[asammons]

Well,
This project has been in the plans for over 2 years and finally I got around it. From solid works to fully functional in less than 6 weeks in spare time.

About the machine:
I wanted to use my existing square column HF 44991 but wanted larger and more rigid table. I have ordered replacement table for HF 33686 round column mill (table, cross slide, base, way guides - $260 shipped on a ship from China) that has table surface of 29 x 9 inches, and married the two.

Mechanics:

• 5/8" x 0.200" rolled ball screws on all axis
• Two ball nuts with adjustable preload (0-125lb) on each axis for backlash elimination
• Custom bearing block with preloaded twin angular contact bearings
• 480 oz-in steppers
• HobbyCNC 4-axis controller
• Toroidal 40VDC 20A power supply

I have successfully ran Mach 3 at 125ipm rapids using unipolar HobbyCNC controller configured for max output - 3A. Initial observations show that the hybrid is substantially more rigid. I was able to attain mirror finish in 6061 aluminum, faster cutting, and substantial reduction in noise. Following "hybridization", final table travel:

• X - 22in
• Y - 8.5in
• Z - 12in

I will install the Z axis for which all parts will be machined using 2D CNC operations with manual control over Z. I will also install an extension on the spindle head to make use of 8.5in of Y travel - stock unmodified 44991 results in 6.5in of travel due to removal of pivoting mechanism which took up over 2 inches of travel....limit switches are soon to follow, soft limits for now.

Cost of conversion if you were to start from scratch:
$499 - HF 44991 square column mill
$260 - HF 33686 table
$50 - separator plate
$40 - precision ground cast square
$210 - screws and 6 nuts
$50 - steel and aluminum
Total: $1,109

And about $5K worth of tools in your garage

Keep in mind that to get absolute backlash-free quiet and reliable movement, precision of bearing block is of paramount imprtance. So is the actual twin ball nut assembly which consists of preloader, retainer, fixator, etc...Cost of making anti-backlash twin ball nut assembly is approximately $45 versus $170 if you were to buy one.

Future things to come:
1. Pneumatic power draw bar
2. Automatic tool changer
3. Lathe attachment
4. And of course, videos!!


Engoy viewing this post!
A.S.

[idtkid]

very cool idea, definitely makes the x2 alot more capable. I bet costs could be greatly reduced if you were to just buy the head and column assembly from littlemachineshop. Did the the "screws and 6 nuts" really cost $210?!

[escott76]

very cool idea, definitely makes the x2 alot more capable. I bet costs could be greatly reduced if you were to just buy the head and column assembly from littlemachineshop. Did the the "screws and 6 nuts" really cost $210?!

Ball screws and ball nuts...

[idtkid]

oh hahahaha i was thinking bolts and nuts :P

What do yo think is the least rigid part of the machine?

[cadmonkey]

Unique idea. I'm sitting here kicking myself saying - why didn't I think of that?!?!

Thumbs up.

Greg

[SScnc]

That's very good thinking !

Nice Job !

[ZipSnipe]

Wow you were able to get that table for $260? Great find !!!! I think it would be even greater to use an X3 column and head with that table !!!!

[hoss2006]

That's a HECK of a lot better than what you would have gotten from cncbridges,
good thing you got your refund early.
I thought about that back then too and got prices from grizzly but they were MUCH higher,
I'll have to remember HF from now on.
How long did it take to get the parts shipped?
Good Job, Hoss

[mrcodewiz]

Looks like a witch doctor shrunk the poor guy's head but I LOVE it. Do you have any pictures of how you pulled the head out from the column?

[kanton]

Excellent!

Please post plans, blueprints and detailed parts list.

[Starleper1]

That's different. I thought alot about how i wanted to make the next best X2 but i realized with the machinery I have access to and knowledge, I might as well make my own Mini VMC. Anyway good work looks good.

[jalessi]

A.S,

Please post information on where to buy the table and the part numbers too.

Thank You

Jeff...

