Troubleshooting Common Issues With Machine Injection Moulding

Troubleshooting Common Issues With Machine Injection Moulding

Troubleshooting common issues with machine injection moulding involves identifying and resolving problems such as sink marks, warping, air traps, and short shots. By thoroughly checking the material for contamination, adjusting mold temperature, setting appropriate vacuum, and inspecting for mold deflection, these issues can be effectively addressed.

Troubleshooting Lubrication Failure on Injection Moulding Machines (2)

Common Issues With Plastic Machine Injection Moulding

Common issues with plastic injection molding machines can include weld lines, sink marks, warping, air traps, and short shots. To troubleshoot these problems, it is important to thoroughly check the material used, adjust mold temperature, set appropriate vacuum, and check for mold deflection.

Increasing pack and hold times and reducing injection speed can also help to address these issues.

Weld Lines:

Weld lines occur in plastic parts when two or more melt fronts come together and meet in the middle. These lines can weaken the structural integrity of the final product, leading to potential quality issues.

Sink Marks:

Sink marks are depressions or dents on the surface of the molded part, often caused by uneven cooling or excessive packing pressure. Addressing these marks is crucial to maintain the visual appeal and functionality of the plastic component.

Warping:

Warping is a common issue in plastic injection molding where the final part deviates from its intended shape due to inconsistent cooling or improper mold design. This can result in dimensional inaccuracies and product rejection.

Air Traps:

Air traps occur when air becomes trapped within the mold cavity during the injection process, leading to unsightly voids or bubbles in the final product. Identifying and eliminating these traps is essential to produce high-quality plastic parts.

Short Shots:

Short shots are incomplete mold fillings that result in missing sections or insufficient material in the final part. Understanding and addressing the root causes of short shots is critical to ensure the uniformity and structural integrity of the molded components.

Troubleshooting Common Issues With Plastic Injection Molding Machines

Troubleshooting Injection Molding Issues

When troubleshooting common issues with plastic injection molding machines, it’s crucial to carefully check the material for any contamination and adjust the mold temperature and vacuum settings accordingly. Additionally, examining for mold deflection and ensuring appropriate settings can help rectify problems effectively.

Regular maintenance and adjustments are key to preventing defects and ensuring efficient production.

When it comes to plastic injection molding, it’s common to encounter various issues that can affect the quality and efficiency of the process. Troubleshooting these issues is crucial to ensure smooth production and minimize downtime. In this section, we will discuss some common problems that you may encounter during the injection molding process and provide solutions to effectively troubleshoot these issues.

Check Material Contamination

Material contamination is one of the primary causes of defects in plastic injection molding. It can lead to various issues such as poor surface finish, discoloration, and weakening of the final product. To troubleshoot this issue, it is essential to thoroughly check the material used for the process for any kind of contamination.

Here are some steps you can take to address material contamination:

  1. Ensure that the storage and handling of raw materials are done in a clean and controlled environment.
  2. Inspect the material for any foreign particles or impurities before using it in the machine injection moulding.
  3. Clean the hopper, feed throat, and screw of the machine regularly to prevent the buildup of contaminants.

Increase Mold Temperature

Mold temperature plays a crucial role in the injection molding process. Insufficient or improper mold temperature can result in issues like sink marks, warping, and poor part quality. Therefore, setting the appropriate mold temperature is essential for troubleshooting these issues.

To increase the mold temperature, you can:

  • Adjust the temperature settings on the mold temperature controller.
  • Check for any blockages or malfunctions in the cooling channels of the mold and rectify them.
  • Consider using a mold release agent or lubricant to improve heat transfer and prevent sticking.

Set Appropriate Vacuum

Vacuum is commonly used in plastic injection molding to remove air or gas trapped in the mold cavity. Insufficient vacuum can lead to defects like air traps and poor part fill. To troubleshoot this issue, it is important to set the appropriate vacuum level.

Here’s what you can do to set the appropriate vacuum:

  • Check the vacuum system for any leaks or blockages and repair them if necessary.
  • Adjust the vacuum level using the controls provided on the plastic molding machine.
  • Ensure that the mold vents are clear and functioning properly to facilitate proper vacuum evacuation.

