Carpet tufting creates a tough environment for linear motion products. In this process, synthetic fibers are applied to a carpet backing using a high-speed machining system. The needle bar, which holds 4,000 tufting needles, employs quick and reciprocating short strokes up to 1600 cycles per minute. The carpet tufting machine is designed to run for long, continuous stretches, and therefore the performance is measured by the life of the system, along with the amount of linear feet that are run between replacement systems.
In this scenario, each carpet tufting machine used 36 ball bushing bearings and steel shafting assembled into a push-down foot system (4 bearings and 2 rods of steel shafting per push-down foot, for an average of 9 push-down feet per machine). Precise and repeatable linear motion would be essential for optimum manufacturing and the minimization of scrap. The manufacturer also employed non-stain oil along the pushdown foot assembly to ensure smooth linear motion and reduced friction.
The environment of the application is typical for industrial machining. While no adverse or caustic chemicals were present, contaminates such as dust, dirt, grease and carpet fiber particles posed a substantial risk for contamination.
This carpet manufacturer was experiencing unplanned downtime due to linear bearing failures and massive profit loss due to thousands of yards in scrapped end-product. Poor quality and damaged carpeting were cited as the main reasons the manufacturer lost up to 54,000 yards of carpet to scrap. The root of the problem was found to be the machine’s ball bushings within the push down foot assembly. Specific issues included:
PBC Linear implemented their Simplicity® self-lubricating bearing into the pushdown foot assembly for the carpet tufting machine. Its close tolerance ID bearing (.6240”-.6245”) and close running clearance (.0015”-.0018”) held the needle bar in tight position. This solved the problem of wear and progressive wander/loss motion.
The bearing’s proprietary FrelonGold® liner ran smoothly along the steel shafting, eliminating wear by evenly disbursing the load throughout the bearing. This successful solution was noticeably different than the previous application, which had only a small point of contact between the ball bushing and shafting products. Since Simplicity bearings contain no rolling elements and thrive in heavy load applications and dirty environments, they were able to push contaminants such as dirt, carpet fiber particulates, and grease to the end of the stroke.
Simplicity bearings were designed to exceed expectations in applications like this. Before Simplicity bearings were installed in the pushdown foot system and undercarriage, the carpet tufting machines were in a state of constant unplanned downtime due to high maintenance costs and upkeep. Now, these updated carpet tufting systems have became the most productive machines in the plant! The linear footage between maintenance rebuilds of the machine were increased from one million linear feet to over three million. The carpet manufacturer was also pleased to report a significant 95% reduction in scrapped product, eliminating millions of dollars in scrap every year that was previously thought of as “an acceptable loss.” Those losses are now profit gains!