THIS PROCEDURE WILL HELP YOU CONVERT YOUR MINI OR MICRO MILLING MACHINE TO A COMPUTER CONTROLLED FABRICATION TOOL. 

 

 
 

DESCRIPTION

CNC STANDS FOR 'COMPUTER NUMERICAL CONTROL' AND IS THE TERM GIVEN TO COMPUTER CONTROLLED MACHINE TOOLS.  USING A COMPUTER TO CONTROL A MILLING MACHINE MAKES IT POSSIBLE TO CREATE ACCURATE, REPEATABLE PARTS QUICKLY AND LESS EXPENSIVE THAN BY HAND.

A CHEAP IMPORTED MILL LIKE THE ONE USED HERE IS AN AFFORDABLE WAY TO START.  IN FACT, YOU CAN PROBABLY GET A MILL LIKE THIS ONE FOR ABOUT AS MUCH AS IT WOULD HAVE TAKEN TO MAKE IT FROM SCRATCH. 
 

MATERIALS        

-A MINI OR MICRO MILL
-3 STEPPER MOTORS, >100 OZ IN TORQUE!
-STEPPER CONTROLLER (ALA WWW.HOBBYCNC.COM)
-MISC METALS AND HARDWARE (TOO MUCH TO LIST)
-JB WELD
-PROJECT BOX

EQUIPMENT        

-COMPUTER
-CUTTING TOOL (DREMEL)
-LATHE

PROCEDURE

 

WHY?

PURCHASE A MINI OR MICRO MILL.  I'M USING A HARBOR FREIGHT 47158.  ITS HARD TO ARGUE WITH THIS CHOICE, $280 SHIPPED IS PROBABLY WHAT YOU'D PAY IF YOU MADE YOUR TABLES FROM SCRATCH.  
UNPACK IT.  THE BAG PROTECTS THE 100 POUNDS OF IRON FROM BEING HARMED BY THE 2 POUNDS OF STYROFOAM.  REALLY.
UNPACK IT MORE.  
THESE ARE THE X AND Y AXES.   
AND HERE'S THE PROBLEM.  STEPPERS COMMONLY HAVE SMOOTH 1/4" SHAFTS.  CHINESE MILLS HAVE ODD SIZED THREADED AND KEYED LEADSCREWS.  ICK.  
X AND Y AXIS MOTOR MOUNTS
REMOVE THE LEADSCREW FROM YOUR AXIS OF CHOICE. 
NOTE, YOU MAY WANT TO SKIP AHEAD AND USE THE MILL TO MAKE ALL THE PARTS YOU'LL NEED.  I TOOK THE SCREW OUT FIRST AND THEN TRIED TO MILL THINGS WHILE HOLDING ONE AXIS STILL WITH MY HAND.  YOU CAN TELL HOW WELL THAT WORKED BY LOOKING AT THE AWFUL CUTS I MADE BELOW.
USING A DREMEL, WHACK OFF THE THREADED PORTION.  THEN, IF YOU LIKE, GRIND OFF THE KEY.  THE LATHE CAN CUT THE KEY DOWN FOR YOU, BUT I THINK ITS EASIER ON YOUR TOOLS IF YOU GRIND IT FIRST.
I'VE BEEN TOLD THE KEYS WILL SIMPLY PULL OUT OF THE SHAFT, BUT I'M APPARENTLY NOT HARDCORE ENOUGH TO ACHIEVE THAT.

AT THIS POINT YOU SHOULD TAKE A DEEP BREATH; YOU'VE JUST RUINED YOUR LEADSCREWS, THERE'S NO GOING BACK NOW.

YOU'LL NEED TO TURN THE LEADSCREW DOWN TO 1/4".  PLACE THE SCREW INSIDE A PROTECTIVE BRASS SLEEVE BEFORE PUTTING IT IN THE LATHE.  DO NOT USE DUCT TAPE TO HOLD THE SLEEVE IN PLACE AS SHOWN; THE DUCT TAPE WILL DECENTER THE SCREW AND YOU'LL GET A SLIGHTLY ECCENTRIC SHAFT (SHIT).
THE BRASS KEEPS THE LATHE CHUCK FROM DAMAGING THE THREADS ON THE SCREW. 
TURN THE SHAFT DOWN TO 1/4".
 
REINSTALL THE TURNED SCREW.  
MAKE 2X OF EVERYTHING SHOWN.  (ER, BUY THE BOLT, DON'T MAKE IT) THESE PARTS WILL BECOME YOUR MOTOR MOUNT.
INSTALL THE MOTOR MOUNT AS SHOWN.
THE BOLTS FOR THE MOUNT ALSO HOLD THE LEADSCREW IN PLACE.
MAKE SOME BRASS SHIMS FROM THIN BRASS SHEET.

THE HANDWHEEL'S CENTER IS SIZED FOR THAT FUNKY CHINESE LEADSCREW.  IT'LL TAKE SOME SHIMS TO PROPERLY ATTACH IT TO THE MOTOR.
SHIM THE HANDWHEEL BY INSERTING ONE SHIM, THEN THE OTHER ABOUT HALFWAY.  SECURE WITH JB WELD BETWEEN THE LAYERS 

THEN INSERT A LENGTH OF 1/4" ID TUBING.  JB WELD.

CUT EXCESS.




VOILA.
ATTACH THE HANDWHEEL TO THE STEPPER.  JB WELD TO SECURE IT.
IF SOMEONE HAS A BETTER IDEA THAN JB WELD, I'M ALL EARS.  I'VE FOUND IT TO BE PLENTY STRONG, HOWEVER, EVEN WHEN YOU'RE REALLY CRANKING ON THE WHEEL.
CUT SOME ALLTHREAD INTO 4 EQUAL LENGTHS.  USE NUTS AND LOCKWASHERS TO ATTACH IT TO THE 4 MOUNTING HOLES.
 
