Need Help!- Boss 5 No Axis Movement

[timprebleco]

I have two boss mills. One is a Boss 6 and it is working fine. A while back a guy gave me a Boss 5. Mechanically it is in really great shape. I have never gotten it to run long enough to run a program.
The drive axis have some sort of an issue. I have gotten all three axis to move for short peroids of time and then nothing. The latest is there is a blown fuse on the Y axis of the SMS board. I have 6 volts on the X & Z fuses and about 70 volts on the center Y fuse. I have checked the voltages comming of of the main transformer (T2) and some time all three match up and sometimes the y axis is real high. I have even replaced the bridge rectifier to the Y axis. Every time I start it up I check the voltages and they are always diffrent (the boss 6 does not do this and are on the same power line). The power coming in seems to be about the same. After I replaced the bridge rectifier the voltage seemed ok for a little bit and then the resistor on the SMS board heated up and the voltage is way high again. Also when I start it up I am getting most of the lights on the control panel light up (HOLD,WAIT,GO TO, RUN) The display reads 6.888 and the clear/reset program switch will not make it clear out. The spindle will always turn though. I have all of the Boss 6 manuals and I am at a loss as to what to check next. I have a freind who has a good supply of parts I just can not figure out what is bad. I need to get this machine running.

[machintek]

These machines run at 60VDC when in rapid and current drops to 2 amps. But when at a standstill the voltage drops to about 9 and the current goes up to 8 amps. If there is no load on the Y axis it will go up to 60 volts if the drives are ON. You may have a bad SMS board AND/or a open resistor on the saturable core reactor on the Y axis. I typically replace these resistors with the same value but double the wattage. They do get hot.

George

[timprebleco]

George,
Thank you for your response.
Starting with the SMS board. It has the same resistance and the diodes all check the same on all three of the lines. Are you doubling the wattage on the SMS board resistors? Are they supposed to be 5 or 10 watts?
I am seeing about 70 volts only on the Y circuit but 6 volts on the other two. This tell me something is wrong only on that circuit. The boss 6 that is running
is only showing about 6 volts on all three circuits.
The Saturable Core Reactor? I don't see that on the schematic. Exactly what are you refering too.

[machintek]

In the back cabinet beneath T2 are 3 wound devices that look like transformers but are not. They are in the drive schematic. These are the saturable core reactors. Used in conjunction with the ACC board, it limits the current going through the motors.
I have seen this many times: the power resistor on these Sat Core Reac suffers from heat, even shows cracking and goes open. This is followed shortly by the SMS burning up and the ACC burning up. I am not saying this is your problem but it may be part of your problem. You have to understand how the drives work. I do not believe your meter is accurate.
Monitor the voltage on any axis on the BOSS 6. At standstill and at rapid.
I believe your Y axis has no load. It may have a open circuit. But that is why your voltage is high.

George

[timprebleco]

George;
Let me say right off. I really want to thank you for your help.

I have 3 meters and the other day I was getting the high readings with all the meters. I made multiple checks on the same points. The longer the machine was on the Y voltage seemed to increase. It was always on the Y axis.
Today I am only leaving the machine on long enough to check the voltage and shutting it off before typing it in on the computer.
The resistors on each of the Staurable Reactors are all checking between 102 & 108 ohms. They are labeled 100 ohms but the wattage is not listed. The Diodes (or that is what they look like) are all checking the identical as well.
I just powered the machine up. Pushed the limit switch in. Started checking voltages.
At the SMS Board I have 7.1, 7.5 & 8.1 DC volts moving from left to right.
This is from the fuse to cabinet ground.
At fuses 15, 16 & 17 I have 4.2, 4.6 & 4.6 DC Volts.
At terminals 40 & 39 The DC voltage is 23.
At Terminals 74 & 76 The DC voltage is 55.
At Fuses 12, 13 &14 I have 8.2 DC Volts to cabinet ground.

The only voltage I can find that is constantly out of spec is the -12 UR to GND it is 16.6 DC Volts (my Boss 6 measures 16.2 and it works so I am not too worried about that one).

If I flip and hold the reset switch, then shut off the machine, power it back up, push the limit switch. I hear the stepper motors "grunt" I can see the Z & Y motors move a step (I have the belt covers off) I can not tell if the X is moving or not. But it will only do this if I reset it before shutting it down.
Except for this none of the axis's will jog or even step.

A bit of history on the machine. It was only used a couple of years and the cost of keeping it running due to board failures and service calls got to be too much. (Inside the cabinets are real clean, the spindle motor pulleys and the ways all look like new). They bought another brand. It set for many years and was sent to a friend of mine to make it a "manual mill". The cost was too high and they never came and picked it back up. It came to me FREE, but with out without an ACC board. I picked up a used one. 4 times I have joged all of the axis, one right after the other and then there will be nothing. It is like something resets every once in a while. This is a really nice looking machine, I have just not been able to spend enough time on it to get it to run.
Thank you;
Tim

[timprebleco]

George;
Would a short in the y axis drive motor be causing the high voltage readings. I have extra motors I could switch it out with. What might be causing none of the axis to move. Is it the ACC board.
Could all of this be causing the control pannel lights and read out to be "locked up".
Seems like I may have several problems.
I don't know where to go from here.

