RF-30 clone CNC conversion- picking up where someone left off- need some guidance pls

[Ve7kilohertz]

Hi guys,

My first post here on CNC Zone and my first milling machine, actually second, but the first hasn't arrived yet. I bought a Craftex 30 a few weeks ago, 1999 model RF-30 clone made in Taiwan, dirty but good shape with some tooling and accessories but buried in a garage for a few more weeks. Then last weekend I bought an unused 2010 King PDM-30 again RF-30 clone, Taiwan, that a machine shop bought new and started a CNC conversion but didn't finish, it's been sitting in storage ever since. Missing a number of items for it to work as a manual mill and would be about $600 to restore it to a full manual machine, so I decided instead to spend the money on finishing the conversion.

So, machining is new to me, electronics and computers have been my whole life so that side of it will be easy for me, what I need some help with is identifying what I already have here and what I need to complete the mechanical side of it. I have been reading various build threads and will continue to do so, many of them on this site, but that will take some time and I would to at least start sourcing the parts.

As mentioned the machine is a King PDM-30 and is missing the following key items, 2 hand wheels, X- axis lead screw bearing holder on one end, quill return spring, quill hand wheel, motor, motor pulley, and a few other non critical items probably not needed for the conversion, even the hand wheels are probably not required. What it came with are ball screws already mounted on the original lead screw nuts, the matching lead screws already mounted in the end bearing holders, most of the balls which fell on the floor when I removed the lead screw to get the table off to move it...ARG.

My plan is to find a 3~ motor and VFD it using a single pulley on the motor and still have 3 pulley speeds.

The items I need some guidance on are how to support the end of the X axis lead screw (LS) opposite the bearing end, probably machine another plate to hold a bearing. Should I direct drive the LS or cogged belt and pulleys? Are the ball screws suitable for this machine? They are .2" pitch, forgot to measure the diameter but smaller than the original. I'm thinking of using a similar LS for the quill rather than driving the sloppy fine control with a belted motor.

Thinking NEMA 34 or maybe 27 motors, controllers and such I can work out later, same with computer and software. I have various 24 and 48VDC supplies suitable for the motors, 12-20amps.

I have two lathes and will have the complete Craftex mill/drill machine in a week or 2 so I can machine some of the parts that may be required.

Hopefully I am off to a good start. Look forward to building this and getting some guidance from you fine folks.

More later.

Cheers

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[toyoman]

Those look like pretty small diameter ballscrews, my guess is they were used because the previous owner figured out how to fit the ballnut inside the existing leadscrew mount. You can order all new balls in case you lost any. Nema 23 motors would work just fine. I would gear them down 2:1 with a timing belt so you gain finer control of the table movement. 1 step of a 200 step motor with a 2:1 ratio and 0.200" lead ballscrew equals 0.0005".

[Ve7kilohertz]

Thanks!

I just got in from the shop and measured the ballscrews, they are 5/8" lead dia. and the balls are .125". Yes, the PO did some work to make them fit inside the lead nut, they look like they are threaded in. Nicely done. New bearings in the end plate for thrust and load. When properly setup with a bearing on the opposite end, do you think these will be large enough?

cheers

[rodw]

Hmm, this looks familiar. I just finished one
I just have not taken any decent photos yet
Linuxcnc, 8 Nm ethercat closed loop steppers
Fabricated HMI
400x400mm enclosure mounted at the back.
16mm ball screws
Mist and coolant
Z axis uses the internal rack and pinion. Smaller NEMA 34 open loop cos the NEMA23 I bought did not like running on the larger drivers.

I just left the Y axis ball screw unsupported at the back. It was good enough for the original machine.

I made the parts on my manual Seig SX3 Mill.

Happy to share my experiences.

[rodw]

Just a few more notes. I replaced the single phase motor with a 1.5 kW 3 phase one. I had a 5.5 kW 3 phase VFD on hand so the spindle is 3 phase.
The VFD is controlled by Modbus over a RS485 link
For the belts, I measured the spindle RPM with a tacho and calculated the ratios.
I then wrote a Linuxcnc component that let me select the front and back belt and it scaled the command to the VFD accordingly. So it supports all 12 speeds!
I installed a Masso optical encoder but I don't yet have an ethercat Encoder interface so its not in use except its tested and working.
https://docs.masso.com.au/wiring-and...ptical-encoder

So its really an over the top build

[rodw]

Re your questions regarding supporting the X axis ball screw, I'm guessing you have a 1605 ballscrew (16mm dia, 5mm pitch)
If it has standard machining both ends, you whould be able to use these. One goes at thew motor end, the other floating one at the non-driven end.
https://www.aliexpress.com/item/3288...21ef1802JyXndQ
So the floating bearing is supported in a similarly mounted plate the motor is mounted to.
Here the PCD feature of your DRO is very handy.

[kawazuki]

But be aware that if you restrain both ends of the screws - 1 end driven, 1 end undriven and the ballnut floating to run on screw but held to table, unless every surface is absolutely parallel and square to each other, you will likely experience a degree of binding between nut and screw at extremes of travel. For the majority of people an unsupported undriven end is ok or provide a loose fitting bushing / bearing that allows a degree of axial movement to minimise screw 'whip' more than anything. Also be aware that these round column mills are really heavy duty drilling machines - the column not being truly rigid enough for sustained CNC work ie. if you automate the quill, everytime you manually raise or lower the head on the column, it is possible to rotate the head fractions of degrees so losing your home points or zero points - bear this in mind if high precision is required.

[rodw]

Its not that hard to realign the head with a dial indicator against the quill or if you are really lazy, attach a vertical line laser pointer and align to a mark on a wall on the other side of the room.
I have not had any binding issues with the ballscrew supported both ends with a standard floating bearing at the non driven end.

[Ve7kilohertz]

Thanks for the replies guys! Rod, nice work on your machine, would love to see some more detailed pics.

As for my ball screws, only one end is threaded, and only enough for the bearing preload locking nut, the other end the screw threads just end, no machined surface. Not sure how to drive this, maybe mill the screw end and machine a rod to go over it and use that as the motor end leaving the preload factory bearing plate as is. Not sure if this is metric or inch, measures about .619" OD, balls are .125". There are no markings of any sort on the screw or nut. I see you direct drive yours, I'm still undecided on this.

Yes the round column leaves something to be desired but as mentioned, there are workarounds and I'm not too worried about it.

Thanks again guys, appreciate the help.

Cheers

[Ve7kilohertz]

Here is a picture of the ball screw end opposite where the bearing plate is currently mounted.

Cheers

[Bubba]

I know I am late to this party as I just stumbled across the thread.
I converted my RF30 of the same approximate vintage back when it was new. I have somewhat documented the process on my website:

Mill

I also used the 16mm leadscrews and they have served me well for all these years.

HTH

[Ve7kilohertz]

Thanks Art,

Yes your thread and a few others from about 8-10 years ago have been my go-to for info. I'll look at your site now as well. I know you were key in a lot of discussions back, thanks for the help.

Cheers

Ok I looked at your site and your method is similar to what has been started with mine. The end caps have the thrust bearings already installed. I see you ground down the end of the X-axis screw to mount the motor opposite the thrust bearing, I am planning the same.

What do you think of my ball nut mounts? They have been threaded into the existing brass lead screw nut and look well done. There is only one ball nut per screw, I could add another for some preload or maybe like you did??

I'm going to pickup my second RF-30 clone next weekend so I will have a complete mill/drill to fabricate any plates or things I need, I also have a couple of lathes in the shop.

Thanks again!