[gridley51]

Gridley, do you have experience with this particular set of BP interact machines? Ever seen these symptoms before? I swore up and down that the SCRs on the THY1R board (at least 1 of them) would have been blown. But they're all OK.

It was me that sent you the schematic for the MT1 board.

[mflux_gamblej]

It was me that sent you the schematic for the MT1 board.

So, have you seen a machine that couldn't get to speed?

[gridley51]

So, have you seen a machine that couldn't get to speed?

Yes,but only at the setup stage.Usual problems I have had are overspeed and MT1 board failure.
I have a few of these drives on machines and repaired many more but not on Bridgeports though.Not that there is anything special about them.
Your big problem is you had a fault which caused your initial problem and since then you have torn it apart.
The KTK drive when designed was away ahead of it`s time with special attention being paid to giving sufficient indicators and test points to allow a fault to be pinpointed in the field.
First thing is to megger field and armature to earth.Make sure the motor is disconnected from the drive when you do that.Then check each for resistance,the expected readings may be in Georges notes.
You need to power the drive up but not give it a speed signal until you check that all voltages are present and correct.The leds you have illuminated at power on are the key to it all.They will let you know whether it`s right or not.You will not get a drive ready signal if there is a fault with the drive.There is also an inbuilt voltmeter which lets you check internal control voltages.Phasing and input voltage and field voltage have to be present and at the correct levels,tacho checked for continuity although the control has field and tacho failure circuits.
It is better when fault finding to disconnect the drive from the cnc control so that you have total control.Use a battery box to do this.
I can`t help you with specifics as all manuals etc are at work and I`m recuperating from a major op and not allowed near the works for another six weeks.
I did have a major library at home but lost that computer a few months back and have not got round to backing it up yet.

[mflux_gamblej]

Yes,but only at the setup stage.Usual problems I have had are overspeed and MT1 board failure.
I have a few of these drives on machines and repaired many more but not on Bridgeports though.Not that there is anything special about them.
Your big problem is you had a fault which caused your initial problem and since then you have torn it apart.
The KTK drive when designed was away ahead of it`s time with special attention being paid to giving sufficient indicators and test points to allow a fault to be pinpointed in the field.
First thing is to megger field and armature to earth.Make sure the motor is disconnected from the drive when you do that.Then check each for resistance,the expected readings may be in Georges notes.
You need to power the drive up but not give it a speed signal until you check that all voltages are present and correct.The leds you have illuminated at power on are the key to it all.They will let you know whether it`s right or not.You will not get a drive ready signal if there is a fault with the drive.There is also an inbuilt voltmeter which lets you check internal control voltages.Phasing and input voltage and field voltage have to be present and at the correct levels,tacho checked for continuity although the control has field and tacho failure circuits.
It is better when fault finding to disconnect the drive from the cnc control so that you have total control.Use a battery box to do this.
I can`t help you with specifics as all manuals etc are at work and I`m recuperating from a major op and not allowed near the works for another six weeks.
I did have a major library at home but lost that computer a few months back and have not got round to backing it up yet.

I'm certain that messing with the pots was a bad idea on my part. I'll get it put back though. Thanks for your help.

I have measured the resistance to Gnd from each motor contact. They're all several megaohms, altho, I don't have a 500V megger.

I am concerned about the noise that the motor makes when you move it CCW by hand. In the CW direction, it is silent. In the CCW direction, it makes an audible clicking sound which sounds like crackling or grinding of loose small parts or gears. I am suspicious of the lower bearing, and of the tacho assembly, and possibly of the 2nd brush which I have yet to reach.

All of these things require me to pull the motor out of the machine.

[gridley51]

I have noticed a very light ticking noise quite often from mill dc motors.They are silent in the usual direction of rotation and tick when turned backwards.I put it down to a sharper corner on the rear of the commutator bar due to most of the rotation being the one way.
If it`s a mechanical roughness which you can feel then you need to look at the motor or brake.
I wouldn`t worry about the tacho at this stage.It was working or you would have either a runaway or a shutdown the last time you ran the motor.
It can be checked once the motor is running.If you want you van put a voltmeter on the tacho leads and twist the motor spindle,you should have some volts there.

[john-100]

with PCB's thats been in service for several years
I'd first check all the electrolytic capacitors (eg C4 , C5 , C6)
and any low value resistor thats used to measure the motor current (eg R27) or resistors of 100k or more used to measure the motor voltage

since your having problems after an overload

its possible a large voltage across R27 could have damaged IC1's input circuit (Pin 9)

also check the circuit around the 12V zener diode D7 and optoisolator OP1
both will affect the ARM VOLTS and MAX FIELD adjustments

with a voltage of 22V across C14 , the current through OP1's LED will be at the maximum current of 20mA
during the overload an excessive voltage across terminals 36 and 37 could of damaged the LED inside of optoisolator OP1

John

[mflux_gamblej]

I replaced the SCR on the MTI-1 Board.

