(this post is automatically translated from the original Italian version for your convenience. Sorry in advance for errors)

A milling machine numerical control (CNC)

I've always been fascinated by the technologies that use electronics and computers to monitor or control mechanical devices.

The CNC milling machine is the object that best represents this concept: know how to properly use and then successfully involves good knowledge of all these technologies.

The milling machine "classical" is manipulated by hand: the axes that move the spindle (which is mounted on the cutter that rotates at a speed appropriate) than the pieces are coupled to the knobs manual.

On the other hand, the axes of CNC work are coupled to a motor controlled by a computer, usually it is a stepper motor.

The stepper motor is basically driven by a suitable controller which exhibits two signals, step and dir.
A transition on the first tells the engine that must take a step in the direction specified by dir, which can be clockwise or counterclockwise.
The magnitude of the step is measured in degrees, 1.8 degrees / step that will mean 200 transitions on the signal so that the step motor axis makes a complete circle.

Some controllers including the one I used also allow the half step, I'm not here to explain what is the technique used to obtain the half step (if you want depth, look for "stepper motor tutorial" in Google), however with the medium Once, it was double the number of steps to make a turn and the motor therefore will move with more fluidity.

The computer takes the place of the operator's hands, planning appropriately moving the axles may carry a lot of machining of high precision, virtually impossible to do by hand.
Realize, machine parts, cut from a sheet of balsa a rib of an 'wing of a model aircraft, engrave an inscription on the wood, it becomes a program that the CNC milling machine is running.

Having discarded the idea of buying a ready-made CNC milling machine, first the high costs, and secondly because the fun for me is building something to learn, I opted to buy a conventional milling machine to be transformed later into cnc.
I took a Proxxon MF70, German-made.

Then I designed the control electronics and the mechanical part to match the stepper motor axes of the milling machine.
The end result is this:
L6208 from STMicroelectronics (DMOS driver for bipolar stepper motor), designed precisely to do this job. And it does so well!
The schematic used is simply that recommended in the datasheet, here however the sketch from which I started ...
78S40, then again from 8 to 5 volts with the classic 7805.
The power supply is in common: the bottom is for a channel.
... The finished result on millefori
language in practice is a file that contains commands that are given to the cutter, with the possibility of defining the "subroutine" a bit 'like the old Basic.

Through Gcode can tell the machine tool to follow the paths that include lines and arcs.
E 'as a pen drive which is said to make a path with a certain speed, only instead of the pen is the mill running at 20000 rpm and "trite" whatever it finds in its path.
It should be given much attention, the program should be done keeping in mind the material and the cutter used.
Speed and size of the groove depends on the type of tool and material do not have to work to the cutter outside of specifications.
Forcing can mean to break the cutter, the router could damage, break the workpiece.
Decrease the speed or make more passes!

To give an idea of what I did get the video: here's one

The writing was developed using EMC2, the gcode file was created with Inkscape, installing a patched version of this plugin.
The files are patched gcode.py and LinuxCnc

CNC & EMC2

Proxxon cnc conversion

info on parallel port

Ah, the disclaimer
The realization of a CNC milling machine, though small, requires a deep knowledge of mechanics and electronics: it is not a walk.
What is written is the result of 'personal experience of the author on the subject:
the author did not assume any liability.

Articles

You are reading "A numerically controlled milling machine (CNC), a post from Fabrizio Zellini

Published: February 6, 2008

Categories: CNC, Mechanical

Dewey Garrett February 9, 2008 at 3:32

Good Day Fabrizio

I noticed on the emc wiki page:
http://wiki.linuxcnc.org/cgi-bin/emcinfo.pl?InkscapeHowto
that you mentioned that you did not do bezier control points.

I had to do these once in tcl (I do not code python) and I
Thought you might be interested in some code fragments that
could be converted to python. I used the source librsvg
code to learn how to do it.

Excerpt:

C (; # cubic bezier (absolute coordinants)
# X, y are last point
September x1 [lindex $ plist $ i] incr i
September y1 [lindex $ plist $ i] incr i
September x2 [lindex $ plist $ i] incr i
September y2 [lindex $ plist $ i] incr i
September x3 [lindex $ plist $ i] incr i
September y3 [lindex $ plist $ i] incr i
September xy [process_cubicbezier $ x $ y $ x1 $ y1 $ x2 $ y2 $ x3 $ y3]
set x [lindex $ xy 0]
set y [lindex $ xy 1]
)
c (; # cubic bezier (ie coordinants)
September x1 [expr $ x + [lindex $ plist $ i]]; incr i
September y1 [expr $ y + [lindex $ plist $ i]]; incr i
September x2 [expr $ x + [lindex $ plist $ i]]; incr i
September y2 [expr $ y + [lindex $ plist $ i]]; incr i
September x3 [expr $ x + [lindex $ plist $ i]]; incr i
September y3 [expr $ y + [lindex $ plist $ i]]; incr i
September xy [process_cubicbezier $ x $ y $ x1 $ y1 $ x2 $ y2 $ x3 $ y3]
set x [lindex $ xy 0]
set y [lindex $ xy 1]
)

proc process_cubicbezier (x0 y0 x1 y1 x2 y2) (x3 y3
September delta [expr 1.0 / $:: PRI (svg, beziersteps)]
for (set i 1; set T $ delta) \
($ i

