Solution for warpage issues and plastic hose bubbles in injection molding

Solution for warpage issues and plastic hose bubbles in injection molding makenica.com/solution-for-warpage-issues-and-plastic-hose-bubbles-in-injection-molding April 16, 2021

MOLD WARPING: Common Issues and Warpage Control Solutions In plastic injection molding service, warpage occurs when the molded part's intended form is distorted during the cooling process. Mold warping can result in the component folding, bending, twisting, or bowing.

To figure out what's causing molding warpage in the injection molding service, you'll need to know the following: How much should the components warp?

What is the most common direction for warpage to occur?

What does this mean in terms of your parts' mating requirements?

There are three fundamental causes of warpage in plastic injection molding service: cooling rate, cavity pressure, and fill rate. However, several factors may contribute to mold issues.

The following are some of the most popular mold warping issues and their solutions in the injection molding service:

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Issue: Insufficient Injection Pressure or Time If the injection pressure is insufficient, the plastic material will cool and solidify before the mold is filled. The packaging process is sped up if the mold injection hold time is inadequate.

If the mold injection pressure or hold time is insufficient, the molecules will not be limited, allowing them to travel about freely during the cooling process. As a result, the component cools at various speeds, causing mold warpage.

Solution: Increase mold injection pressure or hold time Issue: Inadequate Residence Time The amount of time the resin is exposed to heat in the barrel is called residence time. The molecules cannot absorb heat evenly in the material if the residence time is insufficient.

Before the mold is properly packed, the under-heated material may stiffen and cool. Mold warpage occurs as a result of the molecules shrinking at various rates during the cooling process.

Solution: Extend the residence time by extending the cycle's cooling operation. This will ensure that the material has enough time to dry and will prevent mold warping.

Issue: Barrel temperature is too low The resin will not heat up to the correct flow temperature if the barrel temperature is too low. If the resin is forced into the mold before it reaches the correct flow temperature, it can solidify before the molecules are properly packed. Mold warpage is caused by the molecules shrinking at different rates.

Solution: Increase the temperature of the barrel. Ensure that the melt temperature of the material is consistent with the shot size.

Issue: Mold temperature is too low If the mold temperature isn't high enough, the molecules will solidify at various rates before packaging, triggering mold warpage.

Solution: Increase the mold temperature according to the resin supplier's recommendations and change as required. Operators should allow ten cycles for every 10degree shift to enable the process to re-stabilize.

Issue: Uneven Mold Temperatures Mold warpage in the injection molding service is caused by unequal mold temperatures, which cause molecules to cool and shrink at different rates.

Solution: Check all mold surfaces that come into contact with molten resin. Using a pyrometer, determine whether there is a temperature difference of more than 10 degrees Fahrenheit. A variation in shrink rates and mold warping can occur if the temperature 2/6

difference between any two points is greater than 10 degrees, even between the mold halves.

Issue: Nozzle temperature is too low, which is a problem.

The nozzle is critical to examine since it is the final transition from the barrel to the mold.

The resin's travel time can be slowed if the nozzle is too cold, preventing the molecules from being correctly packed. Mold warping occurs in the injection molding service when molecules do not pack equally and shrink at different rates.

Solution: First, the injection molding companies operator should check to see if the nozzle configuration is interfering with the flow rate, as certain nozzles aren't designed for the resin. If the proper nozzle for the flow and resin is being used, the operator can lower the nozzle temperature by 10 degrees Fahrenheit before the mold warpage ends.

Issues: Inadequate Flow Rate For a variety of normal flow speeds, resin manufacturers have specific formulations. The operator can choose a simple flow material for thinly walled products and a stiffer material for thicker walled products based on the normal flow rates.

For thin or thick-walled products, the operator in the injection molding companies should use the stiffest material available, as a stiffer flow increases the mold's physical properties.

The more rigid the material, however, the more difficult it is to drive.

Due to the difficulty in pushing the material, it can solidify before it can be fully packed.

Mold warping occurs as a result of varying molecule shrink speeds.

Solution: Operators can consult with the resin supplier to decide which material has the stiffest flow rate while avoiding warpage.

Issue: Process Cycle inconsistency The processing period is shortened if the operator opens the gate too quickly and the product is expelled before the material has had enough time to cool evenly. Uncontrolled shrinkage rates can result from an inconsistent process cycle, causing mold warping.

Operators should use an automated phase loop and only intervene if there is an emergency. Above all, all injection molding companies' workers should be taught the importance of maintaining predictable process cycles.

Issue: Inadequate Gate Size An insufficient gate size slows the flow rate of molten resin as it attempts to move through. If the gate is too thin, the plastic filling rate can slow down, resulting in a significant pressure loss from the point of the gate to the last point to fill. The molecules can be subjected to physical stress as a result of this limitation. After injection, this stress is released, resulting in mold warp.

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Solution: The size and shape of the mold gate should be configured using data from the resin supplier. Increasing the gate size as much as possible is usually the best option for mold warpage in the injection molding service.

Issue: The Location of the Gate Mold warping in the injection molding service can be caused by various factors, including gate size and position. If the gate is located in a thin region of the component geometry and the last-point-to-fill is situated in a much thicker area, the filling rate will change from thin to thick, resulting in a significant pressure drop.

