Engineering Guide

Guideway Thermal Expansion After PTFE Relining: Check Centre Height at Operating Temperature

A slideway can measure correctly when cold and still change its running condition after the machine warms up. This guide explains how to check guideway thermal expansion after PTFE relining, separate thermal movement from bond or geometry errors, and record centre-height readings at the temperature the machine actually uses.

Direct answer: measure the repaired way cold and warm

The reliable way to judge thermal movement after a PTFE slideway repair is to repeat the same centre-height, straightness and contact measurements at two defined machine conditions: a documented cold state and the normal operating temperature. Do not calculate a correction from a generic PTFE expansion coefficient or from room temperature alone. The measured change belongs to the complete assembly — liner, adhesive, metal way, slide, gib, oil film and machine frame — not to the liner in isolation.

Why a relined guideway can move with temperature

Every part of a guideway assembly changes dimension as it changes temperature. The PTFE-based liner, cured epoxy, cast iron or steel way and mating slide do not necessarily change by the same amount or in the same direction. A nearby spindle, hydraulic unit, cutting process or wash-down cycle can also create a temperature gradient along the travel. The result may appear as a centre-height shift, a changing contact pattern, a tight section or a change in low-speed drag.

Do not confuse thermal movement with a bonding failure

Thermal movement is normally repeatable with the same warm-up cycle. A bond problem is more likely to show local lifting, a sharp step, a new edge gap, trapped contamination or a contact change that does not track temperature consistently. Inspect the liner edges and the running face, but keep the inspection non-destructive. Do not pry at a bonded strip simply because a warm reading differs from a cold reading.

The material orientation still matters: the smooth side of Blue TEBAK slideway liner, Green TEBAK slideway liner, Brown TEBAK slideway liner or Brick Red TEBAK slideway liner is the running face, while the chemically treated side is bonded with the TEBAK Two-Part Epoxy-Adhesive. A reversed face or uneven adhesive layer can create a local mechanical problem that looks like thermal drift.

A repeatable centre-height measurement method

1. Choose a stable datum on the machine structure and record the instrument, stand arrangement, resolution and reference point.
2. Divide the guideway travel into fixed stations, including both ends and the normal working zone. Mark the stations so the warm test uses exactly the same locations.
3. With the machine in its documented cold condition, record centre height, straightness or parallelism as relevant, local temperature and lubrication state.
4. Warm the machine using the real production sequence or an agreed repeatable cycle. Record the time, travel activity and temperatures at the datum, slide and both ends of the way.
5. Repeat every cold-state reading without changing the indicator setup, measurement direction or contact force.
6. Calculate the change at each station as warm reading minus cold reading. Preserve the raw readings; do not report only an average.

Engineering judgement: when the result needs investigation

A temperature-related change needs investigation when it exceeds the machine's agreed acceptance band, changes sharply from one station to the next, or is accompanied by binding, loss of contact, abnormal edge marks or unstable repeatability. The correct response is to identify the heat path and mechanical constraint before selecting a different liner thickness. If the shift is smooth, repeatable and within the agreed machine requirement, record it as part of the operating condition rather than treating every micrometre of movement as a liner defect.

• Compare the thermal map with the error map: a matching slope suggests a temperature gradient, while a local step suggests a mechanical or measurement issue.
• Check that the gib, wipers and oil grooves do not become tighter or drier as the slide warms.
• Confirm the liner has cured and been finish-machined before collecting acceptance data.
• Use the adhesive supplier's stated service-temperature information for the cured bond; do not replace it with a PTFE-only temperature claim.
• Repeat the warm cycle on another occasion before making a permanent geometry correction.

Use verified product limits, not guessed material coefficients

The TEBAK catalogue lists standard liner widths of 100, 200, 300 and 305 mm and standard thicknesses from 0.8 to 3.2 mm. Those are supply dimensions, not a thermal compensation rule. The TEBAK epoxy product record lists a cured service-temperature range of -40 °C to +120 °C; confirm the current product documentation and the actual chemical and thermal environment before approving a repair. If the machine operates near a limit or has an unusual heat source, request a written compatibility review for the liner and adhesive together.

For the broader material and exposure checks, read the PTFE temperature and chemical guide. For load-related changes in contact pressure, compare the slideway liner load and pressure guide. These guides support the thermal check without turning a measured machine result into an unverified universal specification.

Commissioning checklist for a thermally stable relining

• Cold and warm measurement conditions are written down and repeatable.
• The same datum, instrument, stand and approach direction are used in both states.
• Temperature is measured at the way, slide and relevant heat sources rather than inferred from room temperature.
• Centre height, parallelism, contact and drag are recorded by travel station.
• Oil delivery, wipers and gib clearance remain acceptable through the warm cycle.
• The acceptance decision is based on the machine requirement and measured trend, not on a guessed PTFE expansion value.

Frequently asked questions

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