Here, we'll focus on how to quickly improve your injection molding skills from perspective of an injection molding technician. Specifically, we'll discuss how to transition from an operator to a process position, how to learn, where to learn, and what to learn—all of which are important considerations for new injection molding technicians. We'll reorganize previous articles to explain basic steps for learning injection molding and essential knowledge required.
Injection molding is a highly practical technology, requiring injection molders to possess strong professional qualities and a solid foundation.

As an operator in an injection molding workshop or a new college graduate, if you want to learn injection molding process, you must first become familiar with injection molding machine. You must first be able to operate and touch machine, such as opening and closing mold, ejecting, injecting, plasticizing, and drawing glue. You may encounter and become familiar with these movements as an operator, material loader, or mold loader.
Once you're familiar with movements, memorize and practice them whenever possible. After a while, you'll naturally master them. During this process, you should learn how to store and load injection molding process parameters—that is, how to save and import parameters.
This will allow you to assist process personnel with preliminary preparations during mold changes and gradually become familiar with material drying, mold loading, screw cleaning, process parameter recall, and initial commissioning.

Confirm that material drying, mold temperature, heater temperature are correctly set and ready for processing.
Check mold opening, closing, and ejection motion and distance settings.
Set injection pressure (P1) to 60% of its maximum value.
Set holding pressure (PH) to 30% of its maximum value.
Set injection speed (V1) to 40% of its maximum value.
Set screw speed (VS) to approximately 60 RPM.
Set back pressure (PB) to approximately 10 kg/cm².
Set back pressure to approximately 3 mm.
Set holding pressure switch position to 30% of screw diameter. For example, for a 100 mm φ screw, set it to 30 mm.
Set metering stroke slightly shorter than calculated value.
Set the total injection time slightly shorter and cooling time slightly longer.

Close mold (confirm high pressure rises) and advance injection molding seat.
Inject manually until screw comes to a complete stop, noting stop position.
Retract screw to feed material.
After cooling, open mold and remove molded product.
Repeat above steps until screw finally stops at 10% to 20% of screw diameter. Molded product should be free of short shots, burrs, whitening, or cracking.

(1) Correction of metering stroke: At metering end point, injection pressure is increased to 99%, and holding pressure is temporarily adjusted to 0. Metering end point S0 is adjusted forward until a short shot occurs, then adjusted backward until burrs occur, with midpoint being selected position.
(2) Correction of injection speed: Return PH to original level, adjust injection speed up and down, find individual speeds where short shots and burrs occur, and use midpoint as appropriate speed. This stage can also enter parameter setting for appearance problems with multiple speeds.
(3) Correction of holding pressure: Adjust holding pressure up and down, find individual pressures where surface depressions and burrs occur, and use midpoint as selected holding pressure.
(4) Correction of holding time (or injection time): Gradually extend holding time until weight of molded product is obviously stable, which is appropriate choice.
(5) Correction of cooling time: gradually reduce cooling time and confirm that following conditions can be met:
1) Molded product will not be whitened, cracked or deformed when ejected, clamped, trimmed or packaged.
2) Mold temperature can be balanced and stable.

(1) Confirm whether back pressure needs to be adjusted.
(2) Adjust screw speed so that metering time is slightly shorter than cooling time.
(3) Confirm whether metering time is stable. You can try to adjust temperature gradient of heating ring.
(4) Confirm whether there is overflow in nozzle, whether main channel is sticking to mold, and whether there are air marks on finished product. Appropriately adjust nozzle temperature or release distance.

Generally speaking, injection should be done at high speed without affecting appearance, but it should be done at a lower speed before passing through gate and switching to holding pressure.
Holding pressure should be gradually reduced to avoid excessive residual stress in molded product, which makes molded product easy to deform.

After debugging in step 2, product is essentially complete. Now, identify any defects in its appearance.
1. Product defects.
2. Defect type.
3. Defect location.
4. Upper action may have been achieved by shortening mold.

Injection molding product quality issues are numerous. When analyzing specific issues, focus on 4Ms (Man, Machine, Material, Method), then identify root cause through 5Ys.

1. After identifying specific product defect, conduct a comparative analysis of all causes of defect. This involves some guidance from injection molding theory and accumulated experience with specific products.
2. You may use a fishbone diagram to identify cause.

 

New injection molding technicians always want to improve their professional skills so they can better solve problems in production. With millions of injection molded products and countless types of injection molding problems, how can they improve their professional skills? Correct approach is to approach learning with a problem in mind. While there are many types of injection molded products, for products in a specific industry or specifically tailored to your production and processing, defects are often limited or concentrated in a specific type. By approaching this learning process with a business perspective, understanding causes and solutions to these defects, you can more quickly resolve existing problems and memorize corresponding improvement measures.
Building on this experience, you can then study injection molding process theory and use it to explain mechanisms of defect formation. This will help you master injection molding process from essentials to the fullest.