Emerson PCM-22 User Manual

PCM-22

Rotary Knife Controller

Information furnished by EMERSON Motion Control is believed to be accurate and reliable. However,
no responsibility is assumed by EMERSON Motion Control for its use. EMERSON Motion Control
reserves the right to change the design or operation of the equipment described herein and any
associated motion products without notice. EMERSON Motion Control also assumes no responsibility
for any errors that may appear in this document. Information in this document is the property of
EMERSON Motion Control and is subject to change without notice.

P/N 400274-01

Rev.: A2

Date: December 7, 1998

© 1998 EMERSON Motion Control. All Rights Reserved.

PCM-22 Rotary Knife Controller

© 1998 EMERSON Motion Control. All Rights Reserved.

Document Number: 400274-01

No part of this manual may be reproduced by any means without the written permission of EMERSON Motion
Control.

EMERSON Motion Control is a registered trademark of EMERSON ELECTRIC.

Printed in U.S.A.

December, 1998 Revision A2

This document has been prepared to conform to the current release version of the PCM-22 Rotary Knife
Controller. Because of our extensive developments and our desire to further improve and enhance the product,
inconsistencies may exist between the product and documentation in some instances. Call your customer
support representative if you encounter an inconsistency.

ii © EMERSON Motion Control

Customer Services

EMERSON Motion Control offers a wide range of services to support our
customers’ needs. Listed below are some of these services.

Application Engineering [phone]

E-Mail: [e-mail]

An experienced staff of factory application engineers provide complete
customer support for tough or complex applications. Our engineers offer
you a broad base of experience and knowledge of electronic motion
control applications.

EMERSON BBS [phone]

EMERSON Motion Control maintains a electronic Bulletin Board
System which provides you access to software updates, technical
information and services.

Communications protocol: 300 - 28,800 Baud, N, 8, 1.

FAX [phone]
Internet Access www.emersonemc.com
Order / Repair Status [phone]
Sales (800) FX-SERVO

E-Mail: [e-mail]

Service Support [phone]

E-Mail: [e-mail]

EMERSON Motion Control’s products are backed by a team of
professionals who will service your installation wherever it may be. Our
customer service center in Minneapolis Minnesota is ready to help you
solve those occasional problems over the telephone. Our customer service
center is available 24 hours a day for emergency service to help speed
any problem solving. Also, hardware replacement parts, should they ever
be needed, are available through our customer service organization.

Need on-site help? EMERSON Motion Control provides on-site service,
in most cases, the next day. Just call EMERSON’s customer service
center when on-site service or maintenance is required.

See Service Support Check List on the following page.

Training Services [phone]

EMERSON Motion Control maintains a highly trained staff of
instructors to familiarize customers with EMERSON Motion Control
products and their applications. A number of courses are offered, many
of which can be taught in your plant upon request.

P/N 400274-01 Revision A7 iii

PCM-22 Rotary Knife Controller

Service Support Check List

To ensure the most timely and efficient support possible, please have the
following items ready before calling for Service Support.

1. The model and serial number(s) of your FX Amplifier(s) and
manual(s).

2. The model and serial number(s) of your PCM(s).

3. The result (using Terminal Mode) of ID?; 0ID? (zero ID?) if axis ID’s
are used.

4. The result (using Terminal Mode) of ID1?; 0ID1? (zero ID1?) if axis
ID’s are used.

5. A description of the symptom(s) or issue(s) observed including any
fault status codes displayed on the LED Diagnostic Display.

6. Copies of the current uploaded program(s) that are in each of your
PCM(s).

7. The gear ratio, model number and type of reducer(s) used.

8. This manual.

iv © EMERSON Motion Control

Table Of Contents

Introduction 1

Description ................................................................................................................... 1

Features ........................................................................................................................3

Terminology ................................................................................................................. 4

Master Cycle Length .............................................................................................. 4

Follower Cycle Length ........................................................................................... 4

Working Segment .................................................................................................. 5

Cycle Point............................................................................................................. 5

Working Offset....................................................................................................... 5

Variable Segment................................................................................................... 6

Cycle Drop Out Position.........................................................................................7

Working Ratio........................................................................................................ 7

Phase...................................................................................................................... 8

Average Length...................................................................................................... 8

Theory of Operation 11

General Running......................................................................................................... 11

Master Cycle Defined By Sensor Mode................................................................. 12

Master Cycle Not Defined By Sensor Mode.......................................................... 12

Resetting the Master Cycle Processing ........................................................................ 13

How the Master Cycle is Defined.......................................................................... 13

Automatically Resetting the Master Processing..................................................... 13

Manually Resetting the Master Processing............................................................ 14

Starting A Follower Cycle........................................................................................... 15

Homes and the Follower Zero Position ........................................................................ 16

Indexes and the Follower Zero Position....................................................................... 16

Cycle Inter-Relationships............................................................................................ 17

Operational Timing..................................................................................................... 18

Maximum Master Velocity.......................................................................................... 19

Sensors ....................................................................................................................... 20

Selection .............................................................................................................. 20

Sensors: When, Where and Why .......................................................................... 21

Installation Guidelines 23

Attaching the PCM-22 Module ................................................................................... 23

