. That tightness required more torque than my closed loop 3NM stepper could reliably give me. It is the backlash that is my problem. I can not put a larger stepper in because they are too slow and mechanically difficult for the WM210V that I have. I am using a controller similar to the Numobams. I just do not have the time/patience to generate my own controller. For most of what I machine the lathe holds 0.1 mm TIR so I am okay. I was not anticipating having to make my designs tolerate 0.5mm on the x axis but that is required with the current state of the lathe in auto mode. Manual mode with my DRO I get 0.1 mm.

 

[Oxidez]

I had to loosen the grip of the half nut. It originally was set too tight in order to reduce backlash. That tightness required more torque than my closed loop 3NM stepper could reliably give me. It is the backlash that is my problem. I can not put a larger stepper in because they are too slow and mechanically difficult for the WM210V that I have. I am using a controller similar to the Numobams. I just do not have the time/patience to generate my own controller. For most of what I machine the lathe holds 0.1 mm TIR so I am okay. I was not anticipating having to make my designs tolerate 0.5mm on the x axis but that is required with the current state of the lathe in auto mode. Manual mode with my DRO I get 0.1 mm.

0,1mm is a lot of backlash. But as i said, quality for the amount of money payed for that WM210V, is not possible. Higher precision cannot be achieved without some more investment. If i am not wrong, both Z and X axes ball screws, on a C7 grade would not cost so much but definitely will get you around 0,01 backlash, if needed.
As about the torque, 3NM closed loop should be more then enough , if done properly. The lead screw on Z should be 2mm pitch, so for a 1/100 precision and at same time keep a good torque, should go for a 1/2 or 1/4 reduction and modify the micro stepping accordingly.
By the way, when i say reduction, i am not talking about gears (more backlash) but pulleys and belts.

 

[TorontoBuilder]

Well, one of my lathes also had feed rod and leadscrew, but was an easy fix.
I took both out, put an C5 grade 2005 ballscrew with DFU2005 double nut. I took the gearbox out completely, put a NEMA34 8NM on the ballscrew and Z axis is now done. X axis is work in progress, but will be same process ... will take out completely the apron with the leadscrew and put a ballscrew with NEMA34 4NM.
By the way, this is on a Sieg X10, pretty much similar with a PM 1228VF lathe. Until i will finish with the X axis and also install telescopic covers for bed way, plus the DRO ... i have plenty times to decide for electronics. More or less i wanna put something with 2 manual MPG for X and Z, because the handweels will go out.
So if i wont find anything , will use the russian ELS as a base for software and modify it for an STM32F4 with a 5 inch touchscreen.
This sounds like your 1000 projects to do .... not counting the electronics for my mill, who also waits to be CNC-ed.
But hey, all this is fun, especially when you're retired and have not much else to do, right ?

PS: sorry for my poor gramma, english is'nt my native language, i've learn it back in the days when was programming for Z80 with assembler.
Best regards from France and good luck with your projects also.

Not going to happen on our colchester master lathe...

 

[RobZ_ZA]

I have no idea what ELS you using on your lathe, but 4 years ago, i started to look into ELS for lathe and back then the best i could find was the russian ELS based on MEGA 2560. After a short time, i have equipped one of my lathes, a chinese WM210 and started testing. Indeed precision was awful, was having around 0,2 to 0,4 backlash. Solution was simple .... ball screws on Z and on X axis, plus i have changed from open loop to close loop steppers. The result was very impressive ... 0,003 - 0,001 mm on repeatability and very good accuracy. In many cases, my 0,001mm Mitutoyo micrometer was spot on the dimensions i was turning from ELS.
After many tests i did with that ELS, i have observed that passing from 600ppr to 1800ppr on spindle encoder, got me a lot of precision in turning and also threading. Close loop steppers never failed me and no more loosing steps resulted in very nice surface finish and accuracy too.
The way i did all, was a 5mm pitch on ball screws (DFU1605) with 1/5 reduction stepper to ball screw and 1000 micro stepping.
This is how i got to 1 micron precision and was more then i needed as a hobby.

Hi, this sounds exactly what I an trying to do, what size Closed loop Steppers are you using? thanks

 

[Oxidez]

Hi, this sounds exactly what I an trying to do, what size Closed loop Steppers are you using? thanks

I have used Nema 24 close loop motor 3Nm and Nema 23 close loop motor 1,5Nm.

 

[Gouge61]

I have a PM1022 lathe 1 am using to add the clough42 ELS. Am having trouble downloading the code to the Launchpad. Any one else having similar problems?

 

[ttabbal]

I have a PM1022 lathe 1 am using to add the clough42 ELS. Am having trouble downloading the code to the Launchpad. Any one else having similar problems?

I didn't have any trouble. Is it just the flash step or does it have a problem compiling the code? Any red in device manager? Could just be a driver missing. At one point, TI updated the dev environment and I had some compile issues. I think I just found the old version and used that. But James might have fixed it by now, that was a bit ago.

 

[dabear3428]

I still have my manual lathe, I didn't sell it when I bought the CNC. I would really miss it if I didn't have it. They are really 2 completely different machines with different purposes. I have thought about adding CNC capability to the manual lathe, but keeping full manual operation with an instant change over. I have all of the parts on the shelf to do it, but really have not had a need to do it.

My knee mill is almost instantly convertible between full manual, 2, 3, or 4 axis CNC. Many times I use a combination of operating modes on a single job.

Jim, would you point me at any threads on your knee mill?

 

[JimDawson]

Jim, would you point me at any threads on your knee mill?

Here ya go, I think in chronological order

Build Thread Anilam M to DC_CNC Conversion

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Sorry for the off site reference, we lost the one posted here in the big crash a few years ago.

Z-axis Cnc Conversion

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4th Axis Build

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Mill Spindle Direct Drive Conversion

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www.hobby-machinist.com