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Improvements to CNC MkI machine (spring 2007)

In a bid to squeeze a little more life out of my Mk I CNC machine I have embarked on a number of improvements. I have added an oil water coolant system which has enabled me to drill and mill 10mm or more steel plate which I am exceedingly pleased about as a number of machine possibilities now present themselves.

Coolant System

My current machine building plans require cutting lots of metal, both aluminium and steel. With this in mind, the first priority of the overhaul was a coolant system. I had assembled all the bits for this a while back so it was simply a case of connecting it all up and mixing some coolant. The pump is a 12V bilge pump that has already seen much use over the years. It must have spent a couple of years lounging at the bottom of my water butts before being repropriated for loftier pusposes. I had bought a double headed coolant nozzle with magnetic base from Axminster but a length of PVC tube works just as well.

I had picked up a couple of meters of 200mm x 10mm steel plate a while ago with the intention of using some of it for a new work surface for my machine. Working with such a hefty piece of metal was rather daunting, but thankfully with my new metal cutting bandsaw I had a manageable piece cut off in no time.

I clamped the plate to the box section steel frame of my machine with some temporary toe clamps then CNC drilled 5 3.2mm holes either side of the plate for mounting holes and to test the coolant. No drill bits were snapped which was a pleaant surprise. I doubt if I could have managed that on the drill press without some snapages.

I wanted to use the overhaul to test some CamBam code I have been working on. CamBam does not currently support lead in and lead out moves which you can get away with for wood and soft stuff but I didn't like the idea of plunging straight down into steel plate. I knocked up a CamBam script to generate a spiral toolpath to drill and counter bore the mounting holes. After some experimentation I had refined the toolpath so that using an 3mm end mill, it couter bored the hole, drilled a 6mm hole all the way through the plate then milled a 5mm hole through the underlying steel frame. All I then had to do was run an M6 tap through with my cordless screwdriver and the plate could be bolted down. All without having to remove the plate. Each hole took about 5mins to mill at about 50mm/min feedrate.

It soon became apparant that I would need better splash protection to keep the coolant in so I made a 'nappy' for the machine using some damp proofing plastic I had spare. It was good to see gaffa tape making an appearance at this point in the project too.

I wanted to face the workplate, but first I thought I had better face the frame it will sit on and also the underneath of the plate that sits on the frame. Before I got started, and flushed with the success of my bolt holes, I experimented with another spiral toolpath script in CamBam. This script created a facing pattern that sweeps in a largish circle that moves along at the same time. I'm hoping that as well as making a nice smooth surface it will leave a pattern with a bit more asthetics than 'cricket pitch' stripes.

Here is a copy of the spiral facing script. At the moment, this just does one strip. I will modify it to face rectangular areas.

NOTE: CamBam currently has a bug when opening new scripts. It always asks 'Do you want to save changes to Untitled'. Respond NO to this.

Here is a rather shaky video of the spiral facing milling operation underway: Video of spiral facing my machine frame (9MB)

With the machine mounted within the frame I can now replace the wooden top I had made a while back. This will allow me to bring my lathe back over and hopefully encourage me to get the lathe CNC conversion project under way. The frame could also be enclosed to help keep noise and dust in.