Bridgeport BTC 1

[Builder]

Hello All,

I just recieved this machine and need to do a retro on it. I am including a link to the machine since I can not get the photos in here.

http://cgi.ebay.com/ws/eBayISAPI.dll...ME:B:EOAB:US:6

A aftermarket retro for the 3 axis' would be easy but I have no idea how to do the tool changer. Does anybody have any ideas on how to do this at home for a reasonble price? The servos and spindle motor are fine but the control lacks seriously. Please Help

Thanks Tony

[Al_The_Man]

You need a control that has machine control I/O capability, or it can be done with an external PLC with limited communication with the control.
Upper end systems, wether it be PC based that use a motion control card with built in PLC or motion card with separate PC based Digital I/O cards use this method.
Typically when the control tool-change M code is issued this is passed over to the PLC and the control will hang at that line until it receives a 'finish' signal from the tool changer that the tool function or M code has completed.
Al

[machintek]

Not to be negative but this will be a can of worms.
Reason is the way this machine changes tools. Besides a pile of switches to tell the control where the tool carosel is, when you command a tool change:
the quill goes up; the machine files air cylinders to go to low gear verified by a micro switch in the "shoebox'; Volkman drive turns spindle slowly; another cylinder fires and a bar runs along a scroll in the gear that also gives spindle speed and locks it into orient verified by a micro switch; then the tool changer starts moving. this is air over oil and has a pack of micro switches on top to tell the control what is going on because more cylinders fire to slide a plate across the spindle to hold it up while the drawbar fires at the exact moment to release the tool and grab another. The tool arm literally slaps a tool up there. If the carosel needs to move 1 station, it strobes the air solenoid to the air motor to move it slow. If you load up the tool carosel, it must be balanced and you need to adjust a air flow valve to compensate for the additional mass or it will not move correctly. The air over oil arm mechanism also has flow valves but if you change the speed, you will upset the timing of the dozen or so switches involved in a tool change. Most of the solenoids are run by the CPL board in the control. You MUST have the maintenance manual to keep this machine running. It was called a BOSS 7 and was the first BOSS machine to use servo motors instead of steppers and even has backlash comp.

George W.

[Al_The_Man]

It sounds like a mechanical nightmare and writing the logic would be the least of it.
Does the spindle drive perform the spindle orient? or is this achieved with other mechanical means? Is there servo motors in the tool changer?
Al

[machintek]

The orient is actually achieved mechanically. A air cylinder pushes a piece of metal in a groove that gets deeper untill the end of the groove is found which is deeper still. At this point a microswitch tells the control that orient has been achieved. The Volkman spindle drive moves the spindle slowly to achieve orient. Just like a series one standard, there is a backgear but instaed of a lever there are two sets of air cylinders that push against the bull gear and springs. One set gets it to neutral, another set gets it to low gear. There is a cam with notches in it for each of the three gear positions. The control hunts (keeps firing) the specific air cylinders to try and gets the gears aligned. Each attempt includes a small air cylinder. paw, and switch that sees if the position has been achieved.
There are no servo motors associated with the tool changer. Lift the lid, it is hinged, and look in. There is a air over oil cylinder and a complex cam for tool arm motion. The air provides the force. The oil allows better regulation and consistancy of tool arm speed. The tool carosel has a air motor to turn it. A set of micro switches (later prox switches) tells the control were the tool carosel is at.

And yes, it is possible to write a ladder diagram to do all of this, but is it worth it? The drives are obsolete (NC400) and did fail often. The actual control works very similar to all the other BOSS machines. It is fairly reliable but needs a PC for loading programs and editing them. Because of the spindle drive, it can tap. If you still want to replace the control, consider getting rid of the tool changer.
Take it from someone who kept these machines running. There is a lot to go wrong or get out of timeing.

George W.

[harolda]

Sound like advice from the bpt maintance dept.

[colin1544]

The orient is actually achieved mechanically. A air cylinder pushes a piece of metal in a groove that gets deeper untill the end of the groove is found which is deeper still. At this point a microswitch tells the control that orient has been achieved. The Volkman spindle drive moves the spindle slowly to achieve orient. Just like a series one standard, there is a backgear but instaed of a lever there are two sets of air cylinders that push against the bull gear and springs. One set gets it to neutral, another set gets it to low gear. There is a cam with notches in it for each of the three gear positions. The control hunts (keeps firing) the specific air cylinders to try and gets the gears aligned. Each attempt includes a small air cylinder. paw, and switch that sees if the position has been achieved.
There are no servo motors associated with the tool changer. Lift the lid, it is hinged, and look in. There is a air over oil cylinder and a complex cam for tool arm motion. The air provides the force. The oil allows better regulation and consistancy of tool arm speed. The tool carosel has a air motor to turn it. A set of micro switches (later prox switches) tells the control were the tool carosel is at.

And yes, it is possible to write a ladder diagram to do all of this, but is it worth it? The drives are obsolete (NC400) and did fail often. The actual control works very similar to all the other BOSS machines. It is fairly reliable but needs a PC for loading programs and editing them. Because of the spindle drive, it can tap. If you still want to replace the control, consider getting rid of the tool changer.
Take it from someone who kept these machines running. There is a lot to go wrong or get out of timeing.

George W.

Hello George could you please tell me on the BTC 1 what size taper in in the spindle if it is 30 int were the tools held by a pull stud if so are the any spare parts available to retorofit onto a Series 1 CNC bridgeport with a boss 5 and variable speed head if so can you give me an address for them as I would like to use this method with a air over oil cylinder on top like the Interact 4 toolchanger is . Thanks Colin

[machintek]

The BTC-1 used a 35 taper spindle nose with a pull stud. The internal spring stack up has a force of 2100 pounds. The BOSS machines had either a Universal Quick Switch 30 or the Erickson QC-30. The Erickson had a 1/2 X 13 tapped hole in the top. It would accept a Kurt power draw bar which is a air driven butterfly type air impact wrench with a draw bar for quickly swapping out a tool holder.

George

[gus]

not sure what colin is asking, but the spindle parts are not interchangeable with any other machine, complete different head. Also toolholders have integral pull stud, and I don'[t know of any other machine that uses similar. 35 taper really sucks, much more chatter than kwik switch

[Jonp]

Weather or not you decide to retro your BTC I think it would be worth the effort to keep the tool changer, we have two of these machines, we use them all the time, Machintek is right about them being a mechanical nightmare. But once you get the three main systems, tool changing, spindle orient and gear shifting figured out they really aren't that hard to keep going. The maintence manual is very thorough and is a must have. In my opinion its the tool changer that realy makes these BTC's productive machines, just remember they are about 25 years old!!!!!!!

[Bob fran]

I like to hear that Jonp, a bucket of encouragement for the guys who has BTC1. Mine is nolonger a nightmare but still has so much to tackle. Everything works except the tool changer.

[machintek]

Note that the switches for tool carosel position interface to the XTC board on K-9, pins 19,10,9,8, and 7. this is shown on page 7 of the machine wiring schematic. Although the discussion in the maintenance manual shows micro switches with little rollers, the schematic shows prox (hall effect) switches. I have seen both on a machine.
Note that carosel position 14 has all the switches made, and position 24 has all open.

George