I/O Wiring.................................................................................................................. 23

P/N 400274-01 Revision A7 v

Input Wiring ........................................................................................................ 23

Output Wiring...................................................................................................... 23

PCM-22 Rotary Knife Controller

PCM-22 Software Setup 25

Programming the PCM-22...........................................................................................25

Master Axis .................................................................................................................29

Master Cycles ..............................................................................................................37

Follower Cycles ...........................................................................................................42

Input Functions............................................................................................................52

Output Functions .........................................................................................................58

Programming ...............................................................................................................63

Description ...........................................................................................................29

Master Axis Setup.................................................................................................31

Master Cycle Number............................................................................................37

Master Cycle Length.............................................................................................37

Master Phase Distance ..........................................................................................40

Master Cycle Defined By Sensor ...........................................................................40

Cycle Number.......................................................................................................43

Follower Cycle Length..........................................................................................43

Cycle Defined by Registration Sensor....................................................................46

Phase Correction Limit .........................................................................................47

Phase Distance Error Limit (+) .............................................................................47

Phase Distance Error Limit (-) ..............................................................................47

Phase Correction Deadband...................................................................................48

Length Change Increment.....................................................................................48

Master Cycle Number............................................................................................48

Batch Count..........................................................................................................48

Cycle Count ..........................................................................................................49

Working Segment Width.......................................................................................49

Offset/Phase Fine Increment..................................................................................51

Offset/Phase Coarse Increment..............................................................................51

Description of Input Functions..............................................................................53

Typical Input Assignments....................................................................................57

Description Of Output Functions...........................................................................58

Recommended Output Assignments......................................................................62

Additional programming functions........................................................................63

Example program..................................................................................................64

Example Applications 67

Rotary Knife ................................................................................................................67

Seal and Cut Off Packages...........................................................................................68

Flexible Bag Maker......................................................................................................69

Pick and Place..............................................................................................................70

Imprinter .....................................................................................................................71

Maximizing Profile Performance 73

Commands Referenced.................................................................................................74

Minimizing Length Variation......................................................................................74

Minimizing Phase Variation........................................................................................76

vi © EMERSON Motion Control

Tips and Troubleshooting 80

General Issues............................................................................................................. 80

Product Ranges and Limits.......................................................................................... 80

Follower Cycle Will Not Start ..................................................................................... 81

Verifying the Working Segment Position .................................................................... 81

Issues Maintaining Phase............................................................................................ 82

System Calibration Issues............................................................................................ 83

Synchronization Source Issues .................................................................................... 83

Running Into a Length Limit....................................................................................... 84

Missing Sensor Issues ................................................................................................. 85

Extra Sensor Issues ..................................................................................................... 86

Common Operation Issues........................................................................................... 87

Appendix A - Serial Commands 88

CI2 - Executing Master Cycle ..................................................................................... 88

CQ - Cycle Status Query ............................................................................................. 88

FF - Follower Cycle Flags........................................................................................... 91

FM7 - Master Phase Variation In User Units............................................................... 92

FM8 - Follower Phase Variation In User Units............................................................ 92

FM9 - Master Length Variation In Sync. Counts......................................................... 92

FM10 - Follower Length Variation In Resolver Counts ............................................... 93

FM11 - Master Axis Velocity...................................................................................... 93

FM12 - Average Master Length In User Units............................................................. 93

FM13 - Average Follower Length In User Units.......................................................... 93

FM14 - Computed Starting Master Distance In Master Steps ...................................... 93

FN1 - Follower Cycles Per Follower Sensor................................................................. 94

KC4 - Total Cycle Count............................................................................................. 94

MF - Master Cycle Flags............................................................................................. 94

ML11 - Current Master Length In Master Steps .......................................................... 95

PH4 - Minimum Master Velocity For I/O Profile Adjustments .................................... 95

TC5 - Working Ratio Change Increment..................................................................... 95

Appendix B - PCX Cycle Screens to FX Command Cross

Reference 96

PCM-22 Master Cycles Screen.................................................................................... 96

PCM-22 Follower Cycles Screen................................................................................. 97

Appendix C - Master Signal Components 98

Encoder Operation...................................................................................................... 98

Encoder to Drive Cables.............................................................................................. 99

Drive to Drive Cables.................................................................................................. 99

Index 100

P/N 400274-01 Revision A7 vii

This manual provides setup and programming information for the
PCM-22 Rotary Knife Controller Application Module.

It is important that you become familiar with the 230V FX Drives Setup

and Programming Operator's Manual (P/N 400282-00), 460V FX Drives
Setup and Programming Operator's Manual (P/N 400310-00) or 525
Programmable Motion Controller Installation and Operation Manual

(P/N 400276-01) as appropriate.

This manual should be read completely before installing the
PCM-22. It provides the background information needed to setup and

configure the PCM-22/FX amplifier combination using PCX 7.x software.

Description

The PCM-22 Rotary Knife Controller is an application module that
attaches to any EMERSON Motion Control FX positioning servo drive.
The PCM-22 enables a FX drive to automatically calculate and create
motion profiles using sensor information and/or user-defined parameters.

