Motion Casebook - Motion Control Tips

Software tools streamline cable design, management

December 11, 2018 By Miles Budimir Leave a Comment

A critical but sometimes overlooked component, cables come in a variety of customized versions to meet specific application requirements. Cable properties such as the number of solid conductors or wire strands for transmitting power to motors as well as feedback to and from controllers and sensors are an example of what designers must consider when selecting a cable for an application.

In motion control applications, cables typically have to handle tight bending radii, abrasion, flexing, and possibly even torsional motion. On the other hand, cables for VFDs must minimize EMI effects and other sources of electromagnetic noise. Another consideration is the cable jacket material that protects conductors and insulation from harsh environments where exposure to chemicals and oil can damage the cable and interfere with signal transmission. Special varieties are available for use with mobile machinery or machine tools or even welding applications, which may require a flame-retardant material.

Often enough, cables used in the flexing and rotating applications in motion control require high tensile strength and resistance to abrasion and flammability. They’re most often manufactured using polyvinyl chloride (PVC), chlorinated polyethylene (CPE), polyurethane (PUR) and thermoplastic elastomer (TPE).

From this wide array of choices, cable manufacturers can aide designers in selecting the right cable for their applications in several ways, through hands on design assistance but also increasingly via online tools that offer engineering assistance such as product selectors and even design tools. Case in point; Zuken’s E3.series software is being used by UK-based Electroflight to design an all-electric aircraft for the ACCEL All-Electric Flight Research Initiative.

Electroflight is using E3.series to design, build, test and commercialize an all-electric aircraft – all within a 24-month timeframe – as part of the Accelerating the Electrification of Flight (ACCEL) research initiative. ACCEL involves a consortium of partners which aims to address the technical challenges associated with all-electric flight, to develop a more robust supply chain and ultimately contribute to cleaner, greener flight.

Electroflight is using the E3.series software from Zuken to design wiring harnesses for an all-electric aircraft for the ACCEL All-Electric Flight Research Initiative.

“With such a compressed timeframe for the ACCEL aerospace initiative, speed is everything,” says Stjohn Youngman, Electroflight’s Programme Manager. “E3.series was selected because of its ease-of-use, flexibility, and output capability for all data needed to manufacture wiring harnesses, including bills of materials.”

E3.series is already a common design tool in the aerospace industry, but also in the motorsport industry, where it helps meet racing deadlines. Electroflight plans to take advantage of E3.series’ aerospace/motorsport synergies as it will use System 25 mil-spec motorsport connectors and harness construction techniques on the ACCEL aircraft.

Youngman adds: “We’re at the start of an extremely ambitious R&D project. To get from concept to commercial offering in just two years is unheard of in the aerospace industry. Our learning curve has to be incredibly fast.”

Optimization will be key for many aspects of the design of the ACCEL aircraft. This is because for all-electric flight, it’s necessary to tackle the twin challenges of energy storage capacity and powertrain performance. To keep the weight of the aircraft down, Electroflight will be trying to keep cable runs as short as possible – through the smart placement of sources, switches and loads. In this respect, E3.series’ ability to integrate well with leading MCAD tools is an added benefit.

Sensors at heart of bionic robots from Festo

December 7, 2018 By Miles Budimir Leave a Comment

The Festo Bionic Learning Network has released it latest biomimicry innovations to support ongoing research in engineering, manufacturing, and materials science drawn from natural systems. Here are the 2018 additions to the Festo Bionic Learning Network:

A transforming spider that rolls or creeps
A robotic fish that autonomously maneuvers through acrylic water-filled tubing
A semi-autonomous flying bat-like robot with more than a seven-foot (2.28-m) wing span and the ability to self-improve its flight path

Spider-like robot rolls uphill

The biological model for the BionicWheelBot is the flic-flac spider Cebrennus rechenbergi) — a species that lives in the Erg Chebbi desert on the edge of the Sahara.

