Axminster RF40 - CNC and other modifications

Thought I might share my journey of modifying my RF40. I bought this machine from Axminster tools and shipped it to the UAE where I am currently working. The machine had to fit into a 20ft shipping container which was converted into a workshop - so I was limited on the size of machine I could use. It soon became apparent that this mill has many limitations - which I have slowly been whittling away at.

The backlash on the leadscrews was so large that using the dials on the axes was no good for anything requiring precision. The first modification was to install linear scales (bought from China on ebay).

It wasn't long after that I decided to fit stepper motors (also bought from China on ebay). I used a kflop CNC controller which helped to reduce the issues with the leadscrew backlash using feedback from the linear scales.

The first photo shows the mill in this configuration (sorry - I'm rubbish and remembering to take photos).

Attachment 16315

The Z axis drove the drill downfeed via the rack and pinion mechanism built into the mill. This was hopeless under CNC control due to the backlash in the mechanism. More of that later....

In the end I gave up with the ACME leadscrews and poor quality bearing blocks (which contributed to the backlash) and fitted ball screws to X and Y axes (also from China on ebay)

Attachment 16316Attachment 16317Attachment 16318

Now I am dealing with the real issue with the RF 40 mill - the round column. As anyone that owns one of these machines knows - every time you move the head you lose your Zero.

So here are a few photos of manufacturing a new boxway column for the mill.

Attachment 16319Attachment 16320Attachment 16321Attachment 16322

This project is still ongoing - so I'll post updates as it progresses.

All of the modifications outlined above (other than the clever bits) are made from scrap steel from my day job (we build pressure vessels, steel structures and piping for a living). So whilst it has taken a lot of manhours in machining and design - the cost of getting the machine to the state it is now would be a lot less than buying a CNC mill. The machine is now accurate in X and Y to +/-0.005mm and will hopefully be as good in the Z axis by the time I have finished !

very nice job,
Where is the project? I have a very similar machine and i'm curious to see how you turned the round column into a square one.

thx

Hi - Actually I'm in Paris as I write this - but for one day only ! The milling machine is located in a converted 20ft Shipping container in Abu Dhabi at the moment.
I have finished the project now - and it works well - I'll upload some photos on the thread. I modeled the column in Solidworks before I started - so if you have that software - then I can send you the files.

Here's an update on the completed project:
Attachment 18082
Machining the Z Axis Carriage - This is the part where the milling head mounts onto.
Attachment 18083
The completed carriage.
Attachment 18084
Trial assembly of the carriage onto the column with the stepper motor on top

Attachment 18085
Lifting the column onto the mill.
Attachment 18087
The completed column mounted on the mill - with the milling head installed.

I found that this installation is much more rigid than the round column. The stepper motor moves the milling head up and down smoothly using the ballscrew concealed inside the column (I was slightly worried that the motor would not be strong enough - but this works fine). I can now take bigger cuts at higher speed and with less vibration. It is so much easier to step drill a hole - because you can just keep raising the head as the drills get longer, with no fear of losing your position.

I will send some more photos later of the machine working in full 3 axis CNC mode.

amazing work! and I guess you didn't use a other milling machine to make the job?
I don't use solidwork, I use Catia, maybe you can send me a compatible file :)
The big difference between our machines is that in mine I can't rotate the head around the Y axe
but I really want to try such a modification. I'm also interested in converting to CNC.
thanks for sharing your work

First, thanks for doing this, it gives me some different views.
So, if I'm following, you completely discarded the round column, built a new square column, and mounted the head to that. Is that correct ?

What did you use for the main Z drive ? Guessing a pretty massive ballscrew..

Also, if you happen to know the dimensions, it would be greatly appreciated. I have been trying to figure out this issue for some time !