The PCM-22 is designed to maintain a phased relationship between the
motor axis (referred to as the Follower axis) and the motion of an
independent axis (referred to as the Master axis).

Introduction

MSC

CABLE

MASTER REGISTRATION

SENSOR

FOLLOWER

SENSOR

FX AMPLIFIER

WITH PCM-22

P/N 400274-01 Revision A7 1

SCS-4

ENCODER

KNIFE

AXIS

Figure 1 Typical Application - Rotary Cut-Off.

ANVIL

MOTOR

PCM-22 Rotary Knife Controller

The PCM-22 accepts application data relating to the mechanical
dimensions of the system entered using PCX Software. These parameters
along with sensor and synchronization information allow the PCM-22 to
calculate the motion profile necessary to meet the user specified
positioning requirements of the application.

Many parameters relating to the PCM-22 application can be changed
using hardware inputs, PCX software or serial commands. Using these
new parameters, the PCM-22 will calculate the new motion
automatically, without stopping, to maintain continuous machine
operation.

If an axis uses a registration sensor, the PCM-22 can automatically
adjust parameters based on sensor information about that axis. It will,
within user-defined limits, automatically compensate for length changes
and detected mechanical inaccuracies.

For example:
If the distance between registration sensor inputs on the Follower axis

indicate that the length is 8.25 inches and not 8.30 inches as entered
using PCX. The PCM-22 will automatically make adjustments to
compensate for the difference in length.

These capabilities allow the PCM-22 to produce one or more cycles of
motion for every individual cycle of motion produced by the Master axis.
The PCM-22 will position the Follower axis to a corresponding position
and velocity relative to the Master axis while it is executing a cycle.

This type of motion profile is commonly used in cutting, sealing, printing
and perforating applications.

2 © EMERSON Motion Control

Features

Introduction

The features of the PCM-22 Rotary Knife Controller include:

• Set up with easy-to-use PCX software.

• Works with all FX series drive products and 525 PMC products.

• Allows an FX drive to accurately position and match speed based on

data received from a Master axis.

• Drive setup parameters are stored in the PCM-22 module. This

allows the PCM-22 to be transferred to another FX drive of the same
size without losing any setup parameters.

• Calculates cycle profiles based on user-defined parameters

automatically.

• All parameters are in user-defined units.

• Most parameters can be changed automatically, without stopping.

• Two internal counters for each cycle: product cycle counter and

product batch counter.

• 100 programs (with a maximum of 512 steps total for all programs).

• 16 Master axis and 16 Follower axis motion profile definitions.

• 98 user-assignable I/O functions.

• 64 indexes.

• 2 homes.

• Expands I/O line capacity of FX drive with an additional eight

optically isolated input lines and four optically isolated output lines.

• Interactive cycle diagnostic capabilities.

• Always uses linear ramps for Homes, Indexes, Jogs and Follower

cycles for increased accuracy.

Note: Not all of the features available with the PCM-22 will be used in

every application.

For example:

There are 15 programming functions available with the PCM-22
however, a typical rotary knife program will use only a few of
them.

P/N 400274-01 Revision A7 3

PCM-22 Rotary Knife Controller

Terminology

Master Cycle Length

The Master Cycle Length (also called the Master Length) is the
particular distance, in user units, that the Master axis (encoder or
upstream drive) moves during each Master cycle. It is the distance
between two Master Cycle zero positions. See Figures 2 and 3.

If the Master Cycle Defined By Sensor is “Yes”; when the Zero Master
Cycle sensor detects a target on the Master axis, that is the Master zero
position. The distance between two Zero Master Cycle positions is the
Master Cycle Length.

If the Master Cycle Defined By Sensor is “No”; when the first Zero
Master Cycle input is received, that is the initial Master zero position.
This will be the only Zero Master Cycle input required for all Master
cycles following. When the Master axis has moved the user entered
Master Cycle Length, it has moved the distance between two Master zero
positions.

CIRCUMFERENCE OF

ROTARY KNIFE EQUALS

FOLLOWER LENGTH

WORKING SEGMENT

PRODUCT

MOVEMENT

Figure 2 Typical Rotary Knife System Component Locations

Follower Cycle Length

The Follower Cycle Length (also called the Follower Length) is the
distance, in user units, that the Follower axis (PCM-22/FX drive) moves
during each Follower cycle. It is the distance between two Follower cycle
zero positions. See Figures 2 and 3.

If the Follower Cycle Defined By Sensor is “Yes”; when the Zero Follower
Cycle sensor detects a target on the Follower axis, that is the Follower
zero position. The distance between two Zero Follower Cycle positions is
the Follower Cycle Length.

ZERO
MASTER
SENSOR

MASTER PHASE

DISTANCE

PHASE

MASTER
LENGTH

ZERO
FOLLOWER

T

A

O

T

I

R

O

N

CYCLE

POINT

SENSOR

WORKING
OFFSET

4 © EMERSON Motion Control

Introduction

FOLLOWER LENGTH

ONE

CYCLE

MASTER LENGTH

ONE TO ONE RELATIONSHIP (IGNORING SCALE) BETWEEN

MASTER LENGTH AND FOLLOWER LENGTH.

