Shear Feed Rate vs. the Downstream Baler
Your yard runs a 1,000-ton shear feeding a 400-ton baler. The shear operator has been pushing throughput by feeding longer, heavier bundles - up to 20 ft and 8,000 lb - to reduce cycle count. The baler's feed conveyor is rated for pieces up to 12 ft and 4,500 lb; longer pieces bridge the conveyor and jam the baler's feed throat about twice a shift. Each jam costs 25–40 minutes of baler downtime and one near-miss last week when a jammed piece kicked back. The shear is now running 15% above its rated tonnage per hour, and the baler is running 20% below its rated throughput. The plant manager wants to "just add a guard" at the baler throat and keep the shear rate.
1. Analyze the bottleneck and evaluate the plant manager's proposal.
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The system throughput is set by the bottleneck, and the bottleneck is now the baler, not the shear. Running the shear 15% above rate while the baler runs 20% below rate means the excess is piling up as un-baled inventory and jam time - the shear's "gain" is illusory. The jam frequency (twice a shift, 25–40 min each) is 50–80 min of baler downtime per shift, which alone explains most of the 20% shortfall.
The root cause is feed-size nonconformance: 20 ft / 8,000 lb pieces exceed the baler's 12 ft / 4,500 lb rating, so they bridge the conveyor. A guard at the throat treats the symptom (kickback) but not the cause (oversize feed) and may actually increase jams by narrowing the throat. The plant manager's proposal is a safety patch, not a throughput fix. The correct fix is to constrain the shear to produce baler-compatible pieces - cut to ≤12 ft and ≤4,500 lb - even if that means more shear cycles.
2. What control should be put in place, and how would you verify it worked?
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Control: a feed-size gate at the shear discharge - a physical stop or a shear-programmed cut length that prevents pieces over 12 ft from reaching the baler conveyor, plus a weight check on the shear's load cell so no bundle over 4,500 lb is released. Add a kickback guard at the baler throat as a secondary safeguard, not the primary control.
Verification: track baler jam count per shift (target zero bridging jams), baler throughput vs. rated (target ≥95%), and shear tonnage vs. rated (accept a modest reduction in shear rate as the cost of system balance). Also track near-misses. If jams drop and baler throughput rises, the system - not the shear - was optimized. Revisit the shear's rated rate only after the baler is running at rate; then debottleneck the baler if more throughput is needed.