What exactly is sag?
The upper run of an unsupported chain sags slightly under its own weight. A little sag is normal and even desirable: it gives the bend room. Too much sag lets the upper run land on the lower run, causing unpredictable chafing and higher drive forces.
How do you read a load diagram?
Every series has a diagram with fill weight (kg/m) on one axis and unsupported length (m) on the other. Find your fill weight, read the maximum length and keep 15% margin for acceleration and vibration. If your point lies outside the curve, the series is too light.
When do you switch to a gliding arrangement?
As soon as half the travel exceeds the series' unsupported capacity, or sag exceeds 2%. A gliding arrangement always needs a guide trough, glide shoes on the upper run and a slightly longer chain because the driver sits higher. The chain must never glide dry over rough steel.
How much force does the chain demand from the drive?
For a gliding arrangement use F ≈ μ × m × g, with a friction coefficient of roughly 0.25 for plastic on steel. Multiply by 1.5 for start-up. That force adds to the carriage mass and counts in the servo calculation.
| Fill weight | Light series | Medium series | Heavy series |
|---|---|---|---|
| 2 kg/m | 2,2 m | 3,6 m | 4,8 m |
| 5 kg/m | 1,6 m | 2,9 m | 4,1 m |
| 10 kg/m | 1,0 m | 2,1 m | 3,2 m |
| 15 kg/m | — | 1,6 m | 2,6 m |
Frequently asked questions
- How much sag is still acceptable?
- Up to roughly 2% of the unsupported length, so 40 mm at 2 metres. More means the upper run touches the lower run at the far position.
- Can I compensate sag with pre-tension?
- Many series offer a pre-tensioned version that holds the upper run slightly up. That extends the unsupported length by 10 to 20%, but does not replace a heavier series at high fill weights.
- Does this apply to vertical or hanging arrangements?
- No, those use different diagrams and extra requirements for cable relief. Send us the arrangement; we check the load and advise the right series.
Read next
- Plastic or steel cable carrier: when do you choose which?Travel, fill weight, temperature, swarf and noise decide — with concrete thresholds per criterion.
- How do you calculate the size and length of a cable carrier?Five steps from fill to orderable chain length, with the formula Lk = S/2 + π × R + allowance and a full example.
- When do you need a guide trough with glide shoes?Trough width, glide surfaces and wear indication: how to build a gliding arrangement that lasts for years.