After adjusting injection molding process parameters, it is essential to follow a standard procedure for exhaust in the injection mold to ensure the proper release of air or gases trapped in the cavity during the molding process. Proper exhaust helps to prevent defects such as burning, voids, and short shots. Here is a standard procedure for exhaust in injection molds:
- Mold Inspection: Before starting the production run, inspect the mold for any damage, wear, or buildup of debris that might obstruct the exhaust channels.
- Clean the Mold: Ensure that the mold is clean and free from any residual plastic or contamination that could affect the exhaust process.
- Adjust Injection Parameters: After making adjustments to the injection molding process parameters (e.g., temperature, pressure, speed), check the settings to ensure they are appropriate for the specific material and part design.
- Purge the Injection Molding Machine: Before starting the production run, purge the injection molding machine with the selected material to remove any residues from the previous material used.
- Slow Injection Speed: During the initial stages of injection, use a slower injection speed to allow trapped air to escape through the vents.
- Optimize Venting Design: Ensure that the mold has proper venting channels or vents in the areas where air is likely to get trapped. Venting design should be optimized for each part to facilitate the escape of gases.
- Mold Temperature: Maintain the mold temperature within the recommended range to minimize thermal expansion and contraction, which can lead to trapped gases.
- Monitor Process: Continuously monitor the injection molding process, paying attention to any signs of trapped air or gas, such as sputtering, burning, or bubbling on the surface of the part.
- Adjust Cycle Time: Adjust the cycle time, if necessary, to allow sufficient time for air and gases to escape before the mold fully closes.
- Check Ejector Pins: Ensure that the ejector pins are properly aligned and functioning correctly to eject the part without trapping air.
- Inspection and Fine-Tuning: After the initial production run, inspect the molded parts for any defects related to exhaust. Fine-tune the process parameters or venting design if needed.
- Maintain Proper Maintenance: Regularly clean and maintain the mold to prevent clogging of vents and ensure consistent exhaust performance.
By following this standard procedure for exhaust in injection molds, manufacturers can achieve better-quality molded parts with minimal defects and ensure the efficiency and reliability of the injection molding process.
In the process of plastic mold injection molding, problems such as white top, black spot, shrinkage, bubble, silver wire, flash, etc. are often encountered in plastic parts. If the plastic products still have insufficient filling, high internal stress, bubbles and other phenomena after adjusting the injection molding process parameters, this is likely to be the exhaust problem of the plastic mold.
In the manufacturing of injection mold, the exhaust of injection mold is a very important link. The exhaust of injection mold can represent the overall structure of injection mold to the greatest extent. Even if an excellent injection mold does not have a good exhaust, it is impossible to produce products with stable quality. A good injection mold should have a good airtightness, and be able to ensure that the gas is discharged freely, rather than being highly compressed. What are the standards for injection mold exhaust? Next, let’s introduce it to you.
The full exhaust structure shall be made as far as possible. The depth shall be within the plastic overflow value. Full exhaust is the best, but 1/2 of the steel shall be left on the clamping line to compensate the pressure. If the PL surface is irregular and cannot be fully vented, it is better to use a 12mm wide vent slot to the die, and the gas must finally be vented to the atmosphere. The vent slot should be processed with a milling cutter with a flat bottom and chamfer as much as possible. If a spherical milling cutter must be used, it is necessary to calculate that the processing depth is consistent with the processing depth of the flat bottom before using it. The length of the exhaust sealant is the most easily ignored by most people, and is related to the appropriate exhaust problem, On this issue, there are many different opinions about the size regulations. The specification of the material supplier ranges from 3 to 5 mm, but experience has proved that if the length is greater than 3 mm, it will no longer play a good role. Therefore, for safety reasons, we specify that the standard is 3 mm, and the exhaust depth depends on the molding material. If in doubt, you can refer to the processing specification.
One of the most common misconceptions of plastic molds is that too much exhaust leads to flaring. In fact, the opposite direction is correct. Unreasonable exhaust requires too much pressure. When gas is allowed to exhaust, the rubber will go out with the gas. The only reason for excessive exhaust leading to flaring is that the air groove is too deep. Generally, all ejector pins shall be used to exhaust as much as possible. This is especially important for large plastic parts, which of course depends on the diameter of the ejector pin. If this is not possible, the air shall be ground flat, with appropriate length and depth, and the fitting clearance of the ejector pin shall be slowed down. The flow passage, especially the large or long flow passage, must be opened for exhaust.
Another common problem is that when the parts cannot be fully vented, the last glue filling position and the next last glue filling position must be considered, and these two positions must be vented. Exhaust shall be specially considered for deep bone position, column position, small needle dispensing position or thin glue position, or flat thimble, semi needle structure, exhaust steel or even vacuum exhaust device shall be used.
A part cannot exhaust too much, although the mold closing line can do so, this will bring the following problems related to exhaust: there is not enough steel to bear pressure on the mold closing line, and the exhaust on the parting surface is pressed; The best exhaust will eventually disappear. After a certain material circulation, if there is not enough steel to compensate the pressure on the clamping line, the injection mold will bite together, and the air groove will wear. The clamping line should avoid the reduction of the clamping part of the injection mold, which is the biggest problem encountered by the large mold. For the injection mold of the front and rear mold inserts, the front and rear mold kernels cannot be assembled before the mold parting surface of the mold embryo is assembled. The correct way is to use pressure block to close the mold at the same time between the AB plates of the mold base.
The exhaust of injection mold after adjusting injection molding process parameters is a crucial step that ensures the quality of the final product. Proper exhaust can help to eliminate air pockets and bubbles that can cause defects in the final product. This article will discuss the standard for exhaust of injection mold after adjusting injection molding process parameters.
Importance of Proper Exhaust
Proper exhaust is essential in the injection molding process as it helps to ensure the quality of the final product. The presence of air pockets and bubbles can cause defects such as sink marks, voids, and warpage. Proper exhaust can also help to reduce the cycle time of the injection molding process, thus improving production efficiency.
Standard for Exhaust
The standard for exhaust of injection mold after adjusting injection molding process parameters varies depending on the material being used, the design of the mold, and the injection molding machine. However, the following general guidelines can help to ensure proper exhaust:
- Ensure that the vents are clean and free from any obstruction
- Position the vents strategically in the mold to allow for proper air evacuation
- Increase the mold temperature to help reduce viscosity and improve flow
- Increase injection pressure to help push out trapped air pockets
- Increase injection speed to help push out trapped air pockets
It is also essential to monitor the exhaust during the injection molding process to ensure that it is adequate and effective in eliminating air pockets and bubbles.
Proper exhaust is crucial in the injection molding process to ensure the quality of the final product. The standard for exhaust of injection mold after adjusting injection molding process parameters varies depending on several factors, but proper cleaning of vents, strategic positioning of vents, increasing mold temperature, injection pressure, and injection speed are general guidelines that can help to ensure proper exhaust. It is essential to monitor the exhaust during the injection molding process to ensure that it is adequate and effective in eliminating air pockets and bubbles.