Latch lock

The Functions of a Latch Lock:

 

In the two-step parting, two-step ejection or cavity ejection mechanism, a latch lock unit is always employed to control the opening sequence and stroke of each mold plate.

Though latch locks perform similar functions, they have a diversity of different structures. So, it is necessary to select the right latch lock for the right circumstance according the characteristics of the latch lock. The several commonly seen latch lock structures are explained as below.

 

1,Daido Latch Lock: 

  1. Pros: The Daido latch lock features a simple and concise structure, and requires little machining of the mold base. It takes up a little space and can be mounted on the mold freely, so the chances of interfering with the other parts on the mold base are minimized. Daido latch lock is able to control the mold opening stroke flexibly – a stop block can be mounted on the mold base to realize opening stroke control. In addition, it is inexpensive.
  2. Cons: Daido latch lock uses a spring to press the steel ball into contact with the control lever to realize mold closing. As a result, it is not easy to control the clamping force. There are cases of unhooking before reaching the required stroke. It is not so reliable, nor is it easy to adjust.
  3. Applicable Scenario: This type of latch lock is suitable for medium-/small-sized plastic injection molds, which do not require a large clamping force or a high reliability. Usually, it is not selected due to its poor reliability. See figure I: Used for the 2-step ejection of the ejector plate.

Note: The Daido latch lock uses a spring to press the steel ball into contact with the control lever to realize mold closing. As a result, it is not easy to control the clamping force. It is only applicable for medium-/small-sized molds, which do not require a large clamping force.

2,HASCO Latch Lock: 

  1. Pros: Sold at a moderate price, the HASCO latch lock boasts diversified specifications and a wide range of available options; the mechanical closing mechanism is secure, reliable, convenient to mount and requires little machining of the mold base. The lengths of its control lever and hook can be adjusted as per actual conditions.
  2. Cons: When mounting, machining is needed after the location of pin holes and screw holes are determined. It is not easy to change the mold opening stroke after it is designed. Also, the stroke range is limited by the length of the control lever.
  3. Applicable Scenario: The mechanical closing mechanism is secure and reliable, so it is suitable for various large-/medium-/small-sized molds.

 

Note: It is not easy to change the mold opening stroke after the stroke is designed, and the pin hole and screw hole locations are machined. Also, the stroke range is limited by the length of the control lever.

3,STRACK Latch Lock:

 

  1. Pros: The mechanical closing mechanism is secure and reliable. A wider stroke range can be covered by changing the relative location between the control lever and the hook. After the latch lock is mounted, the mold opening stroke is still able to be adjusted by moving the adjusting slider on the control lever.
  2. Cons: Occupy a larger space; complicated mounting process; require a lot of machining of the mold base; high price.
  3. Applicable Scenario: Suitable for large-size molds, and able to cover a wide opening stroke range. Usually, it is not selected due to its high price, unless specified by the client.

Note: After the latch lock is mounted, the mold opening stroke is still able to be adjusted by moving the adjusting slider on the control lever.

4,RABOURDIN Latch Lock

  1. Pros: With a large clamping force, the mechanical closing mechanism is secure and reliable. Its biggest benefit is that the mold opening stroke is able to be adjusted by moving the adjusting slider after the latch lock is mounted, so a wider stroke range can be covered.
  2. Cons: Occupy a larger space; complicated mounting process; require a lot of machining of the mold base; high price.

3. Applicable Scenario: Suitable for large-size plastic injection molds, and able to cover a wide opening stroke range. Usually, it is not selected due to its high price, unless specified by the client.

 

Note: After the latch lock is mounted, the mold opening stroke is still able to be adjusted by moving the adjusting slider on the control lever.

 

 

All copyright reserved by plastic injection molding factory  Sositar Mould

 

Injection molding machine operation instruction and good habit

1.A great habit of injection molding machine operation is of enormous benefit to both machine service life, as well as production safety.

(1)Before the Machine Starts

①Check to see whether there is any water or oil inside the electrical control box. Don’t turn it on if the machine is affected by moisture. It can only be turned on after the parts are dried by the service staff.

②Check whether the voltage meets the requirements, which is usually kept within the range of ±15%.

③Check the effectiveness of the EMERGENCY STOP button, as well as switch of the front and back safety doors. Verify whether the rotating direction of the electric motor and the oil pump are consistent.

④Check to see whether each cooling channel is smooth and free from any blockage, and let coolant into the oil cooler and the water jacket at the machine barrel end.

⑤Check to see if all joints are lubricated, and add lubricant/grease when necessary.

⑥Turn on the electric heat control system to heat each section of the machine barrel. Hold the temperature for a while after each section is heated up to the required temperature, so as to obtain a relatively stable machine temperature. Temperature holding time varies with different equipment and plastic materials.

⑦Feed sufficient plastic materials into the hopper. According to different plastic injection molding requirements, some materials need to be dried beforehand.

⑧Keep the machine barrel covered with a heat shield, so as to save power, and at the same time increase the service life of the electric heater and the contactor.

(2)During the Operation Process

①Do not ignore the importance of the safety doors for convenience.

②Always pay attention to the temperature of the hydraulic oil, to keep it within the allowed range. The ideal working temperature of the hydraulic oil should be kept between 45 and 50℃; usually, the proper temperature ranges from 35 to 60℃.