[machintek]

If the control is locked up then it is not thinking and no axis will move.
So press the reset toggle switch and see if it starts to respond.
If not check the logic power supply WHERE I TELL YOU TO.
There is a small terminal strip, At the top and right of the logic card rack. it has 6 wires that are very thin - 3 are blue and 3 are lavender, Go to the two wires that are blue and lavender side by side. This is where you measure the 5 VDC and adjust it. Now go out one wire in each direction and measure the 12 VDC, the last 2 are for the -12VDC.
There wires come right off the logic boards are are the best place to measure the logic voltage.
You can also pull each logic board out one at a time. clean the edge connector with a soft eraser and put it back in.
If this does not help, it may be a board issue.
I still believe that you have a OPEN circuit. No load Which is why the voltage is so high on the Y axis.

George

[timprebleco]

George,
Thank you!
I checked the Voltages just as you requested. 5.01 v in the center 76 & 79,
12.01 v 76 & 67, -11.9 v 76 & 59.
I removed all the boards and used the eraser on the contact tabs. Reinstalled them and now every thing moves.
I have MDI'ed a program with 10 steps in it. It has ran at least 10 times through this program.
The Y axis is running fine today. I had removed the motor earlier (so I could see in it) found nothing loose inside the cover. Does the possibility of an intermitent open circuit still exist and how would I know.
I am seeing a problem with the Z axis, It does not want to rapid with out stalling out it also seems to have a chatter or vibration in it when it homes in to zero that last .300" or so. The Boss 6 book tells me to lubricate the quill manually, I have. (I put a lot of slow Z moves Feed Rate 300 or less into the program I have been running). It does run fine with out the belt attached in rapid. The book instructs me to check the Z axis step motor static current at Z axis Fuse 14 terminals 33 & 28 for 8.1-8.3 ADC. Make adjustments at P3 of the ACC board. I do not see a #28 wire. How is this test performed?
Having come this far I do not want to mess up something else or undo the progress already made.

[machintek]

A Boss 5 steps in .001 inch steps. so it may sound rough but it is stepping.
The Z has a decel switch. the last .200 inchs it should feed slow.
Flush the quill with kerosene and reoil with vactra number 2.
Check current. Turn off drives. replace DC fuse (fuse 14?) with a meter set to amps (or use a current clamp) turn drives on and set acc (from top to bottom X, Y, and Z, you are adjusting Z) for 8 amps. Turn drives off and then take meter out of circuit and put fuse back in. Do you have snap in or screw in fuses? Screw in fuses are bad.

George

[timprebleco]

George;
I have set the ACC board to 8 amps. I do have the screw in fuses but I have a small clamp meter. I clamped it around the single wire coming out of the fuse.
I have cleaned the quill, I am using Mobil Vactra #2 Way Oil, I have the front cover open and covered the quill and ball screw completly several times. I am running a program with a lot of up and down on the Z. It will run fine at feed 500 but still stalls out in the rapid. Is there something else to check? Other than that every thing else seems to be fine.
Thank you!
Tim

[machintek]

The screw in fuses were terrible in that they developed a high resistance in them. Some would get so hot that the inside of the ceramic fuses would melt out. You can disassemble them and check them or measure the voltage drop across the fuse.
It may be part of your stalling issue. Stalling occurs when acceleration of the motor lags so much that the rotor gets attracted to the following pole instead of the leading pole and this sets up a vibration/oscillation between poles that sounds like a whine. It lags due to friction or a lack of power. Stepping motors suffer from heat and age which makes the permanent magnet field decay which results in a weaker motor. The life of the motors can be extended by turning down the rapid rate on the RCK board. Thus the ramp up is a little flatter and the motor can achieve it without stalling.

George

[timprebleco]

George,
Thank you for the information.
This Boss 5 machine is all original with the screw in fuses. My Boss 6 machine has had the original fuse holders 15,16 & 17 in the back cabinet changed out and 12,13 & 14 in the computer cabinet as well. It sounds like it might be a good idea to follow their example.

The RCK board adjustment...I see 3 ceramic resistors on the edge of the board (like the ACC board for the 8 amp adjustment) is this the adjustment that you are refering to? If so is the Z axis adjustment the bottom one? Assuming that counter clockwise would decrease the ramp up.

I had the same stalling problems with 2 of the motors on the boss 6 (Z,X axis), its a Series II. I have yet to find a motor that will move that big table in rapid on the end of the travel if it has 150 lbs on it. Sounds like I need to try to adjust the ramp up on it as well. I thought it might be a good idea to have an extra so I now have 4 extra motors. Is there a way to check a motor before you swap it out to see if it would be in better condition than the next one. The guy who sold them to me said to turn the shaft and feel the magnets, the harder it turned the stronger it would run. I can not say that this has proved to be a good indicator.
I do not want to buy another motor if it is not better than what I already have.
Thanks again for your time and help, I am still excited just to see this machine run.