SnailPowered
Posts: 1
Joined: Sun Oct 14, 2018 6:33 pm

1945 Craftsman lathe CNC Conversion

Sun Oct 14, 2018 7:24 pm

Hello all, this is my first post here so I hope that is ok. I figured I would start by introducing the project that has me interested in using a RPi to automate movement. I have a 1945 Craftsman 101.07403 lathe that is in excellent shape. I am a machinist and although I can use it as is, I believe that I can convert it to CNC without making any permanent modifications to the lathe. I have access to the necessary machines to manufacture the custom parts I want. My plan is to convert the lead screw and cross slide screws to ball screws. In order to not modify the lathe I plan to replace the apron with a new piece that will attach to the ball screw nut. To attach the ballscrew to the lathe I plan to make new bearing mounts, with the bearing mount on the headstock side including the mount for a NEMA 34. In order to automate the cross slide I plan to remove the stock bearing support/micrometer collar from the cross slide and making a bearing support for the ball screw. On the opposite side of the cross slide there are bolt holes for a taper attachment. I plan to use them as the bolt holes for the NEMA 23 and ball screw bearing supports.

I am a machinist now, for the six years before I became a machinist I was an Explosive Ordnance Disposal (EOD) technician. I have tinkered with electronics including soldering together electrical circuit board kits. I am definitely capable of putting the system together once I know what I actually need in order to make my dream come true. Here is a list of some of the items I have in mind for designing my system.

NEMA 34 - https://smile.amazon.com/stepper-Contro ... op+stepper

NEMA 23 - https://smile.amazon.com/Nema24-Stepper ... op+stepper

Power Supply - https://www.amazon.com/Switching-Supply ... +48v&psc=1

https://ibb.co/g7qV8p
https://ibb.co/mA9ZZU
https://ibb.co/iSGRg9
https://ibb.co/maREZU

User avatar
OutoftheBOTS
Posts: 668
Joined: Tue Aug 01, 2017 10:06 am

Re: 1945 Craftsman lathe CNC Conversion

Mon Oct 15, 2018 9:34 am

Ok I have built a couple of CNC machines, 1 of them was a convert manual Mill to a CNC mill.

My first CNC I made I used RPi to drive it but did discover although it is possible to drive a CNC machine with RPi it is a very poor choice.

Basic parts needed:
1. Stepper motors (for my mill I used nema34 and they had no problem doing the job, my 3D printer has nema 17 and they work fine for a 3D printer)
2. power supply for the stepper motors usually much higher voltage than motors r designed to run on as you will use a chopper driver for the motors.
3. stepper motor driver. These use the power from the supply to create the step pattern for the motors from the signals from the motion controller
4. A motion controller. This sends the signals to the stepper motor drivers.
5. Motion control software Mach3 being most common but lots of software out there.

I used pulley and belt to create drive line from motors to ball screw.

Check out the "diy cnc machines" facebook page :)

Have fun :)

MrGreg
Posts: 65
Joined: Sun Jun 10, 2012 7:25 pm

Re: 1945 Craftsman lathe CNC Conversion

Mon Oct 15, 2018 8:45 pm

I am not too familliar with exactly what a " Craftsman 101.07403 lathe" is, but I understand it is about 12" hobby type machine?
Yes? Or is it something else?

One of the first things to do is choose a suitable stepper motor. Nema xx is a motor frame size specification. it does not tell you much about the motors performance or characteristics. I would guess that A Nema23 size would probably be suitable with the right characteristics chosen. Nema34, the next size up may be too heavy and bulky. Best you go and do A thorough research on motors and then make your choice. The motors are probably the most expensive bit, so it is good to spend a good deal of time getting the right ones first time.

The stepper drivers are a bit more forgiving choice wise, as they can usually deliver a wide range of current and voltage.
The HY-TB6600 series are a common choice for small CNC machines. 0.5 - 4.5A and up to 50V. They are fairly cheap and work quite well. ( I use them)
The driver choice will be dependant on the motor choice and your pocket.

The choice of power supply will be dependant on the motor characteristics. You might want to choose one that has some scope for variable voltage as well as more than enough current. Say a range of 12 - 50V ( I use about 30V which is suitable for my use case)

An RPI is quite capable of controlling a CNC machine if you take some care and go about it in the right way.
The best solution is the most challenging :)
That would be to use "Machinekit" which is the Linuxcnc fork that includes ARM boards like the RPI.
Take a look at
https://www.raspberrypi.org/forums/view ... 37&t=33809
It's a bit dated and full of waffle and kruft. I would just skim read it to start with. Mostly take note of the authors posts "Kinsa"
The two main links are
http://www.machinekit.io/docs/getting-s ... -packages/
and
https://github.com/kinsamanka/PICnc-V2

You might find this of use and interest. It is a similar project using a lathe as the basis for a cnc machine and a RPI to control it. I works very well.
http://www.alloyavenue.com/vb/showthrea ... spberry-Pi

Another couple of options that work are:
This
http://www.ecklersoft.com/
But you will have to compile it yourself for the RPI as there is not a pre built binary. I complied it a couple of years / versions back and it worked OK then. I have not tried the most recent version though. And of course you have to buy the dongle.