Figure 3 Relationship Between the Master Cycle Length and the Follower Cycle Length

If the Follower Cycle Defined By Sensor is “No”; when the Follower cycle
starts, it is at the Follower zero position. When the Follower axis has
moved the user entered Follower Cycle Length, it has moved the distance
between two Follower zero positions. See Homes and the Follower Zero

Position.

Working Segment

This is called Working Segment Width on the Follower Cycles screen. It
is the constant velocity portion of the cycle, usually when the Follower is
in contact with the product. The Follower moves at the Working Ratio
velocity relative to the Master velocity during this distance. See Figures
4, 5, and Cycle Inter-Relationships, Maximum Product Velocity and
Variable Segment.

Note: The Master Length also has a Working Segment. It is not

directly user adjustable, it is computed from the Follower
Cycles Working Segment divided by the Working Ratio. See
Figure 6.

Cycle Point

The Cycle Point is at the center of the Working Segment. It is the
beginning and the end of every cycle. See Operational Timing.

Working Offset

The Working Offset is the distance from the Cycle Point to the Follower
zero position, in the direction of Follower rotation. The Follower zero
position is the same position as the Zero Follower Sensor if used. See
Figures 4, 5, Cycle Inter-Relationships, Homes and the Follower Zero
Position.

P/N 400274-01 Revision A7 5

PCM-22 Rotary Knife Controller

CYCLE POINT

WORKING
SEGMENT

WORKING OFFSET

FOLLOWER

ZERO POSITION

VARIABLE SEGMENT

ONE

CYCLE

ONE TO ONE RELATIONSHIP (IGNORING SCALE) BETWEEN

MASTER LENGTH AND FOLLOWER LENGTH.

Figure 4 Follower Terminology Relationships

B

G

A

FOLLOWER

LENGTH

MASTER
LENGTH

DIRECTION

D

FOLLOWER

ROTATION

C

Figure 5 Circular View of Follower Terminology Relationships

Variable Segment

This is a computed parameter. It is the Follower Cycle Length minus the
Working Segment. This is where all cycle adjustments occur. See Figures
4, 5, 6 and Cycle Inter-Relationships.

When designing a PCM-22 system, the peak acceleration and the peak
velocity required during the Variable Segment must be calculated at
the maximum process speed with the shortest Master Length
spacing. This is necessary to determine the required motor size.

See Maximum Product Velocity.

OF

F

A: FOLLOWER CYCLE LENGTH
B: FOLLOWER ZERO POSITION
C: WORKING SEGMENT
D: VARIABLE SEGMENT
E: WORKING OFFSET

E

F: CYCLE POINT
(CENTER OF WORKING SEGMENT)
G: CYCLE DROPOUT POSITION

WARNING!

6 © EMERSON Motion Control

Cycle Drop Out Position

The Cycle Drop Out Position is the position exactly opposite the Cycle
Point. While Cycle Drop Out input function is active, the Follower will

complete its current cycle and decelerate to this position and hold there.
See Figure 5, the Cycle Drop Out input function, Cycle
Inter-Relationships, Homes and the Follower Zero Position.

Working Ratio

The Working Ratio defines the relationship between the Follower
velocity and the Master velocity during the Working Segment.

For example:
If the Follower is to move the same speed as the Master during the

Working Segment, then the Working Ratio would be 1.00000. This is
common in many applications.

If the Follower is to move 5 percent faster than the Master velocity
during the Working Segment, then the Working Ratio would be 1.05000.
The range is from 0 to 9.99999.

CYCLE POINT

WORKING OFFSET

FOLLOWER

ZERO POSITION

Introduction

WORKING
SEGMENT

VARIABLE SEGMENT

FOLLOWER

ONE

CYCLE

WORKING SEGMENT

WORKING RATIO

ONE TO ONE RELATIONSHIP (IGNORING SCALE) BETWEEN

MASTER LENGTH AND FOLLOWER LENGTH.

VARIABLE SEGMENT

COMPUTED RATIO

Figure 6 Follower Component Relationships to the Master Cycle Length

MASTER

LENGTH

LENGTH

P/N 400274-01 Revision A7 7

PCM-22 Rotary Knife Controller

(

Phase

A repeating pattern is called a cycle. When two repeating patterns are
synchronized there is an inherent position relationship between the two
patterns called phase. See Figure 7.

This means that:

There is a one-to-one positional profile relationship between the
two lengths (ignoring scale) and every point within the two
lengths.

CYCLE POINT

WORKING OFFSET

FOLLOWER

ZERO POSITION

WORKING
SEGMENT

PHASE

Figure 7 Phase Relationship Between Master and Follower Cycle Lengths

The PCM-22 maintains the phase relationship by automatically making
adjustments based on sensor inputs and applying user-defined
parameters. Figures 3, 4 and 6 show a phase relationship of zero.

