BP Boss 5, Z-axis quit, help me please!

[rsr911]

My Z axis quit working on my Bridgeport Boss 5. The motor has holding torque and when I hit the jog button it steps back and forth about one step, it turns freely with the machine off. Any suggestions?

[machintek]

Yes, a few. First, put it in setup, jog, and step. If it does not advance one thou each time you press the - key, it is very possible that you have a blown transistor. They usually short, so the rotor of the motor cannot get away from that field.
This is extremely common but can be minimized. How long have you had the machine? How familiar are you with where the components are? Do you have any spare 2N6547 transistors? Can you use a meter to find a shorted transistor using the diode check (voltage drop across a semi-conductor junction) feature on the meter?

George

[WayneHill]

They can be found on Ebay.

http://cgi.ebay.com/ws/eBayISAPI.dll...60222&tc=photo

[rsr911]

Thanks guys, I'm home for lunch so I called the local electronics supplier. They are expecting their shipment today and are holding 4 of them for me. Should I try to get those diodes as well? The ebay ad just says 1000V fast recovery, do I need any more info than that to buy them? I've had this machine about 5 monthes. I bought it as a hobby and to make a few bucks selling little things. I've been teaching myself G-code as well as how to setup the machine and have made some nice parts with it so far. I have little doubt I blew whatever is blown since I wrote bad code several times and had a G00 rather than G01 for a Z movement which crashed the tool into the stock. Overall the machine is in good shape for something that was in a production environment. I'll check back later when I have the parts.

[rsr911]

I want extend a huge thank you to George (machinetek) who spent over an hour on the phone with me talking about oru favorite brand of cars while he helped me troubleshoot the machine. Turns out one of the transistors is shorted and I'll have a new one tommorrow so if all goes well I'll be up and running again. Seems George and I have a mutual friend who put us in touch. I wish I knew more about CNC and hopefully as I learn I can start to answer questions rather than just ask them. It's communities like this that really make life grand. I'll let you guys know when I have it running.

-Christian

[rsr911]

It's fixed! What a relief, I went ahead a replaced all four transistors with 2N6547's per George's suggestion. Now I'm back on schedule and can cut parts tommorrow. Yeah!

[rsr911]

Well,

Ever since you fellas helped the last time this machine has been running great but today the spindle jammed about 1/4" below the home position. The stepper can't move it up or down and the spindle motor won't turn it. I can't turn it by hand either. Spindle brake engages and disengages just fine. Any ideas?

[machintek]

Oh Boy! Does the Hi/Low shift lever move on the right side of the head? If so does anything else move, like the quill?
With the brake off, you are telling me that you cannot turn the spindle.
The quill will not move if you try and turn the Z motor pulley with the drives off.

I have seen under a very heavy intermittant cut, the spindle splines get a twist and get jammed in the splined gear hub. Then the side lever moves up and down with the quill. But it can still turn.
I have seen the chrome peel off the quill and the quill jam inside the housing. Very bad situation but the spindle will still turn.
Take a break, walk away, and come back with a clear analytical mind and tell us what you find.

George

[rsr911]

Well I pulled the belt cover off the Z-axis thinking the belt had popped off but it's still on there. The shift lever does move because I tried to put it in low and turn the spindle on, still wouldn't turn. I opened the front cover and nothing appears bent or damaged. I took the wiper off the bottom to see if a chip got jammed, nothing. It's weird. I felt like giving it a rap with a deadblow but I'm scared of that idea. There's a collet holder in the spindle so I tried to turn the nut on it with a wrench but no go there either although I didn't use much force for fear of doing more damage.

George, got your email earlier, I've sent some jokes my father sent me. Thanks for the help. I'm going to do a bit more inspecting.

-Christian

[fredhh47]

Is there any possibility that the pulley on the Z-axis motor is binding up against the motor or the housing? If it had been binding previously, that could have caused your earlier transistor failure. In 25 years of running my BOSS 5, I've never had the Z-axis bind up that way. If the spindle itself isn't turning, you may have a seized bearing in the quill, but that wouldn't account for the quill not going up and down. You may have a problem in the top end, perhaps a total disintegration of the speed-changer mechanism. That could put a torque on the quill that could cause it to bind up past the point where you could move it with hand tools. Sounds like you have a serious mess. I'm sorry

[machintek]

These two issues should be seperate.
You did not mention if you could turn the z motor pulley.
You did not say if the spindle brake was released.
Could be electrical issue with a dead control meaning a missing phase.
Pictures were great! thanks.

George

[rsr911]

OK,

I was able to turn the quill motor and one I get it about 1/2-3/4" down it will move up and down fine. The brake is released and I've removed the air from the machine. Well I should say I think the brake is released, the lever that actuated it moves up and down and it's in the off position with no air to the machine.

Seems to me like the spindle drive shaft is bent, twisted or both but I can't be sure yet. The spindle motor does run but only if I pull the hi/lo lever in the middle where the gears are disengaged and hold it there so I don't grind the gears. If I do that the motor spins but I still can't turn the spindle.

Is it even remotely possible to by replacement parts for this machine? Will I have to sell my first born? LOL.

I've got all the manuals at home so I'm going to take a look there for an exploded diagram so I can see how it's put together. This is kinda depressing, I've been having a lot of fun with it lately now that I've gotten good with canned cycles, loops and macros. Still lots to learn but it's neat watching the machine run.

Oh and Fred, no binding of the pulleys, that's the first thing I checked, well after checking the belt anyway. I'm going to take a closer look to see what I have to do to get a look at the brake so I can be sure it's disengaged.

BTW the largest endmill I've ever used was a 1/2" I don't load the machine all that much but I do frequently run near the top of the RPMS cutting aluminum with a small endmill.

Is it possible the topend lube is messed up and the gear case ran dry? I notice way oil on the floor when I run the machine a lot and the ways are in great shape. The quill always appears to be well lubed as well.