And finally this solution. The easyest but not the best. It uses an Arduino for the step generation and you can use an RPI for the GUI interface and Gcode. Works quite well but with some limitations. You want to be using a "Genuine" Arduino Uno NOT a cheap copy. Its pretty much Plug & Play. Might be a good place to start and get a machine going with minimum fuss.
https://github.com/grbl/grbl
This interface GUI & Gcode sender works well on RPi for grbl
https://github.com/vlachoudis/bCNC

There are other solutions for the RPi, but I can't comment as I have not tried them.
Search the forum
Machinekit is the best by far, but will probably be quite challenging.
BTW you can install Machinekit in Simulation mode on an RPi if you want to get a better idea of what it is about.
BTW2 Machinekit can be setup in a dedicated lathe mode with several lathe specific gcodes

Good luck

User avatar
Joel_Mckay
Posts: 150
Joined: Mon Nov 12, 2012 10:22 pm
Contact: Website

Re: 1945 Craftsman lathe CNC Conversion

Mon Oct 15, 2018 9:28 pm

My page about NEMA steppers:
http://www.micrometer.xyz/cdn/node/68

RTLinux Debian Stretch distro focused on CNC (includes lathe specific CAM tools for linuxCNC)
https://sourceforge.net/projects/microm ... spberry-pi
(I plan to get an arbitrary threading encoder setup done next summer)

The board our club uses, and the Makerfaire unit we are giving away Oct31, 2018
http://www.micrometer.xyz/cdn/node/67

It includes everything you will need in one download. ;-)

Cheers,
~J~

User avatar
Gavinmc42
Posts: 2144
Joined: Wed Aug 28, 2013 3:31 am

Re: 1945 Craftsman lathe CNC Conversion

Tue Oct 16, 2018 12:40 am

A lathe is normally only two axis.
A Pi could control the steppers reasonably without extra hardware like an Arduino.

Joan's pigpio is a good place to start and there is also a PiCNC effort now.

To get smooth curves circular interpolation is required and this it timing critical.
Usually the Linix OS gets in the way of this real time stuff.
Linux CNC is probably a better fit than Mach3, but I used to use TurboCNC on FreeDOS.
Wonder if if could be ported to Tiny86?
These days I use Baremetal Ultibo and CNCing is on my long list to try now.

There is a two channel serial bitstream output in the i2s hardware.
I have always suspected this could be used to generate the step pulses?
Lathe and most Mill CNCing is only 2D.

A 23 size stepper with belt reduction might be better than a 34 size direct drive.
Belt drive can also be more compact and easier to fit, with a pulley just replacing the hand wheel and the steppe mounted off to the side.

A DRO might be handy for absolute position feedback as backlash can be an issue.
However with ball screws replacing the normal screws backlash is very low and the actual torque needed by the stepper motor is much smaller too. Thrust bearings will be needed, this can be done with back to back taper ball bearings.

A microstepping driver makes for smoother motion and cuts.
Machining makes a big mess :D
One day I want to try the new Trapezoidal screw, Igus Drylyn nut drives to see if they will work ok.
Cleaning ball slides and ball screws is a pain, lost so many balls :oops:

Replacing the cross slide with stacked ball slides reduces friction and therefore motor size even more.
My next lathe will probably wide linear ball slides on a slant bed with composite concrete base.
I do mostly small stuff and want a desktop lathe.

With ballscrews and ball slides a 23 size motor should be ok.
23 size motors can come with 1, 2 or 3 stack lengths.
I have used 23 longs on a small CNC mill conversion, enough power for dovetail slides and the standard acme screws.
Sloppy and with backlash but I made a small business out of it, before getting a real job :D

If you want to do power feed on long stock then a 34 on the long axis and 23 on the cross slide?
I'm dancing on Rainbows.
Raspberries are not Apples or Oranges

User avatar
Joel_Mckay
Posts: 150
Joined: Mon Nov 12, 2012 10:22 pm
Contact: Website

