Have you started manufacturing genuine leather wallets OEM? Have you encountered the problem that the color is different from last time? “Even though it is the same lot, there are variations in the texture of the leather.”
Natural leather is a material derived from living things. There will always be individual differences and leather lot differences. This is inevitable.
But don’t worry. There is correct knowledge and measures. Prevents product rework. Customer complaints can also be greatly reduced.
From material procurement to final inspection, let’s keep in mind specific points at each stage. You can prevent losses of millions of yen per year. It also protects the credibility of the brand.
This article will introduce practical measures. It is knowledge that can be used from tomorrow.
Measures against leather lot differences in the material procurement stage of genuine leather wallet OEMs
The biggest opportunity to reduce individual differences in natural leather is at the material procurement stage. It will be too late after manufacturing begins. If you make a mistake in the selection method of the raw skin, no matter how much effort you put in the later process, you will not be able to absorb the difference.
Procurement strategy with an understanding of supply chain structure
The Japanese leather industry has a unique structure. More than 90% of tanners are small businesses with fewer than 30 employees. The batch size is small. Inventory capacity is also limited. There is little room to absorb lot differences.
Procurement through leather wholesalers is the mainstream. Direct dealings with tanners are in the minority. This is where the big challenge lies.
The inventory function of leather wholesalers is declining. There are more and more cases where we just mediate orders from manufacturers. It is not possible to secure the same specifications and the same lot for a long time. Wholesalers no longer have the capacity to inspect lot differences and separate inventory.
Consider switching to direct trading. If the number of products is more than 500 pieces per month, a direct contract with a tanner is realistic. Inventory risk increases. However, you can take the initiative in lot management.
In the case of low-volume production, it is essential to use a wholesaler. However, explicitly include “inventory securing and lot separation services” in the contract conditions. It is important to prioritize quality stability even at an additional cost.
The reality and cost judgment of high-quality raw hide procurement
It is possible to procure high-quality raw hides themselves. The problem is the price. European high-quality hides do not correspond to the standard price level of Japanese tanners. It is difficult to continue using only high-quality lots.
The difference in procurement power with European tanneries is overwhelming. It has also been pointed out by leather goods manufacturers.
Embrace the reality of domestic tannery. It is based on the premise of raw hides with a wide quality range. It is an operation that is covered by technology. We absorb differences in chemical formulation and process adjustment. However, it is not possible to narrow down the lot at the raw skin level. It is a structure that is easy to bring in lot differences after the process.
Separate the raw skin grade for each product line. The flagship line fixes and procures high-quality raw hides. Standard liners are stably procured in standard grades. The rule is not to mix.
LWG certification and traceability support
Global brands are switching to LWG-certified leather. Sustainability procurement requirements are becoming more stringent.
Japan’s supply chain has its challenges. It is fragmented. There is a high degree of dependence on leather wholesalers. It is difficult to secure “materials of the same lot and the same standards with traceability”.
If you are aiming for OEM for overseas brands, early response is essential. Secure direct trading routes with LWG certified tanners. There is a trend towards moving away from domestic leather materials. If you don’t get ahead of the competition, you will lose trading opportunities.
Genuine Leather Wallet OEM Communication Strategies with Factories and Suppliers
To prevent leather lot differences, close communication with the factory is the most effective. Material selection and leather quality standards alone have limitations. Information sharing with the manufacturing site determines quality.
Conduct regular technical meetings and factory audits
Set up regular technical meetings at least once a month. Email alone is not enough. You need the opportunity to speak in person or online.
Factory audits once or twice a year are also essential. You won’t know until you see the site. Review the actual defect rate data. Compare the monthly defect rate with the target value. You can also understand the actual state of the quality inspection process. We check whether there is an incoming inspection, an in-process inspection, and a shipping inspection. Also check the frequency of testing.
Let’s check how traceability works. Factories that cannot do lot trace should be avoided.
Effective approach to quotation and price negotiation
Get quotes from multiple manufacturers. Don’t judge by price alone.
Compare lead times. There is a big difference between 30 days and 45 days. We also confirm the minimum lot (MOQ). The initial investment amount varies between 500 and 1,000. We also check whether there is a defect rate guarantee. Choose a factory with a standard such as 0.3% or less.
During price negotiations, we ask for the disclosure of cost breakdowns. You can check the composition ratio of material costs, processing costs, administrative costs, and margins. There is room for cost reduction.
Negotiate a unit price discount instead of committing to an annual order quantity. You can expect a 5-10% discount on a 10,000-unit commitment per year.
Workarounds for manufacturing black-boxing
Request the sharing of the main process flow diagram. If you can’t see the manufacturing process, you can’t find out the cause of lot differences.
When changing important processes, we make it a rule to report in advance and check leather samples. If the process is changed at the discretion of the factory, the quality will not be stable.
We will also clarify the complaint response system after delivery. Initial reports are requested within 24-48 hours of occurrence. Within 1-2 weeks, the cause analysis and countermeasure report are presented. This is the standard of the QC story.
Monthly updates of 3-6 months of rolling forecasts. The factory side can also secure raw materials in a planned manner. It has the effect of reducing lot differences.
Lot management practice in the production process of genuine leather wallet OEM.
If you start production with a vague definition of wallet manufacturing lot management, you will not be able to determine the cause of the problem. Set clear rules for each process.
Lot Definition and Setting of Mandatory Record Fields
1 lot = the quantity produced continuously under the same conditions and with the same equipment is the basic unit. In wallet manufacturing, it refers to a product group made with the same batch of materials, the same line, and the same settings.
