bridgeport discovery 308 info

Hi All,

I have and opertunity to buy 3 bridgeport discovery 308s for cheap money. Two work and one does not.One of the ones that work has a tourque 22 head.I was wondering the good,the bad and the ugly about the machine, Thanks for any info.

I don't know about the torque 22 head, but I do know this about the Discovery 308-SX:
(not in any particular order, not even by level of annoyance).
1. The control uses a very, very obsolete LPM 286-16 motherboard, made for Bridgeport by Western Digital, and never duplicated anywhere. Western Digital doesn't even remember making it. The machine will only handle about 25k bytes of program, no matter how much memory you install. It may or may not support a hard drive, as that was an expensive option when they were sold. If you want to upgrade the motherboard, there is a company (EMI, or Electro-Mechanical Integrators) that will do it for about $800 (warning, 5 year old pricing), and they have to install a special interface to make the new motherboard talk to the B'port control. It will support a hard drive, but they will also offer to sell you a Disk-on-board (a solid-state hard drive). However, upgrading the motherboard will not increase the program storage, but you CAN use the built in DNC mode to drip feed longer programs.
2.The monitors suck. Don't expect them to work and don't expect them to be easy to replace. Pull out the CRT monitor and put in an LCD screen in its place for a lot less headaches. And speaking of the monitor, there are functions presented on-screen that never were and never will be available. Occasionally for no reason, the display will suddenly change the font or start to look like an invasion of fraternities (greek letters or something similar). Only a re-boot will correct it and sometimes it will require several re-boots to do it.
3. The coolant tray under the machine will overflow (the coolant runs out from under the front of the machine) when fine chips plug the strainer screen, or shut off if the intake filter (down in the tank, the messy, smelly tank) gets clogged. Coolant also leaks out of openings in the cabinet that allow the head to slide up and down and other places.
4. The coolant pump may up and die for no apparent reason. Watch out! It runs on 460 volts!, REALLY! Be sure the new pump is wired for 460VAC or you can burn it out.
5. Expect to have trouble with the tool changer rack. It will sometimes mis-index and occasionally blows its fuse. Disconnecting and manually horsing the rack back from the spindle is a real pita, and hard, too. The clips that hold the tools in their proper orientation will loosen up and fall off. The screw that holds the block that keeps them in place is metric, but will probably be stripped after a short time. The spindle start fuse also blows if you do a lot of short cycles.
6. The Z-axis home switch is very unreliable. It will not always home to the same position. It may overshoot or possibly undershoot by one ballscrew rotation (maybe .125 or 3mm?). This can cause disaster if the home zero you set yesterday suddenly is an eighth of an inch lower when you home the machine today, and all of your tool length offsets are suddenly .125 too long. Even if you leave the machine on ALL THE TIME, you will have to re-home it eventually and the problem can occur. When the Z-axis zero is NOT where it was set at the factory (about 50 percent of the time on my machine), the Tool changer will not line up properly and it will make a hell of a noise when the machine tries to change tools. I actually had to make a pointer and stick it to the head, so it aligned with the top bar of the cabinet when the zero was correct. Yes, it was that obvious.
7. There is a very tightly bundled trunk of wires in the back of the machine. This entire bundle moves back and forth constantly as the Y axis moves in and out. The tie-wraps do not allow for the continuous movement of the wires, so eventually, one or more of the wires will either become exposed or break. On my machine it was the control wires for the X-axis that broke. A new cable for the X-axis is not a cheap item (if you can find one) and almost impodssible to install. Only a qualified service person (BIG bucks per hour, plus travel time and lodging if necessary) should do it.
8. Even if you cut every tie wrap and let the wires flop where they may, the insulation does not stand up well to exposure to coolant and oil (go figure that one!) and will dry out and crack.
9. The top bearing on the spindle is a weak point, but you can replace it.
