Hello...
I have had a Knee Mill for a few years (pic below) and have often considered converting it to CNC.
The problem to me has always been how to convert the X Axis. Moving the knee is too heavy, moving the quill reduces Z travel and has some rigidity issues.
I like the machine as it is robust, has good solid tables and enough X & Y travel for my needs but it is manual.
This afternoon I sat down and had a good look at it and an idea came to mind on how best to convert the Z axis.
Here is: (Hope this is clear)
The column is very rigid and has Z Ways built into the column for the knee to move. Now if I move the knee to a low position and lock off that will ensure the table/knee is rigid.
Remove the head and Ram and fit an extension to the top of the column thereby extending the Z axis ways by say 300mm or so. Do away with the ram. machine a steel plate to fit onto the Z ways (with gibs etc) and fit a 1inch ballscrew to the Z slide. The head can then be re-fitted still with the tilting mechanism. This will require some mods to the pulley drive system however I figure I can use a direct drive belt and fit a VFD to the existing motor (3hp).
I know I will lose some Z travel but from my rough callcs will still have around 450mm (18inch)Z travel. Will probably also lose around 1 inch or so of Y travel. Overall the mill will have more travel that any bench mill etc.
Would appreciate your thoughts on this proposed Z axis conversion. The CNC drives/electrics etc are all covered so please do not comment on this.
Look forward to your replies.
cheers
Frans