Just like living flic-flac spiders, the Festo BionicWheelBot propels itself with a tripod gait using six of its eight legs to walk. To start rolling, the BionicWheelBot bends three legs on each side of its body to form a wheel. Two lower-middle legs are folded up during walking then extend and push the rolled-up spider off the ground to propel it forward. An inertial sensor lets the robot track its current pose so it accurately times its next push-off sequence. The robot rolls faster than it walks and can roll up a 5% incline.

Deft underwater navigation by soft-finned robot

For the 15-oz BionicFinWave, the Festo Bionic Learning Network team found inspiration in the undulating fin movements of marine animals such as the polyclad and cuttlefish. Its propulsion mode lets the underwater robot autonomously maneuver through water-filled acrylic tubing. Swimming autonomous robots such as the BionicFinWave could eventually find practical application in inspection, measurement, and data acquisition in water, wastewater, and other process industries. Knowledge gained in this project could also find use in the manufacture of soft-robotics components.

Undulation forces from longitudinal fins also let the BionicFinWave maneuver itself forward or backward. The fin drive unit is particularly suitable for slow and precise motion … and causes less turbulence in the water than conventional screw-propulsion drives. While it moves through tube systems, the robot also communicates via radio to share temperature and pressure sensor readings to nearby I/O.

The BionicFinWave’s two lateral fins are molded from silicone and can move independently to generate different wave patterns (or swim in a curve). The BionicFinWave moves upwards or downwards by bending its body in the target direction. Integrated crankshafts, joints, and piston rod are 3D printed from plastic. Other geometrically complex BionicFinWave components are also 3D printed; this helps keep weight down. Pressure and ultrasound sensors constantly register the BionicFinWave’s distance to the walls and its depth in the water, which prevents collisions with the tube system. This autonomous and safe navigation needed the development of compact, efficient, and waterproof or water-resistant components that can be coordinated and regulated by means of appropriate software.

Flying robot uses machine learning to choose flight path

To emulate the flying fox, among the world’s largest bats, the wing kinematics of the BionicFlyingFox are divided into primaries and secondaries with all the joints in the same plane. To let the BionicFlyingFox move semi-autonomously within a defined space, the robot communicates with a motion-tracking system, which in turn plans the flight paths and issues commands.

Starting and landing are performed by the human operator; an autopilot takes over during flight. Pre-programmed flight routes stored on a computer specify the path taken by the 20.5-ounce (580-gram) BionicFlyingFox as it performs its maneuvers. The wing movements needed to effectively implement the intended movement sequences are calculated by its on-board electronics. The BionicFlyingFox optimizes its behavior during flight and follows the specified courses more precisely with each circuit.

A membrane covering the skeleton was specially developed by the bionics team for the BionicFlyingFox. It consists of two airtight foils and a woven elastane fabric, which are welded together at approximately 45,000 points. The fabric’s honeycomb structure prevents small cracks in the flying membrane from increasing in size. The BionicFlyingFox can thus continue flying even if the fabric sustains minor damage. Due to its elasticity, the flying membrane stays almost crease free even when the wings are retracted. Since the foil isn’t only elastic, but also airtight and lightweight, it could potentially be used in other flying objects or for clothing design and in the field of architecture.

Hygienic, stainless gearmotor designs improve fish-processing plant

December 6, 2018 By Miles Budimir Leave a Comment

Processing fresh fish necessitates a hygienic environment with regular washdowns, followed by frigid temperatures for freezing final products. That’s why machinery in such settings must be extremely rugged — and why one fish supplier has used motors from Bauer Gear Motor for the last few years.

Van Der Lee Seafish processes approximately 200 tons of fresh fish every week. Fish is subject to conveyor-driven sorting, filleting, breading, freezing, and packaging processes. Drives for these conveyors must meet strict food-industry hygiene requirements.

Building reliable processing lines for hygienic environments subject to -43° C temperatures is challenging. One fish supplier recently upgraded its conveyor drives to stainless-steel variants for top reliability. Its fish-processing lines can be reconfigured for different products.

“Product quality is paramount, so fish must be processed quickly and efficiently,” said technical director Willem Van der Lee. “We can have seven processing and five packaging lines operating at any given time, and each one employs many motors and drives. That necessitates spare parts be kept to minimize downtime should a breakdown occur.”

