8 Common extrusion problems and their possible solutions

High motor amperage, uneven flow, rough surface, and interrupted material output are some of the problems encountered in the plastic nail mold process.

It is common in any plant to have to troubleshoot during production.  However, addressing these issues in an inefficient, rapid, and undocumented way leads to increased uncertainty and downtime. Moreover, this lowers product quality and profitability.  

What are the most common problems in the extrusion process?

This article will address eight typical problems in the extrusion process, discussing their causes and the possible way forward to solve them.

1. High motor amperage:

The possible causes for this event can be:

• low resin temperature
• Moreover, poor selection of the plastic nail mold
• blockages in the screens
• Furthermore, engine capacity or contamination within the system

Possible solutions include in the first instance increasing the temperatures and checking the electrical output of the heaters. Similarly, it also changes the perforated plate grids.

In terms of resin selection, the possibility of working with a low molecular weight polymer should evaluate. It is also necessary to evaluate the engine, diagnose its condition and see if it requires maintenance, or slow down. The screw should also remove to check for any contamination.

2. Interruption of plastic nail mold material outlet:

Possible causes of this issue can be hopper caking, bridging, clogging, or problems with the cooling jacket. Possible solutions include reducing the temperature in the feed zone. Furthermore, this uses a ‘cram’ type feeder or extrudes the plastic nail mold into the pellets in a separate operation.

It is also a good option to see the rate of degradation or crosslinking of the resin in the mesh package. Moreover, it is to check that the cooling jacket is not working on the solid areas.

3. Uneven flow of plastic nail mold temperature:

Causes can be unsuitable temperatures, contamination, or melt transport problems. To deal with this problem, a range of activities is opened that can bring us closer to a good outcome: increasing the temperatures in the heating zone can be a way, removing the internal mixer if it is in use.

Lowering the temperature of the feeding zone in case of bridging, cleaning the mesh package, checking for possible obstructions in the hopper, removing the screw and checking for contaminants, or increasing the product’s traction pressure for plastic nail mold.

4. No plastic nail mold material output:

This involves factors relevant to the hopper, the screw, the mesh pack, and/or the extrusion die. To correct this problem, one or more of the following actions must carry out:

• open the distribution valve of the hopper
• use a soft bar to dislodge the bridging
• Moreover, put vibration pads and
• Furthermore, use an agitator in the feeding zone of the hopper.

Other activities that can address this problem of plastic nail mold have to do with the screw. Similarly, it may be necessary to change the terminals of the screw drive motor, make it repair, clean it, use a low friction coating or have spare parts already manufactured and ready to mount. On the other hand, it would also work to dislodge the lock from the feed opening.

5.  Melted particles in the extrude:

The origin of the problem surely comes from the mesh package, an incorrect setting of temperatures, contamination, among others. To repair this affectation, it is necessary to check first if there is any hole to consider in the mesh package to replace.

Subsequently, measures are easy to take such as increasing the temperature in the compression and dosing zones of plastic nail mold.

6. Colorless extrusion profile:

The reason for a homogeneous colorless profile involves polymer degradation, poor or incorrect mixing, and improper die design.

The three alternatives to solve this circumstance can be: first reduce the temperatures or speed of the screw, two, add a mixing head or concentrators to achieve a homogeneous mixture of the pigment, and/or three, optimize the flow in the die or use a Smaller or slower extruder for material output.

7. Rough surface, lines in the die or fracture of the melt:

The root of this problem is located in the isolated zone of the die and the resin. To solve this type of issue, the die design and/or its temperature must be modified.

The melt temperature must be lowered and/or a material with a lower molecular weight or with a broader molecular weight distribution must be common.

8. Benefit of Sharkskin:

This type of defect directly comes with the given extruder, the raw material, and/or the operation. The actions that can solve this problem of plastic nail mold on increasing the melt and die temperature, increasing the resin outlet “gap”.

Using a resin with a lower modulus or with wide molecular weight distribution, and for operational issues, Screen packages should be changed and backpressure and extrusion speed reduced.

9. Plastic nail mold injection system

Both stages of plastic nail mold operate like a conventional injection process, which is easier to configure, maintain and operate continuously, compared to more complex co-injection systems. It is manufactured from two standard molds, designed to produce the individual layers in a precise and repetitive way.

For under landers, the main advantage is significant cost savings, as the thickness of layers incorporating high-cost additives is easy to control. For example, in applications that incorporate titanium dioxide for pigmentation, it has been possible to reduce costs by 15%.

Not only think of applications of for barrier but for example also in pearlescent colors or pearlescent in the inner layer, over-molded with a layer of PET translucent outside, same that gives the preform a glossy appearance.

In our industry, according to studies by the Institute for Plastics Processing almost 7% of the production time is due to damage to the plastic cosmetic mould. In the same study, it is stated that only 30% of plastic injection companies carry out preventive maintenance at fixed intervals and only a third of these (10%) carry out maintenance according to the history of the mold.

Based on these alarming data, this article presents 10 useful ideas for keeping molds in proper service condition.