[asammons]

oh hahahaha i was thinking bolts and nuts :P

What do yo think is the least rigid part of the machine?

I believe the least rigid part of the mill is the point of contact between the head assembly and the square column that relies on a shim michanism, held in place with four set screws.

[asammons]

Wow you were able to get that table for $260? Great find !!!! I think it would be even greater to use an X3 column and head with that table !!!!

Well, I wasn't looking exactly. If you pull up a manual from harborfreight.com for the other mill, you can order replacement parts. The total cost of replacement parts in this case was around $260 with shipping, and includes the base, cross slide, and the table itself. They must have pulled it off from another unit, because in my case, it came assembled with one acme lead screw and both brass acme nuts - which I wound up using...simply retapped existing holes with 15/16" x 16 thread to accept the ball nut.

[asammons]

That's a HECK of a lot better than what you would have gotten from cncbridges,
good thing you got your refund early.
I thought about that back then too and got prices from grizzly but they were MUCH higher,
I'll have to remember HF from now on.
How long did it take to get the parts shipped?
Good Job, Hoss

It took about 7 weeks - I ordered parts by calling harbor freight 800 number, they shipped them from factory to warehouse, and delivered on a semi.

[asammons]

A.S,

Please post information on where to buy the table and the part numbers too.

Thank You

Jeff...

Product page link:
http://www.harborfreight.com/cpi/cta...emnumber=33686

Link to edited product manual:
http://skyaerial.com/cnc/33686.pdf

Page 11 of the manual shows highlighted parts that I have ordered. If you get lucky, they will ship a lower assembly that will have all the nuts and screws, otherwise you will have to buy them individually. Also, the manual exploded view shows the parts and corresponding part numbers, in the parts table however, they are designated by a number that is less than exploded view by "1". So, if a table on the exploded view is labeled #141, the parts list table references table as #140 and that is the correct number when you call in to order - do not go by the exploded view!

[asammons]

Looks like a witch doctor shrunk the poor guy's head but I LOVE it. Do you have any pictures of how you pulled the head out from the column?

I do not, however, it is very straight forward. I raised the head all the way up to where it was flush with the top of the column and secured the rest stop directly underneath. I then unscrewed the 4 set screws holding jib strip in place, making the head assembly "loose", and raised it completely up. It is also easier to just take down the entire column, held in place with three screws...it is a lot easier to work with once it simply lays on the table.

[asammons]

Excellent!

Please post plans, blueprints and detailed parts list.

I have not set out on a quest to create a bill of materials with drawings, specs, and detailed blueprints - such task is truly exhausting unless you intend to resell them. Since I have not seen anything similar on this forum, I wanted to share my unique solution with the rest of the readers as a source of inspiration.

Please keep in mind that the design is not based on best engineering practices, but rather a compromise based on what can be readily built using manual machining. I certainly intend on refining it through CNC.

[SCzEngrgGroup]

I do not, however, it is very straight forward. I raised the head all the way up to where it was flush with the top of the column and secured the rest stop directly underneath. I then unscrewed the 4 set screws holding jib strip in place, making the head assembly "loose", and raised it completely up. It is also easier to just take down the entire column, held in place with three screws...it is a lot easier to work with once it simply lays on the table.

I think what he was asking was what, if anything, did you do to move the spindle further away from the column? If you don't move the spindle further from the column, you won't be able to make use of all that extra Y travel. You actually want the spindle to be a little behuind the back edge of the table when the table is fully forward, away from the column. Without doing that, you won't be able to machine a piece anywhere near 8" in Y.

Regards,
Ray L.

[asammons]

I think what he was asking was what, if anything, did you do to move the spindle further away from the column?
Regards,
Ray L.

If you read my original post carefully, I wrote:
"I will also install an extension on the spindle head to make use of 8.5in of Y travel - stock unmodified 44991 results in 6.5in of travel due to removal of pivoting mechanism which took up over 2 inches of travel...."

In essense, because I do not have an extension at the moment, stock 44991 spindle allows 6.5 of usable travel.