That’s why Van Der Lee Seafish standardized on Bauer’s gearmotors throughout its food-processing facility a few years ago. The AsepticDrive from Bauer Gear Motor (of Altra Industrial Motion Corp.) has a hygienic gearmotor design with smooth surfaces and no cooling fins that can promote bacteria accumulation. Standardizing on the gearmotor minimized spare-parts inventory. What’s more, the permanent magnet synchronous motors (PMSMs) have high energy efficiency, especially under partial load. Plus the synchronous nature of the PMSM motors maintains constant speed independent of load. That means as long as the mains frequency is held constant the motor speed doesn’t vary, even under overloading or voltage drops.

Standardizing on the AsepticDrive units improved overall food-processing facility energy efficiency.

The gearmotors delivered the promised level of performance on almost all counts. One exception was on some motors subject to mechanical damage from other equipment. On these units, degradation of the hygienic coating threatened to compromise the hygienic design. So for certain locations in the plant, Bauer engineers supplied a newer gearmotor — a stainless-steel HiflexDrive variation with maximum mechanical resilience and the ability to withstand harsh washdowns.

VFDs run the gearmotors to allow precise control of conveyor speeds.

“The AsepticDrive has let us trim spare-parts inventory, and the HiflexDrive in stainless steel is a direct replacement for running in frozen storage areas,” added Van der Lee.

Bauer’s HiflexDrive comes in a modular design allowing gearbox, electric motor, and external finish selection. Motors rated up to IE5, according to IEC TS 60034-30-2, offer top energy efficiency, while pairing with variable speed drives allows exact conveyor-speed setting. Including a PMSM in the drives reduces heat losses from the rotor by 100% and total losses by approximately 25% — plus boosts total efficiency by 10% or more. Such savings are significant especially for stainless-steel motor variations that dissipate heat less efficiently than those built with aluminum or cast-iron housings.

HiflexDrive system flexibility lends itself to the food and beverage industry. The stainless-steel construction eliminates hygiene risks posed by mechanical impacts or extended operation subject to rigorous cleaning. Ingress protection is to IP69K — a washdown designation for applications subject to high temperature and high-pressure water.

A new stainless-steel gearmotor variant is now employed where the fish processor needed maximum machinery ruggedness.

Flexible designs also mean Van der Lee Seafish can move its conveyors around to various areas and not worry about drive reliability. Stainless-steel HiflexDrive units ensure maximum productivity.

Medical applications benefit from precision encoders

December 4, 2018 By Miles Budimir Leave a Comment

Encoders are essential to accurate positioning in most motion systems, particularly where high precision is most needed. For instance, applications like semiconductor manufacturing with nanometer precision, or medical applications where there is virtually no room for error, because that could mean the difference between life and death.

Designers of medical equipment are able to use a plethora of new technologies. Motion control is an area where designers need to keep up to date with as technology increases in complexity. Medical applications such as robotic surgery, radiation treatment, and laboratory analysis such as DNA sequencing are all benefiting from advances in encoder technology.

Radiation treatment
Machines that treat patients for tumors with radiation inherently have complicated coordinated motion control. Guiding the radiation beams when the patient is on the table is critical, and any errors in positioning may damage healthy cells. Because of the radiation environment on the machine, communication between encoders and the control is of upmost importance and requires redundancy.

Encoders from HEIDENHAIN are used to provide exceptional repeatability and reliability required for computer tomography.

What caught the attention of medical machine designers is a little known ENDAT function called CRC. ENDAT is the high-speed serial interface from HEIDENHAIN that is RS-485 based and offers a fast bi-directional communication protocol. CRC is Cyclic Redundancy Check and is transmitted along with the position words from the encoder to the control. Basically, the CRC reports the number of bits transmitted to the control, and the control can then evaluate the number of bits and make a checksum. If the number of bits match, then everything is operating normally. However if the checksum does not match, then the ENDAT interface reports an error which the control can then handle and take the proper steps needed for reliable motion control.

