Heat Shrink Tubing Cut Length and Longitudinal Change

Set heat shrink tubing cut length from the coverage required after recovery, then check the material’s longitudinal change and your cutting tolerance. A diameter shrink ratio does not specify length shrinkage. Measure the unheated piece and the cooled assembly separately so a short sleeve is traced to the correct stage.

Start with the installed coverage

A sleeve can leave the cutter at the requested length yet expose part of a splice after heating. Before changing the machine setting, define the region that must remain covered, the required overlap at each end and any area that must remain clear. Use a drawing or agreed assembly sample so everyone measures between the same references.

Also identify the exact tubing grade and size. Single-wall insulation, adhesive-lined tubing and marker sleeves have different intended functions; a cut-length recipe cannot be transferred solely because two rolls have the same nominal diameter. Our heat-shrink equipment guide covers the wider heating and assembly choices.

TE’s tubing selection guidance distinguishes diameter recovery from longitudinal change and says to account for the latter when specifying cut length. Use the property for your tubing, not a percentage borrowed from another product.

Keep three measurements separate

Stage	Record	Decision it supports
Roll identification	Grade, size, lot and stated longitudinal-change limit	Which material the recipe applies to
Unheated cut piece	Length after release, with an agreed measuring method	Whether feeding and cutting meet the requested length
Cooled installed sleeve	Covered region and both end positions	Whether the chosen length and heating process meet assembly needs
Repeated samples	Individual results rather than only an average	Whether the process has enough margin for variation

Do not pull a flexible sleeve taut to obtain a preferred reading. Handle and measure all identified pieces consistently. TE’s measurement guide notes that stretching, incomplete recovery and sticking during heating can distort longitudinal-change measurements. Follow the tubing’s specified test conditions when checking its material property.

An installed assembly and a freely recovered material specimen answer different questions. The first shows usable coverage in your process; the second checks the tubing property under its defined test method. Label the records accordingly.

Calculate a starting point, then prove the result

For a material specified to shorten by a maximum fraction s, a simple starting calculation is:

Minimum unheated length = required final coverage ÷ (1 − s).

For example, an illustrative requirement of 40 mm coverage and a stated maximum shortening of 5% gives 40 ÷ 0.95 = 42.11 mm before allowing for cutting tolerance or positioning variation. These are example inputs, not a tubing recommendation or a measured production result.

Adding 5% directly gives 42 mm, which becomes 39.9 mm after 5% shortening. The distinction matters when coverage is tight. If the tubing specification permits growth, or defines another test basis, use the appropriate limits instead of this shortening-only calculation.

Check the longest acceptable installed sleeve as well as the shortest. Extra material must still clear neighboring terminals, moving parts or other drawing features. The final machine setting comes from the agreed assembly trial, not the calculation alone.

Match the cutter to the supplied sleeve

Our WM-565N heat-shrink tube cutter lists a maximum cutting diameter of Φ38 mm, with larger diameters requiring a custom configuration. Our WM-585 pneumatic-blade cutter lists Ø1–30 mm and belt feeding. We check the actual wall, supplied shape and shortest piece before confirming the setup.

Include cut-end opening in that trial: the sleeve must still pass over the intended component without damaging its edge. A numerical feed setting or rated cutting accuracy does not establish this assembly fit or the recovered coverage.

Approve the recipe as a complete sequence

1. Identify the material roll, required coverage and dimensional references.
2. Record consecutive unheated pieces at the agreed measuring condition.
3. Install identified pieces at the intended position and run the specified heating process.
4. Let the assembly reach the agreed inspection condition; record coverage and end positions.
5. Repeat after a representative restart or roll change, keeping the material and settings traceable.

If unheated length already varies, investigate feeding with our soft-material length guide. If length is stable but recovered results vary, use the heat-shrink defect guide to examine the later process.

Send your tubing specification, coverage drawing and sample assembly. We will demonstrate cutting on your material and agree the dimensional record needed for the quotation.