BEHOLD A SPIDER COUPLING.  ITS IMPORTANT TO USE A FLEXIBLE COUPLING BECAUSE NO MATTER HOW GOOD YOU ARE, THE MOTORS WILL NEVER LINE UP PERFECTLY.
INSTALL THE TWO HALVES OF THE SPIDER COUPLING ON THE MOTOR AND LEADSCREW.  USE LOCTITE ON THE SET SCREW, TRUST ME.
I USED WASHERS BEHIND THE SPIDER TO PREVENT ANY LEADSCREW PLAY.  YOU SHOULD USE A THRUST BEARING, OR A SHAFT COLLAR AS SHOWN ON THE Z AXIS.
INSTALL THE MOTOR, TIGHTEN CAREFULLY, WATCHING THAT YOUR NOT BINDING THE COUPLING OR SLIPPING OUT OF ALIGNMENT. THE ADVANTAGE OF THE ALLTHREAD MOUNTS IS YOU HAVE A LOT OF CONTROL ON THE MOTOR POSITION.  GET THINGS LINED UP WELL.
VOILA!  REPEAT THE ABOVE FOR THE OTHER AXIS.  
Z AXIS MOTOR MOUNT
REMOVE THE Z AXIS SCREW AND TURN IT TO 1/4" AS ABOVE.  I USED A SHAFT COLLAR PREVENT PLAY, IN ADDITION TO THE SPIDER COUPLING.
REINSTALL THE SCREW.  
MAKE A PLATE LIKE THE ONES SHOWN.
REALLY, YOU MIGHT WANT TO COME UP WITH SOMETHING BETTER...
I USED EYELETS AND ALLTHREAD TO ATTACH HALF OF THE MOTOR TO THIS PLATE.
 
INSTALL THE MOTOR. ADMITTEDLY, THIS DOESN'T WORK WELL.  THE HEAD IS SO HEAVY THAT THE STEPPER CANNOT TURN THE SCREW, EVEN WITH A GOOD MOUNT.  WHEN I GET A GAS SPRING TO SUPPORT THE HEAD, I'LL REDO THIS SECTION, I SWEAR.
MOTOR DRIVERS AND CONTROLLER
GET READY TO EXTEND THE MOTOR WIRES, BUT DON'T GO NUTS.  I USED SOME THICK 8 CONDUCTOR WIRE AND 6 PIN MOLEX CONNECTORS. 

FEEL FREE TO USE A 6 PIN CONNECTOR WITH YOUR 8 WIRE MOTORS.  CHECK THE DIAGRAM; TWO PAIRS ARE CONNECTED INTERNALLY ANYWAY.

MOST STEPPER'S WIRES AREN'T LONG ENOUGH TO COVER THE ENTIRE RANGE OF TABLE TRAVEL, EXTENSION IS A MUST.
VOILA.  USING SOME SPLIT LOOM STUFF MAKE IT LOOK ALL PROFESSIONAL. THIS IS REALLY NOT FUN; A LOT OF SOLDERING.
MAKE A BOX FOR YOUR CONTROLLER BOARD.  YOU DO WANT A BOX, GETTING METAL SHAVINGS ON YOUR CONTROLLER IS A DISASTER.  
WIRE UP THE CONNECTORS.  I'M USING A HOBBYCNC BOARD HERE, AND I THINK ITS EXCELLENT. I USE HOBBYCNC CONTROLLERS.  OTHER OPTIONS INCLUDE XYLOTEX, AND TS ENGINEERING (WHO'S LINK I'VE LOST).
A RADIOSHACK PROJECT BOX IS JUST THE RIGHT SIZE, WITH A LIL GRINDING.  
ALL DONE.  I ALSO ADDED A FAN, BUT IT'S NOT NECESSARY.  
DONE!  


RESULTS

I HAVEN'T HAD ANYTHING GOOD TO MACHINE YET (PLUS I NEED A NEW DRAWBAR TO HOLD MY COLLETS).  INSTEAD, I THREW IN A PENCIL AND USED SOME FREE SOFTWARE TO 'ENGRAVE' SOME TEXT IN A CIRCLE.  DID A GREAT JOB!



A SMALL VIDEO OF THIS TEST IS AVAILABLE HERE (MPG, 484KB), AND HERE (MPG, 389KB)
 

SOFTWARE

THIS DEVICE REQUIRES SOME COMPLEX SOFTWARE, BUT THANKFULLY YOU HAVE PLENTY OF OPTIONS SO FINDING SOMETHING USEABLE SHOULDN'T BE A PROBLEM.  YOU'LL NEED A CAD/CAM PROGRAM FIRST OF ALL.  THE 'CAD' PART HELPS YOU MAKE YOUR DESIGN, WHILE THE 'CAM' PART CONVERTS YOUR DESIGN TO A 'G-CODE' FILE THAT GETS SENT TO THE MACHINE.

YOU'LL NEED MILL CONTROL SOFTWARE AS WELL, WHICH MAY VARY DEPENDING ON THE CONTROLLER BOARD YOU CHOSE.  I USE TURBOCNC, WHICH SEEMS TO BE HUGELY COMPATIBLE.  OTHER OPTIONS INCLUDE KCAM, WHICH IS SAID TO WORK IN WINDOWS ALTHOUGH I HAVEN'T TRIED.


R
EADER QUESTIONS

NONE YET, BE THE FIRST!

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