A “many Pictures Few Words” Sieg Super X2plus Mill Cnc Conversion

petcnc

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A. Mill description

Sieg SXL2 Plus is the common X2 Hi Torque Solid Column Mini Mill, sold worldwide with many variations and under many different names. Different companies sell their variation with their brand name. In my case the SXL2Plus has the 500 Watt (0.67 hp) brushless spindle drive motor, a 3MT spindle but instead of the regular X2 mill table it has the extra long table from the X1 mill.
SIEG_SX2L1.jpg
The Sieg SXL2 Plus mill

1st.jpg
My mill

The company that sells it over here in Europe is ARC Eurotrade (I have no association with them) and the main reason I bought it was the extra long table and the powerful motor.

After the long journey of making modifications in order to make it a precision tool (mainly tramming without shims http://www.hobby-machinist.com/posts/268607/ adding bearings to X&Y feed screws and reducing backlash to Z fine feed mechanism) I decided to convert it to CNC.


B. CNC JOURNEY


My initial research lead me to categorize the CNC journey into 4 main categories

1. acquiring the necessary parts
2. make the necessary parts and modifications
3. test and verify the system
4. fit the parts to the mill


As the mill is used mainly for hobby, I tried to keep the costs as low as possible without sacrificing quality and functionality of the whole project.


B1. Parts & costs

I ordered in the last 24 months the following parts:

EUR 45 1x TB6560 controller that proved to be an adventure by itself to make it work as it should (read the full story here http://www.hobby-machinist.com/threads/retrofitting-the-famous-tb6560-cnc-board.34352/).

EUR 63.00 3x NEMA23 stepper motors 57BYGH56-401B (12.6Kgcm 1.8Degre 4Leads 56mm)
EUR 32.68 1x L500mm CNC SFU1204 BallScrew with Single Ballnut End Machined STS (for X axis)
EUR 22.27 1x anti backlash ballscrew 1605-350mm-C7 (for Z axis)
EUR 23.95 1x anti backlash ballscrew 1605-300mm-C7 with end machined (For Y axis)
EUR 1.59 10Pcs 18mm x 10mm x 5.5mm Silver Tone Metal Ball Thrust Bearing
EUR 10.79 8P 4 Pin Male & Female Diameter 16mm Wire Panel Connector GX16-4 Socket Plug AR (to connect the motors to the controller board)
EUR 8.11 PY4: 3x mm PITCH HTD TIMING BELT PULLEY
EUR 28.00 3mm HTD® Timing Belts 6 mm Width (2 belts 285 mm Length + 2 belts 267 mm Length) ( £ 19.03 About € 28)

EUR 3.26 1pcs 3A Analog Panel AMP Current Meter Ammeter Gauge 85C1 0-3A AK (for the power supply unit)
EUR 1.39 1pcs RED LED Panel Meter Digital Voltmeter DC 0-99.9V new (for the power supply unit)
EUR 7.11 4x IC TOSHIBA ZIP-25 TB6560AHQ (to repair the broken controller board)

TOTAL COST € 247,15

TB6560 Board.png
The TB6560 board

Ballscrews1.jpg
One of the ballscrews (Y)

Bearings.png
X&Y bearings

motors.JPG
NEMA23 stepper motors 57BYGH56-401B

Motor pulley.JPG
Motor pulleys

timing belts.JPG
Belts

Voltmeter.JPG
Voltmeter

Ammmeter.JPG
Ammeter

...To be continued...
 
B2. Z AXIS PREPARATION


COLLECTING IMPLEMENTATION IDEAS


I thought that X and Y axes are pretty easy to prepare for CNC (I was WRONG) so I decided to start with Z axis. For that reason I started seeking ideas on easy and reliable ways to convert it.

First idea from several kits: Z ballscrew on the right side of the head
Z Side ideas.JPG
I did not like the idea of a ballscrew hanging next to column though, plus the mill seemed to me “out of balance”.


Using the existing fine feed mechanism was not a good option either due to the massive backlash the fine feed had.
Z Using existing Fine feed idea.JPG
Using the existing fine feed mechanism idea


Next idea from Hoss: ballscrew between head and column
Z Hoss Idea.JPG
I liked the idea but I had a small problem: Hoss had the mill with the old thin & tall motor that leaves plenty of space between motor and column. My hi torque motor is too close to the column to apply this approach.
Z No space for Hoss idea.JPG
So I was looking for a different approach... then I noticed the large hole of the hollow column...

A large hole to use for Z ball screw.JPG
many people use the column hole to place in it the air spring when they convert the mill from torsion spring to air spring.

