How to Calculate Rebar Processing Productivity

How to Calculate Rebar Processing Productivity: Bends Per Hour, Stirrups Per Shift, and Line Throughput

Most buyers comparing rebar processing machines focus on the wrong number: the maximum bend speed printed on a spec sheet. In real fabrication shops, productivity is determined by cycle time, handling time, and how well the machine matches the actual bar diameters and shapes in your project. This guide breaks down how to calculate realistic output for CNC bending centers, stirrup benders, and shearing lines — with concrete examples from Gongda's model range.

1. Bends Per Hour: Start With Cycle Time, Not Speed

The core formula is simple:

• Bends per hour = 3600 ÷ (bend cycle time in seconds + handling time per bend)

On a CNC rebar bending center such as the GJZD6-50CZ (up to 50 mm bar, 420 mm working table), a single bend on a 16 mm bar may take 3–5 seconds of machine time. But the real constraint is often the 420 mm table: long legs, complex shapes, or double-line feeding add repositioning time. For a 20 mm bar with a simple 90° bend, a realistic planning figure is 250–400 bends per hour. For 32–40 mm bar, drop to 80–150 bends per hour because of slower feed and heavier handling.

For heavier work, the GJZD6-65CZ (up to 65 mm) is used on large-diameter foundation and infrastructure cages. Here, expect 40–80 bends per hour on 50 mm bar. If your project mixes diameters, calculate weighted average cycle time rather than using the best-case number.

2. Stirrups Per Shift: The Five-Head Advantage

Stirrup production is where buyers most often overestimate output. A single-head CNC stirrup bender like the GW25 (round steel up to 25 mm) can produce a simple rectangular stirrup in roughly 15–25 seconds, including feeding, bending, and cutting. That translates to about 140–240 stirrups per hour, or 1,100–1,900 stirrups per 8-hour shift — assuming one operator, continuous bar supply, and no shape changes.

Five-head stirrup machines change the math. The ZD-6M-25 (25 mm) and ZD-6M-20 (20 mm) bend multiple sides simultaneously, cutting cycle time to 8–15 seconds for common stirrup shapes. Realistic output is 2,000–3,500 stirrups per shift on 8–12 mm bar. The limiting factor becomes bar feeding and stacking, not bending.

Practical advice: when calculating stirrups per shift, subtract 10–15% for setup, wire/bar changes, and operator breaks. Also confirm your stirrup geometry — hooks and 135° seismic bends add 2–4 seconds per unit.

3. Line Throughput: Shearing, Straightening, and Thread Rolling

For high-volume cut-and-bend operations, throughput is measured in tons per shift, not pieces. The GDQX-500 hydraulic rebar shearing production line is designed for continuous feeding and cutting; on 12–25 mm bar, a realistic throughput is 8–15 tons per 8-hour shift depending on cut length and bundle handling.

Standalone cutting machines follow a different rule. The GQ70A (70 mm capacity, 160-ton shear force) handles large-diameter bar at roughly 20–40 cuts per minute on short stock, but long bars require two operators and a feed table. The GQ50A (6–50 mm round / 6–36 mm ribbed) is the common choice for general fabrication, delivering 30–50 cuts per minute on 16–25 mm bar.

For straightening and cutting, the YGT4-15A (4–15 mm, VFD-controlled) runs at 40–70 m/min. Calculate output as:

• Pieces per shift = (line speed in m/min × 480 min × efficiency 0.75) ÷ cut length

For 6 m cut lengths at 50 m/min, that is roughly 3,000 pieces per shift. Thread rolling on the HGS-40 (40 mm) typically produces 200–400 joints per shift depending on thread length and operator skill.

4. Arc Bending and Special Shapes

Arc and curved bars are slower. The GWH50CG / GWH50CZN (50 mm) and SKDZWH-36 / GDWHWQ-36 (36 mm CNC arc benders) are used for tunnel ribs, bridge diaphragms, and circular cages. Expect 30–80 arcs per hour on 20–32 mm bar. The GDLWZX-32 vertical bending center (32 mm) and GDPMW-60 plane bending center (60 mm) suit heavy precast and infrastructure work, where 15–40 bends per hour is a realistic planning figure for large radii.

5. A Simple Productivity Audit Before You Buy

• List your top five bar diameters and shapes. Productivity is diameter-driven, not machine-driven.
• Measure handling time. On many sites, loading and stacking consume 30–50% of the shift.
• Check model capacity against your heaviest bar. A GJZD6-50CZ covers 50 mm; if you regularly run 40 mm+ at volume, the GJZD6-65CZ avoids cycle-time penalties.
• Confirm certification and support. Gongda offers EAC certification for Russian and CIS markets, with exports to Russia, Spain, Latin America, the Middle East, Southeast Asia, and Africa.

If you want a productivity estimate based on your actual rebar schedules, send your bar diameters, shapes, and daily tonnage to the Gongda team. WhatsApp +86 193 9277 7259 or email yuhua0095@gmail.com for a model recommendation and cycle-time calculation.