BBC Micro Boxford TCL125

Hi, I have a boxford CNC lathe which uses an interface for a BBC. I was wondering if anyone has any experience in if the software that comes with the lathe is worth using or should i convert to mach3 or similar?

Thanks

If you have the BBC computer and can run the software you could try it out to see if it suits your needs.

If you don't have the computer then probably going straight for a retro-fit will be the best alternative.

Emgee

Hi all, I’m new to this so I apologise if this has been discussed before, because myself and no doubt many of you are staying at home and keeping safe.

My question is with ref to a Boxford 125 TCL has Which I’ve had for years and thought I would have a go at getting running, the machine does work in manual mode and it is in a standard form with a gray ribbon coming out of the side of the casing.

I have no computer with it but I have an IDC34 breakout board and a Mach3 interface board and an old tower computer with a 25 pin connector on the rear I think you call it an LP25.

I have in the past had a go at trying to get it running with a Mach3 program but nothing seems to be working perhaps someone has figured out the wiring and I would appreciate any help.

many thanks Len.

While the hardware of a BBC is well documented its entire way of working with peripherals is different to a PC or clone.

There are a number of different interfaces on a BBC Micro and the first this is to discover which one is used bt the Boxford.

Tube - Used to connect a second processor so the least likely however if the Boxford contains a microprocessor it is possible

1MHz bus - used to connect slower peripherals but has a more direct link to BBC hardware so could be.

User port - a general purpose I/O port

Printer - a cut down Centronics interface that may be similar to the 25pin printer port in your PC

Is this any use?

BBC hardware is well documented onine

The most likely are the user port (20pin) or printer port (26way)

The 1MHz bus is 34 pin and the Tube 40 pin

Edited By Nick Clarke 3 on 04/04/2020 17:37:05

Edited By Nick Clarke 3 on 04/04/2020 17:38:53

Hi Nick thanks for the prompt reply, it is definitely a 1MHz bus as this is the 34 pin break out board attached I need it’s the connections between this and Mach 3 interface

Len.

Hi Leonard, I think you will find that the interface is unlikely to work directly with Mach 3.

You would need some sort of software translator; it could probably be done using an Arduino but the effrot required could range from trivial to heavy lifting.

Neil

The subject has come up before. There are a few mentions on this forum, and there used to be several websites where chaps described how they did it. I found this one on mycncuk fairly easily and also Johnsmachines, but not much else. I've an idea there was a Yahoo group, goodness knows where that's gone.

Anyway, it's not a simple rewiring job. While the lathe and motors are good, the electronics and original computer controller (a BBC Micro) aren't Mach compatible. (The BBC Micro is long obsolete.)

So the approach seems to be to replace the electronics with modern Mach compatible motor drivers and to dump the BBC Micro in favour of a PC. A tricky project to tackle on your own without electronics and computer experience.

Although Neil's suggestion of an Arduino converter has legs, it would have to be programmed by someone who understood Boxford and Mach control languages, and the difference between the BBC and PC parallel ports. Looks like a rich mix of easy and difficult, I think easier to replace the old electronics, which is what John' did. It cost him $AUD 800, about £200 today.

Best hope for an easy answer is to find someone who's done it already and copy them! They do exist, try asking on on the forums.

Dave

Thanks Neil and Dave for your reply’s, as you say it’s not an easy fix and it may pay me to replace the power supply and controller boards but where do I stop with old stepper motors as well?

Len.

From a newbie perspective a major issue is the pace of technological change. Generally the things you find on line are relatively old (in electronics terms) and describe what could be affordably done then without unreasonable amounts of engineering. Almost invariable there are limitations in what the results can do and how well it works. But for the time such were more than acceptable.

The original BBC system is seriously limited from modern day viewpoints but it worked. In the context of its time where the nearest "low cost(?)" equivalent might well have been something like a Bridgeport EziTrack, early Haas or one of the relatively expensive small "desktop size" systems it was wonderful. Especially for the money. Not that it was pocket money cheap. More like small car territory!

But a stepper motor is a stepper motor, a limit switch is a limit switch and modern electronics are both powerful and relatively cheap so the dump all the electronics and start over approach has gotten more attractive. I'm rather impressed by the Granite devices blurb **LINK** which implies that you can pretty much wire up a system and have it just work with none of the lost steps and similar issues that plague older approaches if you mess up the set-up. Older affordable systems generally don't have nice easy to follow graphical set up screens, far too expensive then, which really doesn't help the novice.

I'm sure smothstepper and similar buffering interfaces can do the job just as well but how much extra set-up is involved and how tricky is doing the mix an match to the drives on your bench. As an older guy (67 come July) I'd definitely favour the "works out of the box" solution when someone else has done the hard work for me unless its prohibitively expensive. Young Clive would take anything on DIY and spent far too much time for, all too often, working but not really well enough results. But he couldn't afford the good stuff then!

