CNC Conversion of a Sieg X-3
Milling Machine
By Bob Berg
Last update 12/28/05
Goal – To create a fairly
accurate bench top CNC machine at fairly moderate price.
Here are some shop pictures:
Still need to fix that light over the bench
Home Depot $7.95 cheapie!
Update:
Light fixed! (12/28/05)
The base Mill is a Sieg
X-3, this was purchased from www.lathermasters.com who
is the only current importer of this mill.
Priced delivered was about $1,100.00.
This also shows the DRO on top of the
motor.
Update:
DRO is no longer needed now that the mill is
CNC, Anyone interested in a DRO?
This is my Harbor Freight 9X20 lathe with
Quick Change tool post.
The Windex bottle is filled with
Denatured Alcohol I use it to clean EVERYTHING!
Once I received the mill I completely tore it
down and cleaned every piece that was practical with a brass brush, rags and
mineral spirits. After the cleaning it
was amazing how much grit and metal goo was at the
bottom of the cleaning bucket! The mill
was then greased/oiled and then reassembled in its new home. I used the mill for about a year for some
small manual projects. During this time
I got tired at looking at numbers on the hand wheels and dealing with back
lash. I then built a DRO for it and
fitted the X and Y axis with scales.
This single upgrade was time well spent, once you have a DRO you can
never go back!
I knew I wanted to convert the machine to CNC
from the start, so I did a lot of research on the WEB for information about CNC
conversions. I began to look for
components. I first looked at stepper
motors and then servos as many have said that servo performance will be
better. So I decided on the servo
approach.
I first located some very cheap servo motors
from a link I found on www.cnczone.com.
These are Clifton Precision servo motors
rated for 36VDC with a max torque of about 360 oz/in.
These motors were purchased for about $10.00
each!
However, they had no encoders on them, what
do you expect for $10.00! I purchased
some 250 count rotary encoders from US Digital for about $40.00 each and then
mounted them to the back of each motor – Now they are servos!
For
about $50.00 each I have a nice set of servos that should work well. I’m thinking that the power will be marginal
at a 2:1 belt reduction ratio. I toyed around with 3:1 and finally settled on a
2.5:1 ratio. If things don’t work out I
can always change the ratio.
Pulleys and belts were purchased from Stock
Drive Components and should be here in a couple of days (2/16/05).
During the first major shopping trip I
purchased 5/8
Pictures of ball nut components coming soon!
Design the conversion
As I was about to start making chips and
“design as I go” I realized quickly
that I’m going to make a lot of mistakes and I need to better plan the whole
design before I go to town. So I quickly
taught myself Solid Works and began to design the various parts of the
conversion. I was able to model
everything in 3d. This allowed me to see
how things would fit and look. It is like
being able to create a virtual model of my machine before ever cutting a single
chip or drilling any holes. I’m sure it has saved me many hours and dollars of
mistakes!
This is the full assembly of the mill table
with all the CNC components.
This shows the X-axis ball screw details.
The bad thing about modeling in 3d is that it
is so easy to change something you are constantly
Changing things and never reaching a “Final”
design. Also, there is no surprise when
you finish
Making a part, you know what it’s going to
look like before you even start!
I have provided my solid works files free for
download here (use at your own risk!): Solid Files
X,Y & Z Axis Bearing retainers
These
parts trap the bearing in the bearing plates so there is no axial
movement. The bottoms of the retainers
are recessed .100” to the diameter of the bearing. Based upon the depth of the bearing plate
holes these parts give .015” of crush.
Not that it’s all used of course!
Machine the ball screws
I think this was the most difficult part to
machine in the whole process, due to the fact that the ball screw is case
hardened to 56C.
When turning down the ball screw to fit the
bearings I wanted to keep the journal end as concentric as possible in relation
to the screw. Once the ball screw was in
the chuck of the lathe I placed a dial indicator in the thread grove and
rotated the chuck by and hand and also moved the lathe carriage so that the
dial indicator would follow the thread. I had to re-center the dial indicator
via the lathe carriage to the low spot on the thread a little each time as I
can’t follow the thread perfectly by hand.
By doing this I adjusted the lathe chuck so that the screw would run
true by indicating off of the threads not the outside. Once the screw was centered in the chuck I
faced off the screw and drilled a pilot hole so that I can support the other
end with a live center.
The machining process was begun by taking a
hand grinder and removing as much material by hand as possible
To try to remove the
case hardening. Be careful not to take
too much off doing this method as it’s easy to do!
I then turned the rest of the diameter with a
brazed on Carbide tool bit. This worked
pretty good once I figured how much of a cut to
take. I then finished the diameter with
some sand paper. The next step was to
thread a portion of the screw for the locknut.
I used a 7/16-20 hand die to make the threads. I tried to use the lathe
to single point the threads but something wasn’t working (don’t know what) so I
did it by hand.
X-Axis
X-Axis with new ball screw installed with
plates and motor mount attached.
All plates are made from 1” aluminum stock.
I was able to obtain all the aluminum stock
from the scrap bin at work!
The axis is now silky smooth,
in fact I can move the table by just turning the shaft with
my fingers!
I think I’m going to need to put some thought
in keeping the ball screws clean.
They are protected by the table, but I’m sure
some chips will get in and gum up the works!
Y-Axis
Space Plate, Bearing Holder, and Motor Mount
I just need to bore the hole in the bearing
plate and the Y-axis will be ready to go.