Standardize the information associated with each lot. Record the date and time of manufacture. The production line ID and equipment number are also required. List the lot number of the leather material used. Don’t forget to include your worker ID as well. The main condition values are recorded as sewing speed, adhesive application temperature, and pressing time. Please save the test results at the same time.
Without this information, problems arise. Even if uneven color or sewing defects occur, the cause cannot be traced.
Essential Practice of Lot Management by Process
In the material receiving phase, the purchase lot is assigned a unique number. Record the incoming inspection results on a lot-by-lot basis. The thickness, color, and presence of scratches on the leather are quantified. The pass/fail decision will also be specified.
In the cutting and pre-process, all lot numbers of the leather materials put in are recorded. Sometimes you use multiple lots of leather for a single product. Manage many-to-many correspondence. The lot number is also issued for intermediate goods (cut parts). Link with upstream material lots.
In the sewing and assembly process, the production lot number is issued at the start of production. Record conditions such as sewing speed, thread tension, and needle size on a lot-by-lot basis. When the conditions change, the stitches will look different.
In the inspection process, the inspection lot = production lot is set in unit. The number of defects, defect rate, and typical defect contents are stored on a batch-by-lot basis.
In the shipping phase, you associate the manufacturing lot and the material lot to the shipping lot. Traceability can be ensured.
Traceability Practices and Lot Tracking
When a defect occurs, the area of impact must be identified.
Upstream tracking traces back to finished product lots→ intermediate product lots→ and material lots used. You can track “which lot of leather for this wallet came from”.
Downstream tracking identifies the defective material lots→ the intermediate and product lots used → the destination. Track which products the problem leather lot was used for.
Identify the range of eligible lots + equal lots. Collection and isolation can be minimized. You don’t need to collect the entire product.
Genuine Leather Wallet OEM Final Inspection Standards and Defective Product Response Flow
Finished product inspection of genuine leather wallets requires different judgment criteria than industrial products. There are individual differences between natural materials. Let’s set a standard based on this point.
Setting the Appropriate Inspection Level for Leather Products
The target for general manufacturing is a defect rate of 0.3% (less than 3 out of 1,000 products). This is the 3σ level. In fields where reliability is required, such as automotive parts, we have achieved a 6σ level ≈ 3 ppm (3 out of 1 million).
Set realistic goals for leather wallet OEM production. The defect rate of 1% or less (less than 1 in 100) is the practical goal. This is a level that takes into account individual differences in natural materials.
The formula for calculating the defect rate is the defect rate (%) = number of defective products ÷total number of products × 100. Track on a monthly basis. You can see the progress of improvement.
Specific inspection items and standards for genuine leather wallets
Dimensional inspection sets the tolerance of the finished size within ±2mm. Leather stretches and contracts. This is the scope of this point. The thickness should be within ±0.3mm.
Visual inspection is the most important. It is visually inspected at a distance of 30 cm and an illumination of 1,000 lx. Small scratches that are not visible at this distance are good products. Please judge the uneven color of the silver surface by comparing it within the same lot. The difference between lots is not a problem. However, if there is a clear color difference within one wallet, it is a defective product.
During the functional inspection, the opening and closing of the zipper is checked five times in a row. Please verify that it runs smoothly. The card pocket actually inserts and unplugs cards. You can eliminate products that are too tight or too loose.
Check for broken threads and fraying of stitches during sewing inspection. The standard is zero. If there is a thread break in even one place, it is a defective product.
Distinguishing between random inspection and total inspection
In mass production lots, sorting mold sampling inspection is effective. Take 20 samples from the lot. If there is less than one defective product, it passes. If you find two or more, switch to a full test. Completely screen out defective products.
You can also set an AQL (Passing Quality Level). AQL=1.0%. If you exceed the standard by sampling, the lot will fail.
The skiplot type is efficient. If you pass 3 lots in a row, you can skip the inspection for the next lot. However, be sure to inspect it once every 5 lots. Make sure the quality is stable.
Full inspection is mandatory for high-end lines. Think of it as an investment that protects your brand image.
Response flow in the event of defective products
If you find a defective product, isolate it. Do not mix with good products.
Create your initial report within 24 hours. Describe the defect content, discovery process, and estimated cause. Share information with the factory.
We will submit a detailed analysis report within one week. Create in 7 steps of QC story. Clarification of problems→ understanding of the current situation→ goal setting→ factor analysis→ countermeasure planning→ effect confirmation→ standardization and consolidation.
Don’t forget to identify the area of impact. Track for other defective products in the same lot. Check out other products using the same leather material lot.
Recurrence prevention measures will be implemented within 2 weeks. The work procedure needs to be revised. We will also review the inspection standards. Take specific actions such as equipment maintenance.
Verify the effect after 3 months. Check if the defect rate has dropped to the target level. If it does not go down, we will take additional measures.
Conclusion
In order to prevent differences in leather lots at genuine leather wallet OEM, a consistent management system is required from material procurement to final inspection. Close communication with suppliers is key. Share clear quality standards. Bulk procurement in the same lot is also essential.
There is a first step that you can start today. Review your current procurement process. When selecting a leather supplier, we will clearly request “procurement in the same lot and the same dyeing batch”. This small change greatly improves the quality stability of the product. Customer satisfaction increases. It also improves repeat rates.
Thorough quality control can set your brand apart from the competition. This is the greatest weapon.
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