The quality control of production process in die casting workshop involves every link of die casting process, from smelting to production commissioning to inspection control; From key process control to equipment and mold maintenance. The omission of each link may cause quality accidents.

 

Alloy melting

  1. The temperature of the furnace shall be controlled at 630 ℃ – 680 ℃.
  2. Observe the molten aluminum. The molten aluminum suitable for production is bright white. If the molten aluminum is red, it indicates that the furnace temperature is too high. If the molten aluminum is in the shape of ice cream, it indicates that the temperature is too low.
  3. It is strictly prohibited to mix impurities in the process of aluminum melting. It is prohibited for operators to put unqualified products into the furnace for re smelting without permission. If products need to be returned to the furnace for re smelting, they can be put into re smelting only after being inspected and confirmed by the team leader.
  4. Keep the liquid level of aluminum liquid stable without scum and bubbles. When scooping aluminum liquid for die casting, the oxide layer and impurities on the surface of aluminum liquid must be scraped off.
  5. During the production process, powdered refining agent and slag removal agent must be injected into the furnace twice in each shift, on average once every 4 hours. The whole filling process must be carried out under the guidance of the team leader. After the operation is completed, the impurities generated by refining must be cleaned before casting production.
  6. During the production process, the aluminum slag at the bottom of the furnace must be cleaned at least twice in each shift, at least once every 4 hours on average.
  7. All tools in contact with molten aluminum must be dried first, and must be kept absolutely dry and clean. Impurities cannot enter the molten aluminum.
  8. In the process of aluminum melting, if too many impurities are found in the aluminum ingot or return material, immediately stop putting the same kind of aluminum ingot or return material into the furnace, and report to the team leader and workshop director in time.

 

Mold installation

  1. First of all, the accuracy of the mold model should be determined to ensure the integrity of the mold.
  2. When assembling the mold, it shall be completed with the joint assistance of the operator, repairman and team leader.
  3. During mold assembly, the firmness of all fasteners shall be ensured to ensure the safety of the mold in the production process.

 

Die debugging

  1. After the mold assembly is completed, the test machine (inching) can be carried out, and the automatic low-pressure idling can be carried out once a week to ensure the flexibility of the assembled mold.

1) Check whether the screws are loose.

2) Check the equipment for oil leakage or other abnormalities.

3) Check whether the moving parts of the die casting machine and die are refilled with lubricating oil.

 

Mold temperature (mold preheating)

1) Mold surface temperature rises to 180 ℃ – 220 ℃.

2) Check whether the cooling water operates normally.

 

Trial die casting

1) The team leader sets the die casting parameters.

2) Check whether the molten aluminum to be cast is suitable.

3) Observe whether the equipment and die operate normally during die casting.

4) check whether the spray pressure and water quantity of the release agent are normal.

5) Check whether the size and appearance of the die-casting products meet the requirements of drawings and inspection cards, and whether there are product defects.

6) The number of trial die-casting products must be more than 50 (high-speed injection pressure test must be carried out after 20 low-speed injection molds).

7) The die castings finally confirmed to be qualified can be retained as the first inspection products, and the first article inspection form shall be filled in.

 

Die casting production

  1. After the die-casting products are confirmed to be qualified, the set parameters shall be determined, and the operator shall not change the set parameters without authorization.
  2. In case of abnormal phenomena such as abnormal noise of equipment or retention of castings in the mold during production, stop the machine immediately and notify the maintenance personnel. It is strictly prohibited for operators to repair without permission.
  3. In the production process, the operator should ensure the reliability of the mold.

1) Due to the uneven parting surface or much wear, the clamping force is not enough, resulting in more flash of the casting.

2) Aluminum liquid splashing at the injection position due to punch wear.

3) The mold cavity and sliding block are damaged due to misoperation.

4) Due to the long-term use of the mold, the mold material fatigue, collapse and damage, and affect the product quality.

  1. During the production process, the operator shall carry out the product self inspection. It is stipulated that the self inspection shall be carried out for every 20 die-casting products. If the product is abnormal, the production shall be stopped immediately to find out the cause.

1) Because the mold temperature is too low, the temperature of molten aluminum is too low or the filling speed of molten aluminum is too slow, resulting in cold shut of castings.

2) Due to insufficient pressure holding time, the draft angle of the casting is too small, resulting in casting cracks or even tensile cracks.