Average Length

The PCM-22 uses continuous averaging when an axis is defined by
sensor. Continuous averaging provides increased stability by
incorporating every length into the average, starting from the initial
Follower Cycle Length or Initial Master Length. Average lengths are
generated from the following equation for the Master and the Follower
axes:

WORKING SEGMENT

WORKING RATIO

VARIABLE SEGMENT

ONE

CYCLE

VARIABLE SEGMENT

COMPUTED RATIO

FOLLOWER

LENGTH

MASTER

LENGTH

8 © EMERSON Motion Control

Average Length

=

Averaging

Current is equal to the current average length.
New is equal to the new measured length.
Averaging is entered by the user from 1-8.

Current *(Averaging - 1)) + New

Introduction

(

For example:
If eight is entered here the new average Follower Length calculated by

the PCM would be:

Average Length

It takes at least three times the averaging number of cycles on an axis to
“learn” a change in length (e.g. if the averaging is set to eight, the PCM
will need to sense at least 24 cycles to completely adjust for the new
length). See Follower Length Correction Limit and Master Length

Correction Limit.

Therefore, the lower the average the faster length errors are corrected.
However, too low a value adversely affect the drive’s ability to quickly
correct for phase errors by causing overcompensation and instability. See
Maximizing Profile Performance and Theory of Operation.

The Average Master Cycle Length and the Average Follower Cycle
Length are the learned lengths which are used only when defined by
registration sensor.

Current *7) + New

=

Averaging

P/N 400274-01 Revision A7 9

PCM-22 Rotary Knife Controller

10 © EMERSON Motion Control

Theory of Operation

The operation of the PCM-22 is explained in the following sections.

This manual should be read completely before installing the
PCM-22.

General Running

The Master axis position is monitored by the PCM-22 using
synchronization signals. These signals, which come from an incremental
encoder driven by the Master axis or an upstream FX drive, provide the
positioning data to the PCM-22.

In order to maintain the proper phase relationship between the two axes,
the PCM-22 monitors the Zero Master Cycle and Zero Follower Cycle
sensors of both the Master and the Follower axes.

If the Follower axis does not use a sensor then the PCM-22 will use the

Follower Cycle Length parameter entered and only correct for Following
Error. Following Error is the difference between the motor’s

commanded position and it' actual position. No automatic length or
phase adjustments will be made for the Follower axis.

If the Master axis does not use a sensor, no corrections to the Follower
axis’ motion profile will be made for product differences or encoder
slippage.

If the Follower axis is not in phase synchronization with the Master axis,
the PCM-22 computes a correction which is applied in the next Follower
cycle. The Follower axis will speed up or slow down depending on what is
required for the length or phase correction. If both the Follower and the
Master axes are in phase synchronization, no correction is made.

The portion of the motion profile called the Variable Segment is where
all user changes or profile adjustments occur for each individual Master

Length. The remainder of the motion profile is called the Working
Segment. The Working Ratio will always be maintained during the
Working Segment.

Any changes made before the Cycle Point will take place during the next
cycle. If parameters are entered that cannot be accommodated while in
cycle, the Cycle Limit Reached (output function 41), if assigned, will be
activated until the cycle can be executed as defined. See Operational
Timing.

Product (master) positions are continuously tracked whether a Follower
cycle is executing or not. At power-up the PCM-22 is executing the
Master Cycle zero (0) definition. See the MF serial command.

P/N 400274-01 Revision A7 11

PCM-22 Rotary Knife Controller

Master Cycle Defined By Sensor Mode

The PCM-22 handles the Master position information differently
depending on whether a product registration (master) sensor is used or
not. Each of the two ways of handling the Master position information
have different applications but operate similarly in the respect that
Mater position information is continuously tracked whether a Follower
Cycle is executing or not.

When a Zero Master Cycle sensor input occurs, the distance traveled
from the last product position will be checked to see if it is between the
Master Length Upper Limit and the Master Length Lower Limit. This
measured distance is factored into the Average Master Length starting
from the user entered Master Cycle Length. Any necessary corrections
will be made to the next Follower axis motion profile. See Average
Length, Master Cycles screen and Operational Timing.

FX AMPLIFIER WITH PCM-22

FOLLOWER

SENSOR

FOLLOWER

AXIS

MASTER AXIS (SYNC ENCODER)

REGISTRATION

MARKS

MASTER SENSOR

ROTARY KNIFE

Figure 8 PCM-22 Rotary Knife System Example

Master Cycle Not Defined By Sensor Mode

If the Master is Not Defined By Sensor, the user entered Master Cycle
Length will be used by the PCM-22. No corrections to the Follower axis’

motion profile will be made for product or encoder slippage in this mode.

12 © EMERSON Motion Control

Theory of Operation

Resetting the Master Cycle Processing

Resetting the Master Cycle Processing on the PCM-22 involves reloading
the user-defined Master Cycle parameters. This overwrites all learned
and user-defined Master information currently in use. When the Master
processing is reset, the Master Cycle Defined output function is
deactivated until the Master Cycle is redefined. Resetting the Master

Cycle Processing usually happens automatically but may be induced. See
Automatically Resetting the Master Processing and Manually Resetting
the Master Processing.

Note: Resetting the Master Cycle Processing will only occur when a

Follower Cycle is not executing and the Follower axis is not

moving.

How the Master Cycle is Defined

After Resetting the Master Cycle Processing the Master cycle is
undefined and must be redefined before a Follower cycle may begin.

