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WilliamH
02-28-2005, 10:47 PM
Hello,

I own a Bridgeport BOSS 5 mill. My problem is the Z axis stalls. I have changed the driver transistor set and the driver boards near the transistors to no avail.

The Z axis stepper motor moves the quill about one inch and then stops and makes a funny noise.

This machine is very tight and other wise mechanically excellent. If not, I would get rid of it. I have gone through the Bridgeport manual and checked all voltages and currents. Any help would be appreciated.

Thanks in advance,

Will

ibewgypsie
02-28-2005, 11:59 PM
Pull the knob off the Z motor, drop the plate under the motor but over the spindle speed control box.. check the Gilmer belt going into the quill drive.

I think you'll find your problem there. A tooth or two or a wad of crap has gotten into the belt. I had a field mouse living in mine for a while. Instead of getting into the quill, he got into the motor fan and got chewed up. I got sticky traps everywhere now.

David

WilliamH
03-01-2005, 08:54 PM
ibewgypsie,

I did that and found nothing wrong. I removed the belt and the stepper runs fine with belt removed. The quill is free and the ball screw is also nice and free.

I am thinking the stepper motor is on its way out.

Will
<font face="Verdana, Arial" size="2">Originally posted by ibewgypsie:
Pull the knob off the Z motor, drop the plate under the motor but over the spindle speed control box.. check the Gilmer belt going into the quill drive.

I think you'll find your problem there. A tooth or two or a wad of crap has gotten into the belt. I had a field mouse living in mine for a while. Instead of getting into the quill, he got into the motor fan and got chewed up. I got sticky traps everywhere now.

David</font>

JRouche
03-01-2005, 09:20 PM
If you suspect the motor give her a swap with x or y. Can you manually drive z up and down with the motor removed from the belt? JRouche

John Stevenson
03-02-2005, 07:56 AM
Highly unlightly the motor is suspect.
If it can move the Z about 1" then this is roughly ten full turns of the motor.
Motors don't run ten turns and stop.
You have also stated that the Z runs fine without the belt on.

Sounds mechanical on the Z.
try to move the Z up and down by turning the ball screw and seeing what happens.

You must be methodical at finding out what the matter is, only try one thing at a time and make notes on the results.

John S

WilliamH
03-02-2005, 09:41 PM
Gentlemen,

I will substitute a drill motor tomorrow to run the cog belt and see if there is a problem with the quill/ball screw mechanically. Pulling the belt by hand, there is no problem detected. Very smooth. No scratches on quill at all. This machine is in excellent condition otherwise. Very few hours.

The original Z stepper runs fine with the belt removed. I tried another stepper from a Boss 5 that got an upgraded control and that stepper stalled without a belt. My thinking is that that this stepper (replacement) is defective. My stepper will run continuously with no load/belt.

By the way, I have checked and adjusted the axis currents as per factory manual. That is 8.2 amps.

I should have more info tomorrow. Thanks for the suggestions!

William

ibewgypsie
03-03-2005, 09:34 AM
Nothing to do except pull out the scope and the chart recording current probe.
Diagnosis by remote is kinda like a blind man feeling his way down a alley. ("Good evening ladies" as he passes a fish market)

Try swapping the motors as suggested, if it still exists with a "known" good motor it is mechanical or electrical unique to that axis. That rules the motor out. The motors are wired internally with two coils. Perhaps easier is to swap the whole axis motor leads there on the bottom of the righthand rear door terminal strip (one with huge heat sink), they are labeled quite well there. This would allow you to move the Z wiring and outputs to another axis to see if the problem still exists and mechanical or electrical.

The way the boss system works the current is limited though a reactor and several gold colored resistors (look for discoloring) there in the back cabinet, the main power comes from the 3phase 3bank transformer there in the back middle left. This feeds a bridge and the DC capacitor bank unique to that axis, In the rear box, The single transformer looking goodies are the reactors. One for each axis. Poor capacitors could be also the loss in power, discharging internally before dumping to the motor coils.
I guess if motor and mechanically alright it is a supply problem. Not a output transistor problem. Of course I am not there.

I find the Boss stepper system weak, A unipolar design that once you run bipolar on the same motor you are impressed. The gilmer belts running off the motors to the drive screws should not be large enough for that much torque, but nobody I have talked to has seen one stripped out.

If you can not fix the problem I suggest you do as I did. Strip it to the basic core machine and build your own. Several others here have done similar jobs like that. Shame for a good machine to be sitting collecting dust.

David

WilliamH
03-03-2005, 09:41 PM
ibewgypsie,

Thanks for the additional suggestions. Also, the "fish market" analogy was the best thing I heard all day. Still laughing!

I think I will have some time tomorrow to spend on the BOSS 5 project. We have three extra axis motors I could try, plus your suggestion of swaping drive axis cables at the terminal strip. We do not have a scope to track current.

I would like to upgrade the control but my partner is too tight to spend the money. So I am spending hours on a known faulty/unreliable control system.

William

BAB
10-12-2010, 05:11 PM
When I try to jog the X axis I can hear the motor running but the pulley just quivers or moves sporadically. I have changed out the stepper motor with another and the problem is still there. Seems to be no blown fuses, or resets to press. I have the same problem on the Z axis on another which seems to be related to either E-stopping OR a crash.

mc_n_g
10-12-2010, 07:40 PM
Sounds like the transistors are bad or something is loose with the bayonet fuses.

Liger Zero
10-12-2010, 08:03 PM
Based on experience with mine... there is a short somewhere due to rotted wiring or a loose solder joint somewhere.

Good luck! Best bet is to strip the old control and put a new on in.

BAB
10-12-2010, 08:31 PM
Bayonet fuses?

BAB
10-12-2010, 08:42 PM
That could be on the one, but the other was running fine until after the crash, It doesn't make sense!