View Full Version : CONVERSION: Boxford VMC 190

Andy Cooke
28-11-2016, 12:44 AM
Somehow I've ended up buying a VMC 190.

I've been through this loop once before with a Denford Micromill. I bought the Micromill as a learning excercise, as a step towards converting my RF-45 clone manual mill, I thought it might be useful to make parts for the big mill. I learnt plenty... I learnt how to connect a parallel BOB to LinuxCNC, I learnt about CNC workflow, I learnt that the micromill was a bit 'floppy' for what I wanted to do, and I learnt that I couldn't be bothered to convert the manual mill.

Time passed...

I found myself looking at parts to build a mill that could cut aluminium, not particularly big things, as you'll know,that stuff starts adding up.

So I bought a VMC 190, I'd have loved a 300, or a Triac, but there is no way I'd get something that size in, so here's hoping the 190 is rugged enough.

After the Denford the lack of info on the Boxford came as a shock, I'm hoping to add some of the specs that I'd have liked to have known, and probably plenty that I wouldn't :D

Before getting on the the VMC 190, I'll say that I plan to use a DDCSV1 this time, I didn't want to use parallel again, I have played with a BBB running LinuxCNC, and I will use that for something, but not this mill. I started thinking that a CSMIO/IP-M was in my future, but having to buy Mach3 was putting me off. Anyway, the DDCSV1, I read the long thread about it, and it seems to fit this simple build well, time will tell, I can always rip it out if we don't get on :)

I realise that the 190 isn't going to be able to attack aluminium with big cutters, but I'd like to be able to use cutters in the 6-8mm. This is where I hope I can get some advice, namely how much load I can sensibly put into the machine, and how to achieve it, I suspect the spindle will need more power and speed, but that's for later.

Anyway, stuff I now know after a few hours of ownership:

Z axis stepper is an HY 200-2240-2.9, data exists on this, in short it's NEMA23 sized, cylindrical motor 4" long, 2.9A 1.48Nm holding torque. 1/$" spindle.
The stepper has a 12 tooth pulley using a HTD 3M 9mm wide belt (HTD 186 3M) the ballscrew has a 20(?) tooth pulley.

I can't read the number on the X axis stepper, it's similar but shorter, maybe an HY 200-2231? It has the same pulleys with a shorter HTD 105 3M belt.

No idea what the ballscrews are yet, or what voltage the steppers run at.

The tool holders are of the EasyChange type and I have 6/10/12/16mm versions.

The drivers are mounted on a single PCB and are 2/2.5A single/half step devices.

I think the machine warrants a change of steppers and drivers, I get the feeling that it was built rugged and low power to limit the damage the kids could do, I hope so anyway.

Crikey, I have waffled on a bit, hope you're still awake.


28-11-2016, 05:57 PM
Personally, for simplicity I'd stick with the existing steppers, unless you really want to change them, as you won't get that much of a performance boost from changing them. And it avoids the hassle of trying to get pulleys that fit new steppers, as most new steppers come with metric sized shafts.
I would however fit new drivers, but spec them so you can upgrade the motors later.
You'll most likely find lack of spindle power will limit what you can do, long before the stepper motors do.
As for the existing motor specs, the X and Y will very likely be identical.
Just make sure as you learn part numbers/sizes/details, write them down somewhere, so you can find them later. I personally create a word document for each machine I have, where I enter any information I think might come in useful later.

Andy Cooke
28-11-2016, 11:46 PM
Thanks m_c, I see your point.

I've just been out in the cold trying to check the pitch on the ballscrews, it seems to be 2.5mm, so with the drop from the belt that's 1.5mm per stepper turn. At the advertised 2000mm/min that motor will be running at 1333rpm, so fairly humming, it's also a mad 0.0075mm per whole step. It looks like I'd need to change the pulleys to go faster, there seems to be space to go 1:1, so maybe that's also one for the future.

I'd been contemplating 'Leadshine' AM882 drivers, but I'm wondering now if they're a bit too much, I guess they'll give plenty of headroom :D

John S
29-11-2016, 12:07 AM
542's or equivalent will be fine for a machine this size and still be upgradeable.

Andy Cooke
30-11-2016, 09:13 AM
Thanks John S, I've taken on board your sizing advice, and probably made a huge mistake by ordering 3x DM556s, I'm a sucker for a gizmo :)

I've also got a 33V toroidal on the way for a 46V supply.

On the subject of drive ratios on the X and Y axes, I have a '92 machine and that has 12/20 pulleys to give 1.5mm per rev or 0.0075mm per whole step. I noticed in mikegolding's thread "Boxford VMC190 Retrofit Problems, axis sounds very rough" that his '98(?) machine had 16/20 pulleys to give 2mm per rev or 0.01mm per whole step. He gets the more pleasing 100 steps per mm compared to my 133.3333333333333333333333333333333333333333333333 333333333333333. My OCD is kicking in... At this point I don't intend to do anything with steppers or gearing, but clearly the options are there.

Andy Cooke
11-12-2016, 08:11 PM
I've finally got around to getting the mill out of car, and into the workshop. Gravity is a wonderful thing...

I've got some more parts identified:

The speed controller is a Lenze 534_e.1B
Spindle motor is marked GEC Alsthom, RS420J R1000(?), 60V 6.8A, 3000rpm. It has a belt drive, not worked out the gearing yet.
The Y axis stepper is as suggested the same as the X axis, but this time I could read the number as HY2002-2232-190-A4, so it's 1.9A, 1Nm?
The Y axis belt is the same as the Z axis ie HTD 186 3M
ballscrews are 8mm OD

I can see no sign of homing switches, I think I'd like to run them, so if anyone has any suggestions or images showing how Boxford have installed them on the larger VMCs I'd be grateful.

I bought this mill as broken, the spindle ran, but the steppers juddered a bit, but that's all (driven from the front panel). I pulled off the steppers to get an idea where the problem lay. With no load the steppers shudder at best when driven from the front panel, they do at least hold steady and I can't turn them under power, this suggests to me that the steppers are working, and the driver is working at a low level. I'm assuming that the front panel is an MPG and I should be able to check it with a 'scope. At this point I'm just trying to find out the extent of what's faulty and what I can use before stripping it apart.

With the motors off the X and Y ballscrew pulleys were very tight to turn, I've backed off the gibs and they now move pretty well, I'm not sure if the machine is just gummed up, or someone had set the gibs too tight, it looks like it was last used for machining brass, and it is quite sticky. At the moment it moves, so I'm happy.

If anyone has any wiring diagrams, or knows how to test the front panel I'd be grateful, I can start poking about with a scope if not.