10. The z-axis encoder is a weak point and will cost hundreds to repair or replace. It (AND the servo motor) must be sent out for diagnosis and repair. Estimated at $300 just for diagnosis, to $800 if you'd actually like them to fix it.
11. The VFD is a weak point and will cost hundreds to replace. Should be done by a service man unless you have big, brass ones......
12. In the control circuitry, there is an integrated circuit chip called a DAC (digital to analog converter). When (not "if") one fails, they are no longer available in the US. I found them being hoarded by a jobber in China. The original chip sold for about $6.00, but it cost me 10 times that amount to buy from the Chinese jobber, and I had to buy a minimum of 4. With shipping, over $250.00, and that was 5 years ago. The machine will tell you which axis is bad, but you have to locate the right chip to replace. (Hint: it says DAC on the chip, but there are three of them.)
13. The rubber gaskets around all of the windows will dissolve from extended contact with water soluble coolant, and they will fall out. You will end up making new, bigger windows and screwing them in place. The gooey rubber is a nasty mess.
14. The door interlock will drive you insane. It is supposed to make it safer to operate the machine, but it only makes it harder. You have to enter a special code to override the interlock (while it is not already locked) to be able to turn the spindle on with the doors open. The override allows you to run the machine when you are not in Setup Mode, and must be entered over and over. If the machine will not power up, you can't open the doors. (There is a small hole that allows you stick a small rod in to mechanically defeat the interlock, if you do it jusssssst righhhhhhht........ You will probably end up trying anything to defeat the interlock (removing the latch from the door and taping it in place in the interlock unit works well. The latch MUST be engaged with the interlock unit for the machine to work). If you can read the schematics, you might be able to permanently override the interlock at the circuit board level.
15. The fans that cool the cabinets and the one on top of the spindle are LOUD.
16. You cannot program the maximum spindle speed in a program, or you will get an error condition. If you have a 6000 rpm spindle, for instance, you cannot use S6000 as a speed. I use S5950.
17. You can easily enter a letter "O" instead of a Zero, or make some other error in a program, and you will get a "parser error" message that does not tell you what or where.
18. There are cables that tie the doors together, so when you close one, both are supposed to close. They will fail. The rollers that support the doors will become loose or fall off, and need to be checked regularly.
19. The so-called waterproof work light is probably already shorted out and worthless. Coolant sprays around the machine with such abandon that no light inside the machine is safe.
20. The pendant arm is usually in your way, doesn't swing far enough, and God help you if you stand up under a corner of it.
21. The machines are capable of 400 ipm traverse, but are light enough that if you use that without anchoring the machine to the shop floor, the machine will walk across the floor. You have to change one of the paramaters (in a little file that is supposed to be read-only, and is read into the control circuitry every time you start it up) to reduce the Rapid to about 250 IPM to keep it from moving without anchoring It. Believe me, 250 IPM is scary fast, especially when you are operating with the doors closed and trying to figure out what is going on through the coolant-washed windows. You get about one-tenth of an Ohno-second before the crash when you do something stupid. The parameter file is mentioned, but not documented in the paperwork or manuals.
22. While I'm at it, that same little file contains various other bits of info that appear meaningless to you, but are super critical. Make a backup copy of that file and store it somewhere off the machine computer, if possible (copy it to a floppy disk, write it down in your manual, or something). One of the bits in that file is the exact, factory-measured height of the spindle nose, measured from the table, when it is precisely lined up with the tool changer rack (assuming the same home zero is registered as the day it was measured.) Another tells the machine control the exact distance it can travel from home zero before it hits the "soft limit" (read, about one ohno-second short of a crash). This parameter for X, Y, and Z is what allows the control to tell you IN ADVANCE that the move you are about to make will exceed the machine limits, thereby avoiding a crash.

