Enco (Rong Fu RF30) Mill/Drill Conversion

[cfellows]

I've been talking about this in another thread under Tool Modifications and decided it properly belongs here.

I bought some SFU1605 Ball Screws with Ball Nuts on Ebay a couple of months back. These were threaded end to end so I had fit machined shafting on the ends to adapt them to my mill/drill. The ball screws are hardened but I was able to turn down the end with a carbide insert and finish it off with a small grinder attached to the lathe tool post.

Here are some pictures of the Y-Axis that I've been working on the past couple of days. First picture is the exiting Y-Axis lead screw nut and the machined aluminum replacement that will attach to the ball nut.

Here's the original lead screw nut as it attaches to the Y-Axis Slide.

And here's the aluminum replacement shown in place...

And with the ball screw and nut in place...

Here's the ball screw with the end turned down. I actually had to extend the turned part another 1/4".

Here's the ball screw assembly with the machined extension attached. It was turned from 1" 12L14.

And with the attachment...

And here's a picture of the ball screw assembly in place...

Next I'll be working on the X-Axis...

Chuck

 

[cfellows]

Had to do a bit of fiddling with Y-Axis, including adding about .030" in shims on top of the Y-Axis ball nut attachment. Now it's smooth as silk with no binding.

Today I started on the X-Axis. Here is a picture of the ball screw, nut, and the two 12L14 pieces that will be turned to form the extensions.

That ball is about 1.25" shorter than the table but I don't think the table ever would move to the extreme on either end, so hopefully no real estate lost.

I'm comfortable now that I will be able to finish this project so today I bit the bullet and ordered a Gecko G540, 4 axis controller/driver. It has lots of good features and will drive steppers up to 3.5 amps. I think I will be able to use the MDI functions in the MACH3 Demo to move the axes around manually.

Chuck

 

[stevehuckss396]

I think I will be able to use the MDI functions in the MACH3 Demo to move the axes around manually.

Screw that!! The tradition is to write your name with a felt tip fine point pen. PM me your email address and ill send over the gcode. Board wont let me attach it. Hope you like Times New Roman.

 

[cfellows]

One end of the X-axis now machined and fitted.

Aligns nicely as is, no binding.

Chuck

 

[cfellows]

Forgot to include a picture of the X-axis ball nut attachment fixture. It's made from 2" x 2" x 1/4" angle iron, milled and cut to shape.

The contact surfaces are also milled flat and square to each other.

Chuck

 

[kuhncw]

Chuck, I'm enjoying your posts on converting your mill drill to CNC. I think you will be surprised at how much use you will get out of it, even for one off parts.

At the absolute very least, operating in manual input mode, it will be like having a smart power feed on your mill.

Regards,

Chuck

 

[cfellows]

Chuck, I'm enjoying your posts on converting your mill drill to CNC. I think you will be surprised at how much use you will get out of it, even for one off parts.

At the absolute very least, operating in manual input mode, it will be like having a smart power feed on your mill.

Regards,

Chuck

Thanks, Chuck. I've always felt like CNC was a money pit that I didn't really need. However, being a tinkerer and a lover of all things mechanical I've longed to have a CNC setup for many years. I finally decided that having the manual input movements would tip the scales in favor of having it, so here we go.

So far I have about $650 invested and I'll probably buy Mach3 which will be another $175. Hopefully FreeMill, which is free, will take care of my CAM needs.

Chuck

 

[cfellows]

The mill/drill is back in play, ball screws and nuts installed on the X and Y axes.

Both axes move freely with no binding and no discernible backlash. Now I gotta start on the stepper motor mounts and finally, what to do with the Z-axis.

Chuck

 

[Herbiev]

Great work Chuck. Looking forward to the z axis mods.

 

[cfellows]

Thanks, Herbie.

Got started on the Z-axis mount. Here's a picture of what will be the stepper motor mount. It's 3.625" x 5.25"

I decided to mount the plate on the face of the Z-axis crank assembly.

I don't think two, 10-24 screws is enough support, so I decided to add a couple more.

Here I'm making a drilling jig to bore the two extra holes in the casting.

It will also serve as a drilling guide for boring the mounting holes in the aluminum plate.

And here is the casting with the two addition threaded holes.

Here's the mounting plate with the mounting holes in place.

Next I'll need to machine the mounting holes for the stepper motor and finish machining the contours around the outside.

Chuck

 

[LSEW]

Chuck, Looks really good so far. I was wondering, have you thought about what you will be using the mill for? From what I've seen on your Z work, it appears you were not planning to use a ball screw. If you want to do any 3D work, you may wish you had spent the time. Just a thought. Keep up the good work.

maury

 

[cfellows]

Chuck, Looks really good so far. I was wondering, have you thought about what you will be using the mill for? From what I've seen on your Z work, it appears you were not planning to use a ball screw. If you want to do any 3D work, you may wish you had spent the time. Just a thought. Keep up the good work.

maury

Thanks, Maury. I do plan to do some contour work which will require the Z-Axis to work with minimal backlash. The quill is spring loaded and I can increase the tension on it if I need to. If that doesn't work, I can always go back and change it although I expect that would take an inordinate amount of effort.