Check For Mold Deflection

Mold deflection can occur due to various reasons such as excessive clamping force, inadequate mold support, or worn out mold components. This issue can negatively impact part quality and consistency. To troubleshoot mold deflection, it is important to identify and address the underlying causes.

Here are some steps you can take to check for mold deflection:

  1. Inspect the mold for any signs of wear or damage and repair or replace the affected components.
  2. Ensure that the clamping force is properly calibrated and not exerting excessive pressure on the mold.
  3. Provide adequate support to the mold to prevent deflection during the injection molding process.

By taking the necessary steps to troubleshoot common issues, you can optimize the performance of your plastic molding machine and achieve high-quality, defect-free products.

Common Defects In Injection Molding

In plastic injection molding, common defects such as weld lines, sink marks, warping, air traps, and short shots can occur. Troubleshooting these issues involves checking for material contamination, adjusting mold temperature and vacuum, and inspecting for mold deflection.

Burn Marks:

Burn marks are one of the common defects in plastic injection molding. These marks appear as discolored areas on the surface of the molded plastic and are often caused by excessive heat or resin degradation. When the resin in the mold gets overheated, it can cause the material to burn, resulting in brown or black marks.

Vacuum Voids:

Vacuum voids are another common defect that can occur during plastic injection molding. These voids are gas trapped within the molded plastic, creating small air pockets or bubbles. They can be caused by inadequate venting or improper material flow. Vacuum voids can compromise the strength and integrity of the molded part.

Warping:

Warping is a defect that causes the molded plastic part to deform or twist. It occurs due to uneven cooling or uneven material distribution within the mold. This defect can be minimized by optimizing the cooling system, adjusting the mold temperature, and ensuring balanced material flow.

Sink Marks:

Sink marks are depressions or dents on the surface of the molded plastic part. They happen when the material cools and shrinks unevenly, resulting in localized areas of reduced volume. Sink marks can be caused by improper gating, inadequate packing pressure, or insufficient cooling time. To eliminate sink marks, proper packing and cooling parameters need to be set.

Jetting:

Jetting is a defect that occurs during the machine injection moulding process when the molten plastic forms a visible stream or jet as it enters the mold cavity. This defect results in poor surface finish and reduced part quality. Jetting can be caused by high injection speeds, narrow flow paths, or improper gate design. Optimizing the gate design and adjusting the injection speed can help minimize jetting.

Flow Lines:

Flow lines are lines or streaks visible on the molded plastic surface, indicating the path of molten plastic flow. These lines can be caused by inconsistent material flow, improper gate design, or inadequate mold temperature. Flow lines can lead to reduced part strength and compromised aesthetics. To avoid flow lines, it is important to optimize material flow, gate location, and mold temperature.

Troubleshooting Lubrication Failure on Injection Moulding Machines (4)

Troubleshooting Mold-related Problems

Mold-related problems can significantly impact the quality and efficiency of plastic injection molding machines. Effective troubleshooting of these issues is essential to maintain production consistency and minimize downtime. Here, we’ll explore common mold-related problems and their troubleshooting techniques.

Misalignment

Misalignment within the mold can lead to subpar product quality and potentially cause damage to the plastic molding machine. It is crucial to address misalignment promptly to prevent further issues. Common indicators of misalignment include uneven parting lines and excessive wear in specific areas of the mold.

Wear

Wear in the mold can result from prolonged usage, leading to compromised product precision and potential part defects. Regular inspection of molds for signs of wear, such as surface erosion and dimensional inaccuracies, is imperative. Addressing worn molds promptly through maintenance or replacement is key to preventing production disruptions.

Improper Cooling

Optimal cooling is critical for achieving uniform part quality and minimizing cycle times. Inadequate cooling can result in warping, sink marks, and other defects. Monitoring and adjusting cooling parameters, such as coolant flow rate and temperature differentials, are essential for troubleshooting cooling-related issues.

Preventing Molded-in Stress

To prevent molded-in stress in plastic injection molding machines, it is important to carefully check for any contamination in the material, adjust the mold temperature, set proper vacuum, and inspect for mold deflection. Proper troubleshooting techniques can help address common issues and ensure quality production.