I know there are other wonderful things I could tell you about the machine, but I'm getting tired of typing.

Now, if you still like the machines, I think you should buy all three. For the right price, I'll sell you mine and throw in the an Edsel, a Corvair, and a Studebaker Avanti as well. Just kidding. Only the machine is for sale.

Thanks for the input.. Luckily I went in a different direction and got a anilam control 3 axis bed mill

thanks again

Fred

That is one insightful review of a Brigdgeport 308.

Thanks for taking the time to write and post it.

Jack

I am trying to find a service manual for a Bridgeport Discovery 308. Please help I am willing to pay. I would like the whole manual set or just the service section I have been able to get the machine running from memory of an older machine that I had. However I need to make some adjustments and I also need to have the power transformer retap to 220 instead of 230 3 Phase any help here would be great. I am almost there I think the manual can take me the rest of the way. Thanks Jim 828-527-8443 Call me anytime.

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Originally Posted by fredhh47

I don't know about the torque 22 head, but I do know this about the Discovery 308-SX:
(not in any particular order, not even by level of annoyance).
1. The control uses a very, very obsolete LPM 286-16 motherboard, made for Bridgeport by Western Digital, and never duplicated anywhere. Western Digital doesn't even remember making it. The machine will only handle about 25k bytes of program, no matter how much memory you install. It may or may not support a hard drive, as that was an expensive option when they were sold. If you want to upgrade the motherboard, there is a company (EMI, or Electro-Mechanical Integrators) that will do it for about $800 (warning, 5 year old pricing), and they have to install a special interface to make the new motherboard talk to the B'port control. It will support a hard drive, but they will also offer to sell you a Disk-on-board (a solid-state hard drive). However, upgrading the motherboard will not increase the program storage, but you CAN use the built in DNC mode to drip feed longer programs.
2.The monitors suck. Don't expect them to work and don't expect them to be easy to replace. Pull out the CRT monitor and put in an LCD screen in its place for a lot less headaches. And speaking of the monitor, there are functions presented on-screen that never were and never will be available. Occasionally for no reason, the display will suddenly change the font or start to look like an invasion of fraternities (greek letters or something similar). Only a re-boot will correct it and sometimes it will require several re-boots to do it.
3. The coolant tray under the machine will overflow (the coolant runs out from under the front of the machine) when fine chips plug the strainer screen, or shut off if the intake filter (down in the tank, the messy, smelly tank) gets clogged. Coolant also leaks out of openings in the cabinet that allow the head to slide up and down and other places.
4. The coolant pump may up and die for no apparent reason. Watch out! It runs on 460 volts!, REALLY! Be sure the new pump is wired for 460VAC or you can burn it out.
5. Expect to have trouble with the tool changer rack. It will sometimes mis-index and occasionally blows its fuse. Disconnecting and manually horsing the rack back from the spindle is a real pita, and hard, too. The clips that hold the tools in their proper orientation will loosen up and fall off. The screw that holds the block that keeps them in place is metric, but will probably be stripped after a short time. The spindle start fuse also blows if you do a lot of short cycles.
6. The Z-axis home switch is very unreliable. It will not always home to the same position. It may overshoot or possibly undershoot by one ballscrew rotation (maybe .125 or 3mm?). This can cause disaster if the home zero you set yesterday suddenly is an eighth of an inch lower when you home the machine today, and all of your tool length offsets are suddenly .125 too long. Even if you leave the machine on ALL THE TIME, you will have to re-home it eventually and the problem can occur. When the Z-axis zero is NOT where it was set at the factory (about 50 percent of the time on my machine), the Tool changer will not line up properly and it will make a hell of a noise when the machine tries to change tools. I actually had to make a pointer and stick it to the head, so it aligned with the top bar of the cabinet when the zero was correct. Yes, it was that obvious.
7. There is a very tightly bundled trunk of wires in the back of the machine. This entire bundle moves back and forth constantly as the Y axis moves in and out. The tie-wraps do not allow for the continuous movement of the wires, so eventually, one or more of the wires will either become exposed or break. On my machine it was the control wires for the X-axis that broke. A new cable for the X-axis is not a cheap item (if you can find one) and almost impodssible to install. Only a qualified service person (BIG bucks per hour, plus travel time and lodging if necessary) should do it.
8. Even if you cut every tie wrap and let the wires flop where they may, the insulation does not stand up well to exposure to coolant and oil (go figure that one!) and will dry out and crack.
9. The top bearing on the spindle is a weak point, but you can replace it.
10. The z-axis encoder is a weak point and will cost hundreds to repair or replace. It (AND the servo motor) must be sent out for diagnosis and repair. Estimated at $300 just for diagnosis, to $800 if you'd actually like them to fix it.