3) Due to the deviation of molten aluminum material, rough surface of mold cavity, insufficient demoulding dose or failure, the casting sticks to the mold.

In the production process, if the mold is found to be slightly broken, but the casting only needs to be repaired in appearance, which will not affect the performance, it shall be reported to the team leader and workshop director in time. The treatment methods are as follows:

1) According to the actual situation, the production may not be terminated, but all casting products must be repaired. After the die casting of this batch of products is completed, the mold must be repaired. This situation is applicable to products with small batch.

2) Stop production immediately, dismantle the defective mold for maintenance, and continue to put into production after maintenance and trial die casting to confirm its integrity.

 

Release agent

  1. Before die casting in the production process, release agent must be sprayed on the die.
  2. Check whether the injection pressure of release agent is suitable for die casting production.
  3. Check whether the release agent flow is suitable for production.
  4. Check whether the release agent is invalid.
  5. In case of the above problems, the team leader and workshop director shall be informed immediately, and the injection pressure, flow and release agent ratio shall be adjusted in time until it is applicable to production.

 

Production inspection

Confirmation and assembly of dies

  1. The team leader must confirm the conformity of the mold model to be assembled, and the product model must be consistent with the production order.
  2. The team leader must confirm the integrity of the mold and avoid the installation and production of damaged mold.
  3. For the assembled mold, check its tightness and add lubricating oil to ensure the flexibility of mold operation.
  4. It is necessary to confirm the conformity of the test die-casting products of the die.

First inspection of products

  1. The team leader must confirm whether the first die casting produced meets the drawing requirements.
  2. When conducting the first product inspection, the team leader must confirm whether the dimensions and appearance of die castings meet the requirements of drawings and inspection cards.
  3. During the first inspection of products, the team leader must confirm the good operation of die-casting equipment and molds.

Patrol inspection

  1. The team leader shall conduct patrol inspection on each running equipment at least once every hour to correct the bad operation of the operator.
  2. Carry out patrol inspection on each machine and spot check on the products being produced to confirm the immediate conformity of the products.
  3. The team leader shall deal with the production abnormalities in time, and report major quality problems to the workshop director in time.

Other

  1. The team leader shall verify and record the shift handover procedures at each shift handover.
  2. The team leader shall fill in the work diary, record the quality problems and production situation of the current shift, and give work tips to the next shift.

 

Quality control

Full inspection of products

  1. The full inspector shall carry out full inspection on the die-casting products.
  2. It mainly tests the appearance, defects and other items of the product.
  3. During the whole inspection process, if many quality problems are found in the products, the situation shall be reported to the team leader and workshop director in time.
  4. The full inspector shall classify and record the quality problems of the inspected products.

Product sorting

  1. The full inspector shall sort the products inspected and resolutely remove the unqualified products.
  2. The nonconforming products removed during the whole inspection shall be classified, isolated and identified according to different quality problems.
  3. Products of different types and models shall be placed differently to prevent mixing of different products.

Product identification

  1. Products that have been fully inspected must be identified, and products of different types and models must be distinguished.
  2. In the product identification, the model, type and quantity of the product, the station number of the die casting machine, the name of the operator and the name of the full inspector must be indicated.
  3. Nonconforming products must be identified and isolated to prevent the selected nonconforming products from mixing into the qualified products again.

Sampling inspection of products

First inspection of products

  1. The quality inspector must participate in the first inspection of the first product.
  2. The quality inspector must confirm that the first inspection products fully meet the drawing requirements before continuing production.
  3. For the unqualified products in the first inspection, the quality inspector is responsible for requiring the operator and the team leader to adjust or repair the equipment and molds until the qualified products are produced.

 

Product inspection

  1. The quality inspector shall inspect each product under production at least once every hour to confirm whether the product under production meets the drawing requirements.
  2. The quality inspector shall conduct a patrol inspection every hour for the products being fully inspected and sorted by the full inspector to confirm whether the products being fully inspected meet the drawing requirements.
  3. In the process of patrol inspection, the nonconforming products found shall be marked and isolated immediately, and the quality inspector is responsible for urging the operator and team leader to correct them.
  4. In the process of patrol inspection, if major quality problems or serious hidden dangers are found, they shall be immediately reported to the workshop director and the quality department for timely treatment.
  5. In the process of patrol inspection, if minor quality problems that can be repaired are caused by problems such as equipment and molds, the quality inspector shall timely inform the workshop director and quality supervisor. If this kind of situation can be solved by repair afterwards, production can continue. After the completion of mass production, relevant personnel shall be notified to repair the equipment and molds in time.

