How to Reduce the Scrap Rate in Aluminum Alloy High-Pressure Casting
I. Introduction: Scrap Rate, a "Hidden Cost Bomb" for Global Buyers
As a global wholesale buyer of aluminum alloy high-pressure casting, do you often face these problems:
10%-20% of the received goods are scrapped due to defects such as porosity, shrinkage cavities, and cracks, directly increasing procurement costs;Rework of scrapped goods leads to delivery delays, missing downstream order delivery windows;Suppliers implicitly pass on scrap costs, quoting inflated prices that are difficult to verify;Bulk scrapping causes supply chain disruptions, affecting end-market layout.
The scrap rate in aluminum alloy high-pressure casting (industry average 3%-15%), seemingly a supplier's production problem, actually directly determines the buyer's profit margin and market competitiveness. This article will take the buyer's perspective and teach you how to systematically reduce the scrap rate from source to end by "choosing the right suppliers, controlling the process, and building strong mechanisms," achieving a win-win situation.
II. Core Dimension One: Choosing the Right Supplier – Ensuring Strict Risk Control at the Source
The scrap rate is essentially a reflection of the supplier's overall strength. When selecting partners, buyers need to move beyond price comparison and focus on the following four core indicators to mitigate high scrap risks from the outset:
1. Verify the supplier's "hard power certifications":* Quality system certification: Prioritize suppliers certified by ISO 9001 (basic requirements) and IATF 16949 (high-requirement scenarios such as the automotive industry). These certifications represent standardized production control processes, making scrap rates more manageable.* Equipment and process level: Require suppliers to provide a list of die-casting machine models (e.g., high-precision equipment with clamping force ≥2000T) and mold processing equipment (CNC machining centers, coordinate measuring machines). Advanced equipment reduces human error; for example, high-precision molds can reduce scrap caused by casting dimensional deviations.* Engineering team and technical reserves: Focus on whether the supplier has professional die-Casting Process engineers and a mold maintenance team, and whether they can provide PFMEA (Potential Failure Mode and Effects Analysis) reports—a mature technical team can anticipate scrap risks in production and optimize processes in advance.
2. Verify “Past Cases and Scrap Rate Data” Suppliers are required to provide scrap rate statistics reports for the past 12 months (categorized by product model), and 3-5 batches of quality inspection reports should be randomly selected for verification of data authenticity. Priority should be given to suppliers with experience in large-scale wholesale orders in the same industry (e.g., automotive parts, industrial machinery). These suppliers have accumulated solutions for handling batch production scrap; for example, when supplying aluminum alloy shells to a car manufacturer, they have kept the scrap rate below 3%.
3. Assess “Raw Material Control Capabilities” The purity and compositional stability of aluminum alloy raw materials directly affect the quality of castings (e.g., excessive impurities can easily lead to cracks). The purchaser must explicitly require suppliers to: provide proof of raw material procurement channels (e.g., cooperation agreements with well-known aluminum ingot brands); and provide material analysis reports (spectral detection results) for each batch of raw materials, ensuring that the content of elements such as Si and Mg meets procurement standards (e.g., the Si content of A380 aluminum alloy is controlled between 7.5% and 9.5%).
III. Core Dimension Two: Controlling the Cooperation Process – Using “Procurement Standards” to Drive Down Scrap Rates
After selecting the right supplier, the buyer's process control capabilities are key to reducing scrap rates. By clearly defining requirements and strengthening supervision, the supplier's production process can be made “regulated and traceable”:
1. Develop “Zero-Scrap Oriented” Procurement Specifications The procurement contract should clearly define the following details to avoid ambiguity: Scrap Judgment Criteria: Clearly define quantitative indicators such as pore diameter ≤ 0.5mm, number of pores per casting ≤ 3, and shrinkage cavity area ≤ 0.1% of the total casting area (refer to ASTM B179 standard); Division of Responsibilities: When the scrap rate exceeds 5%, the supplier must unconditionally replace the goods and bear the logistics costs; when it exceeds 10%, the buyer has the right to terminate the contract and claim compensation; Testing Requirements: Require the supplier to provide a third-party testing report (such as an SGS non-destructive testing report) for each batch of products, with the testing costs borne by the supplier.
2. Require suppliers to optimize production processes (key aspects that can be monitored by the buyer) As a buyer, you don't need in-depth knowledge of die Casting Technology, but you must clearly require suppliers to do well in the following four high-impact aspects to reduce scrap rates: * **Mold temperature control:** The mold preheating temperature should be stable at 180-220℃ (slight variations depending on the material) to avoid uneven cooling and shrinkage of the castings, which can cause cracks. * **Injection parameter optimization:** The injection speed should be controlled at 3-8m/s, and the injection pressure ≥100MPa to ensure sufficient filling of the molten aluminum alloy and reduce porosity. * **Mold maintenance cycle:** The mold should undergo a comprehensive overhaul every 5000 production cycles, replacing worn parts to prevent dimensional deviations in the castings due to mold aging. * **Ventilation system design:** The mold venting groove width should be ≥0.2mm and the depth ≤0.5mm to ensure smooth exhaust of gases from the molten aluminum alloy.
3. Implement a dual supervision system of "sampling inspection + on-site supervision". For bulk purchases, sample and inspect according to AQL 2.5 standards (e.g., 50 pieces per batch, with a minimum of 3 non-conforming pieces allowed). If non-conforming pieces are found, immediately expand the sampling scope. For high-value, large-volume orders (e.g., single purchases exceeding 100,000 pieces), third-party supervisors can be stationed on-site to focus on three key aspects: raw material warehousing inspection, production process execution, and finished product inspection, providing real-time feedback on any issues.
IV. Core Dimension Three: Strengthening the Cooperation Mechanism – Achieving "Long-Term Win-Win Waste Reduction"
Reducing the scrap rate is not a one-time action, but a continuous optimization process through long-term cooperation. Purchasers need to establish a collaborative mechanism with high-quality suppliers to jointly reduce scrap rates:
1. Hold regular "Quality Review Meetings" Hold online meetings with suppliers every quarter, focusing on the following:Reviewing the previous quarter's scrap rate data, analyzing scrap types (e.g., 60% porosity, 30% cracks) and their causes;Jointly developing improvement plans, such as requiring suppliers to add venting channels or optimize injection speed for porosity issues;Setting scrap rate targets for the next quarter (e.g., reducing from 8% to 5%), and linking target achievement to the next quarter's purchase volume.
2. Promote "Technological Collaborative Optimization" If the procured products have complex structures (such as irregularly shaped parts or thin-walled parts), share the product usage scenarios with suppliers in advance, invite suppliers to participate in the Design for Manufacturability (DFM) review during the product design phase, and optimize the product structure (such as adding rounded corners and thickening weak parts) to reduce the risk of scrap from the design perspective; Encourage suppliers to introduce new technologies (such as vacuum die casting and squeeze casting), and be willing to appropriately adjust the purchase price for the increased costs brought about by technology upgrades (such as accepting a 2%-3% increase in the purchase price if the scrap rate is reduced from 10% to 3%), to achieve a win-win situation.
3. Establish a "Supplier Tier Management" System. Suppliers will be categorized into three tiers (A, B, and C) based on their scrap rate performance:**Tier A (Scrap Rate ≤ 5%): Increased purchase volume, extended cooperation period, and preferential payment terms (e.g., extending payment terms from 30 days to 60 days);**Tier B (Scrap Rate 5%-10%): Required to rectify the issue within 3 months, with reduced purchase volume during the rectification period;**Tier C (Scrap Rate > 10%): Suspension of cooperation and blacklisting.
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