I finished the Y-axis bearing plate here it
is with its mating parts and assembly (2/18/05)
Y-Axis ball nut mount
Y-Axis with old acme nut removed and new
holes drilled for new ball nut mount
Y-axis new nut mount installed. The electronic device mounted on the left is
a reader head from a harbor freight 6” electronic caliper.
This is used for the Y-Axis DRO Scale. When I put the Y-table back on the scale
just slides back inside the head!
Z-Axis
–
I still
need to design how I’m going to approach the Z-axis. I will most likely drill a hole in the top of
the column and mount a bearing plate and motor mount for the ball screw on the
top. I will need to make a new mount for
the ball nut. I’m not sure if I will
need to support the screw from the other end with a radial bearing. I’m also
not sure if I will disconnect the hand wheel gear or make so that I can engage
and disengage the hand wheel from the ball screw. If I do use the hand wheel I will definitely
need to support the other end of the screw.
Before conversion:
The following have been added (12/28/05)
After Conversion
Here is the new ball screw, preloaded nut and
mount installed!
I decided to support the screw at the
opposite end. I used the existing
bearing holder, removed the thrust bearings and replace with radial
bearings. I have decided to leave the
crown gear off so the hand wheel is now disconnected. I don’t need it anyway!
Here is the pulley and empty motor mount on
the side of the mill.
The plates are 1” alum.
The little white switch is the upper Z limit
switch
Here is the X axis ready to go!
And the Y
Just need to finish up some wiring!
The following is a list of all the “major”
components that I used, approximate cost and source:
|
Vendor |
Web Site |
Part Number |
Description |
Approximate Cost |
|
Stock Drive Products |
A 6A 3-20DF03708 |
Motor Pulley -.200 (XL) Pitch, 20 Teeth, Aluminum Alloy
Timing Pulley |
$9.25 |
|
|
Stock Drive Products |
A 6A 3-50NF03710 |
X & Y Pulleys .200 (XL) Pitch, 50 Teeth, Aluminum Alloy
Timing Pulley |
20 |
|
|
Stock Drive Products |
A 6R 3-082037 |
X Belt - .200" (XL) Pitch, 82 Teeth, 3/8" Wide,
Neoprene Belt |
$5.55 |
|
|
Stock Drive Products |
A 6R 3-102037 |
Y Belt - .200" (XL) Pitch, 102 Teeth, 3/8" Wide,
Neoprene Belt |
$6.01 |
|
|
Stock Drive Products |
A 6A 3-17DF03708 |
Z - Motor Pulley - .200 (XL) Pitch, 17 Teeth, Aluminum
Alloy Timing Pulley |
$9.21 |
|
|
Stock Drive Products |
A 6A 3-50NF03710 |
Z Big Pulley.200 (XL) Pitch, 50 Teeth, Aluminum Alloy
Timing Pulley |
$20.91 |
|
|
Stock Drive Products |
A 6R 3-102037 |
Z Belt .200" (XL) Pitch, 102 Teeth, 3/8" Wide,
Neoprene Belt |
$6.01 |
|
|
|
|
|
|
|
|
Industrial Hobbies |
http://www.industrialhobbies.com/ |
|
5/8" |
$22.00 |
|
Industrial Hobbies |
http://www.industrialhobbies.com/ |
|
5/8" 5 TPI |
$51.00 |
|
Industrial Hobbies |
http://www.industrialhobbies.com/ |
|
3 Gecko 320 Combo (Servo Drives) |
$342.00 |
|
VXB Ball Bearings |
http://stores.ebay.com/VXB-Bearings-Skateboard-and-Slotcar |
7201B 12x32x10 |
Angular Contact Bearings (2 Per Axis Back to Back) |
$15.00 |
|
ColdFusionX |
Ebay |
|
Digital and Analog Panel Meters |
|
|
Ebay |
|
Controller Box |
75 |
|
|
Cabelldesigns |
BreakOut Board |
Parrallell Break out board |
137 |
|
|
US Digital |
E2-250-250 |
250 Count Encoders (For the servo motors) (3 Pcs) |
120 |
|
|
Avel Lindberg |
http://avellindberg.com/index.html |
Y236951 |
30AMP Toroid Transformer (32Volt) |
82 |
|
CNC Zone. |
http://www.cnczone.com/forums/showthread.php?t=2082&highlight=cheap+servos |
|
Surplus |
$30.00 |
|
Jeff Davis |
http://www.homecnc.info/cnc-main.html |
|
Preloaded Ball Nut Plans - Also Sells Servo Motors that
would be good for the X-3 |
7 |
(Update – 12/28/05)
I have not updated this site in a long while,
sorry! I will be adding more detail in
the very near future. As of now I have
completed the CNC conversion of the mill almost 9 months ago and everything
works perfect! The Z axis has been
converted to ball screw and has full range of motion and works great, the servo
has no problem lifting and lowering the head.
I have since remove the hi-low speed change gears and now have a direct
belt drive from the motor to spindle. I
plan on replacing the DC motor with an AC VFD drive.
I’m currently running about 100 inch/minute
in rapids. I could get it to run faster,
however for the size of the machine I don’t need it any faster. Most of my cutting is under 20 in/min. It has ton’s of power, able to snap 3/8 end mills
and keep going like nothing ever happened!
The X travel is 16.6 inches and Y is 6.4”,
this is more then stock! Not sure about
Z but it also has more then stock.
I will be posting more pictures and details
soon.
Bob