Master Cycle Defined By Sensor Mode

When the first Zero Master Cycle sensor input is received, the product is
at the initial Master zero position. When the second Zero Master Cycle
sensor input is received, the Master Cycle Length will be defined and the
Master Cycle Defined output function will activate.

Master Cycle Not Defined By Sensor Mode

When the first Zero Master Cycle input is received, the product is at the
initial Master zero position. The Master Cycle Length will be defined at
this point and the Master Cycle Defined output function will activate.
This will be the only Zero Master Cycle sensor input required for all
master cycles following.

Note: For situations where there is no need for any master axis

alignment, you can wire the Follower Cycle Defined output to
the Zero Master Cycle input to define the Master Cycle position
automatically.

Automatically Resetting the Master Processing

• If the PCM-22 has been powered-up but has not yet executed a

Follower cycle, it is executing the Master Cycle 0 data definition. The
first time after power-up the Y Execute Follower Cycle program step
is executed in a PCX program, the Master processing will be reset.
See the MF serial command.

• When the Y Execute Follower Cycle program step is executed in a

PCX program and the Master Cycle definition specified in the

Follower Cycle screen, is not the same as the currently executing
Master Cycle definition then the Master processing will be reset. See
the CI2 serial command.

P/N 400274-01 Revision A7 13

PCM-22 Rotary Knife Controller

Manually Resetting the Master Processing

• Setting the Force Reset Master Processing bit using the FF serial
command will automatically cause a Reset of the Master processing
every time a Y Execute Follower Cycle program step is executed in a
PCX program. See Starting A Follower Cycle.

Manually Resetting the Master Cycle Processing is particularly useful for
troubleshooting product handling (slippage or registration) issues.

The PCM-22 provides two ways for resetting the Master processing
manually by:

• Writing the MF serial command.

• Reset Master input function 115.

These methods allow the user to reset the Master processing as the
application requires. The result is the same as selecting a different
Master Cycle definition for the same Follower cycle on demand.

14 © EMERSON Motion Control

Starting A Follower Cycle

An initial Home or Index is required to move the Follower axis to the
Follower zero position before the Y Execute Follower Cycle statement is
executed. This will determine, using the Working Offset, the position of
the Cycle Point on the product. When the Y Execute Follower Cycle
statement is executed, the Follower Cycle Defined output function will
activate and if the Master cycle is defined, the Follower cycle will start.

When the PCM-22 axis starts moving from the Follower zero position,
Home position or the Cycle Drop Out Position, a linear acceleration is
used to get to the correct velocity at the beginning of the Working
Segment. The PCM-22 checks the first product’s (Cycle Point) position to
see if it can reach the correct velocity (Working Ratio * Master velocity)
in the distance it would travel from the Follower zero position to the
beginning of the first product’s Working Segment. If this is not possible
(i.e., the start-up distance is longer than the first product position), the
PCM-22 will check the second product position. If it can not make the
second product position, it will check the third and so on, until the
PCM-22 finds a product position that will allow the Follower axis to
reach the product’s Working Ratio velocity at the beginning of its
Working Segment. The Follower axis is not moving while it is
determining which product position to try for. See Figure 9 and Master
Phase Distance.

Theory of Operation

DIRECTION OF FOLLOWER ROTATION

ZERO
MASTER
SENSOR

MASTER PHASE DISTANCE

PRODUCT MOVEMENT

Figure 9 PCM-22 Starting Cycle Ramp

WS

ZERO FOLLOWER

SENSOR

WORKING

OFFSET

When the Follower has passed the first Cycle Point after the Master has
moved the Master Phase Distance, the In Phase output function will
activate.

In Master Cycle Defined By Sensor mode, it is possible for the start-up
distance to be greater than the Master Phase Distance. If this is the case
it will generate product positions to target before the sensor using the

Average Master Length. Please note that the entered Master Cycle
Length is only equal to the Average Master Length just after the Master

processing is reset.
The Follower will start executing the computed starting ramp distance to
the targeted product position. Any products that pass the Cycle Point
before the Follower has completed the initial acceleration will be ignored.
See Figure 10, Average Length, and Resetting the Master Processing.

P/N 400274-01 Revision A7 15

PCM-22 Rotary Knife Controller

DIRECTION

ZERO MASTER

SENSOR

CAN

MAKE

IT

AVERAGE

MASTER
LENGTH

Figure 10 When the Follower Start-up Ramp Exceeds the Master Sensor Distance

CAN NOT

MAKE IT

PRODUCT MOVEMENT

OF ROTATION

ZERO FOLLOWER

WORKING

WS

OFFSET

SENSOR

Homes and the Follower Zero Position

In order to obtain the highest accuracy, certain types of homes are
recommended for use with the PCM-22: Resolver Offset and
Feed On/Off. Make sure the “On” move is in the direction of travel and
the “Off” move is much slower in the opposite direction. The goal of this
is to have the Follower’s starting position be the same as the Follower
zero position when the cycle is running. A reducer’s backlash is minimal
compared to an inaccurate initial reference position during the first
several cycles.

Ensuring a correct starting position goes far in eliminating length and
phase variations when the Follower is executing its first several cycles
and learning its length the fastest.

