Designing comprehensive automation for high-speed pick-and-place applications is among the most challenging tasks faced by motion engineers. As robotic systems become more complex and production rates climb ever higher, system designers must keep up with the latest technologies or risk specifying a less than optimal design. Let's review some of the latest technologies and components available, plus take a close look at where they find use.
Robot arms suit compact designs
Industrial robot arms are not usually known for being light on their feet. Rather, most have substantial constructions that must support heavy end-of-arm tooling. Despite the advantages of a sturdy design, these robotic arms are too heavy and bulky for delicate applications. To make nimbler arms more appropriate for light tasks, engineers from igus Inc., working in Cologne, Germany, set out to develop a multi-axis joint to allow small loads to swivel around a jib. The new joint is well suited for delicate pick-and-place applications where the gripper force can be adjusted as needed.
Flexibility and light weight are key design parameters for the new joint, which consists of plastic and cable controls. (Called Robolink, this device recently won two “Best by Design” awards from this magazine, both a Readers' Choice and a Judges' Choice award.) In short, cables are moved from the arm's shoulder joint by FAULHABER compact brushless dc servomotors (from MICROMO, Clearwater, Fla.), which prevents inertia in the arm, facilitates dynamic movement, and minimizes the design footprint.
Engineers based much of their design on the human elbow joint, so two DOFs — rotation and swivel — are combined into a single joint. Similar to a human arm, the weakest part of the robot arm is not the bones (the robot arm's body tube) or muscles (the drive motor), but the tendons, which transfer power. Here, high-tension control cables are made of a super-strong UHMW-PE polyethylene material featuring a tensile strength of 3,000 to 4,000 N/mm2. Beyond traditional robot arm functions such as pick-and-place applications, the joint is also well suited for special camera fittings, sensors, or other tools where lightweight construction is required. A magnetic angle position sensor is built into every joint for high precision.
The electronically commutated servomotors feature a low moving mass suitable for dynamic use: The 24 Vdc operating voltage is designed for battery power, crucial for use in mobile applications, while the 97 mNm motor torque increases the diameter-compliant planetary gearheads to the values required for arm operation. What's more, these brushless drives have no wearing components besides the rotor bearing, ensuring a service life of tens of thousands of hours. For more information, visit igus.com or micromo.com/brushless-dc-motors.aspx.
Linear motion system speeds lab automation
Beyond traditional packaging and assembly operations, pick-and-place is also proliferating in high-speed lab automation. Imagine manipulating millions of bacteria samples every day and you'll have an idea of what today's biotech labs are expected to handle. In one setup, an advanced linear motion system is enabling a biotech laboratory robot called RoToR to pin arrays of cells at record-breaking speeds of more than 200,000 samples per hour. RoToR hails from Singer Instruments, Somerset, UK, and is used as a benchtop automation system for genetic, genome, and cancer research. One of these robots often services several different labs, with scientists reserving short time slots for replicating, mating, re-arraying, and backing up bacteria and yeast libraries.
A real-time controller from Baldor Electric Co., Fort Smith, Ark., called NextMove ESB-2, manages RoToR's motion control. The controller handles the three motion axes that coordinate the robot's point-to-point pinning moves, as well as a sample-handling axis, and also interfaces with the robot's GUI. In addition, the controller also manages all I/O channels.
Besides the controller, Baldor also supplied a linear servomotor and drive and three integrated stepper motor and drive modules. The robot makes point-to-point transfers from source to destination plates along a linear servomotor axis that runs along the machine's width. This axis supports a two-axis stepper motor head that controls the pinning action. In fact, the combined X-Y-Z motion can even stir samples using a complex helical motion. The separate stepper motor axis controls the pinheads' loading mechanism. Pneumatic grippers and rotators control other machine movements, such as the pickup and disposal of pinheads at the beginning and end of operations.
Singer originally intended to use a pneumatic drive for the main transverse axis, but this design couldn't supply the desired positioning resolution or speed, and was too noisy for a lab environment. That's when the engineers began to consider linear motors. Baldor created a custom brushless linear servomotor with mechanical modifications to the linear track, allowing it to be supported only at its ends, rather than along its length — so the motor's forcer acts as an X-axis gantry that carries the Y and Z axes. Finally, the linear motor's magnet design minimizes cogging to allow smooth motion. For more information, visit baldor.com/products/motioncontrol/nmes.asp or singerinstruments.com.
