Introduction
In the PET preform production process, mold alignment and calibration are crucial for ensuring product quality and production efficiency. High-speed PET preform molds typically operate at speeds exceeding thousands of cycles per hour; even minute deviations can lead to product defects, mold damage, or even equipment malfunction. Therefore, mastering scientific and effective mold alignment and calibration methods is essential for production stability and product quality.
Basic Principles of Mold Alignment
Mold alignment refers to ensuring that the moving and fixed molds achieve precise concentricity and flatness requirements when the mold is closed. The basic principles include:
1. Concentricity Requirement: The mold's central axis must coincide with the injection molding machine's central axis, with a deviation typically controlled within 0.02mm.
2. Flatness Requirement: The mold parting surfaces must remain parallel, with a parallelism deviation not exceeding 0.03mm/m.
3. Guiding System Matching: The clearance between the guide pillars and guide sleeves must be maintained within the range of 0.02-0.04mm.
4. Thermal Expansion Compensation: Consider the thermal expansion factors at the mold's operating temperature and allow for an appropriate compensation amount.
Specific Steps for Mold Alignment
1. Pre-installation Inspection
Before installing the mold, the following preparations are required:
- Clean the injection molding machine template and mold mounting surface, removing oil and impurities.
- Check the mold guiding system for integrity, ensuring guide pillars and bushings are unworn.
- Confirm the mold lifting device is safe and reliable.
- Prepare necessary calibration tools: dial indicator, feeler gauge, level, etc.
2. Initial Mold Installation
- Smoothly lift the mold between the injection molding machine templates.
- Initially fix the mold, but do not fully lock it.
- Use a level to check the mold's levelness and adjust it to an error ≤ 0.02mm/m.
3. Center Alignment Calibration
Mechanical Calibration Method:
1. Install a calibration ring on the injection molding machine template.
2. Use a dial indicator to measure the concentricity of the mold and the calibration ring.
3. Adjust the mold position to ensure the radial deviation is ≤ 0.02mm.
Optical Calibration Method:
1. Install a laser alignment device.
2. Emit a laser beam through the center of the mold.
3. 4. Observe the position of the light spot at the receiving end and adjust the mold to center the light spot.
5. Parting Surface Parallelism Calibration
1. Place a precision level on the parting surfaces of the moving and fixed molds.
2. Measure the height difference between the four corner points.
3. Adjust the mold mounting bolts to ensure the parallelism error is ≤0.03mm/m.
4. Use a feeler gauge to check the uniformity of contact on the parting surface.
6. Guide System Inspection
1. Manually close the mold until the guide post just enters the guide sleeve.
2. Measure the clearance around the perimeter to ensure uniformity.
3. Check the smoothness of the guide during the entire mold closing process.
4. Apply special grease if necessary.
7. Final Tightening and Verification
1. Tighten the mold mounting bolts gradually in a diagonal sequence.
2. Use a torque wrench to ensure even force on each bolt.
3. Perform 3-5 low-speed no-load mold closing cycles.
4. Recheck all parameters to confirm no changes.