It is not recommended, but it is possible, once the home is completed, to
move to a different location which will be the Follower zero position. It is
from this point that the Follower cycle will start. If this is not the actual
Follower zero position and the Follower cycle is defined by sensor, the
PCM-22 will perceive this as an error and correct for it.

Indexes and the Follower Zero Position

An index may be used instead of a home to move the Follower axis to
the Follower zero reference position. It behaves the same as a home but
there are more options for positioning the Follower axis before actually
starting the cycle.

For example:

• A Registration index.

• A Feed to Sensor index.

• A home followed by an Incremental index.

The index must not be compounded and must finish before the Follower
cycle begins.

Ensuring a correct starting position goes far in eliminating length and
phase variations when the Follower is executing its first several cycles
and learning its length the fastest.

16 © EMERSON Motion Control

Cycle Inter-Relationships

Every cycle has certain relationships pertaining to the Working Segment.
These relationships must be maintained for the PCM-22 to execute the
motion profile required by the Follower axis for each product on the
Master axis. Please refer to the Terminology section for clarification of
terms.

The following relationships are considered the rules for cycle
operation.

1) The Working Segment must be less than the Follower Cycle Length.

2) The Working Segment divided by the Working Ratio must be less
than Master Length Lower Limit.

3) The Working Segment must be less than the Upper Working Segment
Limit.

4) The Working Segment must be greater than the Lower Working
Segment Limit.

5) The Working Segment must not overlap the Follower Zero Position.
A) The Working Offset must be less than the Follower Cycle Length

minus one half of the Working Segment.

B) The Working Offset must be greater than one half of the

Working Segment.

This means that the follower sensor must not be inside the Working
Segment.

The above Cycle Inter-Relationship cross-checks are performed against
the following cycle parameters every time a cycle is started and every
time one of these parameters is changed while the Follower is in cycle:

• Working Segment.

• Working Offset.

• Follower Cycle Length.

• Master Length Lower Limit.

If the profile is determined invalid due to one of these cross-checks when
the cycle is started, the cycle will exit and Cycle Error (output
function 66) will be activated. The Follower Cycle will not start and the
CQ serial command will have flags set indicating where the problem is.

If the profile is determined invalid due to one of these cross-checks while
the cycle is running due to a user change, the requested change will be
ignored. The CQ serial command will have flags set indicating where the
problem is and Cycle Limit (output function 41) will be activated.

If the Working Segment flag is set within the CQ serial command
response then additional flags will be set indicating where the conflict is:
Working Offset, Follower Cycle Length or Master Cycle Length.

Theory of Operation

P/N 400274-01 Revision A7 17

PCM-22 Rotary Knife Controller

Operational Timing

FOLLOWER VELOCITY

For every cycle, there is a one-to-one positional profile
relationship (ignoring scale) between the Master cycle and the
Follower cycle.

The PCM-22 may adjust the motion profile because of:

• User requested changes using I/O or serial commands.

• Learned length and/or phase variation changes if an axis is defined

by sensor.

MACHINE CYCLE

WORKING SEGMENTWORKING SEGMENT

WORKING

RATIO

VELOCITY

ZERO

VARIABLE SEGMENT

CALCULATED BY

CYCLE POINT

THE PCM

CYCLE POINT

MASTER

POSITION

MASTER CYCLE

FOLLOWER CYCLE

Figure 11 PCM-22 Motion Profile

In both cases, all motion profile changes (user requested changes,
learned length and/or phase variations) occurring before the Cycle Point
will be applied when the PCM-22 calculates the next Working Segment
location.

When the Follower reaches the end of the current Working Segment, the
new motion profile is used to move to the next Working Segment. See
Figure 11. This new motion profile is the typical machine cycle which
starts when the Follower axis leaves the Working Segment and gets clear
of the product (e.g. the rotary knife comes out of the product).

18 © EMERSON Motion Control

Maximum Master Velocity

For every set of Master and Follower cycle parameters, the user must
limit the maximum velocity of the Master so that the maximum velocity
of the Follower is not exceeded. This is critical for product lengths
shorter than the Follower Cycle Length.

Theory of Operation

Maximum Master Velocity

=

FVS / MVS *2 - WR

( )

MAV

Where:

MAV =Maximum Allowable Velocity of the Follower from the Limits

screen.

WR = Working Ratio.
FVS = Follower Variable Segment =

Follower Cycle Length - Working Segment.

MVS = Master Variable Segment =

Master Cycle Length - (Working Segment / Working Ratio).

Note: The above equation reflects ideal conditions and the user must

reduce the calculated Maximum Master Velocity due to the
effects of inertia, friction, encoder slippage, sensor, mechanical
issues to allow enough velocity headroom for any motion
corrections. Usually, this velocity reduction needs to be
approximately 20 percent.

V

-

V

Peak

V

Peak

T

Peak

Follower Acceleration =

Working Ratio

-

T

Working Segment End

Velocity

VARIABLE
SEGMENT

V

Working Ratio

WORKING
SEGMENT

WORKING
SEGMENT

0

T

Working Segment End

Figure 12 Variable Segment Acceleration

At the Maximum Master Velocity, VPeak = MAV.