A short/inadequate fill may occur as a result of this substantial pressure loss.

Solution: To achieve the finished product's mechanical part properties, the mold can need to be redesigned to shift the gate position. Additional gates may be needed in some cases to minimize pressure loss and molded-in tension.

Issue: Lack of Ejection Uniformity If the ejection system and press on the mold aren't tested and modified regularly, they may malfunction, resulting in unequal ejection force or part perpendicular inaccuracies.

As the mold attempts to avoid ejection, these malfunctions can cause stress. After the mold has been ejected and cooled, the stresses cause it to warp.

Solution: Operators of the injection molding companies should check and change the ejection mechanism and press regularly. All adjusting devices should be locked down to ensure that components are properly lubricated and that slipping does not occur.

Issue: Geometry of the Product A problem with product geometry may also cause mold warpage. Part geometry can result in a wide range of filling patterns, causing plastic shrinkage to vary across the cavity.

Warpage may occur if the geometry produces an inconsistent shrink rate, mainly if there is a high-pressure loss in thin vs. thick wall stock areas.

Solution: To find the best solution, talk to custom plastic injection molding companies specializing in engineering-grade resins.

Switch to the experts at Makenica- one of the top injection molding services, if you're having problems with warpage in your injection molding that you can't seem to fix.

DEALING WITH PLASTIC HOSE BUBBLES A variety of issues are often found in the injection molding companies during the extrusion of plastic pipes. Apart from cracks, black bars, moiré, and other issues on the surface of the high-pressure hose, there are also bubbles in the high-pressure hose.

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The plastic hose produces bubbles, which are usually related to the moisture content of the resin and modifier. If the humidity level in the environment is too high, the plastic hose can bubble and develop a porous structure.

To solve this issue, all that is needed is to keep the raw materials' moisture content within the effective range and keep the normal moisture content of the raw materials between 0.3 and 0.5 percent.

As the vertical injection molding machine's raw materials are combined, the high-speed mixer can only extract a portion of the water. Furthermore, careful attention should be paid by the injection molding companies to the selection of stacking locations when storing raw materials, particularly when it is raining, avoiding moisture in the raw materials.

Since wet and cold PVC epoxy resin cannot be baked by fire right away, it isn't easy to dissolve. If it needs to be fried, thickeners may be added ahead of time. The mixed raw materials can also be air-dried before the application after a few days of rainy storage.

Suppose bubbles are discovered in the vertical injection molding machine's plastic hose.

In that case, the mold temperature should be reduced slightly, and the extrusion rate should not be too high to eliminate the bubbles.

The driving force and the heating element of the injection molding machine can be split into two parts for environmental conservation and energy savings.

Part of the heating system that is environmentally friendly and saves energy. The majority of environmental protection and energy savings in the heating component were achieved using an electromagnetic boiler, with environmental protection and an energy-saving average of 30 percent to 70 percent compared to the old resistor circle.

Furthermore, when the forming water is cooled, it is not recommended to cool the water too quickly. The plastic hose can easily cause bubbles in such a situation.

There's also a good chance that the solution contains too many aeration tanks or has bad exhaust pipes, resulting in residual vapor in the plastic hose, so live with it! The extrusion process is the leading cause of scorch marks and wrinkles on the plastic hose. The plastic pipe extruder's extruder screw diameter is 4563 mm, the aspect ratio is 20, and the compression ratio is 34.

The extrusion temperature of a plastic hose usually is lower than a rigid plastic pipe's extrusion temperature during the extrusion process.

The plastic hose of the vertical injection molding machine will have scorch marks if the mold temperature is too high; if the mold mouth's temperature is too low, the surface of the plastic hose will be dull.

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The plastic hose surface is very likely to trigger wavy lines if the extruder screw speed is too slow. The vertical injection molding machine's plastic hose is very vulnerable to slub problems if there is extrusion pulsation.

The friction between the surface of the plastic hose and the abrasive tool will create scorch marks on the surface of the craft if the screw speed of the extruder of the vertical injection molding machine is too high. As a result, the extruder's screw speed ratio can be set between 20 and 40 revolutions per minute.

When the traction belt speed is too high or too slow, the vertical injection molding machine's plastic hose will fold horizontally and vertically, and the surface layer will wrinkle easily.

Often known as an injection molding machine or injection machine, an injection molding machine is a type of injection molding machine. This is the main forming machinery and equipment for forming thermosetting plastics into various plastic products using plastic forming molds. It is divided into three types: column, vertical, and all-electric.

The injection molding machine heats the plastic, then applies high pressure to it, causing it to blast out and fill the mold cavity. As a result, the traction rate must be calibrated to account for the plastic hose's various diameters.

E.g., the lead rate for plastic hoses with a diameter of 9-16 mm can be set to 8-12 m/min, while the lead rate for plastic pipes with a diameter of 21-20 mm can be set to 4-8 m/min.

When extruding plastic hoses in the injection molding companies, keep an eye on the temperature of the vertical injection molding machine's abrasive equipment, the speed of the extruder screw, and the speed of the traction belt.

Only in this manner will scorch marks and wrinkles on the extrusion surface of the vertical injection molding machine's plastic hose be avoided by the injection molding companies.

Read More : TROUBLESHOOTING – LIQUID SILICONE RUBBER INJECTION MOLDING

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