DV-59 Hardinge Lathe going CNC

[rrossey]

DV-59 Hardinge Lathe going CNC

I started under another thread. A member gave a good suggestion to start a new thread, so here is the first posting.

Hi!
I am new to this forum.
A few details first:
Location: Montreal, Canada
Objective: To learn and have the basic insight of CNC
Project: To convert a Hardinge DV 59 manual lathe to CNC lathe
Material to machine: Stainless Steel 316
Size of Components: About 75% of the items will be 1” dia or less with a max. length of 2” and the remaining 25% can go up to 2.5” dia and 4” in length.

I propose to complete this project in two phases

Phase I
I will keep the head and spindle of the DV 59 lathe as it is, driven by 1 HP induction motor.
The bed of this lathe is having a longitudinal slot in the middle of the bed and chamfers through out the length.
The existing Hardinge cross slide can be moved and fixed on the bed of lathe. Due to the size of this slide, I do not like to modify this slide but intend to proceed as follows:

1. To purchase an imported heavy duty mill & drill table (sold on ebay item # 7578353458) The table has11” longitudinal and 7.5” cross travel
2. Remove both the lead screws and replace with rolled ball screws and two nuts on each screw. The screw size will be ¾” or 5/8” dia depending upon the available space to mount nuts.
3. The guide ways of the cross table slides will be scraped and improved upon as required, to a reasonable condition.
4. Stepper motors will be mounted on both axis of the table, directly coupled to the ball screws if space permits, or else through timing belt and pulleys. The torque of motors will be decided depending on the condition of table.
5. The table is to be mounted on the lathe bed and fixed to the bed so that the cross slide - 7.5” travel of the table is Z axis of the lathe and the longitudinal slide -11” travel is X axis.
6. The above arrangement will give sufficient place on the longitudinal slide of the table to mount three or four tools and possibility of mounting a live tool also.
7. Initially the setup will be tried for drilling, boring, turning and facing operations only, with the spindle running with the existing arrangement of induction motor drive.
8. The spindle axis is at 4.5” height from the top face of the bed whereas cross table height is going to be 5” when fixed on bed. So for initial trials the tools will have to be mounted in special tool holders to match the spindle axis. Alternately depending on the dimensions of the longitudinal table, holes can be drilled and reamed in the side of the table so that the tool mounting arrangement is similar to the Hardinge turret tool mounting system.

Phase II
On successful completion and testing of the above, I will proceed to raise the height of the spindle head by providing spacer on the bed and the spindle will be driven by a servo motor of suitable power. This will enable to cut threads and provide full CNC capability.

Thanks,

RRossey

[rrossey]

The mill and drill table is expected in two or three days. I will open it up to measure the available space for mounting ball screw and nuts.

A concept drawing is attached to show how table will be mounted on the lathe bed.
The spindle head will be raised by providing a spacer above the bed.

[rrossey]

The imported mill and drill table purchased from ebaystore.

[Ken_Shea]

Loooooking good rrossey

I see what you were referring to on the slot in the bed, that should come in very handy, is it wide / deep enough to accommodate the screw ?

There are three or four of us doing similar conversions with enough variations for plenty of ideas for others who are considering this, so I am very happy to see you start your own thread/conversion log.

Ken

[djshop]

I built a small lathe using a precision x-y table and stepper motors that I use every day. I primarily turn wood with it so I left the leadscrews in to see how well it would work - good enough for what I need. Someday I will replace them with ballscrews. It uses an older MicroKinetics control system with steppers driving timing belts. The tool changer is a manual turret off of an old Logan 9" lathe that I have. The headstock is from an old photo engraving lathe. I use a 1-1/2 hp 3 phase motor and a VFD. A real pile of parts works great. All this to say... Go for it!

[djshop]

I tried to include pictures in the last post.
try again.
Not shown is the tailstock or dust control enclosure.
dave

[rrossey]

Nice job DJSHOP.
What is the torque of stepper motors?

[rrossey]

Ken Shea
The slot width is 7/16" and 22" long, it goes through the full depth of bed between the two supports of the bed. It can not accomodate the screw, but is good for bolting the cross slide table. The position of the table can be shifted/adjusted as per the job length, if required.

I received the cross slide table. I can fix 5/8" ball screw but some machining will be required to accomodate the rectangular ball nuts.

[djshop]

The steppers are 1125 oz-in motors from Microkinetics (www.microkinetics.com) I found the complete retrofit system on eBay which included the Microkinetics controller, computer+software, two stepper motors, some mounting hardware and all of the cables. The z axis is lifting quite a bit of weight with the slide and tool turret so I am glad for the beefy motors.

[rrossey]

The first view shows the cross table assy with new end plates fixed to the top table and blue coloured ball screw end projecting out. The ball screw will be 5/8" dia with sq. ball nuts.

In the second view, the top table is removed. The green coloured ball nuts are fixed to the red coloured block that is bolted to the cross slide.

Due to the limitation of space, the ball nuts must be fixed in this position. So the preloading has to be done to get this particular position, probably by providing shim washers, by trial and error.

Any suggestions?

The ball screw is mounted in the two end plates in two angular contact ball bearings # 7202: 15mm x 35mm x 11mm. Again the shims and spacers are to be provided to eliminate back-lash.
Another alternative can be to provide both the angular contact bearings on one side in a thicker housing, that is the motor mounting side, eliminate the back-lash and mount a plain roller ball bearing on the other side.

Which is the better way?

[djshop]

Looks good. shims will work. One suggestion: only "fix" one end of the ball screw with your angular contact bearings. The other end should just be supported by a plain bearing and allowed to "float" a bit along the length of the screw. This is because of possible changes in rates of thermal expansion.
dave

[NEATman]

rrossey-
Nice Lathe! I have the exact same model, except mine has a turret tailstock.

Regarding the preloading of the ballnuts, you can use the thread of the screw to your advantage. Solidly mount the nut closest to the motor, just as you have shown. Next, mount a block to the rear ballnut, but allow it to freely spin with the nut up and down the screw. When you turn the second nut and block toward the solidly mounted nut, it will contact the red mounting block. Now, it you make the block that is attached to the free ballnut spring loaded with a torsion spring, it will hold the "free" ballnut against the red block. This is the same effect as having two nuts on a piece of threaded rod. If you tighten them against each other, they each press against a different side of the thread. This is the same effect, just fine tune the torque, and there will be a constant, automatically adjusting preload on it.
http://www.kerkmotion.com/learn/kerk...h-overview.asp

As far as the bearings to support the ballscrew, you should have a preloaded pair at one end, and a radial bearing at the other. If you were to put one angular contact bearing at each end, it would be tough to remove the backlash. Also, as the screw heats up from continious running, it will expand, and possibly bind the bearings at the ends. Using one pair at one end and a radial bearing at the other allows the radial bearing end to expand axially.

What software are you using? Could I get a copy of your model? Perhaps a IGES or Step?

Do you have a collet closer for your lathe?

This is what mine looks like...

Neatman