T

Peak

Time

WARNING!

When sizing a system, keep in mind the velocity and acceleration of
the Follower during the variable segment for the shortest product
length because the Follower acceleration and deceleration rates are
not controlled by PCX Limits.

P/N 400274-01 Revision A7 19

PCM-22 Rotary Knife Controller

Sensors

Selection

In a typical rotary knife system, the rotary knife will be designated as
the Follower axis and the product or material conveyor as the Master
axis. A sensor on the knife (or Follower axis) is strongly recommended
since the exact position of the blade typically changes due to mechanical
imperfections.

The Zero Master Cycle and Zero Follower Cycle, input functions
45 and 46 respectively, must be assigned to separate FX drive high
speed inputs 1 and 2.

The PCM-22 reacts to learned sensor information by adjusting the
motion of the Follower to match the Master axis. If the sensor
information is inaccurate or not consistent, it will be reflected in the
accuracy of the Follower positioning.

The general guidelines when selecting a sensor are related to machine
issues such as the type of material being detected and the rate of input
occurrences.

The sensor type is dependent on what the sensor detects, called the
target. The surface area of the target should be as large as the sensing
face of the sensor to minimize hysteresis effects as defined by the sensor
type. This determines how consistently the sensor can be activated by
the target.

For a target larger than the sensor moving at a constant velocity, the
sensor should be selected be selected so the following equation is true:

Response Time

As the target becomes smaller approaching the size of the sensors’
detection field, at a constant velocity, the sensor should be selected be
selected so the following equation is true:

Response Time

The response time of a sensor is defined as the elapsed time from when
the target is detected until the signal appears on the sensor output. The
response time of the sensor will have a direct impact on the system
performance and accuracy. The response time of the sensor is part of the
switching frequency of the sensor.

The switching frequency is the minimum time from when a sensor is
triggered until it can be triggered again. Which is the time between
successive sensor triggers. Both of these parameters should be fast
enough for the application.

Width of target - Detection field size

≤

Width of target

≤

Velocity of target

Velocity of target

WARNING!

If the sensor switching frequency or response time is too slow for
the application, poor system performance will result and can cause
the Follower axis’ position to appear to shift phase as the system
speed is increased (i.e. the Cycle Point is in the wrong position).

20 © EMERSON Motion Control

For example:
The target is moving at 48 inches/second and is 0.1 inches wide. The
detection field of the sensor is 0.062 inches wide. The response time of
the sensor would need to be faster than 1264 Hz.

Sensors selected, should have a directed detection field such as a D.C.
shielded inductive proximity sensor or a focused contrast/registration
photo sensor.

Note: Electrostatic Discharge (ESD) sensors, such as spark gap

sensors, should never be used with FX products because the
intense electrical noise they generate can affect the electronics
in the FX amplifier.

Refer to manufacturer’s information concerning sensor selection,
application and installation.

Sensors: When, Where and Why

Master Sensor

A Master sensor should be used for any of the following situations:

• When the products are randomly spaced and an average product
length is desired.

• When we need to stay in phase with registration marks or products
outside of a Follower cycle.

The Master sensor, ideally, should be positioned between one and two
Average Master Lengths away from the Cycle Point to minimize the
effects of product slippage and to allow the PCM-22 to correct for any
phase variation on that product. See Operational Timing.

Follower Sensor

A Follower sensor must be used if the Follower Cycle Length is not an
exact number of motor steps (i.e., no fractions of steps). If the Follower
Length is not an exact number of steps, the Follower can drift out of
position due to rounding. The precision of the data entered in the PCX
software is the most common cause of drifting.

The recommended solution is to use a Follower sensor to let the PCM-22
determine the real Follower Length and allow it to compensate for any
discrepancies.

Stable sensor characteristics are especially important for the Follower
axis because the Follower sensor is in the Variable Segment which is
always accelerating or decelerating.

The Follower sensor should be positioned so that it does not interfere
with machine operation and so that the acceleration/deceleration is
minimal. See Maintaining Phase Issues. Ideally, the sensor should be
placed so it would be activated at areas of the Variable Segment where

the change in velocity is low (i.e., the beginning or middle of the Variable
Segment).

Theory of Operation

P/N 400274-01 Revision A7 21

Note: Typically, if the Master cycle is defined by sensor then the

Follower should also be defined by sensor for the greatest
accuracy.

PCM-22 Rotary Knife Controller

For example:
The Follower axis is moving at a specific acceleration and its sensor has
a response time (R.T.) of 1000 Hz (0.001 seconds). The acceleration and
response time effects on sensor accuracy are shown in the following
table.

Working
Segment

Velocity
(W.S.V.)

10 in/sec 0 in/sec
10 in/sec 10 in/sec
10 in/sec 20 in/sec

Follower

Acceleration

(F.A.)

See Figure 12

Time

Factor

(T.F.)

= W.S.V.

F.A.

2

2

2

0 sec 0.010 in
1 sec 0.020 in
2 sec 0.030 in

Sensor Accuracy

W.S.V.

= * T.F. + 1

( )

R.T.

22 © EMERSON Motion Control