③Don‘t forget to adjust each travel distance limit switch, to avoid collision during machine operation.

(3)After the Operation

①Before turn the machine off, thoroughly clean the machine barrel, so as to prevent the residue materials from oxidation or decomposition caused by long-time heating.

②Open the mold to keep the elbow-bar mechanism locked.

③The workshop needs to hoist all the equipment. Carefully handle the heavy mold parts and components during the assembly/disassembly process, to ensure production safety.

 

  1. Instructions on Injection Molding Machine Debugging

(1) Purpose

Meet product quality requirement with the fastest speed, the lowest cost and the optimal molding cycle.

 

(2) Scope of Application

Applicable for machine debugging and work process adjustment of the Injection Molding Dept.

 

(3)Work Preparation

①No matter it is a new or an old product, production process documents, product samples, material performance documents, as well as the documents of product weight and mold structure need to be available. As for an old product, find out its production process document and input it to a computer, and then adjust the mold and equipment to the required status.

②Check whether the status of equipment, mold and material allows debugging, e.g. whether materials are dried, whether the mold is cleansed and functions well, whether barrel temperature reaches the molding requirements, and whether the cooling system is on, etc.

 

(4)Machine Debugging

For an old product, input process parameters before performing regular operation, and start massive production after quality inspection. If it is a new product, the operation steps are as follows:

①Set material barrel temperature to regular molding temperature. Set melt and injection travel distance on basis of product weight.

②Identify injection pressure and speed based on the injection molding process. Usually, medium pressure (50~80MPa) and speed (30~60mm/s) are applied.

③Identify pressure holding time based on gate types and sizes. Pinpoint gate, 6 – 8s; side gate and direct gate, 8 – 10s.

④Identify cooling time based on cooling channel layout and product thickness, preliminarily set it to 15 – 20s.

⑤Start the injection molding process manually; raise or lower relevant data based on the defects of the molded product, till product quality meets the requirements and allows continuous operation.

⑥Switch the machine from manual mode to semi-automatic and adjust the parameters during production, so as to achieve the best injection molding cycle. Injection Molding Cycle = mold open/close time + injection time + melting time + cooling time, all of which need to be minimized. Generally speaking, for a 100g injection molding machine, if a 2-plate mold is applied, the mold open/close time is kept at about 2s, or appropriately longer if there are sliders. Injection time should be reduced progressively by 0.5s till defects occur. Then stop adjustment and return to the previous data. With regard to melting time, try to reduce back pressure and quicken up melting speed, to avoid air mixture and air bubbles, etc. The adjustment of cooling time is similar to that of injection time: reduce progressively by 1s, and then compare the molded product with the standard sample. If the two share the same quality, it is deemed the best cooling time.

 

All copyright reserved by injection molding company Sositar Mould

The reason and solution for surface roughness

Surface roughness means there is a lack of precision in the surface of a molded part, or an inconsistent level of precision all over the surface, e.g. some areas are glossier than the rest. The main reasons for surface roughness might lie in the injection molding machine, the mold, the process or the material.

(1)Injection Molding Machine

①Insufficient material supply;

②Material barrel is not thoroughly cleaned when changing material;

③Check for cold melt leakage at the nozzle;

 

(2)Mold

①The gate is too small, or the runner is too thin – increase the gate size, or adopt the film gate;

②The surface of the mold cavity is rough – polish the cavity surface and check if there’s any leakage;

③Poor venting – add vents in the location with poor glossiness for an improvement;

④Increase the size of or add a cold slug well to collect the cold material;

⑤Mold temperature is too low – raise mold temperature;

⑥Might be affected by mold release agents – stop the application of mold release agents;

 

(3) The Injection Molding Process

①Increase melt temperature (check whether the heating zone of the material barrel is in disorder – non-uniform temperature, local temperature too high or too low, etc.);

②Increase nozzle temperature;

③Over shear caused by over-speed injection – lower injection speed appropriately;

④Increase injection pressure;

⑤Increase material injection time;

 

(4) Raw Materials

①Raw material is not dried;

②Too much recycled materials are added, or repeatedly recycled materials are decomposed;

③Excessive application of mold release agents.

Dimensional instability in plastic injection molding process

Dimensional instability means the dimensional changes of a molded part exceed the tolerance limit, for which the reasons might lie in the injection molding machine, the mold or the injection molding process.

(1)Injection Molding Machine

①The application of different types of injection molding machine leads to the differences in injection molding conditions;

②Melt temperature fluctuation – check for failure of the thermocouple or the temperature controller;

③Instable screw speed – check the hydraulic system;

④Instable injection pressure – check whether there’s consistent buffering during each cycle, or whether the plastic non return valve leaks, repair or change it when necessary;

 

(2)Mold

①Check whether the gate is blocked by residue;

②Check whether the mold temperature is stable, whether the coolant flows smoothly, and whether the cooling circuit is correctly connected;

③Check for failure of molding components;

 

(3)Injection Molding Process

①Non-uniform mold temperature or unreasonable cooling circuit leads to improper mold temperature control – make adjustments accordingly;

②Injection pressure is too low – raise injection pressure;

③Appropriately increase injection time and holding time;

④Material barrel temperature or nozzle temperature is too high – make adjustments accordingly;

⑤Filling speed is too low – increase injection speed, or adopt multistage injection.