Fabrizio February 11, 2008 at 11:29

Thank you Dewey, but I'm not the author of the plugin, i have only patched it.
However your code is interesting, with bezier curves the plugin would be complete.
Compliments for your woodturning works! Very cool.

Savy.uhf February 12, 2008 at 1:00

Good job, congratulations!
I just wanted to know what kind of stepper motor you used and where did you buy it.

Thank you.

HELLO!
Savy.uhf

Fabrizio February 12, 2008 at 9:51

Thanks, the engines are "size 23", I've purchased from Micromed in Rome.

Simone Tripodi February 14, 2008 to 14:47

You are always the best Duca Conte!

pacman February 24, 2008 at 10:52

Hello and congratulations for your work, I installed the patch for inkscape, but when converted into
g-code me 'this error:

Traceback (most recent call last):
File "/ usr / share / inkscape / extensions / gcode.py", line 153, in?
e.affect ()
File "/ usr / share / inkscape / extensions / inkex.py", line 90, in Affect
self.effect ()
File "/ usr / share / inkscape / extensions / gcode.py", line 90, in effect
ngcfile = open (filename, 'wb')
IOError: [Errno 13] Permission denied: '/ home / prova.ngc'

It seems a permission problem, but I have no idea how to act, you have some idea? and 'I was looking for so that a new system to use only Linux for the CNC.
thanks
Pacman

Fabrizio February 27, 2008 at 16:11

Hello pacman, the error would appear that the script fails to write to the filesystem.
Usually the / home directory is not writable by a user who is not root.
Try to write the file in the home dir of the user who uses (usually / home / <username>).

Hello, Fabrizio

. ste July 23, 2008 at 18:27

Hello. I found very interesting your work. But I wanted to ask you something: EMC2 can interface with the CNC only through the parallel port? Because the newer computers often do not have it and I wanted to know if it was possible to use a serial port, receiving commands via a microcontroller.

Thanks!
. ste

Fabrizio July 26, 2008 at 14:39

I have not investigated but given the modular structure of EMC2 guess you can try asking here.

maurizio August 6, 2008 at 16:09

Hello Fabrizio
I'm trying for several days on the internet to find some scheme to make a cnc milling machine, I saw your project, I'd try to design the cards, if possible, you could give me some more particular 'connection
the control board, not in Schedule I realized that you used integrated.
Thanks anyway,
article 'very interesting for someone like me starts to penetrate into the cnc world ...
hello
sm

Antonio August 12th, 2008 at 2:09

Hello Fabrizio, I'm glad to have found this your project with the stepper motors. are Brazil and perhaps like you I had adiritura build my own car, um small lathe. but I'd like it to work using CNC PC, you can use this system? thank you for your ATTENTION and I salute you.
cioa antonio

Antonio August 13th, 2008 at 2:27

would be possible to mount this kit on a small lathe?
thanks. antonio

Fabrizio August 13, 2008 at 20:50

Mauritius
the control board I used:
for the portion of food:
78S40 and 7805
For the part that generates the signals for the control board:
4046, 74LS153, 74LS157 and optoisolators TLP620 because I was already going well but also 4N25

Fabrizio August 13, 2008 at 20:57

Antonio
with this scheme you can drive the stepper motors that then you can safely use to control a small lathe.
If you use EMC2 refer to LinuxCnc to configure the program.
Enjoy!

gianni September 17, 2008 at 20:46

Congratulations on this achievement.
I would have only one request from you, how you define the zero of the machine when you start milling a piece?

Andrea September 18th, 2008 at 9:39

Fabrizio
I have a small production of spare parts in steel purtoroppo not justify the expense of conventional CNC lathes and milling machines. You could implement the project exposed to c / third?. the stepping motor has enough torque to push metal cutting alloy steels also quite difficult to work with?
thanks
Andrea

Fabrizio September 19, 2008 at 11:52

for Gianni: zero Linuxcnc with the septum, which harbor the cutter to the point of starting work and then seven 0, at this point I start the program.

to Andrea: I told you in private.

gianni September 20, 2008 at 17:14

How to manage the recovery of the games machine?
Especially in the change of direction the game between the worm and the nut is not negligible, however, and depends on the type of machine. Not having a tool position feedback on what happens if the engines are being eroded?

gianni September 23, 2008 at 11:42

With engines SIZE 23 Micromed Can milling of aluminum?

