Service Tips From The Experts:
Spindle Drive - One
of the most common problems with a spindle drive running in the
Vector mode is caused by the spindle motor encoder. Missing encoder
pulses will basically confuse the drive and cause vector
miscalculations which result in too much current output to the
motor. One sign is that the load meter will usually "peg" or
pulsate. Another sign is the RPM will not be stable. Too
often the drive is misdiagnose as being "bad" when it's actually the
encoder causing the problem.
The
best method of testing is to use a oscilloscope to view the A/B
channels. Pulse errors can easily be detected. With our
new Baldor H2 drive, we simply switch the drive into open loop Inverter
mode and you can see the encoder RPM calculations changing
erratically with the drives diagnostics feature.
One simple way to manually test an encoder is by using a FLUKE meter, set it
to AC input. When checking from the encoder supply power common to one of the
A+,A-,B+,B- encoder signals on the spindle drive encoder input
terminal, you should
see approximately 2.8 VAC when turning the spindle at the
orientation speed. The digital pluses look like an AC voltage
to a FLUKE meter.
Another important way to test the encoder is by checking the state
of each channel. With a voltmeter in the DC setting, from encoder
supply power ground to
the A+ encoder input, you should measure either 0 or 3.5 VDC.
The state is either high or low. If A+ is high (3.5 volts) then
the A-
channel must be low; A+ and A- can never be the same. The same logic
goes for the B+ and B- channels. If you rotate the spindle and
let it stop, you'll should see the states changing.
Testing Motor Encoders - A
simple way to test the motor encoder is by using the control
diagnostics.
At ENTER NEXT COMMAND enter the DI command then type G 0 3000 and
press ENTER to begin the diagnostics. They are menu driven and
easily navigated. Locate the function TEST ENCODERS (1010-4).
The display shows the encoder data for all the axis boards.
Press the Emergency Stop button and rotate the motor by turning the
Ballscrew. The counter will change if the encoder is sending
pulses. All the encoder ports are the same, so you can move
the connector to another board to verify that the board itself is
not a problem. The axis motors have one index pulse per
revolution, this is used only one time for the Cold Start procedure.
The spindle encoder does not have an index pulse.
To exit Diagnostics; you'll need to power off/on the machine.
Spindle Failures -
Bearing failure is the most common reason for a spindle to fail.
Today it seems the "end all" solution is
to sell you an "upgrade" to Ceramic Bearings.
Ceramic bearings are not new, they've been around for over 30 years. While ceramic bearing are in some
cases "better", as the saying goes "Better is the enemy of Good".
First off, not all ceramic bearings are the same, secondly if
ceramic bearings were so good, they'd be the standard of the industry.
There are many different ceramic bearings; the best are solid
ceramic while the cheapest are steel bearings coated with ceramic.
The basic advantage of a ceramic bearing is roundness, stiffness and
weight, which depending on the application can make the difference
between success and failure, especially above 20,000 rpm.
Stiffness can cause chatter which is a factor of bearing stiffness,
span, preload and shaft design. It's all a balance of design,
the ultimate design is to have more bearing preload at the lower rpm and less
preload and the higher rpm range. In the early development of
the Fadal spindle we actually had experimented with a dynamic
preload spindle. It automatically changed the preload
according to the rpm.
Unfortunately it was too complicated for production.
The correct preload is a balance between spindle rpm ranges- higher rpms
require less preload between the bearings. Less preload
reduces the heat but increase spindle "chatter" during low rpm
cutting.
The biggest cause of spindle failure is
Contamination and/or Heat. Below is a list of common reasons
why spindles fail.
Contamination: Typically, coolant gets by the
labyrinth seal at the spindle noise and brakes down the spindle
grease. It's easily detected as the grease turns a milky white
color.
Heat is another spindle killer. Duty cycle
and preload contribute to spindle heat failure. A simple way
to tell when a spindle is running hot is by checking half way up the
spindle taper. At this point the inner race of the bearings is
at the thinnest point of the spindle shaft wall thickness. The
rule is "if you can't keep your finger on it at this point; it's too
hot".
A simple warm-up procedure; 5000 rpm for 20
minutes in the morning is very important for all grease pack
spindles. It helps to distribute the grease evenly, after
sitting over night.
Belt Tension - The HI/LOW idlers need to be cycled.
Shifting ranges relieves the belt tension caused by the hydraulic
idlers. The torque of the belt causes the idler to keep going
inward which increases the belt tension between the spindle motor
and the spindle pulley. This causes an excessive load on the
top spindle bearings which increases the heat factor. This heat
factor can cause the grease to migrate down away from the top
bearings. Also,
cycling the idlers will increase the belt life by reducing tension
on the belts.
Another important check is to verify the idler air supply is less
that 70 psi. The machine has two regulators; one for the tool
in/out and one for everything else. Too much pressure to the
idlers will cause excessive belt tension and damage the top
bearings.
Spindle Coolant - verify that the coolant flow
hasn't been reversed. The coolant must flow into the
bottom of the spindle and out the top of the casting (return line).
It's easy to get the lines backwards.
Verify the chiller system is full and cycling correctly. The
temperature differential of the chiller input verses its output is
about 1.5 degrees. The BTU capacity of the chiller must not be
exceeded by the run time of the spindle; the chiller system needs
spindle off time to reduce the heat inside the spindle. For
excessive duty cycle, considers adding another chiller.