Laboratory analysis
Machines that are performing large amounts of chemical analysis like drug testing machines or those that sequence DNA are also reliant upon high quality encoder feedback. For drug testing machines, they typically use pipettes and a high number of wells per tray. Smooth reliable motion is critical here as the machines are usually left to operate overnight and sometimes 24 hours a day. When moving the pipette array or trays, a motion that is jerky or somehow unsmooth can destroy data, as liquids can spill from the pipettes into unwanted wells.

HEIDENHAIN encoders help with accuracy, speed control, and limit splashing in medical fluid handling test equipment.

Repeatability is also critical. As the machine operates and heats up, the shape of the machine may change. Linear encoders that report the real position versus a rotary encoder/ ball screw set up are more accurate, the latter possibly causing repeatability issues that can even lead to the pipette array missing its targeted wells or causing a crash.

DNA sequencing machines are those that use flowcells, which are a “Lab on Chip” and may contain several billion micro wells. Colors need to be detected from these tiny wells and the motion system with cameras is designed for sub-micron repeatability. In these fine resolution applications, the interpolation error of the encoder (or sub-divisional error) is critically important. When the encoder signal periods are electronically subdivided to gain more resolution, errors can happen within that signal period and then eventually lead to errors in data collection from the camera. One encoder, the HEIDENHAIN LIP 200, has interpolation error at +/- 1 nanometer. This kind of encoder helps to ensure the stability of the image required to evaluate the colors of the wells on the flowcell.

Robotic surgery
Surgery robots that are surgeon-assist based are becoming more accepted in the medical world. In fact, over 80% of prostate surgeries done in the U.S. today are done with robotic assist surgery robots. Some surgery robots need to have redundancy for the motion control components, while others can drill and measure distances at the same time, making accuracy especially important. Here again, a reliable high-speed serial interface such as ENDAT as well as a full line of rotary and linear encoders that are Functionally Safe with various mechanical options can fulfill the need for these applications.

This human joint replacement demonstrates the exacting standards for surface finish precision that HEIDENHAIN 5-axis controls enable.

Casebook example: Programmable AutoMet grinder-polishers by Buehler for high-throughput manufacturing

December 1, 2018 By Lisa Eitel Leave a Comment

ITW company Buehler now offers AutoMet semi-automatic grinder-polishers. The AutoMet 250, AutoMet 250 Pro and AutoMet 300 Pro grinder-polishers are ideal for customers in material testing or demanding environments needing to process a high volume of samples. They feature a brand-new intuitive touch screen interface that is simple to learn and quick to operate. The AutoMet Pro models also include advanced programming features such as method storage and z-axis material removal to ensure consistent results regardless of operator.

“From speaking to our customers, we knew that production labs need to move quickly, and they need a reliable grinder polisher that can be programmed no matter who is working the shift,” says Buehler global product manager Matthew Callahan. “So, the Buehler innovation team created the AutoMet Pro grinder polishers to expedite the sample preparation process and improve the quality of the samples while saving time and money in the training of laboratory technicians.”

“The machine eliminates constantly setting the machine and the possibility of human error. It supports complex lab applications … so it also suitable for high-throughput labs — especially in the automobile, aerospace, medical device, electronics, heat treat, metals and other manufacturing industries.”

Buehler’s non-programmable AutoMet 250 Grinder-Polisher offers push-button controls and digital readouts. All AutoMet models have been redesigned for a new look and feel, while retaining the reliability that comes with the Buehler name. Quick cleaning features including an adjustable water spout, 360° bowl rinse, and bowl liners save time and effort during daily cleaning.

Reproducibility and automation can be further improved by integrating the Burst Dispensing System, which also optimizes abrasive usage to save on consumables spend. Another new highlight of the AutoMet grinder-polishers is Rinse and Spin … which cleans polishing surfaces and the platen at the press of a button. For more information, visit buehler.com.

How a supercharger (blower) works: New animation from Ogura

December 1, 2018 By Lisa Eitel Leave a Comment

Ogura Industrial has created a new animation showing how a supercharger (air blower) works. Many people are familiar with the term supercharger from the automotive world … but are unaware of the many other uses of these high-performance units.

