Denford Starturn 4

From Field of Cows

I was after a tailstock for my Boxford 125 TCL CNC Lathe and found someone selling a complete lathe with tailstock. After contacting the seller, I was informed that it had been sold but was asked if I would be interested in purchasing a Denford Starturn 4 for £240. Well, I snapped it up!

Starturn2.jpg

The machine is in fantastic condition with no wear whatsoever. When I obtained the machine, the emergency stop button was pushed in and I was not supplied with a key but after some successful lock-picking (easier than I expected!) I managed to release the button. The spindle didn't work but it turned out to be a simple case of a sticky safety switch on the guard.

Machine Description

The Starturn is a small benchtop CNC lathe. I imaging they were primarily used in schools and colleges for training purposes but can be used for real work. There were different revisions of the lathe that included different controllers and interfaced to different computers.

My lathe contains only very basic control capabilities. The host computer is used to send steps directly to the stepper motors controlling the axes. In my case, the host computer is a BBC or Archimedes computer (I'm not sure which). Needless to say, without the computer or software, this had to go.

The Starturn lathes come with a very nice multifix toolholder. Mine came with two toolholders and I was very lucky to buy two more at a very reasonable price.

Retrofit

As mentioned above, the lathe was not meant to connect to a modern PC. Therefore I set about converting the electronics to remedy this. This did not turn out to be difficult at all.

The lathe includes two stepper drivers, both Parker Digiplan CD20 units. The documentation for these is readily available- they can be downloaded at http://www.denfordata.com/downloads/dos/cd20-30.pdf.

I purchased a CNC4PC C11 breakout board (see http://www.cnc4pc.com/Store/osc/product_info.php?cPath=33&products_id=161) and used an existing logic IC on the main circuit board for interfacing to the drivers (I'll try to post more details when I get around to it but if you are trying to do the same thing then email me and I'll give you the information).

It turned out that one of my stepper drivers had failed and was blowing fuses but a simple rectifier diode replacement fixed this so I now have both axes under PC control.

That's about where I've got to at the moment. I intend to interface with the VFD to allow the spindle to be controlled as well as connecting the spindle encoder to allow threading. Luckily, circuit diagrams are available for the existing electronics so this should not be too difficult.

Useful Information

There is quite a lot of information out there on this lathe. Far more than for my Boxford. Here are a few useful links:

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