Short Shot Injection Molding

Inox Cast as your Short Shot Injection Molding Service Experts

Inox Cast is your trustworthy short shot injection molding solution and service provider with a rich history in this field. Due to our all-inclusive devotion to extreme efforts, we can provide super-advanced, top-quality, and precise short shot injection molding solutions plus excellent customer care.

Inox Cast is completely expert in the entire short shot injection molding process which the main service is to fix deficient mold products caused by mold stopping short of utterly filling the mold cavity. This issue leaves thin and void areas at the edges of the final mold products.

Inox Cast Short Shot Injection Molding Advantages:

• Redesign the mold with wider channels or gates for better flow.
• Increase injection speed or pressure or choose a thinner base material to improve flow.
• Increase mold temperature to prevent material from cooling too rapidly.

Performing short shot injection molding will help to fix the short shot problems in the final mold products. You must allow Inox Cast to perform it for your best! With our many years of experience in this field, we can promise to give you the best solution for any quality issues like short shots.

The final mold products by Inox Cast short shot injection molding process is used in several industries, most especially in electronics. During the manufacturing process, we make sure to use the right molding machine to produce an efficient solution. It can also avoid pressure and flow issues.

It’s important to depend on the best experts in short shot injection molding for your short shot fixing needs. In short, depend on Inox Cast and give all your trust! Since 1997, Inox Cast became experienced integrated into mold design, parts fabrication, and tooling. We also have customer-oriented staff who willing to give you extra care and support.

Contact us now to consult on your present project and all the services you need. Inox Cast is always at your service!

Short Shot Injection Molding-The Ultimate FAQ Guide

Injection molding is a commonly used parts fabrication manufacturing process.

Perfect as it might be, it is a method that also faces several challenges making it difficult to achieve accurate injection molds.

These challenges can lead to several defects, including short shots that can significantly affect the quality of parts and products.

Keep reading this guide to find out what causes short shots, how to prevent them, troubleshooting tips, and more.

1. What Is a Short Shot In Injection Molding?

A short shot in injection molding is a defect where portions of the final product are not filled wholly or accurately, as shown below.

Short shot in injection molding

As you know, injection molding uses molten material to create product designs. The melt is injected into the mold under high pressure and then cooled.

This allows the material to solidify in the mold and create the desired shape.

Therefore, the material does not fill the entire cavity with a short shot. The melt cools before it can fill the flow paths designed by the mold.

Note that short shots in injection molding mainly occur during startup, although some may occur during processing.

Either way, the results and impacts on production are the same.

2. What Causes Short Shot Injection Molding?

Generally, short shots are usually equipment, process, or material related. The actual cause for the defect can be due to a range of factors including but not limited to:

Poor material flow rate

In any injection molding process, the flowability of the material is vital. The more flowable it is, the better the results will be.

But if the material is not flowable, the results might be flawed with defects such as short shots, shrink marks, flow lines, etc.

Low injection pressure

Injection molding machines are designed differently, each with its unique injection rate. Therefore, if your machine’s shot rate is too low regarding the melt mass needed, it can produce incomplete parts.

Variations in molding part wall thickness

Significant short shot defects can occur when the part wall thickness is too thin. This can create a discrepancy where material cannot fill the thin wall sections of the mold.

Insufficient melt temperature

If the melt’s temperature is too low, the material will not be able to complete the injection process resulting in a short shot.

Poor venting

Inadequate space for gases to escape during injection molding can cause bubbles and other insufficiencies in the final mold.

Obstructed runner

Blocked mold cavity

Prolonged use without maintenance can cause residual material to block the runner. In this case, the material cannot flow properly, which contributes to short shots and other defects in injection molding.

Excessive use of lubricants

Excessive use of lubricants in injection molding increases the chances of shorts shots in the molded part.

Inadequate material in the hopper

Not enough material in the hopper will result in insufficient material injected into the mold. This is often an operator error where inadequate material was put in the hopper or failure to check the hopper frequently.

Other causes:

• Variation in the material used for filling
• Small gates (could be a design issue or obstruction from residues)
• Improper gate location
• Excessive check valve clearance
• Deficient barrel capacity

3. How Do You Prevent Short Shot In Injection Molding?

Mold manufacturing

Several things can be done to prevent short shots in injection molding. Employing these tricks, you or your manufacturer will be able to avoid short shots and make the highest quality parts and products.

