Home » Plastic Injection Molding Process
1. The components of plastic injection mold should be cleaned of burrs and dirt before mold assembly, and then assembled before cleaning.
2. Each component should be handled with care, do not allow the hammer to directly hit each component during the assembly process.
3. When cleaning the mold discharge port during the production process, it should be scraped with a copper blade or cleaned with a bamboo knife. It is not allowed to be cleaned with a hard steel knife to prevent scratching the parts.
4. If plastic injection mold is not used temporarily, all components should be assembled after algae oil. The inlet and outlet ports should be sealed and stored on a dry and ventilated wooden frame. No heavy objects should be placed on the mold.
5. When the thickness of plastic products is uneven, adjust the gap between the die and the mandrel. Pay attention to loosen the screws on the thinner side and then tighten the thicker side screws to avoid damage to the injection molded parts or to break the screws.
What makes customer and plastic injection molding manufacturer most feared is the deformation of plastic mold. Plastic mold deformation will affect the injection molding process. So, how to prevent plastic mold from deformation?
1. Mold dimension accuracy
Mold dimension accuracy should be appropriate. The design, fabrication and molding process of mold should be considered according to the drawings. The key is to ensure that the actual mold size is within the dimensional tolerances required by the drawings. This is also the problem that designer must solve. Otherwise it will affect plastic mold quality.
Machine aspect
(1) The nozzle hole is too large so as to the melt flow backward which lead to the shrink, but if too small, the resistance is large so as to the melt is insufficient and the shrinkage occurs.
(2) If the clamping force is insufficient, the flash will generate so as to shrink occurs. Check whether the clamping system has any problems.
(3) If the amount of plasticization is insufficient, a machine with a large amount of plasticization should be used. Check whether the screw and the barrel are worn.
2.Mold aspect
(1) The injection molded parts should be designed to make the wall thickness uniform and the shrinkage is consistent.
(2) The cooling and heating system of injection mold should be designed to ensure that the temperature of each part of molded product is consistent.(3) The gating system should ensure the smooth of melt flow, resistance can’t be too large. Such as, the size of main runner, branch runner and gate should be appropriate, the finish should be sufficient, and the transition zone should have a circular transition.
(4) For thin plastic parts, the temperature should be raised to ensure smooth flow, and the mold temperature should be reduced for thick-walled injection molded parts.
The injection molding process involves melting the plastic in an extruder, injecting the plastic into the mold with an extrusion screw, and cooling the plastic in the mold. In the injection molding process, since the profit margin is usually below 10%, speed and stability are the most critical factors for success.
When it comes to plastic parts manufacturing, injection molding is the cheapest. Due to the initial investment in the mold, the ROI should be an important consideration in deciding what type of part of the production process to use.
It is no exaggeration to say that plastic is the cornerstone of our society. The first step in the injection molding process is the clamping of the mold. This clamping device is a standard part of an injection machine. Mold, clamping device and injection device. The clip is a mold that melts the plastic injection, the injection mold is held under pressure, and the plastic is cooled.
Injection molding is a popular manufacturing method for many reasons. It has proven to be particularly valuable in consumer product development. Plastics The main component of many consumer products, injection molding is one of the best ways to make plastics. Let's take a quick look at the injection molding process.
In my opinion it is better to have invested in whatever it takes to get your testing tools performing correctly and let the supplier base know that you have the tool and know how to use it correctly. Melt flow index results are not the end all or the be all, but they are a significant indicator that something is not right in the reacting/extruding/pelletizing process, or in the material handling/molding process.

The alternative is to fly mostly blind and react only after a problem develops that could be extremely expensive. I don't know if you have dealt with the automotive industry or not, but if they get a chance to hang all their warranty costs on you, especially if you send them 100,000 defective (5, PPM or more) moldings they will not hesitate to charge you for their full warranty costs, and the costs to keep their assembly lines running during transition to good product. This could, depending upon the situation, bankrupt your company.
The old school understandings around processing are pretty much proven the wrong way to work and knowledge more than 10 or 15 years old is way out of date, get current. There is much written about and many good trainers who can help bring your processing ability to state of the art. I recommend this as I continue to find that too little of good engineering practice is being used to the detriment of everyone involved. Strong and robust methods will bring rewards ten-fold back not to mention a bit of excitement at how the trade is changing.

It's about the plastic not the machine, the true melt temperature is the 30-30 check. The best way to check it is to check the melt after the machine runs a few cycles. This way you get a true melt from the screw running under a full load. If you do it on a purge shot you may not read the true melt. You can also sensor the injection mold with temperature sensors to read the melt of the plastic when it enters the mold cavity. I have found this to be very helpful also. This will show you the shear heat from the barrel into the injection mold as it goes through whatever runner system the mold is equipped with.
I have found that the injection molding process monitoring systems are often taken off of machines and packed into boxes to collect dust.

This even after they have been successful in optimizing a process and served to create 100% bad part containment. It is obvious that many who find success with this technology fail to understand that it is only a "tool" that requires continued training to live beyond one problem mold or project. I know of other molders who literally have e-Darts on every machine in their plant and claim to save hundreds of thousands of dollars every year in gained efficiency.

It is interesting (and sometimes frustrating) to see injection molding companies purchase half-a-million dollar machines, but refuse to invest less than twenty thousand dollars to optimize the process that is paying for the machine and justifying its existence. I truly believe that this scientific approach to injection molding is the only right way to mold. Yet I am surprised at how many molders reject the technology. My intent in starting this conversation is to get a better idea of why some companies fail and others succeed in utilizing this technology.
If you are going to implement proper process control, buying and installing the equipment is just the start. The challenge is this: You must have personnel who know what they are looking at. Unfortunately, there are not a lot of qualified people out there. Secondly, you need to develop the means to correlate the data from the monitoring system to the data your end customer cares about.

Process monitoring is not a silver bullet. If it is to pay off, it requires process discipline and a systematic approach. I have used several of the systems mentioned above and some that were designed for specific applications. If there was process discipline and a systematic approach to interpreting and acting on the data, the payback was quick and dramatic. If those elements did not exist, the project was looked on as a waste of time and money.
The only way to run a successful injection molding operation is to have an outstanding process monitoring system to go along with the injection molding machines. There are several parameters that need to be monitored, with the goal to minimize variability in the process itself, which in turn will minimize variability in the product.

Parameters include (not in order): Times (Cycle, Fill, clamp, etc), Pressures (pk hyd, hold, back, in-cavity, etc), Temps (water, oil), Distance (Cushion, etc).
I am amazed at the number of companies that do not monitor their processes. I think it is because of the variability of the process from job run to job run. This variability is a built in rationalization for non-investment in monitoring hardware, software, etc. One needs to be convinced of the immediate and long term cost savings before an investment will be made.
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