Aluminum Bench Top Mill

[siam]

Although still a work-in-progress, my little bench top Mill is nearly finished. For several reasons, I wanted to keep the overall weight down as much as possible so I used 1/2" thick aluminum for most of the frame; I even used a few pieces of surplus stock (the black and brown anodized parts are all surplus). All 3 stepper motors are 3.6V/3A/1.8 deg NEMA 23, and have more than enough power; the mill head assembly weighs approx 25lbs and the Z stepper easly moves it up at a respectable rate.


I decided to buy the mill head instead of build my own from scratch; the mini-mill head assembly has an R8 spindle, 1/2HP DC motor and variable speed control box. You can see the adapter box I needed to make to attach the mill head to the Z saddle in the side view below. The adapter box allows the head assembly to swivle to any angle so I can use the mill as a horizontal mill as well.


I machined hex-nut ends onto all three 5/8" ball screws so that I can easly turn any of the axis manualy with a socket adapter in my electric drill. The red box on the top-rear part of the mill is the DC motor control box and dirrectly below that is a 36VDC @ 12 Amps switching power supply for the steppers.


I still need to mill the T-slots into the Aluminum table, which is 1" x 7.5" x 16" "Jig" or "Fixture" stock which is ground finished to a few thousandths. Design travels are: X - 16", Y - 7", Z -14". I'm not sure how durrable an Aluminum table will turn out to be, which is why I designed the mill so that the table is held onto the saddle with 4 socket head screws and is easly removed and replaced.

The stepper motor control box contains 4 SLAm control boards and the BOB (Break Out Board). I've already modified the box since these pics were taken, by installing a mini-6 connector which brings out the wires for the "stop" sensors that I still need to install.

I will post some pics of the inside of the controler box in my next post.

As I said, this is still a work-in-progress and I have not yet made the time to determine rates of travel for any of the axis, but I will post that info once I know what it is.

[hesham morsy]

excellent work

[skmetal7]

nice. get a belt drive on it, asap! and you might want to enclose your power supply on the back, chips chips chips!!

travels?

[packrat]

@siam, GREAT JOB!!! Instead of 'T' slots, why not drill and tap holes in a 1" center to center pattern? Think of a machining center, thats the way most are made. Again, you can be proud of your work!!

[shedbob]

Thanks for posting pictures and details siam.I agree with packrat turn your table into a tooling plate,it
seems a much easier solution,if slightly less flexible.Can you tell us what the overall weight is,it must
be light with its all aluminum structure.Impressive.

[siam]

all dimensions are inches.

Over all: 18 deep, 28.5 high, Frame base is 6 wide.
Travels are: X - 16, Y - 7.5, Z -14
Table: 16 x 7.5 x 1
Weight: 118.4 lbs (without Table)
Table weight: 12 lbs (unfinished, no T-slots or threaded holes)
Total w/Table: 130.4 lbs

Steppers: Model # 57BYGH405A, NEMA 23, 3.6V @ 3 Amps
Power supply: 36VDC @ 12Amps

Controler boards from PMinMO.com; 4 SLAm boards set for 1/16th micro-step (based on Allegro SLA7062 chip) and one BOB.
Old Dell Insperion laptop running Mach3

[siam]

Skmetal7, First, I just finished reading through your X2 conversion thread from a few years ago, and you do very nice work.

You recomended that I convert to a belt drive and I'm guessing that you have some experience in this area, so why use a belt instead of replacing the plastic gears with metal gears? Besides a quieter operation, what advantages does a belt have over metal gears? Do you ever get chips in your belt assembly?

[siam]

Here's an up-to-date pix of the control box; I added a small mini-6 connector which brings out wires for +5V, Ground, and the 4 e-stop wires from the BOB. This is the same type of conector used on older style keyboards & mouses, and pre-made cables with male connectors on both ends are easy to find, and cheap. The small black Junction Box seen on top of the larger control box will be mounted permantly to the frame of the mill and contains the same type of screw-down connectors that were located on the BOB. Wires from the Mill's e-stops will go into the junction box, which is then connected to the Stepper control box via the dirty white cable shown coiled on top the control box.



A peek inside the control box shows the 4 SLAm stepper driver/control boards and the BOB.



The Junction box is much less crowded on the inside than the control box. I plan to use Hall sensors instead of micro-switches for the e-stops/home position sensors, which is why I brought out +5V and ground wires along with the 4 "switch" wires from the BOB.

[aarggh]

Fantastic job! Very impressive work. Have you posted any videos of it in action, i'm particularly interested in the Z axis motion.

cheers,
Ian

[siam]

Sorry Ian, no videos yet,...I'm barely able to post pictures, and I dont think I'm doing that right; I end up with thumbnails at the bottom of my post,...not sure why.

I can tell you that the Z motion moves just as fast as the X & Y. Initialy I was concerned that I might need to make a counter weight system to help the motor lift the 25 lb mini mill head assembly, but when I tested it using Mach3 I tryed to stop the UP motion by pushing down, HARD, with my hand, and I could not cause the motor to even skip or miss a single step. I absolutely must install e-stops, 'cause this thing is scarry strong!! I did not expect this kind of power from stepper motors.

BTW, I'm still learning how to use Mach3 and the only tests I've run were before I purchased the full license which (I think) allows you to set up even faster clocking speeds that may allow the motors to spin even faster. If someone has experience with this, please let me know.

[HorridHenry]

Hi Siam

Not impressed with the control box,this is far too cramped for the drivers and BOB,even though you have a small fan in there I don't think it will be enough to circulate cool air and the main chips on the drivers do get considerably warm/hot when under constant load.

Even its case I cannot see any venting to blow out warm air.

[siam]

The inside of the stepper controler is actualy a lot less crowded than the top view photo might lead you to believe; beneath all those ribbon cables is mostly empty space.

Below are a few more pics of the bottom of the controler, outside and inside. The fan blows air into the center of the box and the air is then forced to make a U-turn along both sides and exit the box through the two rows of vent holes on the bottom. The vent holes are on the bottom of the box to help prevent chips from entering; the fine mesh screen covering all the holes is there to help keep out insects and spiders that just love building there homes inside electronic boxes.

HH (aka HorridHenry) are you using PMinMO's SLAm boards or Allegro SLA7062 chips to drive your steppers? What size heat sinks have you used and at what current and voltage are you driving your motors?