• Allow part and mold redesigns to avoid design-related short shots. Redesigning before mold build will help enhance a molding window and ensure part and product quality.
• Proper venting is essential to ensure air can escape from the mold during the filling process.
• The correct amount of material should always be loaded onto the hopper and checked regularly to ensure sufficient flow during filling.
• Always set a high pack and hold pressure before beginning injection molding. Having the pack and hold pressure high enough is essential as it makes it easier for the material to flow through the flow paths even as it gets thicker and thicker during the pack and hold phase.
• Choose thinner based materials to maintain the proper flow of material
• Set and maintain higher mold and material temperature to prevent premature cooling
• Having a suitable and optimum injection speed is also crucial in preventing short shots.
• Before filling, always ensure that machines are thoroughly checked for obstructions in the vents and runners.

4. Can You Predict The Possibility Of Short Shot In Injection Molding Before It Occurs?

Yes

You can do this by appraising the process and geometric parameters likely to cause short shots in injection molding.

5. How Do You Troubleshoot Short Shot In Injection Molding?

Knowing the root causes of short shots is essential in finding solutions to help you prevent costly reworks and production stalls.

Since you already know the root causes, here are some troubleshooting tips to help you identify and solve short shot problems.

5.1. Evaluate The Molding Process

Process control variables in injection molding

Several factors in the molding process can instigate a short shot. If the process parameters are not set up accordingly, it may be challenging to accommodate constant variations in the filling process.

Here is how you can troubleshoot process-related short shots in injection molding:

Proper shot size

Defining the ideal injection rate is essential to ensure consistency in part size, properties, and function during injection molding.

Apparent viscosity vs. shear rate curve sample

You will need to determine apparent viscosity. Start by filling up the mold between 95% and 98% on the first stage, stop and fill up the remaining part using pack and hold.

Afterward, set up the shot size and transfer position to provide the final process parameters.

Injection speed/pressure

As I mentioned, low injection speed is a common cause of short shots in injection molding.

Running apparent viscosity vs. shear rate curve can help solve this problem from occurring during startup. It will help ensure that the viscose curve is at its flattest, making it easy to overcome viscosity variations that may occur during filling.

If a short shot occurs during the normal production cycle, you can try increasing the injection pressure. If this doesn’t make a full part or 95% of full part, then increase the injection speed by 5%.

Melt temperature

Low melt temperature will make the material solidify prematurely in the mold cavity.

This problem can be fixed in several ways:

1. increase the barrel temperature to its uppermost limit(check the material supplier’s temperature processing range), so it can trigger an increase in the melt temperature
2. increase back pressure setting

• check for broken thermocouples and heating components on the barrel and heating components

1. check the PID controller and ensure that it is calibrated to reflect the appropriate melt temperature setting

Mold temperature

Injection molds should always stay hot to ensure that the material stays molten for longer and thus flow to all paths of the mold before solidifying. If the mold is too cold, the material will cool faster, making it difficult to travel and fill the entire mold cavity.

To rectify this issue, increase the mold temperature until the material gains a proper flow. Use the material supplier’s recommendations for this process.

5.2. Evaluate The Mold Design

Deficiencies in the mold design can make it difficult for the material to flow correctly into the mold.

So if you suspect a mold design issue, here are some troubleshooting tips you can try:

Gates

Ideally, gates in an injection mold should be located away from thin wall sections so that the thick wall sections can fill first. If the gates are too close to thin wall areas, hesitation during filling can occur, which creates defects in molded parts.

Hesitation is when material fills the thick areas of a mold and stagnates in the thin areas, allowing the melt to freeze prematurely.

It is best to reevaluate the mold design to ensure the gates are the right size and positioned correctly. Increasing the thickness of thin wall areas can also ease short shots caused by hesitation.

If modifying the location of the gates is impossible, try using a less dense material to ensure proper filling.

Mold vents

Injection mold vent nomenclature

In the case of insufficient vents, add more vents to the areas where air traps occur. This will help the material freely flow into the melt pathways without added resistance.

We often recommend grinding thin pathways about 0.0005” to 0.002” on the shutoff sections of the mold cavity.

