[UKRobotics]

Over the last few months I've been slowly piecing together all the parts of the puzzle that is my bridgeport series II interact 4.

Since purchasing the maintaince manual direct from bpt/hardinge and unscrewing almost every nut bolt and cover on the machine, I have built up a fairly good understanding of how everything works but there are just a few more gaps in my knowledge which I have been unable to solve myself and I'm really hoping somone on here may be able to help.

I need to know how the power drawbar and associated sensors are supposed to operate. At one end of the system there is a pneumatic input which goes via a solonoid valve through a 'booster' which converts the gas into hydraulic pressure 25x greater than that of the gas. When the solonoid is powered, this triggers a small hydraulic ram above the spindle which forms part of the drawbar mecanism.

In addition to that there are two sensors; one microswitch and one proximity switch. The microswitch is connected to a lever which is positioned beneath what looks like a very small hydraulic ram which is connected to a T-piece which also connects to the main hydraulic ram for the drawbar.

At the moment the switch is pushed in constantly. It looks to me like when the main drawbar hydraulic ram is actuated, the miniture one is also actuated at the same time, which in turn moves a lever, releasing the switch.

My guess is that this some sort of saftey mechanism so the computer knows when the main ram has been fired and when it has returned to its resting position.

The other sensor (the proximity sensor), is positioned at the front and appears to be checking that the quil is in a retracted position.

Now all of this is just assumtions I've made based upon observations, I havent put power (or air) to anything yet for fear of breaking somthing!.

My questions are as follows:

What are each of the sensors for and under what conditions are the supposed to operate ? Were my assumptions correct ?

My thoughts are that bridgeport wouldnt have put those sensors there without good reason so I wish to replicate their original function correctly in my pc based retrofit, so could somone please explain what they are meant to be doing and when.

My guess is that they are to prevent the drawbar operating when it is not in the correct position, and I'd imagine there was another mechanism to stop it operating while the spindle was rotating, but neither of the sensors i've mentioned appear to have such a property.

I would also be very greatful on any advice on wiring up the proximity sensor. It has three wires comming from it one blue, one brown and one black. I have never used a proximity sensor before so i'm not famillier how they work or how they should be connected. Guessing from how its mounted i'm assuming its measuring the proximity to a piece of metal but as to the electrical side i'm a little clueless. What power source does it need and how should i go about wiring it into the pc parrallel port ?

Another more general question: how does the drawbar work overall - by that I mean how is the tool held in and released. Does the large hydraulic ram release the toolholder ? and if so what holds it in ? Similarly if actuation of that ram holds in the tool, what mechanism releases it.

I have tried to explain everything as clearly as possible, but as they say, a picture is worth 1 thousand words, so here are a few photographs to illusrate what I was saying:

This is a photo of the microswitch positioned above the metal lever:



This photo shows what I believe to be a miniture hydraulic ram which pushes down on the lever:


This is the T-Piece which splits off between the main hydraulic ram for the drawbar and the small lever/switch mechanism:


This is the proximity sensor:



Appologies for writing a small novel here, but answers to these questions are really quite critical to my retrofit project and I would be incredibly greatful to anyone who could shed some light on the questions i've raised.

[machintek]

I have to look the prox switches up in the schematic to see what they do, but I remember that the paw 9short arm) and associated switch hold the quill from being forced down by the drawbar actuator and at the same time the Z drive is shut off and the control ignore the Z position (because it will move). When the drawbar releases, this all goes back to normal with Z position back to where it was. I am fairly certain that one prox switch is for Z in tool change position so the drawbar actuator will have enough stroke.
Prox switches are miniature metal detectors. Thus they have a power, and ground, and a signal wire. Check your schematic.

George

[UKRobotics]

George, do you know what a 'DOG' means in terms of bridgeport electrical stuff?

There are numerous references to it in my manual eg. "Drawbar DOG microswitch"

[machintek]

A "dog" is a piece of metal used to actuate a plunger type switch on a Bridgeport.

George

[UKRobotics]

the paw 9short arm and associated switch hold the quill from being forced down by the drawbar actuator and at the same time the Z drive is shut off and the control ignore the Z position (because it will move). When the drawbar releases, this all goes back to normal with Z position back to where it was.

Why is it necessary to disable the drives during this procedure ? What would happen if they were not ?

[machintek]

Strain on motor, drive and belt, etc as they try and maintain position.
Very possibly a gross positioning error thus shutting drives off. I believe this would be a fatal error requiring rebooting of the machine.

George

[UKRobotics]

I am retrofitting this machine with rutex drives so going by what you describe I guess the same would apply.

Question is, should I use it to disable the 24v logic supply or the 140v motor supply ?

[machintek]

I believe that each axis had a relay to enable it with a signal from the TNC. This allowed only the Z axis being shut off. Check your wiring schematic.
It did not shut off the 24V power supply nor the axis drive power supply.

George

[UKRobotics]

So after the tool had been changed, would everything automatically return to where it was (via the drawbar mechanism) or would the z drive have to measure & compensate for any change in position ?

[machintek]

Yes, the Z turns back on and returns the z to the position prior to the tool change.

George