Converting Rong-Fu 25

[adryan]

Hi all,

first a small introduction
I'm Adryan, studied for mechanical engineer (graduated 8 years ago) and work with my RF-25 mill and a lathe as a hobby. I also fly homebuild model turbine driven airplanes...enough for the introduction

After seeing the site of Jeff Davis, I decided to convert my mill to CNC.
The mill I have is a Rong-Fu 25 with a 1 bhp motor. It's one of the old models with a steel v-beld protection cover. I bought this machine second hand 3 years ago for $650.

I order the drawings and found out they didn't fit to my mill. The sizes of the RF-25 are quite a bit smaller.
I redraw most of the drawings using the drawings from Jeff as a guide and made some minor modifications (e.g. preload to the ballscrews)

Here are some pics of the rebuilding of the mill I'm starting this week.
-I cleaned-up the base and the x-y table
-I lapped the ways.....I know it's not everybody's favorite, but I'm very pleased with the result!
-Next was the priming and painting.
-Installing the x-y ballscrews

[Runner4404spd]

any chance of getting some more pics. also, i've got an RF-25 and was waiting to disassemble it to measure all the mounts for the ball screw nuts. if you can email me those drawings i would appreciate it. it will save me from disassembling, reassembling, machining, then reassembling and rebuilding.

jczub at hotmail dot com

[adryan]

Here are some more pics of the controller box I have made for it and of the parts for the conversion.
One thing I remarked when I removed the round colum, the were some thin shim plates beneath it. Has anyone seen this before on a RF mill?

[Runner4404spd]

yup, i had the shim plates beneath mine as well. i also had shims where the bearings go for the handles on all three positions.

[Chris D]

The shims are put in to make the colum square to the table. When you re-assemble the machine, you will have to tram the spindle to the table. Make adjustments with shims in the same place.

Couple of questions...

What is that white stuff at the ends of the ball nuts? I realize you are using it for a wiper, but what is it?

You are using DB9 pin connectors for your steppers? If so, are your motors at a low enough current where they won't heat up?

Keep posing the photos and information! It's a great big help to those of us in the planning stages of such a conversion!

Thanks

Chris

[adryan]

Chris,

the white stuf is silicone. I first applied some oil to the screws then put the silicone on it. Let it dry overnight and than you can twist it gently and the "joint" to the screw will break.

The connectors I'm using for the servo's are speakon conenctors (see picture they are rated 20 Amps)
the sub-D 9 pin are for:
-encoder (one each)
-limit switches
-emergency switch
I also have 4 euro connector outputs for mill motor/pump/.../...

Today I worked some more on the mill and installed the limit switches for the y-axis (using microswitches ,IP65 sealed) and shielded cable.
This is also a litlle bit different to the plans from Jeff, but I didn't like having the cables/switched beside the y-slide.
I also made a lubrication connection to the bearings/ballscrews for central lubricating

[adryan]

Time for the next part,

I installed the limit switches for the x-slide (on the inside of the table so you don't see anything on the outside)
You can also see the lube line comming into the table for the bearing and the slides.
I also took apart the head of the mill, so I can grind it and repaint it. The top bearings in the v-belt pully are worn, so I have to replace them. I also think the bearings of the spindle are worn/dry because I can hear them ratling.
Does anyone know how to take the spindle apart? at which side should I start, and what an I expect?

[Runner4404spd]

i've taken my spindle appart plenty of times. you need to loosen the two nuts that are in your last pic on the previous thread. unscrew those and the spindle will pull out. on the bottom of the spindle the collar is screwed on not pressed on. the bearings are tight on the spindle and will probably need to be pressed off. i would tell you what bearings but mine might be different than yours.

[adryan]

spend another 6 hours today on the mill...
I cleaned all the paint and plaster from the head and painted it. You can also see the extra holes I've made for the cables from the encoder and servo.
Also in the front of the head is the enlarged hole for puting the Z-axis servo assembly in.
I took the spindle apart and found there were some fine chips in the lower bearing. After cleaning everything the bearings are still o.k.

[adryan]

some more work done this weekend....
I installed the z-axis servo inside the head, also the microswitch is inside.
I replaced the 3-wire cable for the power supply with a 5-wire so I can use one cable instead of 2. The power supply wire goes to the box on the motor.
..hope do do some sest runs next week.

[ngr1]

Hello, your conversion looks great!

Can you please provide more details regarding you oil/lube configuration for the ways?

I am beginning to see more examples of this but no one has provided any details regarding its design and operation.

Thanks... Norman

[adryan]

Today I did some tests with the mill for checking the backlash.
on the X-axis I had 0.02mm (0.00078") and on the y-axis 0.06mm (0.0023").
With the z-axis I could very much notice there's no preload on the ballnuts. I had a random backlash from 0.05 till 0.1mm.
I tried fitting the spring (see picture) to create a preload on the nut, the backlash changed to a constant 0.05mm (0.0020")
Does anyone know if these values are normal, or can they be improved (tuning the servo's/increasing the preload)??


Norman,

I just grinded a z-shaped slit in the ways as can be seen in the pictures. The slot is about 2 mm wide and 0.5mm depth. I drilled several holes through the table base to get the possibility to connect it to a central lube-tube.