For design engineers who have wondered, a new three-minute animation provides a quick understanding of how a supercharger operates for engine applications … and in a variety of other applications — such as air blow-off and drying systems; agricultural sprayers; and fuel cells. In these applications, the blowers boost efficiency.

Ogura superchargers come in eight different standard models and can provide a discharge volume from 100 to 2,800 cc per revolution with many units comfortably operating at 12,000 rpm.

Watch this new video here:

Ogura has been producing clutches and brakes since 1938. Over that time, we have developed over 5,000 different models of clutches and brakes. Although Ogura primarily produces electromagnetic clutches and brakes, we also produce magnet particle, mechanical, pneumatic, hydraulic and a variety of specialty products. Ogura is the world’s largest manufacturer of electromagnetic clutches and brakes. Current manufacturing capacity is over 30 million units per year. To provide localized support, we have manufacturing plants spread throughout the world in Asia, The Americas, and Europe. All manufacturing facilities are ISO certified and conform to ISO 9001;2008, ISO 140001, and ISO/TS 16949.

Engineers needing Ogura to build a special product (or modify an existing standard model) should call (732) 271-7361 or visit www.ogura-clutch.com.

Geared stepper motors drive movements of Breakfast Brixel moving architectural wall

November 13, 2018 By Lisa Eitel Leave a Comment

A new architectural wall called the Breakfast Brixel is making some installations more dynamic. The system is built from dozens of digitally controlled rotating bricks that act as pixels to create waves, stripes, and undulating shapes on the moving walls. Brixel installations can even run customizable artwork and facades to evolve in response to real-time data and software commands.

Breakfast engineers designed everything from scratch — PCBs included — and employ geared stepper motors to rotate the bricks.

In addition, the center support shaft of each Brixel column allows each brick to spin endlessly in either direction without tangled wires or the use of slip rings.

“A computer runs a fully featured application in the background. It sends data to the Brixels with movement commands that include speed and direction. We can also set custom acceleration and deceleration curves at any time on the fly when the Brixels are moving. This lets us create beautiful and organic displays — such as wind animations,” explained Breakfast CTO and cofounder Mattias Gunneras.

For high-level programming of animations and interactive movements, controls were dynamically scripted was Python, OpenCV-Python, and Numpy. In addition, for Brixel Silhouette — a Brixels mode that causes the wall to rotate bricks to mirror the shapes and movements of people in front of the installation — Breakfast engineers used 3D simulation for testing through a VR headset. That let the team get a feel for the displays before a prototype physical installation was ready.

“We’re using stitched-together 3D depth cameras to create a point cloud of the scene in front of the installation,” said Gunneras. With this technique, we can create the mirroring effect to map a person … regardless of how close they stand to the installation.”

Breakfast Brixel walls are customizable to work as facades, railings, dividers, and fences. The design allows an unlimited number of rows and columns.

When there’s nobody standing in front of the installation, kinetic animations and relevant information can play across the installation in the form of letters created by positive and negative colors and space.

Brixel walls can display an array of digitally programmed visuals and movements. The bricks come in an array of sizes, shapes, materials, and colors.

A Linux controller sits at the heart of each installation to execute programs that process visual data and pass high-level data to the bricks. Data goes via RS-485 connections to controller PCBs at the bottom of each column. Each controller PCB then sends the data over serial lines up the columns to each individual brick. Brixel installations are controllable and updated via a web-based app running off the Linux controller — for access from any mobile device. Users can upload content, create playlists, and set schedules.

HMI simplifies setup of robot-assisted automation for one integrator

November 12, 2018 By Lisa Eitel Leave a Comment

Integrator Inovatech Automation recently decided they were spending too much time programming expensive HMI and PLC platforms, so contacted Pro-Face America for help.

The integrator needed an HMI capable of universal robot and I/O-Link integration, legal for Inovatech Automation branding, and easy to program.

“I was apprehensive at first because we have a lot of projects going … so timing is short,” said Inovatech director of operations Travis Buset. “More specifically, I had concerns about learning something on the fly — and feared the onboarding experience and programming were going double our time investment.”

