Since the U.S. Patent Office opened for business in 1838, it has granted more than 4,400 patents for mousetraps.
Systems integrator Isthmus Engineering & Manufacturing (Madison, WI) can’t lay claim to building a better mousetrap. However, it can boast that it found a way to build mousetraps better. Recently, the company designed a system that automatically assembles and packages mousetraps. The traps are assembled on a rotary indexing dial and then transferred to an automated packaging station.
In this profile, sales engineer Jane Feller rats out the system’s secrets. For more information, call 608-222-9000 or visit www.isthmuseng.com.
What are the dimensions of the finished assembly? The trap is 3.25 inches by 1.75 inches. The traps are sold in packages of two. The package is approximately 6 inches by 5 inches by 2 inches.
How many parts are assembled? The trap has four parts: the top, bottom, actuator and spring.
What are the parts made of? The top, bottom and actuator are plastic. The spring is a coil-steel extension spring. The packaging is card stock.
What equipment feeds the parts? All four parts are fed from vibratory bowls and feed tracks to pick-and-place stations, where they are placed into fixtures around the perimeter of the indexing dial. A SCARA robot transfers the assemblies from the dial to a linear indexer, which guides them to the packaging station. There, they are loaded two-up onto the card stock, which is then folded, glued and placed on a belt conveyor to exit the system.
What methods are used to assemble the product? The parts assemble with snap-fits. The packaging is folded with a custom servo system and bonded with hot-melt adhesive.
What checks or inspections are included in the assembly process? Each assembly station is equipped with photoelectric sensors to check that parts are present. Before the finished assemblies are transferred to the linear indexer, a custom-tooled unit sets and actuates each trap to ensure that it works correctly. The SCARA robot sorts rejected assemblies by category or places good assemblies into fixtures on the linear indexer.
What is the production rate? The dial assembles 900 traps per hour. The packaging station produces 450 retail-ready packages per hour.
How did you help the customer design the product for efficient automated assembly? Some of the snap-fit lead-ins and chamfers were adjusted in their dies to accommodate automated assembly.
Can the system accommodate product variants? The machine was not designed for large variants or different products without retooling. However, the packaging station is completely adjustable to accommodate variations in card stock.
What was the most challenging aspect of designing and building the system? Custom folding the packaging was quite a feat. The packaging is a custom design. Maintaining perfect bend angles and alignment was done with coordinated servo and pneumatic positioning. This took a little debugging and testing on our assembly floor, but the result was a robust and accurate packaging station.
Editor’s note: Whether you’re a systems integrator or the inhouse automation team of an OEM, if you’ve designed a system that you’re particularly proud of, tell us about it. Send an e-mail to John Sprovieri, editor of ASSEMBLY, at email@example.com, or call 630-694-4012.