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Whether you're an experienced user with MT Works2's visual programming environment, or
a first-time user, it's always helpful to understand how these virtual components align
with the actual machine. Here, you'll see that the rotary knife servo represents the
cam output module. The master encoder provides input to the servo axis, translating it's
information through the electronic clutch and differential gear. Lastly, the photoeye
mark sensor on the machine provides information to correct the position of the servo. This
takes place through the virtual auxiliary servo motor.
An important part of the setup for the rotary knife application is establishing the correct
electronic gear ratio for 1-to-1 follow with the encoder. This guarantees the rotary knife
blade doesn’t damage the material so it provides a clean cut every time. The product
length setting provides information to the servo so it can consistently cut the material
at the right distances. The rotary cutter servo resolution and diameter define the amount
of pulses per inch for comparison with the encoder’s values, Pe and De. Lastly, the
cut area angle is defined as a window of distance for synchronized travel with the encoder.
To provide compensation during non-cut regions, it’s necessary to calculate how much distance
and speed should be commanded into the system by the virtual auxiliary servo motor. A picture
of the auxiliary virtual motor is shown as V.1 in the drawing here. This axis is used
to provide the compensation via a Virtual Servo Move, which requires a target position
and speed command. These values are programmed as indirect addresses that change depending
on the line speed of the conveyor. To determine these speeds, a series of calculations is
required.
In the first calculation, the time required for the compensation to take place is calculated
as the compensation area divided by the belt speed.
The second step is used to determine the amount of pulses required for the travel distance
and is comprised of user-defined variables. Step three combines the time and distance
calculations to create the compensation speed.
In the end, the compensation amount and speed results are used to control the virtual servomotor.
For machines configured to cut automatically without a mark sensor in place for correction,
the motion controller's limit output data function is configured. This data is set according
to the cut area and compensation area settings. Here, you'll see 8 bits defined for a machine
with 4 blades. The limit output data is used for machine types with 1, 2 or 4 knives.
Programming with registration provides a huge advantage to adjust the accuracy of each cut,
which ultimately guarantees a higher quality end-product through preventing the negative
side effect of position displacement through unexpected stretching or binding of the material,
for example. The math provided compares the difference between marks with the actual product
length and then uses the error amount to provide adjustment. Here, the actual length is subtracted
from the measured distance between marks, and ideally, this error amount should be zero.
An alternative method is to capture the position of the servo motor relative to the position
of each mark from the encoder, and then compare that difference repeatedly. If the difference
fluctuates, the auxiliary virtual servo motor is commanded to correct the servo's position.
An HMI operator interface connected to the MR-MQ100 motion controller provides easy control
for the rotary knife application. A GT12 Series terminal is used in this application
with screens for operating the machine, setting parameters, and for monitoring the performance.
Here you'll notice a JOG Operation function, which allows you to JOG the rotary axis in
the forward or reverse direction to determine the home position. Tweaking the rotary cutter's
diameter setting affects how accurately the knife will follow the encoder and needs to
be programmed very accurately. On the monitor screen, the product count is displayed along
with several other pertinent machine values.
In summary, the rotary knife solution from Mitsubishi Electric provides an easy-to-understand,
flexible representation of the system through visual programming with MT Works2. This reduces
the development time up to 30% and provides an advantage for machine builders who would
like to tweak a virtual version of their system quickly and easily.
High-speed mark registration provides on-the-fly corrections to keep the rotary knife axis
on track at all times. This directly results in higher quality production with less machine
downtime.
Finally, ethernet communication provides a fast open network that machine builders are
familiar with and can rely on. Standard cabling reduces machine cost and simplifies the setup
to other devices. Alternative solutions from Mitsubishi Electric
include all of the other motion controllers that can process encoder feedback for encoder
following. These include the Q170MCPU stand-alone motion controller for control of up to 16
servo axes. This controller comes in handy for converting solutions where a material
gets passed through several stations before entering the rotary knife station. A Q172D
or Q173D motion controller could also be used for larger machines to control 8 or 32 axes
of servo. For additional digital and analog I/O control,
the MR-J3-D01 I/O card can be attached to the servo amplifier. Additionally, a VFD such
as the D700 could be used to control the conveyor. For further information on the Mitsubishi
Electric solution for Rotary Knife machines, material can be found in five separate components;
A double page quick reference guide, a detailed application note, complete programming files,
images and movies, and this presentation. All of this material is available on the MEAU
website at www.meau.com. Just click on the “Industry Solutions” link to find your
way to the material.
And that brings me to the end of this Application Solutions webinar. I would like to thank you
for taking the time to listen to this presentation.