Fabrizio September 23, 2008 at 18:00

If the engines lose the shots clearly you miss it, to mill metals using a feed rate very low (partly because the cutters are expensive) and I do not ever give out the engines.
The games are original in their mechanics because the engines are coupled directly through a bush to the original knobs.

Gianni October 13, 2008 at 15:38

I can not find the ICs L6208N, where did you purchased?
Are there alternatives?

Fabrizio October 21, 2008 at 22:11

I've taken it online Distrelec.

Smida Rochdi December 7, 2008 at 20:45

Fabrizio hello congratulations for ment ... I realize I have a Tunisian CNC lathe Fanuc control is stopped for some time due to malfunction in the electronics repair can not find one capable of doing my part to do so by an Italian firm costing me a fortune . seeing your mill you did wake my nostalgia for my tornietto (denford Cyclone) and I wonder if you can run it in your own way, thanks Rochdi

DAVIDE February 25, 2009 at 21:20

Hello ... you're a legend! Dienes years ago I began to want to build an interface to 3 stepper motors connected to the PC. On the Internet there was almost nothing and I do not know anything about electronics. The company has been in vain ... and after many trials I left. For several days I returned on my steps and discovered that the web is full of these things that I had only planned on paper. I'd like to try the experiment but, unfortunately, I can not weld and NN understand much of electronics. What I would ask and I can build a "box" type your own ... and devote myself solely to programming. If you can make this thing (I prefer) or help me step by step (you will receive at least 10 mails a day =^^=) please let me know.
THANKS .. David.

Fabrizio February 25, 2009 at 21:43

David, I replied privately

Paul March 17th, 2009 at 11:46

Hello Fabrizio, thanks for all the information that provides. I wanted to ask EMC in the configuration file with which parameters you set the working area of MF70
Axis 0 (X) Min / Max
Axis 1 (Y) Min / Max
Axis 2 (Z) Min / Max

Thanks

lucio April 6, 2009 at 18:03

Hello Fabrizio
First I wanted to compliment the site and for the realization of Proxxon MF 70 changed into a magnificent cnc, I'm also trying to make this change.
I wanted some information regarding the installation of Inkscape on Ubuntu for the realization of gcode file.
I installed Inskape and I can not perform the procedure that you have applied.
If possible, I deschi the steps to be performed and what should I write in Terminal.
Waiting for enlightenment, I thank you in advance.

Fabrizio April 10, 2009 at 17:40

Hello Lucio, unfortunately this plugin does not work with the latest versions of inkscape, which version are you using?

lucio April 13, 2009 at 18:28

Fabrizio hello and thanks for the interest,
mine is a version of Ubuntu 6.06 with EMC2 already installed, including any updates and I also installed inkscape, but I can not go forward with the plugin.
I'd be really grateful if you could give me a practical description of how to proceed in several steps. Thanks in advance. Lucio

Fabrizio April 14, 2009 at 10:13

Lucio, simply follow these instructions,
however this is to copy the 2 files in the directory / usr / share / inkscape / extensions, you have to copy them as root.
sudo cp gcode.inx gcode.py /usr/share/inkscape/extensions

lucio April 15, 2009 at 0:58

Thanks Fabrizio, I managed to copy the files in the directory, I tried to do a test following the lead then gcode exporting, but when the rescue comes an error dialog:
Traceback (most recent call last):
File "/ usr / share / inkscape / extensions / gcode.py", line 144, in?
e.affect ()
File "/ usr / share / inkscape / extensions / inkex.py", line 90, in Affect
self.effect ()
File "/ usr / share / inkscape / extensions / gcode.py", line 89, in effect
ngcfile = open (filename, 'wb')
IOError: [Errno 13] Permission denied: '/ home / t.ngc'
What could this mean.
Thanks in advance. Lucio

Fabrizio April 15, 2009 at 9:04

The error appears that the script fails to write to the filesystem.
Usually the / home directory is not writable by a user who is not root.
Try to write the file in the home dir of the user who uses (usually / home / <username>).

lucio April 15, 2009 at 14:20

Thanks Fabrizio, I've also solved this step, I admit to being embarrassed, but about a month playing with ubuntu. Congratulations again on your skills and knowledge to different ...., To the next.
Lucio

Croton May 15, 2009 10:30

Hello Fabrizio, first of all, congratulations for your work!
I wanted to ask you a question! How much does all the necessary equipment to achieve your cnc? I am a designer and I have not much knowledge regarding electronics ... Thanks in advance!