Re: 1945 Craftsman lathe CNC Conversion

Tue Oct 16, 2018 1:58 am

Gavinmc42 wrote:
Tue Oct 16, 2018 12:40 am
A lathe is normally only two axis.
Unless you add a tool turret rather than multiple posts. ;-)
Gavinmc42 wrote:
Tue Oct 16, 2018 12:40 am
A Pi could control the steppers reasonably without extra hardware like an Arduino.
Not from our personal experiences, as an Arduino can do "Real-Time" control using a low-level timer interrupt, and runs off a fixed clock (we used the atmega2560 chip so people could understand the familiar open firmware easier). Even the RT Linux kernel compiled for the Pi is only good up to 5kHz latency at best. But realistically, the issues have more to do with synchronous movements in a spline path (there is a distinct difference between position errors, and theoretical resolution).
Gavinmc42 wrote:
Tue Oct 16, 2018 12:40 am
Joan's pigpio is a good place to start and there is also a PiCNC effort now.
Maybe for a plotter or something else low-precision like an engraver we'd agree. :-)
Gavinmc42 wrote:
Tue Oct 16, 2018 12:40 am
To get smooth curves circular interpolation is required and this it timing critical.
Usually the Linix OS gets in the way of this real time stuff.
Linux CNC is probably a better fit than Mach3, but I used to use TurboCNC on FreeDOS.
Linux CNC does magic interpolation on splines to ensure constant surface cutting speeds, and improved contour accuracy. I won't comment on Mach3, as it is the only option for windows users... good enough for hobbyists anyway. ;-)
Gavinmc42 wrote:
Tue Oct 16, 2018 12:40 am
Wonder if if could be ported to Tiny86?
Probably, as there are gcode parsers for the ATmega328, and the performance is fine.
Gavinmc42 wrote:
Tue Oct 16, 2018 12:40 am
Lathe and most Mill CNCing is only 2D.
It is supposed to be a cylindrical coordinate system abstraction, but by convention most use XZ axis in gcode as you stated.
Gavinmc42 wrote:
Tue Oct 16, 2018 12:40 am
A 23 size stepper with belt reduction might be better than a 34 size direct drive.
I was always told that NEMA Size standards have nothing to do with the motor torque rating. Then I read the standard, and it does seem to be a size rating.. ;-)
Gavinmc42 wrote:
Tue Oct 16, 2018 12:40 am
Belt drive can also be more compact and easier to fit, with a pulley just replacing the hand wheel and the steppe mounted off to the side.
Agreed, makes things quieter, better (no micro-stepping placebo), and safer to operate the machine.
Gavinmc42 wrote:
Tue Oct 16, 2018 12:40 am
A DRO might be handy for absolute position feedback as backlash can be an issue.
Most machinery is meant to operate in conventional milling mode, and the CAM software should be configured to account for this recommended wear life precaution (if your boss says to ignore this on his machines to save operation cycle time, than go for it...) However, mills/lathes can use the backlash compensation constant in LinuxCNC by measuring it using an actual dial-indicator. It really depends on the machine, as often servicing the gibbs or split-nut variant can bring it to negligible levels.
Gavinmc42 wrote:
Tue Oct 16, 2018 12:40 am
However with ball screws replacing the normal screws backlash is very low and the actual torque needed by the stepper motor is much smaller too.
Not worth the money in my opinion, as Way Covers are never perfect.... especially if you chew though a piece of brass at some point.
Gavinmc42 wrote:
Tue Oct 16, 2018 12:40 am
A microstepping driver makes for smoother motion and cuts.
Don't get fooled by the 3D printer-driver marketing, as it has a lot of trade-offs that take a bit to explain.
We don't use anything beyond half-step mode for CNC machines that need to hold position of tooling (i.e. choose a finer resolution stepper, and or better belt reduction drive ratio) :-)

Cheers,
J

User avatar
OutoftheBOTS
Posts: 668
Joined: Tue Aug 01, 2017 10:06 am

Re: 1945 Craftsman lathe CNC Conversion

Tue Oct 16, 2018 7:25 am

I replaced my RPi with this $25 motion controller and running mach3 on my PC https://www.aliexpress.com/item/USB-MAC ... st=ae803_5

It can run 4 axis at 100Khz via USB and supports limits switches, probe, emergency stop and hand wheel.

The other advantage I found with Mach3 is it is super commonly used (especially by professionals) so getting advice on it was very easy.

User avatar
Gavinmc42
Posts: 2144
Joined: Wed Aug 28, 2013 3:31 am

Re: 1945 Craftsman lathe CNC Conversion

Wed Oct 17, 2018 3:34 am

The other advantage I found with Mach3 is it is super commonly used (especially by professionals) so getting advice on it was very easy.
Yep the only reason to not use a PC is because you want to learn how to do it on a Pi.
Learning and using is not the same thing, especially if you actually want to be productive and make stuff.

The fact that can be done on a Pi (nearly?) just goes to show how the cost of computing has fallen
I'm dancing on Rainbows.
Raspberries are not Apples or Oranges

Return to “Automation, sensing and robotics”