Giant machine's actuators give the gift of Pop-Tart
Who doesn't love a good Pop-Tart now and again? This was the premise behind “Pop Tarts World,” a temporary store set up in New York City's Times Square last winter. One of the main attractions was a robotic Pop-Tart Varietizer powered by linear actuators from Macron Dynamics Inc., Croydon, Pa. Actuators were placed on the front of the giant vending machine, which uses a robotic shuttle to provide the X-Z motion that allowed visitors to create a custom box of Pop-Tarts from 23 flavors.
Though its operation appears effortless, the machine executes complex pick-and-place movements internally when users select their Pop-Tarts. Two actuators provide the Z-axis motion while a third enables motion for the X-axis. A gantry connection kit couples the Z-axis assembly, for a basic X and Z gantry automation system. For more information, visit macrondynamics.com.
Pick-and-place quick links
Baldor Electric Co. • baldor.com/products/motioncontrol/nmes.asp
Balluff Inc. • balluff.com/SuperShorty
Festo Corp. • festo.com/usa
Haydon Kerk Motion Solutions Inc. • haydonkerk.com
igus Inc. • igus.com
Lenze Americas • lenze.com/8400
Macron Dynamics Inc. • macrondynamics.com
MICROMO • micromo.com/brushless-dc-motors.aspx
Singer Instruments • singerinstruments.com
Tolomatic Inc. • tolomatic.com
Linear actuator suits pick-and-place needs
The motorized SplineRail Linear Actuator combines a mechanical drive, guidance, and stepper motor in the form of a Size 17 single stack, or a double-stack stepper with either a 1.8° or 0.9° step angle. The actuator is useful in pick-and-place mechanisms and robotic assemblies for life sciences instrumentation, semiconductor equipment, packaging, and assembly. An integrated connector comes solo or with a harness assembly; the connector is RoHS compliant, rated for up to 3 amps, and can handle wire sizes from 28 to 22 gauge. The SplineRail includes a Kerk precision rolled lead screw, supported by bearings and contained within a concentric aluminum spline.
Innovator: Haydon Kerk Motion solutions Inc.
Frequency inverters enable precise control
Most mechanical processes require varying amounts of power that depend on external parameters, such as production volume: Typically, a frequency inverter matches speed and torque to these process requirements. One such unit, the Lenze 8400 Inverter Series, features L-Force automation technology for tailored motion control and dynamic performance in myriad material handling and logistics applications. Basic inverter versions of the 8400 satisfy simple continuous-motion applications, such as driving a conveyor; servo-inverter models control complex synchronized pick-and-place applications. The new inverter series also incorporates memory modules, online diagnostics, and an optional integrated safety system.
Innovator: Lenze Americas
Sub-compact prox sensors fit tight spots
SuperShorty inductive proximity sensors fit into spaces as short as 6 mm and install directly into grippers or speedy equipment with frequency ratings to 3 kHz, such as pick-and-place machinery. Although small in size and light in weight (some models weigh just 0.7 g), they have all the features of standard-size sensors. All models are reverse polarity protected, short circuit protected, IP65 or IP67 rated, and have a current capacity of 150 mA. Housing styles include 6.5 mm smooth metal, M8 threaded stainless steel, and 6.5 mm plastic. SuperShorty sensors with 1.5 mm sensing range come in both PNP and NPN styles, and normally open and normally closed versions as well.
Tiny RoHS-compliant slide maintains jaw-dropping parallelism
The electric EGSL mini slide executes strokes to 300 mm (with 300 N of force) for both vertical and horizontal applications with variable positioning, even under workloads to 14 kg. Linearity and parallelism are in the 1/100-mm range, and the slide's acceleration and deceleration (to 15 m/sec2) and speed (1.3 m/sec) benefit fast, controlled, pick-and-place applications.
Innovator: Festo Corp
Drive and controller unit eases linear motion setup
The ACS Stepper Drive/Controller is a low-cost drive and controller unit compatible with most 24-Vdc stepper motors, for use with electric actuators. It executes 4, 8, or 16 move command modes (absolute, incremental, or jog) and adjustable motion profile parameters (position, velocity, acceleration/deceleration, force) that are independently configurable for each move. The ACS also allows definition of linear motion in either mm or in., and has built-in configurations for the ERD — Tolomatic's rod-style actuator. The latter is designed as a replacement for pneumatic cylinders, and is suited for pick-and-place applications.
Innovator: Tolomatic Inc.