11. The VFD is a weak point and will cost hundreds to replace. Should be done by a service man unless you have big, brass ones......
12. In the control circuitry, there is an integrated circuit chip called a DAC (digital to analog converter). When (not "if") one fails, they are no longer available in the US. I found them being hoarded by a jobber in China. The original chip sold for about $6.00, but it cost me 10 times that amount to buy from the Chinese jobber, and I had to buy a minimum of 4. With shipping, over $250.00, and that was 5 years ago. The machine will tell you which axis is bad, but you have to locate the right chip to replace. (Hint: it says DAC on the chip, but there are three of them.)
13. The rubber gaskets around all of the windows will dissolve from extended contact with water soluble coolant, and they will fall out. You will end up making new, bigger windows and screwing them in place. The gooey rubber is a nasty mess.
14. The door interlock will drive you insane. It is supposed to make it safer to operate the machine, but it only makes it harder. You have to enter a special code to override the interlock (while it is not already locked) to be able to turn the spindle on with the doors open. The override allows you to run the machine when you are not in Setup Mode, and must be entered over and over. If the machine will not power up, you can't open the doors. (There is a small hole that allows you stick a small rod in to mechanically defeat the interlock, if you do it jusssssst righhhhhhht........ You will probably end up trying anything to defeat the interlock (removing the latch from the door and taping it in place in the interlock unit works well. The latch MUST be engaged with the interlock unit for the machine to work). If you can read the schematics, you might be able to permanently override the interlock at the circuit board level.
15. The fans that cool the cabinets and the one on top of the spindle are LOUD.
16. You cannot program the maximum spindle speed in a program, or you will get an error condition. If you have a 6000 rpm spindle, for instance, you cannot use S6000 as a speed. I use S5950.
17. You can easily enter a letter "O" instead of a Zero, or make some other error in a program, and you will get a "parser error" message that does not tell you what or where.
18. There are cables that tie the doors together, so when you close one, both are supposed to close. They will fail. The rollers that support the doors will become loose or fall off, and need to be checked regularly.
19. The so-called waterproof work light is probably already shorted out and worthless. Coolant sprays around the machine with such abandon that no light inside the machine is safe.
20. The pendant arm is usually in your way, doesn't swing far enough, and God help you if you stand up under a corner of it.
21. The machines are capable of 400 ipm traverse, but are light enough that if you use that without anchoring the machine to the shop floor, the machine will walk across the floor. You have to change one of the paramaters (in a little file that is supposed to be read-only, and is read into the control circuitry every time you start it up) to reduce the Rapid to about 250 IPM to keep it from moving without anchoring It. Believe me, 250 IPM is scary fast, especially when you are operating with the doors closed and trying to figure out what is going on through the coolant-washed windows. You get about one-tenth of an Ohno-second before the crash when you do something stupid. The parameter file is mentioned, but not documented in the paperwork or manuals.
22. While I'm at it, that same little file contains various other bits of info that appear meaningless to you, but are super critical. Make a backup copy of that file and store it somewhere off the machine computer, if possible (copy it to a floppy disk, write it down in your manual, or something). One of the bits in that file is the exact, factory-measured height of the spindle nose, measured from the table, when it is precisely lined up with the tool changer rack (assuming the same home zero is registered as the day it was measured.) Another tells the machine control the exact distance it can travel from home zero before it hits the "soft limit" (read, about one ohno-second short of a crash). This parameter for X, Y, and Z is what allows the control to tell you IN ADVANCE that the move you are about to make will exceed the machine limits, thereby avoiding a crash.

I know there are other wonderful things I could tell you about the machine, but I'm getting tired of typing.

Now, if you still like the machines, I think you should buy all three. For the right price, I'll sell you mine and throw in the an Edsel, a Corvair, and a Studebaker Avanti as well. Just kidding. Only the machine is for sale.

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Thanks for the info on this.. A company I make posts for has a machine like this one. It is a 308 like here

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http://www.youtube.com/watch?v=9204MH4kUTE

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Would it be worth it to make a post for this machine? If so do you know someone that has one.. It can be for Mastercam or Esprit or NX..

Thanks :D

I know this is resurrecting an old thread but I have read through the extensive write up of the nuances of the Discovery 308. I am looking at one too however, if I plan to replace all the electronics and servos with more modern components, how would your assessment change if this machine? Are the mechanical tidbits strong enough to warrant a rebuild of the machine and bringing it to the modern age? I believe this is also a Romi built machine, no?