Capacity calculations are usually done at the end of the project, when the layout is fixed. They should be done at the beginning, because they determine the line length, the number of stations and the drive size.
Key takeaways
- Throughput is speed divided by pitch, with corrections.
- Station time, not conveyor speed, sets the output of a manual line.
- Accumulation capacity is a separate calculation from throughput.
- Use a 15–20% margin for real production.
Formula 1: throughput from pitch and speed
For a continuous conveyor with equally spaced carriers, the theoretical throughput is:
Q = v / p × 3600, where Q is units per hour, v is speed in m/s and p is pitch in metres. At 0.2 m/s and a 0.6 m pitch, Q = 1,200 units per hour.
This is the maximum. It assumes no station stops and no gaps. A real line with stations runs at 70–90% of this number.
Formula 2: takt from output
Takt = available time / required output. For 430 minutes and 2,150 units, takt = 12 seconds. If the line has a 12-second takt and a 0.6 m pitch, the required carrier speed is 0.05 m/s, or 3 m/min. A speed of 20 m/min would be unnecessary and would increase wear.
Formula 3: accumulation capacity
Buffer = longest stoppage / takt × safety factor. A 90-second stoppage at a 12-second takt needs 7.5 positions; with a 1.3 factor, 10 positions. The buffer length is the number of positions multiplied by the pitch.
Do not confuse buffer length with line length. A 10-position buffer at a 0.6 m pitch is 6 metres of line, which may be a significant part of the layout.
| Parameter | Formula | Example |
|---|---|---|
| Throughput | Q = v / p × 3600 | 0.2 / 0.6 × 3600 = 1,200/h |
| Takt | T = available time / output | 25,800 / 2,150 = 12 s |
| Buffer | B = stoppage / takt × 1.3 | 90 / 12 × 1.3 = 10 |
| Drive power | P = F × v / η | See motor sizing |
Formula 4: drive power
The drive power is the force required to move the loaded conveyor multiplied by the speed, divided by the efficiency. The force includes friction, incline and acceleration. For a horizontal conveyor, friction is the main term: F = μ × (m_product + m_belt) × g.
Use a starting factor of 1.5–2.0 for a fully loaded conveyor. A drive that is sized only for running load will trip on restart.
Correction 1: station time
For a manual line, the output is set by the slowest station, not the conveyor. If the station takes 14 seconds and the takt is 12, the line runs at 86% of the calculated capacity. No conveyor speed can fix that.
Correction 2: product gaps
Products are not perfectly spaced. Operators leave gaps, and transfers create gaps. A line with a 10% gap runs at 90% of the theoretical capacity. If the gaps are larger, the loss is larger.
Correction 3: availability
A line does not run for the full available time. Breakdowns, changeovers and material shortages reduce the available time. Use an availability factor of 85–95% for a well-maintained line, and lower for a new or complex line.
Putting it together
Start with the required output, calculate takt, choose the pitch and speed, then check the station time and the availability. If the numbers do not meet the requirement, change the layout or the station count, not the conveyor speed.
The calculation should be documented and shared with the supplier. A supplier who receives the calculation can quote accurately; a supplier who receives only a product drawing will guess.
Frequently asked questions
What pitch should I use?
The pitch should be larger than the longest product plus a gap, and small enough to meet the throughput. For a 300 mm product, a 400–600 mm pitch is typical.
How much margin should I add?
15–20% for a new line, and 10% for a line with a stable process. More margin adds cost and floor space.
Does conveyor speed affect quality?
Yes, at high speed the product may vibrate or shift. Keep the speed as low as the throughput allows.
Send your product data and target output to our engineers through the contact page; we will check the calculation and the layout.