Lower Injection Velocity

One of the key factors that contribute to molded-in stress in plastic injection molding is the injection velocity. When the machine injection moulding velocity is too high, it can result in excessive shear and heat generation, leading to stress and related defects in the molded parts. To prevent this issue, it is important to lower the injection velocity to a level that ensures proper filling of the mold cavity without causing excessive shear. By carefully controlling the injection velocity, you can minimize the chances of molded-in stress and improve the overall quality of the molded parts.

Increase Mold Temperature

The mold temperature is another critical parameter that can impact the occurrence of molded-in stress in machine injection moulding. When the mold temperature is too low, it can cause rapid cooling of the molten plastic inside the mold cavity, resulting in internal stresses in the molded parts. To prevent this, increasing the mold temperature to an optimal level can help slow down the cooling process, allowing the molten plastic to flow and solidify more evenly. This helps minimize the development of internal stresses and improves the structural integrity of the molded parts.

Here’s a table summarizing the steps for preventing molded-in stress in plastic molding machine:

Prevention MethodDescription
Lower Injection VelocityAdjust the injection velocity to a suitable level to prevent excessive shear and heat generation.
Increase Mold TemperatureRaise the mold temperature to slow down the cooling process and minimize the development of internal stresses.

By implementing these preventive measures, you can significantly reduce the occurrence of molded-in stress and improve the overall quality of plastic molding machine parts.

A Practical Guide to Injection Molding Plastics Engineering (3)

Final Thought

In troubleshooting common issues with plastic injection molding machines, it is crucial to address each problem with precision and attention to detail. By checking the material, mold temperature, and injection speed, the potential for defects and issues can be significantly reduced.

Implementing these remedies will lead to improved efficiency and product quality for the injection molding process.

 

Frequently Asked Questions On Troubleshooting Common Issues With Plastic Injection Molding Machines

What Are Five Common Problems With Injection Molding Of Plastic Parts?

Common problems with injection molding of plastic parts include weld lines, sink marks, warping, air traps, and short shots. These issues can be addressed through measures like adjusting injection pressure, increasing packing pressure, and controlling mold and melt temperatures. Regular maintenance and thorough material checks are also crucial.

How Do You Troubleshoot An Injection Molding Machine?

To troubleshoot an injection molding machine, follow these steps: 1. Check for material contamination. 2. Increase the mold temperature. 3. Set the appropriate vacuum. 4. Check for mold deflection. 5. Reduce melt temperature, mold temperature, and injection speed to prevent defects like burn marks, voids, warping, and sink marks.

What Troubleshoots Are Seen In Case Of Injection Moulding?

Common injection molding troubleshooting includes reducing melt temperature, reducing mold temperature, reducing injection speed, and increasing pack and hold times. Other common issues include burn marks, vacuum voids, warping, sink marks, weld lines, jetting, and flow lines. To troubleshoot an machine injection moulding, check for material contamination, increase mold temperature, set appropriate vacuum, and check for mold deflection.
 
It is also important to lower injection velocity to prevent molded-in stress and part cracking.

What Are Common Defects When Doing Injection Molding?

Common defects in injection molding include burn marks, vacuum voids, warping, sink marks, weld lines, jetting, and flow lines. These can be prevented by adjusting melt and mold temperature, injection speed, pack and hold times, and reducing melt temperature. Troubleshooting also involves checking for mold deflection and material contamination.

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Frequently Asked Questions

Daoben has the SOP (Standard Operation Procedure) and all the production steps must follow up this SOP. Every machine needs at least automatic running over 72 hours and must be inspected carefully before shipment.

Actually, the delivery time of the machines is depended on the machine options. Normally, the delivery time of a standard machine could be within 1-2 months.

12 months warranty after shipment for mechanical parts, hydraulic parts, and electric components excluding the screw and barrel 6 months (not including use for recycled material or reclaimed material).

Yes, Daoben will provide one set of standard spare parts to the customer including a heater, filter, screw head, screw washer, checking ring, sealings, etc.

Surely, we have experienced technical engineers for oversea service, they would help you install machines and support training to workers also. Currently, we provide visits online by video call for COVID-19.

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