Case Study| Howa Machinery, Ltd.

We standardize the sizes of parts so that the same workers can use the same tools, thereby improving work efficiency.

We manufacture street sweepers designed to collect litter and other debris from the road and store it inside the vehicle. The waste collection bucket is mounted on top of the vehicle.To transport the trash to the bucket, it is placed on a large, diagonally mounted conveyor belt (approximately 1.5 m wide × 3 m long) and moved into the bucket.

　For belt conveyors, the most common method involves securing both ends of the belt and rotating it in that position. The belt is typically made of solid rubber, which is also used in street sweepers. A wire is embedded inside the belt to prevent stretching, but since it is constantly under tension and exposed to various vibrations while traveling on roads in different conditions every day,

　As a result, the belt tends to loosen, so we perform regular maintenance to adjust its tension.
During maintenance, we also loosen and tighten the numerous nuts used around the conveyor. Because there are many parts, we standardize their sizes and have the same person use the same tools to ensure efficient maintenance.

We were experiencing issues caused by damage to peripheral equipment during maintenance

The nuts installed on the belt conveyor only needed to be small for power transmission purposes. However, to improve maintainability, we standardized the part sizes and opted for a larger size.

　However, using larger-than-standard nuts led to over-tightening, resulting in problems such as belt breakage, bearing damage, and shafts bending or breaking—all caused by damage to peripheral equipment.

　Although we had established standard values for belt deflection when setting belt tension, it was difficult to adhere to these standards in actual field operations, and the belts were often over-tightened.

When a single-axis robot using a brake from another company caused issues in the market and we were struggling to find a solution, Miki Pulley introduced us to a brake manufacturer, which allowed us to resolve the problem.

Since then, I had hoped to work with Miki Pulley one day. Later, when I was put in charge of developing the YK400XR small SCARA robot, I reached out to Miki Pulley, and we decided to adopt the “BXW (non-excitation type brake) model.”

Thanks to their cooperation in delivering the performance and cost we expected, we were able to develop an attractive product. During evaluation and durability testing, Miki Pulley’s development team also went above and beyond, allowing us to launch the product smoothly.Thanks to their support, the YK400XR compact SCARA robot has become a flagship product that underpins our sales. Currently, the YK400XE-4—a successor model with further improved performance over the YK400XR (and, of course, equipped with the BXW model)—is now on the market.

To prevent the belt from becoming too tight due to over-tightening of the nut, we decided to reevaluate the nut design. That’s when we came across Miki Pulley’s “Torque Limiter (Torque Tender/Overload Protection Device).”We commissioned Miki Pulley to develop a “nut-type torque limiter” as
a custom product—a device that combines the function of the torque limiter (torque tender/overload protection device), which disconnects the input and output to protect the machine during overload, with the function of a standard nut.

　By having Miki Pulley develop a nut-type version of their “Torque Limiter (Torque Tender/Overload Protection Device),” we not only solved the initial problem of conveyor belt damage caused by over-tightening the nuts, but also made it possible for anyone to perform maintenance with the same level of precision.