Wireless Bobbin Lock Detection

Problem: The 2^nd stage of tire building of the mining tires we make is completed on a machine we call a BNS. On the BNS there is a rotating carousel assembly that feeds different product bobbins to the tire building platform. This rotating carousel is called the Noria. Operators load product bobbins at the Noria buckets at the ground level and bobbins are unwound for tire building at the top of the Noria which is approx. 22 feet above the floor. The Noria rotates bobbins in full rotation so only mechanical assemblies are able to be used on the product buckets. The bobbins are locked in the buckets by manual locking assemblies. If the operator either does not lock the bobbin or the bobbin lock does not fully seat, the bobbin can have one of two problems to occurs as it unwinds at the high machine level. One, the bobbin can unwind all of its product into the Noria and require a maintenance technician to work at heights to rewind the product onto the bobbin which requires being at an irregular posture and position, and dealing with weight is excess of 80 lbs. Two, the bobbin can come unseated from the bucket and have over 100lbs of material and bobbin to fall to the floor. The worst case scenario would be a bobbin falling to the floor while a operator is exchanging bobbins in a lower Noria bucket. Both instances require calling for a maintenance intervention in which a maintenance person has to lock out the machine, tie off with their harness, and climb out onto the top of the Noria to wind up the product or put the bobbin back in place and lock it back in while working it an irregular posture in an irregular position and working with weight up to 100lbs. There is a average of 4 unlocked bobbin buckets that leaves the load/unload station per month per machine.

Investigation: We brought together a team to collaborate on the problem and possible solutions. We evaluated work method changes, adding vision camera systems, and wireless sensors onto the bucket locks. From our evaluation we decided on the wireless sensors to further investigate as it was the best option since it can detect bobbin lock state of a bucket at any rotation position of the Noria. A vision system can only detect the bucket locked state at one Noria rotation position per camara. With wireless sensors being a true monitoring system of the locks, it is a poke yoke solution compared to a possibly improved work method. The current work method already asked for the bobbins to be verified locked after loading.

Trial/Prototype: We met with the wireless sensor sales engineer to better understand the benefits and limitations of the technology. We borrowed a test setup from the sales engineer and verified it was a viable solution to try on one machine. We purchased the needed wireless sensors and communication hub to be able to place a wireless sensor on each product bobbin lock on all buckets and be able to monitor the switch change of state within the PLC of the machine. The PLC is the machines computer controlled process system.

Installation: After the wireless system as been installed on the 1st machine for over 6 months, no unlocked product bobbins have been able to leave the load/unload station without being corrected and no bobbins have unwound and/or fallen out on this machine. If a bobbin is left in an unlocked state and the operator tries to rotate the bucket to another rotational position, a fault will be present making the operator aware that one or both bobbin locks are in an unlocked state. The operator can then correct the locked state without maintenance needing to be called. This solution allows the operator to have full control of detection and correction of bucket product bobbin locks.

Results: After a successful testing of this solution on one BNS, parts have been purchased and proliferation completed of this wireless buck bobbin lock detection on the other 3 machines. Both machine operators and the safety officer are excited about the success of the lock detection system.

Cost and ROI: The cost of this detection system is $5,417 per machine, $21,668 for all 4 BNS machines. This improvement eliminates the safety risk of a bobbin falling out during upper unwind and the possibility of hitting someone below. This improvement eliminates the risk of a maintenance technician having to work at heights in an irregular posture while handling weight up to 100 lbs. This improvement eliminates the downtime of maintenance having to remove the product and/or bobbin or rewind the whole bobbin which averages 1 hour of downtime per work order call. The downtime of this problem is equal to $30,000 of lost profit per year. The ROI of this project is a little over 8 months.