Please note that the injection material generally determines the mold venting depth. Deeper vents are suitable for highly viscous material, but thinner vents are advised if the melt is a little runny. The idea is to quickly eliminate air and gas from the mold with as deep a gate as the material viscosity will allow.

Part design

Mold parts with multiple gates, cavity tools, or multi-cavity tools with improper flow balance can cause short shots.

Using mold-filling simulation software can help balance multi-gated/cavity parts.

5.3. Evaluate the Material

As I mentioned earlier, the flowability of the material used in injection molding may affect the quality of final parts and products.

If the short shot you’re experiencing is a result of material flowability, you may want to try these solutions:

• Use material with a lower viscosity
• Add some more ingredients to improve the flow of the melt
• If the short shot coincides with a new batch of material, check the new batch against what was previously used. Quality control is significant in this scenario.
• Check the hopper to ensure a proper and consistent supply of material.

6. How Can Software Simulations Help Mitigate Short Shots In Injection Molding?

Mold flow analysis

Indubitably, an accurate mold is critical in achieving quality injection molding parts and products-ones that are consistent through and through.

A sure way of achieving this is by conducting software simulated analysis on your mold design before tooling production.

It gives you a virtual preview of the filling process using your material of choice and other select parameters.

With software simulated analysis, you can put things into perspective, i.e., the mold quality and the appearance and performance of the product.

Simulations can also help you visualize potential problems such as short shots and solve them early on. This helps to prevent costly reworks and hold-ups later on during manufacturing.

7. What Is The Long-term Cost Of Not Fixing Short Shot Injection Molding Issues?

Quality short shot injection molding

Not fixing short shot issues can have several impacts on your production cycle and/or business, such as;

Increased tool maintenance costs

Trapped air and gas, for example, is one of the most common causes of short shots in injection molding.

Likewise, it can cause dirt to build up in vented pins, necessitating endless production interruptions to clean the tool. Additionally, trapped air can cause the tool to corrode, assuming it is made of metal, increasing tool maintenance costs.

Apart from that, faulty molds can damage the injection molding machine.

Again, this will necessitate frequent maintenance to fix the broken equipment. The effect of this extensive equipment maintenance is expensive downtime, man-hour expenses, and the ongoing risk of future machine failures.

Expensive production downtime

Detecting short shots late into the production cycle will lead to a halt in the process.

Production downtime can be costly in the long run as it risks production budgets, inventory, and customer deliveries.

Bad reputation

Failure to address short shot problems can negatively impact your brand. Constantly producing defective parts and products will attach your brand to quality and productivity issues. This will make customers lose confidence in your brand.

Besides, quality and productivity issues also result in wasted time and resources.

The bottom line is that not fixing short shot problems can cost more in the long run. This is why you should consider working with a reputable injection molding manufacturer like Inox-to reduce your end costs.

8. What Are The Advantages Of Using A Chinese Short Shot Injection Molding Manufacturer And Supplier?

Chinese mold manufacturing

The quality of your injection molded parts is only as good as the molding process; Chinese short shot injection molders guarantee this quality.

China manufacturers like Inox have extensive experience in the industry. This makes them competent enough to fight short shots in injection molding and other problems. This way, you can be confident that you are getting quality parts that will get you the right results for your products.

Chinese short shot injection molds are available for all products, including garden tools, electronic products, kitchen appliances, etc. Parts can be made from various materials, including plastic, metal, glass, and other polymers.

Apart from experience, a manufacturer from China offers more cost savings, up to 50%, than mold makers from other regions.

In addition, they guarantee fast design production and speedy prototype delivery.

There are other benefits of working with a mold manufacturer and supplier from China, such as:

• Creating larger volumes
• Possibility of cheap surface finishing of molded parts.
• Availability of complex parts and their structures
• High efficiency coupled with simple and easy mass production of parts and components
• Flexibility in terms of materials and colors
• Easy engineering of the molding process
• Excellent customer service

In summary, short shot in injection molding is prevalent. But with a quality manufacturer, you can easily keep this visual defect at bay. So choose a mold maker you can trust to provide quality parts and products.

Inox short shot injection molding manufacturer and supplier are competent and will give you the best results!

Contact us for all your injection mold tooling.