Start with the strip specification
PA66 with 25% glass fiber, commonly described as PA66GF25, is widely used for thermal-break strips. Specify the grade, supplier, strip geometry and relevant material documentation rather than purchasing by appearance alone. Moisture conditioning, temperature exposure and the strip manufacturer's processing limits affect performance.
High-temperature suitability must be checked against the actual powder-coating cycle. A suitable PA66GF25 grade can be specified for a curing process in the approximately 180–200°C range, but oven settings do not establish the temperature of every assembled part. Check the supplier's permitted part-temperature and exposure time. PVC should not be treated as an interchangeable substitute for a specified PA66GF25 strip.
The strip head and aluminum groove have to work together. Where the project requires a strip-head dimensional tolerance such as ±0.05 mm, put it into the approved specification and inspection plan. Material certification alone does not prove that the assembled profile has the required fit or mechanical strength.
Three stages of thermal-break assembly
- Knurling: the aluminum strip-retaining grooves are prepared with controlled teeth so that the strip can be mechanically retained after rolling. Inspect the groove condition and avoid inconsistent or damaged teeth.
- Threading: the specified I-shaped, C-shaped or hollow insulating strips are fed into the paired aluminum sections. Check orientation, strip continuity and the alignment of both shells.
- Roll-forming: controlled rollers close the retaining grooves onto the strip heads. Roller position and pressure must provide the required retention without distorting the section or damaging its finish.
A profile that looks straight immediately after assembly may still have a weak connection. Conversely, excessive rolling pressure can deform the groove, change the overall section width or damage the surface. The setup needs both dimensional inspection and mechanical checks, with records linked to the production batch.
Coat before assembly or assemble before coating?
| Production route | Useful when | Points to confirm |
|---|---|---|
| Coat first, then assemble the thermal break | Inner and outer aluminum shells need different colors or different decorative finishes. | Protect the finished surfaces during knurling and rolling; inspect the completed interface and dimensions. |
| Assemble first, then coat | Both shells use the same approved coating system and color. | Confirm that the strip grade and assembled section are suitable for the complete pretreatment and curing route. |
Coating the shells separately is the normal route for a dual-color design, such as a dark exterior and white interior. It also keeps the insulating strips out of that coating-oven cycle. Assembly before coating can be suitable for a single-color design when its materials and processing route have been validated. The correct choice follows the approved system, rather than a blanket preference for one sequence.
Strength, alignment and appearance checks
Agree the required longitudinal shear and transverse tensile testing with the applicable system specification before production. Specify the sample conditioning, test method, sampling frequency and acceptance criteria. A successful dimensional check does not replace these tests, and a strip manufacturer's material result does not replace a test of the assembled profile.
Dimensional inspection should cover the overall section, the spacing of the aluminum shells, strip engagement, straightness and the alignment of the faces that will be miter-cut or joined. Trial corner assemblies help reveal problems that separate section measurements can miss. Clean, protected rollers and appropriate handling reduce scratches on coated surfaces.
Guantian coordinates these checks with the extrusion and finishing teams. Confirm the inspection records required with the order, including batch identification and the dimensions that are critical to your hardware, gaskets or window-system assembly.
Frequently asked questions
Which strip widths can be considered?
Common project requests include 14.8, 20, 24, 30 and 45 mm, along with wider or customized designs. Availability and feasibility depend on the selected strip supplier and the paired aluminum sections. Width alone does not determine the thermal performance of a completed window.
Can we specify a strip brand?
Yes. State the brand, grade and documentation you require, whether a named supplier such as Technoform or an agreed qualified alternative. Substitutions should be approved in writing before production.
How are assembled profiles protected during shipment?
Packaging should support both aluminum shells, protect the finished faces and limit movement or end impacts that could stress the strip connection. Bundle spacing, end protection and container restraint are agreed for the profile length and delivery route.
Information for a thermal-break quotation
Send the inner and outer section drawings, strip specification, required inside and outside colors, order quantity and assembly requirements. Include the performance standard or system approval you need. Start the discussion on WhatsApp so that our team can agree the manufacturing route, sample checks and quotation scope with you.