BBC Micro Boxford TCL125

Just so happens I'm finishing up converting a Boxford TCL 160 to PlanetCNC control. Should be a handy machine. To build, the PlanetCNC stuff is excellent, and the support is good too. Only done a few test cuts so far, I need to get it some cutting tools and sort a decent CADCAM out. Hopefully I'll get it wrote up at some point.

I thought I would give you all an update on my Boxford 125TCL I actually looked through loads of specifications on motors, drivers and power supplies and thought I would look on eBay and found an easy option, a bundle with two stepper motors, drivers and a power supply, I already have a Mach3 breakout board.

They were Nema 23 type with a 270oz rating the higher powered ones had a longer body length particularly for the x axis, I removed the old microprocessor and stepper boards inc a large capacitor and the associated wiring, fitted the replacement motors etc and after a lot of fiddling about got it to run on Mach3 demo. I have wired up the z stop micro switch n/c so there is no chance of running the tool into the chuck, I’m using Mach3 Turn but I don’t seem to be able to set up the soft limits, any help would be appreciated.

The motors seem to have plenty of power although I haven’t started to cut anything yet, with the help of Graham with his advice and a wiring diagram I’m hopefully wiring in a double relay to enable the motor to run forward and reverse, I’m still waiting for this item at the moment. This has been an interesting project for me as a novice and great to get the steppers controlled by a computer, I know I haven’t finished yet but thanks to you all for your help and encouragement.

Len.

I think for soft limits to work you need to have the machine zeros set to the same place everytime. This probably requires home switches on the axes. There is also the problem with a lathe that the z axis limits can vary so much between collets, faceplate and chucks. I have a clamp on limit switch that doubles as a home switch for the z axis so I don't use soft limits.

Does the Boxford have limit switches?

Have you set the x and z axes to homed in Mach3?

Have you checked the machine coordinates in Mach3 to see if they are some silly value such as 5000mm before trying to set soft limits to a few 100s of mm?

Martin C

Hi Martin the answers to your questions are the Boxford has a z switch fitted as standard Which I have wired to my breakout board, there are switches everywhere on this machine two on the Perspex cover and hinges the rear and side covers etc, I think because it was designed as an educational machine they went over board to stop little fingers fiddling.

I have not set x and z yet but it seems that you don’t need limit switches to set up soft limits as long as the machine is not moved manually when the Mach3 program is switched off, I have tried setting the the z axis to - and the x axis to + so the chuck end and up as my zeros and then putting in the travel for each axis as 100.00mm but I keep getting out of limits, there seems to be a difference between Mach3 lathe and Mach3 turn, which is best? as the Mach3 turn doesn’t seem to have a soft limit button and the Mach3 lathe uses the page up and page down keys instead of the up and down arrows, if you set one up the axis go a different way on the other, it’s probably me but do you initially set up the lathe or the turn versions?

And I haven’t got the spindle moving yet.

Len.

Just a quick update to my last post, I have at last got the soft limits to work the problem was that when I pressed the page up and down arrows it moved my z axis which is ok for a milling machine but on a lathe it moves the carriage to the left and right, so I went into config and system hotkeys and set up my keyboard accordingly now it works on the up and down, left and right arrow keys it now makes sense.

Len.

Mach3 lathe has lathe wizards, it automatically works in the correct plane and the tool path display is in the correct orientation. If you have the correct type of board connected to it you can do threads if you have a spindle index pulse. Or are you planning to use the parallel port?

I use a mini wireless USB keyboard to move the axes manually and have the keys set to the way I want them to work using the key setups. These keyboards cost less than £10.

Martin C

Mini keyboard

Edited By Martin Connelly on 21/04/2020 15:43:53

Thanks for that, I’m hopefully using a parallel port to switch the motor from forward to reverse and variable dc voltage to the spindle controller and use the on board speed sensor to send a signal to Mach3.

Well that’s the theory I just hope it works in practice, that remote keyboard is very interesting but I’m not very keen on wireless controls, I think I’m over cautious with these machines.

Len.

I've looked at soft limits in Mach3 turn and they work - if. The if is "if you have a modified screen set with a soft limits toggle".

Martin C

Martin I toggled when on Mach turn and yes up came soft limits, many thanks again.

Len.

I ordered a PlanetCNC setup yesterday for my Denford Orac conversion. A 4 axis board, a board to control a VFD and a software license. My plan is to get it running on a raspberry pi with a touchscreen and try to recreate the original Orac design that had a small VDU built into the base of the lathe.

I seriously considered Centroid Acorn and it looks solid, it needs a high spec Windows 10 PC though and ideally a high res touch screen which really racks up the cost.