After that, I carefully followed George's KTK Maint. notes to setup the KTK Drive and MTI-1 field control board.

The motor will reach speed now, but is not in great shape. At 4000 RPM the whole machine (and room) vibrate violently.

In addition to the vibrating, there are some discrepancies with the control behavior:

• The tacho voltage is approximately 2X what the maint. notes calls for.
• The spindle does not repsond well to changes on the spindle override (on the TNC 151). It seems that the motor doesn't reach the desired speed quickly enough and it simply shuts off. At lower speeds, e.g. 1000 RPM, the spindle override works OK.
• The armature voltage set point that I am having to use is higher than the KTK notes say to use. If I setup the voltage to be 400 (or so) at 4000 RPM, the machine will not reach 4000 RPM and will turn off the spindle (again timing?). For now, I've got it bumped up slightly higher and it will reach speed.
• The spindle will not reverse at high speeds either - again I believe this is a 'didn't get there fast enough, so shut down'. at lower speeds, the spindle will instantaneously reverse as expected

I am suspicious that the motor is deformed or that the bearings are ruined from the 'brake on crash' and the motor controller is pushing a damaged motor very hard to reach it's set points.

Any thoughts on reducing vibrations unrelated to the bearings? (I am not hopeful here, but will try everything before buying another motor).

[keebler303]

Vibration and excess tacho voltage would make me think the motor is going too fast. How are you measuring the 4000 RPM?

Matt

[gridley51]

Agree with the previous poster.Check the spindle speed with a tacho but allow for any gearing between motor and spindle.
Check it has the correct tacho fitted,work out what speed the spindle should do to get the motor to run at 1000rpm and check tacho voltage.
Is crossover setup correctly for field weakening?

[mflux_gamblej]

Agree with the previous poster.Check the spindle speed with a tacho but allow for any gearing between motor and spindle.
Check it has the correct tacho fitted,work out what speed the spindle should do to get the motor to run at 1000rpm and check tacho voltage.
Is crossover setup correctly for field weakening?

The field weakening is working correctly. I also am suspicious of the motor going too fast.

The way that I am measuring the tacho voltage is to check between pins 6 and 8 on the FAC1-R board (the KTK spindle drive controller board).

I have a table that shows what the voltages should be for certain spindle and motor speeds. The motor is at 6000 RPM when the spindle is at 4000 RPM. It is belt driven with the gear ratio as above.

The table: (spindle speed : Armature Voltage : Tacho Voltage) 40 RPM : 8.2 V : 1.2 V, 1800 RPM : 370 V : 54 V, 2667 RPM : 380 V : 80 V, 4000 RPM : 400 V : 120 V

There is another place in the maintenance notes which has you check the tacho voltage on the FAC1-R at 400 RPM. The voltage should be 12 V.

I measured 22.3 V.

So, I wonder why the controller might be doing double RPM? I will make more measurements to see if the 'acutal' RPM vs. Tacho voltage curve is non-linear, and how offset it is.

In the case the the motor is actually running 2x, I better be damn careful to not ruin my spindle bearings.

I can set the armature voltage on the MTI-1 board using a pot. If I setup the machine as indicated in the table (above), the spindle will not make it to what it believes is 4000 RPM. I have to crank it up very slightly.


Something of interest that could be relevant: FAC1-R board is configurable for 50 Hz / 60 Hz. I am in the USA, and need 60 Hz. I don't know the machine's full history, maybe someone didn't commision it right the first time here in the US. The board is configured for 50 Hz.

I imagine that this could cause a speed offset of either 60/50*SpindleSpeed, or the other way around 50/60*SpindleSpeed.

If it is option 1, then when called for 4000 RPM, the spindle would actually be trying to run at 4800 RPM.

This might explain why the armature needs to be bumped up some to get there.

Also, the machine does actually respond pretty well up to about 3000 RPM to changes on the spindle override.


I've been out running the spindle some at various speeds to learn more about it's behavior. The vibrations really don't get horribly bad until above 3000 RPM or so. Any vibration makes me nervous, but maybe I am over-reacting some. When turned by hand and forced around by hand to see if the motor bearings are loose or rattling, it doesn't sound bad. The is some noise that I believe that the brushes are making.

[keebler303]

I think you need an accurate speed measurement before you can go much further. Can you measure the speed independent of the control?

Matt

[mflux_gamblej]

I think you need an accurate speed measurement before you can go much further. Can you measure the speed independent of the control?