Pro-Face America supplied its LT4000M HMI plus Control unit. This hardware reduces costs by eliminating the need for an external PLC. In addition, for Inovatech Automation the LT4000M halved engineering time for configuration; offered easy integration to a Universal robot and IO-Link network; and was delivered with a custom overlay for machine-branding purposes.

Inovatech uses Pro-Face America’s LT4000M HMI plus Control unit on its modular automation station.

Trimming the time for setup was the most important benefit, though.

“Another platform needed two different pieces of software. In contrast, Pro-Face uses one software with drag-and-drop functionality. What once took me 32 to 40 hours to program now takes eight hours on the Pro-Face.” In fact, Buset had one programmed in eight hours his first time trying.

“This a powerful unit and well worth its cost for the level of configuration it allows.” Inovatech estimates it’s now operating 75% more efficiently than before.

Conveyors with direct-drive motors offer key advantages to Pa. facility

November 11, 2018 By Lisa Eitel Leave a Comment

American Axle Manufacturing (AAM) is increasing the functionality of its St. Mary’s, Pa. manufacturing operations with conveyors sporting advanced drive technology. Small yet powerful direct-drive motors from Electric Torque Machines actuate Dorner conveyors that move small parts around the AAM facility.

AAM designs, engineers, validates, and manufactures an array of driveline, metal-forming, powertrain, and casting technologies — and is known for manufacturing large components such as axles and differentials. However, the AAM St. Mary’s facility manufactures many of the small and lightweight parts that go into AAM drivetrains. Transporting these parts from station to station and within workcells requires small and precise conveyors. The challenge is that the compactness of such conveyors is degraded by the bulk of traditional gearmotors. That’s what prompted AAM to specify conveyors driven by Dorner’s Universal Drive offerings — with direct-drive motors from Electric Torque Machines at their core.

Dorner Conveyor and Electric Torque Machines helped improve the material handling setup inside the Pennsylvania facility of American Axle Manufacturing.

The direct-drive motors have high continuous torque density (particularly at lower operating speeds) to eliminate the need for a bulky gearbox. Integrated into Dorner’s 2200 Universal Drive — which includes the motor, configurable motor mount, and controller — they reduce the conveyor-drive size by nearly 70% while boosting functionality and maintaining required output torque.

“We chose Dorner’s Universal Drive for its unique motor,” said AAM facilities engineer Michael Vandervort. “The motor is smaller and lighter than traditional ac motors … and can run in designated working areas unguarded, because the motor runs cool. In contrast, traditional ac motors are too hot to touch.”

ETM’s direct-drive motor imparts advanced functions to simplify automated tasks.

Vandervort also cited the wide speed and torque ranges of the Dorner Universal Drive as key benefits. “The drive lets us use the conveyors for applications such as slow pass-under vision tasks; heavy accumulation tasks; and high-speed part transfers.”

The on-conveyor inspection function is especially challenging. “At our facility, we use a lot of small conveyors to move light loads. Electric Torque Machines developed motor tuning functions to help stabilize our vision imaging on pass-under applications with very low torque requirements. We really appreciate ETM working with us and developing solutions for our specific needs,” Vandervort added.

“It was energizing to work with industry leader AAM — and encouraging to see the industry ready to adopt new technologies. AAM’s application illustrates the advantages of direct-drive motors,” added ETM V.P. of engineering Scott Reynolds.

Digital printing pairs with a machine capable of handling its varied output

November 11, 2018 By Lisa Eitel Leave a Comment

VITS International makes sheeting and finishing machines for packaging, printing, and converting. The OEM saw the digital-printing market needed finishing capable of commercial production speeds. So VITS designed and built the SPRINT Variable Data Finisher with a Bosch Rexroth drive and control platform to meet the demand.

This is a VITS Variable Data multi-web finisher.

