Technical Guide
Stick-Slip on CNC Guideways: Why PTFE Soft Liners Stop It
Stick-slip on CNC guideways is the familiar cycle of hesitation, sudden release and uneven low-speed travel that makes a machine feel rough even when the drive system is healthy. This guide explains the friction mechanism behind guideway stick-slip, why PTFE soft liners change the motion, and what rebuilders should check before choosing a slideway liner.
What stick-slip feels like on a machine tool
Stick-slip is a low-speed motion problem. An axis appears to hold position while the drive continues applying force, then breaks free and jumps ahead. The cycle repeats as small surges. On a CNC machine, the result may be waviness on a finish, inconsistent feed movement, noise from the way, or uncertain fine positioning. It is especially noticeable during slow traverses, reversal, probing and handwheel movement.
The friction mechanism behind guideway stick-slip
The basic mechanism is a difference between the force needed to start motion and the force needed to keep motion going. Static friction holds the sliding member in place. As the drive force rises, the contact eventually releases; once the surfaces are moving, dynamic friction can be lower. The stored force then accelerates the member until friction rises again or the control system corrects it. Lubrication, surface condition, load distribution and way geometry all influence the cycle.
| Condition | Effect on low-speed motion | What a rebuilder checks |
|---|---|---|
| High breakaway friction | Axis hesitates before moving | Way surface, contamination and liner condition |
| Large static-to-dynamic friction change | Movement releases in small jumps | Material running face and lubrication film |
| Uneven contact or geometry | Motion changes along the travel | Bearing contact, centre height and alignment |
| Poor or interrupted lubrication | Friction and wear rise together | Oil delivery, grooves and compatible way oil |
Why a PTFE soft liner helps
A PTFE-based slideway liner places a low-friction running surface between moving members. Instead of relying on metal-on-metal contact, the axis runs against a material designed for sliding motion. The smaller friction change makes the transition less abrupt, so a correctly rebuilt way can move more evenly at low feed rates. The liner can also be finish-machined after bonding to restore geometry.
TEBAK supplies the same material family in Blue slideway liner, Green slideway liner, Brown slideway liner and Brick Red slideway liner. The colour identifies the product on the workshop floor; the running behaviour comes from the PTFE-based compound and the finished way condition.
A liner is not a cure for every rough axis
Stick-slip can also come from a damaged oil system, an incorrectly adjusted gib, a distorted way, a worn screw, servo tuning or contamination. Installing new tape without finding the source of the friction change can move the symptom rather than solve it. Check the axis with lubrication working, inspect contact across the travel, and separate mechanical resistance from drive or control behaviour before planning a relining job.
Questions to answer before relining
- Does the hesitation occur only at low speed, or also during rapid travel and reversal?
- Is the oil film reaching the full guideway length and all oil grooves?
- Does contact change from one end of the way to the other?
- Will the finished liner restore the original centre height after machining?
- Are the metal surface and the etched liner face clean enough for a structural bond?
How the TEBAK system fits the repair
The liner works as part of a complete guideway repair, not as an isolated plastic strip. The etched side bonds to the prepared metal surface with TEBAK Two-Part Epoxy-Adhesive, while the smooth PTFE side becomes the running face. After curing, the liner is finish-machined and the lubrication arrangement is checked. Our skived PTFE slideway sheet guide explains how the two faces are made for different jobs, and the Turcite B comparison guide places soft liner against other repair materials.
Frequently asked questions
Can PTFE liner eliminate every instance of stick-slip?
No. It can reduce friction-related low-speed surging when the way is correctly prepared and lubricated, but geometry, adjustment, contamination and drive conditions must also be checked.
Is stick-slip only a CNC problem?
No. Manual lathes, milling machines, grinders and other sliding ways can show the same behaviour whenever static and dynamic friction differ enough at low speed.
Does the colour of a TEBAK liner change its stick-slip performance?
No. The TEBAK colours identify the same PTFE-based material family. Motion depends on the compound, finished surface, load and lubrication rather than the colour.
If the axis only sticks at low feed, note the feed rate, way-oil grade and current gib setting before ordering: TEBAK will confirm whether the fix is a PTFE liner, a lubrication change or a gib adjustment.