Len, if you play around with Mach3 turn and soft limits you will find there is a small problem with soft limits and manual data input. That is that the only screen with the toggle and led for soft limits is the first auto screen. Since there is mdi input on the manual screen and the diagnostics screen they should have the toggle and led for soft limits as well hence my post earlier about a modified screen set. Using the standard screen set, mdi and soft limits on the manual or diagnostic screen requires you to go to the auto screen to toggle soft limits and back to the screen you want to use. This screen flipping will be required if you trigger soft limits using mdi in manual or diagnostic screens as you need to toggle soft limits or over ride limits to reset after a trip.

Martin C

Hi Len

How's your refit going?

Glad you mentioned about the contactor drive being on he stepper board, I hadn't realised.

With that in mind I have bought a 6 axis break out board with 3 relays.

I have got my tool turret mostly fitted just need to fettle M6 to M5 screws. I rejigged the turret driver software from my Denford and it seems to be working.

Cheers Michael

Hi Michael, yes I have the X and Y working ok inc the steps per revolution in Mach3 it’s so easy and seems very accurate, the spindle drive is a bit of a problem Graham has been a great help on my first ever go at CNC machines.

I have the forward and reverse controller to operate but the speed is a problem, the Gemini speed controller is tripping out within 5 or 6 seconds after it receives the 0-10v signal from the breakout board, I have disconnected the motor then the spindle controller but the problem is still there.The motor did run in the beginning but at full speed and there seemed to be a clunking as if it was being switched on and off very quickly, so more investigation required.

Len.

Hi everyone just another update, this morning I carried out tests on my as I thought damaged Gemini board, removed the variable resistor from the front panel and connected it to the board as per Graham’s diagram and guess what the motor started with full power as before, but on this occasion I was at the rear of the machine and could see was happening, there was a growling noise and I could see arcing from the rear of the spindle motor so I turned the resistor down and the motor slowed down so the board is ok.

I turned the max speed adjustment pot on the right of the board now the motor works up and down through its full range, now all I need to do is to get my breakout board to vary the voltage I presume this can be done using a voltmeter in dc voltage between pins 0-10 and ground?

Len.

I had a problem with the spindle cutting out on mine. Actually turned out to be a faulty e-stop, the vibration from the spindle made the switch lose contact. Cleaned it up and now all is well.

If you don't go the 'free' Fusion 360 route, then I can recommend eCam for lathe. It has done everything I've needed it to do, including drilling, which I couldn't find as a separate machining operation within Fusion 360, but maybe it's just buried away somewhere or I couldn't see the wood for the trees.

eCam lathe is €150.

Martin.

Thanks Martin. I've found DolphinCAM lathe basic, which is £150, that works nicely. I also use nanocad free for drawing the profiles as dxfs.

None of the free stuff seemed to work, it's either too router/mill focused, or full of bugs. Or both. No doubt someone more computer literate than I could fix them, I just want something that works.

Just a question to all Mach3 users, how do you set up the actual spindle speed to match the speed you enter, I have on my Boxford an optical sensor and has an index pulse and a 100 pulse per rev, and have set up the Bob with pin 12 for index and pin 13 for timing.

Is there an easy set up for this.

Len.

Hi everyone just a question for you, I have my Boxford TCL125 up and running the only problem is this Gemini spindle controller board seems to be playing up now.

I switched the machine on a few days ago and it clunked as normal a few times but then the spindle went to full speed so had to shut down, now when I start the spindle it just goes up to max revs which is not normal.

I removed the 0-10v wire from my breakout board to pin 2 on the Gemini and still the motor runs away I’ve checked the voltage on pin2 and it’s 10v to 10.8v it’s almost as if pin 2 is being fed from somewhere in the board, has anyone come across this before?

Is there a company that repair these boards or is there a motor and controller I could fit, I’ve seen 3phase motors with a vfd does anyone know of the size and power required.

Len.

Edited By Leonard Newton 1 on 18/01/2021 12:25:21

Hi all a carry on email from my last one almost a year ago, I have both axis operational and have carried out some machining of parts but still had problems with the spindle motor and the Gemini drive. So decided to remove this and fit a 240v ac motor and a VFD drive this gives me soft start variable speeds in forward and reverse and the options for jog etc in fact I find this a better control unit.

I carried out this conversion back in the summer and had to move the motor further towards the rear this was carried out by cutting the side casing welds and opening the motor mount cut out to enable a larger diameter one to fit and be fully adjustable, re weld the side casing back on, the motor I had spare one was brand new from a wood lathe the variable frequency drive was from memory about £80.00 a new drive belt, a fairly cheap conversion that works well.

Len.