Converting a Boxford 250B

Einar wrote: As far as I can find the machine have an inductive limit switch for Z that will sense both ends of travel. Homing is done as a combination of this and another inductive switch sensing a disc on the end of the ballscrew.

That should allow for very accurate homing. Depending on homing speeds, axis acelleration and how long the sensing disc is active for this might be easy to configure. If the axis can stop from homing speed inside the distance that both the bed-sensor and the the disc-sensor are active then you can just and2 the two switches together. If there is a danger of the axis passing out of the other side of the active region then you might need to get a bit clever, maybe with HAL components to make a latch (disc-sensor signal can only go low when bed-sensor is low, homing is a search, back-off find slowly).

Then there is an additional limit switch that is activated by an adjustable rod on the Z slide.

Possibly to protect against hitting the tail-stock?

The spindle sensors are one index sensing a slot in the disc on the spindle. The other senses 50 holes in the disc.

That will work nicely for threading, but as it can't sense direction it won't support rigid-tapping. This may not be anything you ever miss, though. You will need to configure the encoder counter for single-channel + index, which I don't have enough experience with the USC hardware to know how to do. You could consider adding a 3rd opto-sensor or possibly swapping the existing hole-detecting sensor for a two-channel style. uk.rs-online.com/web/p/slotted-optical-switches/1711830/

The VFD is controlled by a direction signal, a run signal and a 0-9V signal controlling the speed up to 175Hz = 3000RPM on the spindle.

There are a number of ways to handle this. The simplest might involve reconfiguring the VFD to give full speed for 5V input, as this is often configurable in the VFD.

The step signals start at 500Hz and increase to 6100Hz in 200ms. There is a bit of jitter at the higher frequency, so with a signal that have less jitter it may even go higher.

The USC should be able to do a lot better there.

Thanks for your comments Andy.

Yes, I think it will be a pass both sensors, back up past the disc sensor, then slowly approach it again.
The slide sensor has a bit hysteresis, but on the disc sensor it is negligible.

The adjustable rod is on the other end. It can be adjusted to avoid tools running into the chuck. Well sort of, it does not take into account that boring tools will stick out further than surfacing tools. This is a machine mainly targeted at schools, so that may be the reason it's there. Hitting the tailstock is not avoided in any way. Except that the step motors will stall before any damage is done.

I can easily add another sensor to the spindle to get A & B signals. But rigid tapping is probably not possible. The spindle motor is an AC Async motor. The slowest speed is about 300RPM at the spindle. Nominal speed (at 50Hz) is appx. 850 RPM at the spindle. So torque at tapping speed will be very low. Even if this is a 2.2KW motor.

I have no way of reconfiguring the IMO Jaguar VFD, as I don't have the manual for it. I will try to contact IMO to see if I can have a copy.
Or wire up an amplifier to get the voltage I need. ..... Just checked, and the DAC for USC can output 0-10V, so that will be fine I guess. I put it on the order I',m preparing for Pico Systems.

The jitter number I got for my PC seemed huge! It got better after I put in a video card instead of the built in video. But as I understand it this is less important with the USC board? I need to find another video board, as this one is somewhat jumbled on the top and bottom. If it does not work out, I can use another PC. Although it seems overkill to use a really fast modern PC with a gaming video card for this I think.

Einar wrote: Yes, I think it will be a pass both sensors, back up past the disc sensor, then slowly approach it again.
The slide sensor has a bit hysteresis, but on the disc sensor it is negligible.

This may require a bit of HAL logic, but is otherwise straightforward.

I have no way of reconfiguring the IMO Jaguar VFD, as I don't have the manual for it. I will try to contact IMO to see if I can have a copy.

It is probably online. www.drivesdirect.co.uk/Downloads/IMO%20CUB%20Manual.pdf for example.

Although it seems overkill to use a really fast modern PC with a gaming video card for this I think.

Big fast modern PCs often give very poor jitter numbers.
The favourite for a long time (though now hard to find) was the Intel D525MW. It has low jitter, a parallel port, and is very cheap.

Thanks to you and Cradek (Cris?) for helping me yesterday. I really appreciate it! Even if we did not get it sorted it feels good not just fumbling in the dark. And I did learn a lot, although I felt like I was asked to type commands in chinese. :lol:

My Jaguar is older than those and other IMO drives I found. It also seems mine is made by IMO, while the newer are relabelled Fuji drives or some other brand.
Which makes me think the parameter set will not be the same. And not having the manual I don't want to poke around and mess up a working VFD. A >5KVA drive is not cheap, even today.

Interesting what you write about the PC. What I have is not top modern. It was 3-4 years ago. I will install the CD on another PC, probably today. It just sits there gathering dust. And I can make errors much faster using 2 PC's than one. :silly: No, it's more just in case I did something silly when installing. Not knowing what I do I might be more lucky next time around.

I just got the old USC card running with LinuxCNC.
I had to update the install to 2.6.
Now it does not crash anymore.

I installed resistors where the relay coils would be on the USC.
Then LED8 lights up when I turn machine on. I take that as a good sign.

The config I downloaded is for a mill.
Which is OK for the old USC as I want to use that on my mill.
So installing on another PC is still on. But before preparing a PC for the mill I will have the lathe running.

Reconfiguring it for lathe should be mostly removing stuff from the mill files I suppose?

And there are some things that needs to be done so it will run the 2.6 instead of the old one.

Things looks a lot brighter today.

Been away for some time on this. But did some the last few days, and hope to be able to hook it up to the hardware soon.
I was Haunted by following errors, but now it's up to the same speed as the original Controller, but it will throw a following error if I try to accelerate as quickly as the original. I have to fiddle about With that.

The stepper Controller manual specifies a low time of between 5us and 25us. That means that at rest the signal should be high. So I have to invert the step signals from the USC card.

Note to self: this may be useful when I shall Interface the spindle Encoder: www.linuxcnc.org/index.php/english/forum...-encoder-on-pico-usc
Is Encoder 3 a good Choice for this? It seems Encoder 1 is free since I have no Y axis.
I may need another "axis" for the tool changer if I don't run that from a microcontroller Board.