Precautions After the Mold Arrives at the Factory

I. Inspection Before Trial Run

01. Items to Inspect on the Die Head

1. Check for steps or dead zones in the flow channel:
   The channel must be streamlined; otherwise, it will affect uniform material flow and may cause material degradation.

2. Check for rough or uneven surfaces in the flow channel:
   The surface roughness of the cavity that contacts the material should reach a mirror finish, Ra ≤ 0.4 μm, to ensure consistent extrusion speed.

3. Check the alignment between the die head and the extruder.

4. Check that the die lip gap deviation is less than 0.03 mm.

5. Ensure flat contact between the die head and the heating elements.

6. Ensure positioning pins are accurately and firmly installed.

02. Items to Inspect on the Calibration Mold

1. Check assembled dimensions:
   The overall assembly dimensions must be accurate, with deviations no greater than 0.05 mm. The outlet dimension of the final cooling calibrator should generally be 0.5%–1.5% larger than the target profile dimension. The geometrical dimensions of each section should gradually decrease by 0.1%–0.2% from front to back or remain roughly consistent; large differences are not allowed.

2. The internal cavity surface should reach mirror-level roughness, typically Ra ≤ 0.4 μm.

3. Ensure consistent cavity height and centerline alignment for all sections.

4. Check whether any calibration plates are deformed.

5. Inspect for possible intersections between water and air channels.

6. Check smoothness and continuity of the cooling water channels.

7. The inlet of the first calibrator cavity should have a tapered lead-in angle.

II. Achieving Uniform Extrusion Speed

Based on the results of cut-section analysis, adjust and polish the die head to preliminarily achieve uniform extrusion.

01. If Certain Areas Extrude Too Slowly

If local extrusion is slow, measure and analyze whether the die gap is correct, and check whether the flow distribution or compression feeding system is undersized. Identify where the adjustment is needed—generally, this is corrected by increasing the compression feed area to provide more material flow. Adjustments to the straight section of the die lip should be made very carefully, as improper modification can damage surface finish and may be difficult to repair.

02. If Certain Areas Extrude Too Fast

If local extrusion is too fast, verify whether the die gap and flow distribution are oversized. Identify the area causing excessive flow speed—commonly resolved by adding a throttling insert to restrict flow in that region. Alternatively, one can enlarge the compression feed system in the slower areas, which avoids the risk of local blockage or material degradation caused by inserts, though this method requires more work.

III. Coordination Between Die Head and Calibration Mold

During this stage, the calibration mold should be mounted, and a trial extrusion of the profile should be performed in accordance with the profile production standards. The focus is on ensuring stable movement of the profile, avoiding vibration or jamming. Check the vacuum degree, cooling efficiency, and particularly whether grooves (e.g., for glass bead or sealing strips) have sufficient space.

Once the profile moves stably, cut a sample and analyze whether it matches the drawing dimensions and geometry before proceeding to fine adjustments.

IV. Precise Adjustment

This is the key stage of the trial process. The goal is to gradually eliminate all abnormalities so that the profile achieves the geometric shape and dimensions specified in the drawings. At this stage, a projector should be used to compare the actual profile’s geometry and dimensions with the theoretical ones, clearly showing the deviation areas and their sizes.

Technicians must then make targeted mold corrections to progressively approach the drawing requirements.
Evidently, decision-making in mold correction is the most critical step in the entire process.