This morning I finished the Z axis mounting bracket.

I would liked to have done it on the Tormach down at the TechShop, but I'm still struggling with getting a drawing processed all the way through FreeMill, the free CAM program I'm using for the moment. So, I just machined it manually. Boy, you're right about the axes unwinding on you if you don't have the locks clamped down nice and tight. Even with a 3/16, 2 flute endmill running at pretty high RPM I could see the slot beginning to creep sideways on me.

 

[cfellows]

I'm pairing 20 tooth with 48 tooth pulleys on the X-Y Axes. I need a smaller pair for the Z axis and happened to have a 15 tooth pulley for the motor so to keep the ratio the same as the other axes, I needed a 36 tooth pulley. I know it's not necessary to have the same gear ratio on all axes, but I like consistency. I didn't have a 36 tooth pulley on hand and I didn't want to pay the outrageous price for one, so I decided to make one. Here's a picture of the blanks I turned.

I already had a cutter I had made a number of years ago from a 1/8" slitting saw. I had beveled the edges to the proper angle and used it once before to make another pulley. Here it is chucked up in the mill, teeth already cut. I'm using my Arduino powered dividing head to index the blank as I gut the gulleys.

Unfortunately, I cut two of the gulleys twice as deep as they should be. I had forgotten that my ball screws move the axes twice as far as before! Made the correction and cut the rest of the teeth. I don't think it was make much difference.
Here's the (nearly) finished pulley.

Still need to bevel the edges of the teeth and bore out the hole in the center to the correct diameter.
I also just realized that the electronic dividing head will make a nice 4th axis when I everything up and running. Guess that 4th axis on the G540 will come handy after all!

Chuck

 

[cfellows]

Got the X-Axis motor bracket nearly finished. Here's the part that attaches to the mill table, with clamping screws drilled, tapped, and mounted.

And here it is with the motor attached.

Will trim off the bottom part of the motor bracket later when I get closer to finished with the project.

Chuck

 

[cfellows]

Still plugging away on this thing. I've spent the last few days experimenting with a couple of new Y-Axis bearing blocks. I'm not happy with either one, so I'm back to using the original casting. I am, however, replacing the two thrust bearings with somewhat larger angular contact bearings, back to back, to handle the side thrust from the belt tension. Won't receive those until Tue or Wed, so I've been filling in with other parts.

Here's a picture of the Y-Axis motor mount (so far). Still have to make the part that attaches the motor to the arm.

Some folks on the CNCZone forum have expressed concern about the size of my steppers. Hopefully they will be beefy enough if I don't try to coax too much speed out of them. Otherwise, I may have to move up to Nema 34 motors with a higher torque rating.

Chuck

 

[stevehuckss396]

Some folks on the CNCZone forum have expressed concern about the size of my steppers.

Chuck

The guy's at the zone expect results like a real production machine. Just get the best rear ratio physical size will allow. Put the biggest gear on the screw as you can and not hit anything, and put the smallest pulley on the motor as you can. That will give maximum torque. you wont have big speed for rapids but you will have the torque for cutting. Your not making 1000 of anything so who cares.

If I remember correctly you have Gecko drives so if you want to post up the motor specs I can calculate the best input voltage to your drives, for your motors based on the inductance of the coils. Thats if you haven't done it. That will also improve torque through out your RPM range. The higher the RPM the greater the benefit.

 

[cfellows]

If I remember correctly you have Gecko drives so if you want to post up the motor specs I can calculate the best input voltage to your drives, for your motors based on the inductance of the coils. Thats if you haven't done it. That will also improve torque through out your RPM range. The higher the RPM the greater the benefit.

Thanks, Steve. The motor inductance is 6.8 mh per phase, 1.6 ohms resistance and are rated at 3 amps. The holding torque is 280 N cm which converts to about 396 oz in. I bought a 24v, 15 amp power supply specifically for this application, but could buy a different if there would be a significant performance boost. The driver is a Gecko G540 and will handle up to 50 volts DC for the motors.

As you said, speed is of little consequence to me. I have 20 tooth pulleys for the motors and either 48 or 60 tooth pulleys for the ball screws.

Here's the Y-Axis motor mount. It will be attached to the mounting arm with two 5/16" bolts through the 1 5/8" long slot. The bolts will be 3/4" apart which will give me 3/4" belt adjustment.

I realize this could still slip, but with two bolts holding it, it should be much more secure.

Chuck

 

[shepdog]

Excellent work...I've been hemming and hawing over CNCing my busy bee 1997 mill...don't suppose you have any saved drawing's you'd care to share?

 

[canadianhorsepower]

I think I will be able to use the MDI functions in the MACH3 Demo to move the axes around manually.

Mach 3 has a nice jog mode, just tap your tab key and it will come up

 

[LSEW]

Chuck, that is good placement for your "Y"motor. Good thinking. On my conversion the pulley for the "Y" limits the travel a little, making parts with just over 8" in the "Y" impossible.

You may want to also check out the pulley size for the "Y" so this doesn't happen to you. You will want all the "Y" you can get.

maury