Tool Crash - Crashing the tool into the part can
cause bearing ball/race damage and/or actually bend the spindle
shaft enough to cause bearing failure.
CNC Memory Errors
- The CNC memory uses a "checksum" method to verify the integrity.
If the memory becomes corrupted (fails a checksum test), the "memory
error" message is displayed. One of the most common reasons for
this is the battery on the 1400 CPU board is failing. The battery backup design uses a
combination of a capacitor and a battery to maintain the memory
after the power is off. The capacitor does most of the work;
it last approximately 3 days. The battery power switches in
after that point. Even thought the battery might measure 5
VDC, it's only under a load that the battery can be properly tested
to see what voltage it can hold when under the load from the memory
chips. Dropping below 3.5 volts for 100 nanoseconds will cause
a memory corruption.
Many CNC problems can happen if the memory does become corrupted.
It depends on the area of memory that has been corrupted.
Sometimes the keyboard will even quit responding.
In most cases the battery needs replacing and it is best to send it
in to us for in-circuit testing and battery replacement.
You can usually recover temporally by zeroing the CNC memory using
the control diagnostics. Be sure to save your program, offset
and record the machine parameters (SETP) before zeroing all the
memory because you'll need to restore them after zeroing all of the
control memory. Leave the control power on and push in the
E-stop button instead of powering off the machine. This will
prove the battery or the switching circuitry is faulty.
Resolver Faults - A
resolver fault occurs when the axis controller card doesn't detect
the returning sign wave signal from the resolver. The resolver
signal originates from the clock board and is shared by all the axis
motors. If one resolver shorts the sign wave; all the
resolvers will fail.
We
added the 1060-0-1 board (it plugs into the motherboard) to separate
the signal for each individual motor and help identify which axis is
failing. This board could be bad a not allow the resolver
signal to reach the motor. Early model machines did not have
this board.
Another potential failure is with the resolver connector at the
motor. The six pin Molex has been know to fail and give a
marginal connection. You can put pressure on it in various
direction while having someone try and reset the fault.
The resolver bearings can fail and cause problems with the signal.
Bearing failure is often due to the misalignment of the motor end
shaft and the resolver shaft. The Helical coupler does not
allow for parallel shaft misalignment over .005" and simply
replacing the resolver will eventually fail again. You need to
replace the resolver coupler with a better designed coupler.
Contact us for more information.
Testing a Resolver -
You can test a resolver to see if it is indeed bad by using a
voltmeter and measuring the resistance of the coils inside the
resolver. The Resolver is constructed of three coils; two
excitation coils and one reference coil that is connected to the
axis controller card.
The image shows the interface connector and the associated coil
connections.
1) Check Resistance:
Pair A = 70 to 80 Ohms
Pair B = 190 to 220 Ohms
Pair C = 190 to 220 Ohms
B and C will have the same values; the actual value depends on the
manufacture.
2) Check for Coil-To-Coil shorts:
Any other pin combination besides the three individual pairs must
result as an open circuit.
3) Check for Short to ground:
Check resistance of each pin to Resolver frame (case). They
must not be shorted to the resolver frame.
4) Check the voltage when connected:
Pair A = 1.7 VDC
Pair B and C = 3.5 VDC
Pair A goes directly to the 1010 axis card; J2 bottom bullet
connector
RS-232 Using A USB Port Adapter
- Many customers using software to upload or download with the Fadal
machine have been experiencing problems after upgrading to a new PC.
The problem is most new computers do not have physical RS-232 serial ports. The
solution is to use a USB to Serial adapter. The problem is
some of the adapters do not work with existing software; such as
NCFadal or MasterCam. Not all adapters are the same; many of
them are made from inferior components and/or the device drivers are
poorly written and are not
very compatible with the latest Windows operating systems (IRQ type conflicts).
The simple solution is to use a industrial grade adaptor.
We've had customers solve their problems using a $36.50 product from
usconverter.com
Click Here for more information.
More
Service Tips coming soon... check back often.
Total Engineering Support! -
With
us you're not just getting the usual "Part In A Box!"
Here's four key examples of the Total Support our customers
receive:
Diagnoses - Direct help in determining if you
really do need to replace the part. When working with engineers
that design the machine, we can help determine if there's other
elements in the system that also need to be addressed before
replacing a suspected failed part.
Documentation - We provide very simple and concise, step by step
enhanced instructions
on how to install and get your replacement part in and running.
With our documentation we also include Preventative Maintenance
tips to help avoid future failures.
Warranty - Just like "the old days", we value our
relationship with each and every customer. We are driven by
fairness and committed to your satisfaction. Click on the
About Us page to learn about what made
Fadal so successful and how it guides us today.
Support - With the combination of our Fadal engineering knowledge and direct
interaction with Baldor and Glentek engineers, you are getting the absolute
best product support possible at installation and beyond.
Here's one example of True Engineering support:
Why keep replacing Resolvers when they fail? Fix the real
problem and your Resolver problems will go away!
It's not a matter of using better bearings as some might tell
you, call us at 888-727-1887, and we'll explain the real problem and the
best solution.