Digital inkjet printers can execute output comparable to that of traditional web-offset printing — at near-commercial rates to 1,000 feet per minute. Digital printing also allows variable data printing to dynamically vary the number of pages and content on the pages — even handling significantly varied page dimensions. Such capabilities enable incredible customization but complicates the finishing of printed web. So finishing systems on digital printing lines must be able to quickly cut, collate, and assemble disparate pages into final readable pieces.
“We decided to develop such a finishing machine to support both offline and inline finishing,” said VITS International president and CEO Deirdre Ryder. The result is VITS’ SPRINT Variable Data Finishing System that turns variable print material into finished product at up to 1,500 fpm. The SPRINT machine works for inline systems (which get and finish a single web directly from the digital printer) and offline multi-web finishing (for processing multiple webs into a single finished signature or book).

“Our printing customers want to output larger products at faster rates of speed,” said VITS director of product applications Kim Markovich. “Particularly for direct mail, being able to finish multiple webs and ribbons with suitable register control means printers can assume more work.” SPRINT finishing machines include independently driven axes controlled by a Rexroth IndraMotion MLC motion control system. A Bosch Rexroth L45 controller employs Sercos III for deterministic synchronization of drives and fieldbus communication for I/O.

The inline machine version usually has 10 to 12 driven axes; multi-web offline versions can have up to 30. A Rexroth cross-communication card with Sercos-III-based communication helps synchronize VITS finishers with inline-mounted printing presses (also sporting Rexroth controls). Machine modules trigger various functions to convert printed web into books or mailers with Rexroth IndraDrive servo drives and IndraDyn servomotors for actuating the functions.

Offline multi-web machines interface with paper rolls on register splicers. These continuously feed web at a constant-tension infeed with precise gain and control to prevent issues.

The paper goes through a station that slits it in half and stacks the halves.
The paper halves travel to a ribbon-gathering station and onward to a station that folds the ribbons in half.
The paper web goes through a shear-slitting station for edge trimming.
Finally, the web goes through a variable-data rotary cutter that slices each page to size and collates finished product for the final binding or saddle stitching.

Maintaining registration for all these steps is core to ensuring all pages in all signatures are cut to the same dimension. Nothing prints perfectly, so the length of any print usually varies ±0.001 in. from page to page … which is an error that can accumulate quickly over hundreds of fast-moving pages.

“We use the built-in intelligence of Rexroth drives to dynamically maintain web registration — and keep the central controller’s processing power free,” said integrator Bruce Parks of Parks Consulting, who helped on the machine design. A virtual master holds all drives in synchronization. Tension zones between drives maintain tension during web splitting, merging, and cutting. Controls can also command groups of drives to adjust tension … and bring the web into register with the virtual master.

SPRINT Finishing machines use the Rexroth IndraMotion for Printing automation platform with independently driven axes under a central IndraMotion MLC motion controller (similar to the one here).

SPRINT engineers used the IndraMotion for Printing version of Rexroth’s MLC system to automate tasks via IEC 61131-compliant motion logic and PLCopen function blocks — and software libraries specific to printing and converting. “IndraMotion for Printing includes tools for most web-handling tasks. These and Rexroth’s PLCopen function blocks helped us build functions and camming profiles for our proprietary Clear Channel registration,” said Parks. Clear Channel registration control allows the cutting thousands of pages per hour while maintaining precise page registration impossible with legacy finishing systems. It enables faster size changes as well as cut tolerances impossible with standard finishing systems.

Another strength of the SPRINT machine is its rotary cutter … capable of handling images of 5 to 25 in. and configurable to cut different width chips — blank spaces between pages on the paper. Machine operators trigger the change with a push of a button. At the cutter station, twin knives slice the chip out; the knives are spaced by the width of the chip … and cutting must be synchronized with the speed of the web through the station. “Our camming lets users cut output of variable size with multiple knives and still maintain chip size — because the camming always synchronizes with the web speed through the cutting zone,” said VITS director of new product development John Salamone.

This is the first machine series VITS built on a Bosch Rexroth control and drive platform. “We had a great relationship with the previous supplier. Bosch Rexroth gave us similar commitment … and Rexroth technology let us quickly develop equipment with accuracy no competitors have. So now Rexroth-equipped machines of ours working flawlessly all over the world.