4、 Final inspection of products (sampling inspection before warehousing)

  1. The quality inspector shall conduct the final sampling inspection for the products before entering the warehouse.
  2. The inspection of product performance, size and appearance shall be carried out according to the production drawings.
  3. Unqualified batch products can be scrapped, repaired and inspected according to the actual situation.

5、 Other

  1. Be responsible for the inspection and acceptance of die-casting molds and the filling of inspection records, and timely report the relevant daily quality report.
  2. Be responsible for the process control of the workshop, the first inspection, patrol inspection and warehousing inspection of products, and fill in relevant inspection records.
  3. Be responsible for the final inspection and warehousing (ex warehouse) inspection of products, and unqualified products shall not be warehoused (ex factory).
  4. Supervise and inspect the work of part-time inspectors and full inspectors, and coordinate and deal with the quality problems of the workshop.
  5. Be responsible for keeping the quality inspection records of the workshop and assisting the workshop in handling customer returns.
  6. Assist the workshop to put forward product quality improvement plan and improve the manufacturing process level.
  7.  

Other problems needing attention in process control:

Key processes shall be controlled.

For die castings that are easy to cause product deformation due to long core pulling, the operator, team leader and quality inspector shall strengthen their inspection and focus on them, so as to ensure that qualified products flow to the next process.

The semi-finished products completed in the process shall not be stacked too high during the full inspection. For products of different specifications with similar appearance, effective product positioning identification shall be carried out between different products to prevent major confusion in the process of handling, moving and production due to too close distance between different products.

Control of nonconforming products

  1. In the production process, if the die-casting products are found to be unqualified or the mold is damaged, the discoverer shall report immediately. The team leader, quality inspector or workshop director shall organize the identification and isolation of nonconforming products, and place the nonconforming products in the designated area.
  2. In the detection process, if the nonconforming products can solve the relevant quality problems through technical treatment, the full inspection and quality inspector can require the production line to make technical treatment, and the treated products must be re inspected.
  3. For nonconforming products found, the workshop quality inspector shall fill in the quality report and report it to the quality supervisor. The quality supervisor shall convene relevant personnel of the workshop to analyze the nonconforming products and make a written decision on treatment.

The quality inspector can summarize the quality status of workshop production once a week or a month, including product quality, customer returns, customer quality complaints, etc., and report to the quality supervisor, who will make the final monthly quality report.

Assay, test, batch number management of raw materials and timeliness treatment of die castings

 Test and die casting of raw materials (aluminum ingot)

  1. All incoming aluminum ingots must be tested by the physical and chemical room. Only qualified aluminum ingots can enter the die casting workshop for trial die casting.
  2. The newly arrived aluminum ingots that have not been tested can be put into the warehouse for temporary storage. The warehouse keeper shall strictly distinguish this batch of newly put aluminum ingots from the aluminum ingots currently in use, and mark this batch of newly put aluminum ingots for temporary storage. The same batch of aluminum ingots with different stacks shall be marked.
  3. Aluminum ingots newly stored temporarily shall not be distributed to the production workshop for use without permission. This batch of aluminum ingots is marked. There should be a clear code, quantity, purchase date of the material alloy and the inspection status of the aluminum ingot (the newly warehoused aluminum ingot without test and trial die casting must be hung with the mark to be inspected).
  4. The qualified aluminum ingots must be tested in the die-casting workshop. The test die-casting products must not be less than 2000 small pieces and 800 large pieces. The test die-casting products must be inspected by the workshop director and the quality management department, and must be inspected after aging treatment, such as crack, crack, deformation and so on.
  5. For aluminum ingots that pass the test, trial die casting and aging treatment inspection, the quality inspector of the quality management department can confirm them as qualified raw materials only after filling in the aluminum ingot inspection report. According to the above test report, the quality management department signs and confirms on the warehouse receipt, and indicates that the batch of aluminum ingots has passed the above two inspections. At this time, the materials can be officially put into the warehouse, and the warehouse keeper officially hangs the inspection mark, indicating that the materials can be officially put into production.