Matt

I do not have an independent way to measure the speed.

Any suggestions?

I expect that there are instruments available to do this with.

Update: I ordered a laser tachometer. $20 on amazon.com - this will be good enough I think.

[gridley51]

The motor won`t go to top revs at the correct armature voltage because the feedback voltage from the tacho is telling it,it is already there,so turn the armature voltage down to what it should be and find out why the tacho is giving you more volts than it should.
Either someone has fitted the wrong tacho,or you have noise on the feedback circuit,or you simply have a wire in the wrong place.
Before you start doing other things you need to get the motor running at base speed or lower with the correct armature and field voltage and the correct feedback voltage.
If you cannot achieve that then there is no point in progressing further.
BTW,it would not be spindle bearings I would be worrying about if you are seriously overspeeding that motor.

[gridley51]

I do not have an independent way to measure the speed.

Any suggestions?

I expect that there are instruments available to do this with.

A simple hand held tacho is all that is required.Put something in a collet in the spindle to run it on.
You appear to be seriously under equipped to be messing about with spindle drives.

[mflux_gamblej]

It will be interesting to see the results using the laser tach that I ordered.

I am pretty suspicious of the 50/60 Hz problem.

The FAC1R has two pins that you change to convert the system to 60 Hz. I am unsure, though, if further changes would be required.


In the mean time, I'll keep the set point under 3500 RPM.

I have an additional problem, that is, the 'auto' brake mode does not release the brake when you start the spindle. Also, when you press the 'spindle off / tool change' button, the spindle fan shuts off. George's KTK maint. notes say 'make sure the spindle blower doesn't shut off when you press the spindle off button.'

Somewhere there is a relay, or maybe a machine parameter on my TNC 151? That isn't doing it's job of automatically releasing the brake. For now I've wired up an annoying piezo buzzer that is on when the brake is applied to remind myself to turn off the brake ASAP.

[mflux_gamblej]

A simple hand held tacho is all that is required.Put something in a collet in the spindle to run it on.
You appear to be seriously under equipped to be messing about with spindle drives.

Under equipped or not, I intend to get my CNC machine making parts! This is an after-hours operation for me, funded by my personal money. I can't afford a new HAAS, or a field service engineer to make my life easy for me.

I'll get the machine to behave..

[gridley51]

I'll get the machine to behave..

I`m not saying you won`t,but you need to stick to basic procedures and you will get there a lot quicker.

[Al_The_Man]

Get some thing like this, they work fairly well, but remove the battery between use, as it drains pretty rapidly.
[ame=http://www.amazon.com/Professional-Digital-Laser-Tachometer-Contact/dp/B004Q8L894/ref=pd_cp_e_1]Amazon.com: Professional Digital Laser Photo Tachometer Non Contact RPM Tach: Home Improvement[/ame]
They are all over the web, so there are many sources.
Al.

[mflux_gamblej]

I measured my spindle speeds using the laser tach from amazon.com.

The spindle is 180% faster than the setpoint. This relationship is linear throughout the RPM range.

I made sure the laser tach is sane by counting the rotations in a 1 min period. My count and the tach's count are the same.

I have the idea that it might have been 120% overspeed because the board is config'd for 50 Hz and I am running it in the USA at 60 Hz.

180% over doesn't make sense yet.

However, no wonder the machine sounds likes its going to rocket apart when set up at 3000 +, because at 3000 its already at 5500 RPM (1500 over the design limit!!)

I could definately use some help here. Is there anything I need to do to setup the machine for 60 Hz other than config the two jumpers on the FAC1R board?

Data is below.


Spindle Speed Measurements
8/11/2012
Bridgeport Interact 1 mk 2
KTK Spindle Drive
9.25 HP Sicme Motori DC Spindle Motor (P90-L)
MTI-1 Interface card (field control)

Sanity check on laser tachometer:
Counted rotations for 1 minute using stop watch
counted: 72 Rotations / 1 minute
Laser tach shows 71 RPM


Spindle Speed Set Point (RPM), Laser Tachometer Reading (RPM), Ratio
40, 71, 1.775
80, 143.5, 1.79375
100, 180.6, 1.806
200, 361.5, 1.8075
400, 725, 1.8125
800, 1453, 1.81625
1000, 1818, 1.818
1500, 2733, 1.822
2000, 3650, 1.825
2500, 4573, 1.8292
3000, 5502, 1.834

[john-100]

you may of fixed the fault on the MTI field control board and now have a problem with the board that controls it

with the motor speed and the tacho output is 180% of that expected

its now possible the board that the tacho is connected to is either faulty or misaligned
so just over half of the tacho output is being compared with the control voltage for the programmed spindle speed

there must be a gain control to adjust the tacho output


John