Fabrizio May 15, 2009 at 10:45 am

I have not kept track but spans between bearings, motors and electronic components, I'd say around 100/150 euros.

James June 2, 2009 at 15:32

Hello my heartfelt congratulations for the work you've done.
I am a fan of electronic computing. I have built a contact printer long ago 'I realized circuits. How much would you tell me everything you've achieved? I would like him too. Bellissimo merge electronics computer mechanics. hello appearance response.

Fabrizio June 3, 2009 at 7:31

Thanks, I will have cost around 100/150 euro, more time and patience.

Roberto June 25, 2009 at 14:00

Congratulations, a really nice job!
You can not add photos to the other side of the files?

Fabrizio June 25, 2009 at 15:39

Thanks Robert, now all I disassemble specially fitted to make him, just get the chance I'll definitely

Baron Alexander August 20, 2009 at 8:43

Dear Fabrizio, complimentoni sincere to your capacità.Sono a fan of electro as you but not your livello.Mi you tell if two stepper motors may be operated by commands similar type potenziometri.Stò realizing with a camera crane PAN and Tilt.
Pending I offer you my most cordial greetings
Alessndro

Fabrizio August 22, 2009 at 18:11

Alexander, it can be managed, but we need a microcontroller that samples the output voltage of the potentiometers stepper motors and drivers accordingly.
If you need to make a rapid prototype you could use Phidgets.
Eg you could drive the motors with these drivers for stepper motors and potentiometers sampled with this card.

havana7 October 13, 2009 at 9:57

You really are a myth!

I tried to use the plugin for Inkscape version 0.46 and Ubuntu 8.04 does not work! Someone has some advice for me to make them work?

Thank you very much

David November 24th, 2009 at 16:07

I wanted to congratulate you for what you have done, I want to take the cue of the evening for the group I belong to linux with the theme: the use dell'Arduino to handle the stepper motors. I thought of using the pattern that you used too, I noticed that compared to the version that's on the date of the L6208 have used 2 capacitors than those reported, respectively, C2, and on that date are from Cen: 100 nF and 5.6 nF whereas you have used 470 uF to 50 V and 10 nF and Ren from 39 K instead of 100K I know why, thanks. Congratulations again for what you did, I hope to make some beautiful evenings thanks to your work.

Fabrizio November 24, 2009 at 23:40

Thanks for the compliments.
The 470uF capacitor is simply a filter capacitor in parallel to food (in the application notes is C1), with respect and Ren Cen (which are the low pass filter on the signal of enable) the values I used an increase little time constant of the filter and then filter out any spikes better.

Giuseppe Musumeci December 5, 2009 at 18:42

hello ... you Fabrizio additions is an understatement ...

are one of the many admirers of this wonderful world that is the movement of stepper motors.

we come to the point ;-)

I read it for months that I browse and try to inform me I have nothing more ... in electronic baby I gpe mount kit (one in 100 stand it any) re-ele ... etc etc. I know we say Paciocco ...
instead of mechanics are a little more Bravin, in fact clouded by my ability I have developed a pantograph entirely of aluminum with useful measures 40 x 30 except that now it's the most painful ... and electronic engines, I've seen kits around ready to costs their economies and given the strict time constraints of DIY ... I thought you would be willing to help me?! maybe all the necessary documentation and procedures, or I would really like to know they can count on a package and made it yourself ;-)

a fond farewell
Joseph

emanuele lorenzoni March 7, 2010 at 21:08

Hello Fabrizio is a boy who I enjoy spending time with the electronics and the moment I'm a go "at Realaze a CNC milling machine" we say to leave me enough to run a stepper motor with a L6208 I built the "draiver "I took the pattern datasheet from ST and now looking at your blog I saw the same pattern very similar and I said maybe he can help me ...
coming to the conclusion I can not understand how to communicate using the serial port as a program integrity Mach3. How do I know what the wires to be connected to the inputs to the former cloock reset control, etc. ... I hope you have understood me thank you in advance
congratulations for the beautiful circuits realizate

Fabrizio March 8, 2010 at 21:52

The serial port of your PC integration?
The serial works in signal levels that are not compatible with those of 6208, so you should first convert them to something like MAX 232, so usually we use the parallel port.
To configure Mach3 can not tell you, I know of that program, you should refer to the documentation (I guess is here)

emanuele lorenzoni March 8, 2010 at 23.04

excuse me I am confused with the paralela I am using the paralela thanks

Fabrizio Zellini

A milling machine numerical control (CNC)

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