Worth remembering that Mach is very old technology too. Probably should look for something more up to date.

Or maybe the complete Chinese control boxes would be better approach altogether. The late (Sir) John Stevenson was impressed by these so they'd have to be a least pretty darn good in practice. Some discussion on earlier threads.

Clive

I have Just looked on line at the 2 axis nema 34 stepper motor kits which includes a pair of motors, drivers, and power supplies a breakout board and a what looks like a 25 pin lead for almost £200.00 ( 24vto 80v kit ) any comments welcome.

Len.

Hi Len

Does your cable plug into a board like this?

From memory(very dangerous). I removed the board and made my own interface PCB which then plugged into a generic 5 way break out board which then went to mach3 through a parallel cable.

Cheers Michael.

I would approch this as if you were looking at concverting a manual mill and had already mounted the stepper motors. Look at the mill and get motor part numbers and see were the limits switches are located. With that informtion look at the guides for a CNC conversion. As others have said, it's not worth reverse engineering the old electronics. New stepper drivers will work fine with older motors, at most you might have to adjust the suppply voltage or current settings.

Robert G8RPI

Does your lathe have a thread cutting capability? If so, you'll need a control system with that too.

LinuxCNC, Centroid Acorn and PlanetCNC have good thread cutting implementations, many others are only geared towards milling machines & routers, but not lathes.

I have PlanetCNC fitted on my Denford lathe and it was quite straightforward to retro-fit. Have a look at the manual for the 4-axis board (which I have), in particular, the wiring examples towards the end of the document.

Martin.

Hi,

I have recently converted mine to Linux cnc. I choose to ditch the stepper drivers as they are based on old technology and can suffer resonance at certain speeds and lack speed and acceleration compared to modern drives. I also upgraded the X an Z to use slightly larger motors, on mine they were nema 23 size. For drives I initially used the cheap ebay "TB6600" ones at 48v but they blew up. They were advertised as working to 48v at the time (They are not now, I wonder why!), so I swapped to "Gekko G201x", these have been perfectly reliable.

TBH the stepper motors were the least of my problems. By far was the spindle motor drive, It needs a 0-10v speed signal. Again I turned to ebay and got a breakout board that provides it, however the spindle speed was not very controllable and it hunted. All the ebay boards I could find used PWM and a capacitor to provide the signal. I tried various boards and homemade solutions but none really worked. In the end I got Linux CNC to output an 8 bit speed signal on a second parallel port then used a digital to analogue converter to feed that to the drive, both the electronics and software programming were very much non trivial! I be very curious to know what others have done and how they perform.

One big thing, if you are using the original spindle drive "GEC Gemini", please please please replace the "Rifa x2" capacitors on the board with suitable modern replacements if you haven't done so already. These will be at the end of there lifetime and the body will almost certainly be cracked. They can and do explode and catch fire if left. Please view the following youtube video for more detail:

https://www.youtube.com/watch?v=XAbrU17hLTM

I have a wiring diagram for lathe and a home made schematic of the spindle drive if that's of any help, I've also found a picture of my drive before I changed the caps, so I circled the caps that need changing. You can just about see the cases are cracked in the photo.

Graham

Edited By Graham Mcconnell on 05/04/2020 14:51:55

Thanks everyone for your help and yes Graham I’ve had to replace the two capacitors in the Gemini controller several years ago, after a loud bang and smoke I thought that sounds expensive, but thankfully just replacement parts and a bit of soldering.

So perhaps I will work out stepper motor sizes and go from there, and after getting it going again yesterday in manual mode the motor starts and the variable speed works but only one way for some reason, the reversing relay is not working, more to have a look at, so any diagrams would be helpful.

Len.

Thanks as well as well to Michael and yes my board is identical to the one you have sent in a picture of, it’s tucked under the stepper motor drivers.

I would attach some photos but I can’t seem to transfer them from my album.

Len.

Hi Len, Please send me an email to "[email protected]" and I'll reply with the schematics I have. If anyone else wants them please feel free to email also.

All the best

Graham

Hi graham been trying to get information on the boxford and would appreciate any help and information my email address [email protected] regard norm

Hi just an update I’ve just ordered a pair of stepper drivers and motors and a power supply, I see from the circuit diagram that the original steppers are an 8 wire configuration with 4wires from the stepper driver board and the other 4 wires paired and then supplied with a 24v through six resistors three for each phase.

so rather than risk blowing up my drivers I will fit the new ones, they are 4wire bipolar, the only thing that concerns me is that once I remove the stepper driver board and the microprocessor board I see that the spindle indexing and the forward and reverse for the spindle will no longer work, is there an off the shelf controller for this?

Thank you Graham for the board diagram but I’m not as I said an electronic wiz kid and building a board from scratch is beyond me so would like advice from you guys.

Len.

Edited By Leonard Newton 1 on 12/04/2020 18:33:09