I have no intention to change the stock torsion spring for an air spring
Z Keep spring mech.JPG
The stock torsion spring mechanism.


Moreover with this design of the ballsrew inside the column, the ball screw will be protected from debris...


So back to the drawing board... Making blueprints for the implementation.

Z axis mounting.jpg
The motor will be installed on the top of the column and drive the ballscrew through a timing pulley. The stepper motor and pulley mechanism will be secured on 3 aluminum plates bolted on the top of the column.


..... to be continued...
 
FROM Z BLUEPRINTS TO IMPLEMENTATION


installation of the timing pulley and the ball nut needed some work around as In my design the ball nut would be rotating driving the ballscrew up and down and the ball screw will be connected to the head driving it up and down.

Z axis mounting nut.jpg
My design of the ballscrew implementation


To achieve the above implementation I needed to machine threads on the ballnut in order to screw a security nut at the bottom of it.


As you can imagine the ballnut is made of HARD STEEL. Too hard for the tools of my little lathe to be able to make threads on it. Using conventional threading tools (with inserts) I barely managed to scratch the surface of the ballnut on my 7X12 lathe.


So I was seeking a better tool for the job...


Some head scratching later, I managed to thread it using my dremel tool and a disk instead of a conventional threading tool on the lathe (the full story here http://www.hobby-machinist.com/posts/260477/).

Z nut before.JPG
Ballnut before threading

Z nut after.JPG
Ballnut after threading

Z nut threading.JPG
Threading procedure.

Z nut Security nut.JPG
“Security nut for ballnut

Z nut with security nut.JPG
ballnut with security nut on it.

Next I prepared the column to screw the supporting plates on it

Z column top preparation.JPG
Drilling and tapping the column

Z column plates fit.JPG
Column with plates on it

... To be continued...
 
Great problem solving!! I like it.
 
CONSTRUCTION OF THE TIMING PULLEY.


The problem with a conversion of my mill was that I did not have access to another mill in order to machine parts for the conversion. So the mill needed to be used manually to make the parts. This necessity lead me to design the conversion in a way that the mill could be used manually during the conversion especially for the Z axis.

To make the 72 groove pulley I started by cutting a round aluminum part

Z cutting pulley.JPG
HARD work!!!

Then, calculated the dimensions
X&Y Pulleys distance.jpg
Dimensions calculator.

And machined the pulley...
Z making pulley.JPG
Machining the grooves


I followed the “one pass” procedure as I was not sure that I could avoid mistakes making several passes. I used a “special tool” for the job made from a “concrete nail” as we call them over here (a nail designed to penetrate concrete).
Z pulley cutter.JPG
My “special tool” in action


Pulleys ready
Z & X pulleys.JPG
Z (72) and X (36) pulleys. Some minor mistakes in calculating rotation angles during construction left a few grooves wounded.


Testing the pulleys with the belts.
Z Testing belt fit.JPG
Seems ok!

Testing the motor fit
Z testing motor distance.JPG
Looks ok as well!

Z ballscrew closup.JPG
Column with plates, timing pulley and ballscrew in place.

... To be continued...
 
CONNECTING THE HEAD TO BALLSCREW.


My initial thought was to make a “crane like” construction to connect head with ballscrew as I have seen it in some CNC kits.

Z My initial Idea.png
After sketching it I hated it so I looked for something less bulky and more “elegant”.

Looking in my scrap bin I noticed some long engine rods that connect engine head to engine body...
Z engine rods for head.JPG
They were exactly what I was looking for.

The only problem was that they are custom made for the particular engine and they were threaded in an uncommon 9X1.5 mm.

If I use it I had to make some 9X1.5 nuts for them...

A few cuts and grinding later I had the tap ready.

Z 9mm tap.JPG
And with the tap I made some nuts for the rods
Z 9mm nuts.JPG

Next the Rods were cut to length and threaded at other end
Z rods ready.JPG

Then they were connected to the head. On the fine-feed mechanism at the right side.
Z Fine feed with rod on mill.JPG

on a custom made plate at the left side of the head
Z left side rod connection to head.JPG

Finally both rods and ball screw fitted on the mill
Z ball screw & rods fit.JPG

They look a bit strange as they nearly touch the ceiling at full up position
Z ballscrew & rods up to the ceiling.JPG

Next I prepared the ball screw end for rod connection
Z screw end transform.JPG

and connection of rods and ballscrew through an aluminum block
Z screw & rods connection.JPG

And the motor in its place as well

Z screw rods & motor.JPG

A close-up of the final assembly.
Z screw rods & motor2.JPG

That concludes the Z axis.
I will upload next the X & Y axes.

Thank you for reading this

Petros
 
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