1. PREVENTIVE MAINTENANCE SCHEDULE FOR PLASTIC COSMETIC MOULD

It must be recognized that in these times there are already companies in Latin America that are applying the preventive strategy. However, most are still supported by corrective or “fire” action, which is nothing more than the reaction to unanticipated interruptions that can cut demand production in half.

Moreover, adequately following each stage of preventive maintenance with scheduled and non-emergency shutdowns, plastic cosmetic mould allows for effective and constant production over time. All this is linked to the fact that having interruptions in the workshop and production schedule, the risk is low.

Otherwise, the failure will enter the waiting room for the machining center and technical resources, which has no consequences other than productive inefficiency and low profitability of the product.

2. COOLING CIRCUIT OF PLASTIC COSMETIC MOULD

Water treatment is a potential bottleneck that we must tackle. A cooling circuit must not only recirculate the water to keep the inlet and outlet temperature of the chiller controlled. The cooling lines for an injection plant must have an entire filtering system.

This allows reducing the oxide in the cooling channels of the plastic cosmetic mould as much as possible.

As a micro reservoir adheres to the wall of the cooling channel, a reduction in the diameter of the channels begins. It is easy to check the flow rate in the check valve system. Moreover, it comes between the molds, the waterline.  Here the pressure drop and the thermal difference between the inlet and outlet of the mold is easy to calculate.

Another functional method is to have the measurements of the start of the mold. It is to have a comparison pattern and to establish an accurate diagnosis.

3. DEEP CLEANING OF THE PLASTIC COSMETIC MOULD

This tip directly connects with the first point. It has already become a pure theme of the plastic cosmetic mould as an isolated control volume of the system. Each plant has its own strategy for cleaning molds. Moreover, this ranges from the classic to the application of high-tech equipment.

Moreover, the mold maintenance team must be very clear. Without this stage, the mold will lose its useful life and productive level. To clean the tempering channels, a jet detergent solution is common to mechanically remove oxide deposits that are not otherwise achievable due to their geometry.

There are several recipes and cleaning kits. However, the hydrochloric acid solution with corrosion inhibitor and diluted in water is a remarkable success in the industry. Despite being functional, the search for a more competitive product forces plastic cosmetic mould maintenance leaders to streamline their processes.  This translates into investment in technology.

Why ultrasonic mold cleaning is preferred?

Ultrasonic mold cleaning has advantages in:

• reducing maintenance times
• improving cleaning effectiveness
• reducing damage to mold components

This consists of immersing the mold in an electrolytic bath at 20 kHz.  This generates cavitation in the fluid. Moreover, it generates better removal of the adhered material without affecting the edges of the mold or affecting the coating layer of the same.

4. CHANGING CONSUMABLE COMPONENTS

For both technologies described in point two, it is important to be clear that nipples, screws, nuts, plugs, etc., are consumable components and large accumulators of deposits, therefore, with maintenance, new ones should be installed.

5. CLEANLINESS OF PLASTIC COSMETIC MOULD SURFACES

At the end of production, the plastic cosmetic mould must be free of any adhering plastic residue. It should be regardless of the type and quantity of material. For this, the chemical attack must be common which, depending on the aggressiveness of the polymer, will be more or less concentrated.

For this idea, it is also important to remove the lubricant residues from the moving side of the mold with a degreaser.

6. CHANNEL OR HOT RUNNER SYSTEM

In summary, after a demanding productive run, the thermocouples, cartridges, and heating bands should be checked with a millimeter to compare with the datasheet that is within the normal range.

This is a very specialized system that must be supported by the system supplier since assembly and maintenance training should be carried out with the delivery of the plastic cosmetic mould.

7. SLIDE GUIDES FOR CLEANING

In the moving half, the guides require particular care. On the one hand, it is important to clean with acid and resin-free lubricants, and, on the other, to check the cylinder seal level in case of having hydraulic actuators on the slides and inserts.

8. CONTACT BETWEEN NOZZLE AND MATERIAL INLET TO THE MOLD

This area is subject to high loads during operation. There is a free space where the material can flow and relieve pressure.

However, this burr must not exceed the limits; if this happens, the area must be correct or the temperature profile configured in the machine must be reviewed.

9. PROPER PLASTIC COSMETIC MOULD HANDLING

The problem of damage provided to the plastic cosmetic mould lies, especially in operating and assembly errors. This problem is also attributed to poor communication between the design and maintenance teams.

Everything clearly starts from the fact that each mold is unique and it is not correct to generalize the maintenance process. It must start from a general protocol. Moreover, each mold must have its resume documented and the workshop must have adequate equipment.  Hence, it allows the mold to handle correctly.

10. PLASTIC COSMETIC MOULD INSTRUMENTATION

The production documentation is useful. Moreover, it is to find out that there is a problem. Furthermore, the information available will be much more effective if we have a plant that really applies the concept of Industry 4.0.

This is possible by implementing sensors for temperature, pressure, humidity, flow rate, number of cycles, the exact time the mold was open, etc. in each mold.

This is the beginning of a plastic cosmetic mould, allowing establishing the cause and/or root of the problem, effective maintenance times of the mold, and making correct decisions in real-time.

During household appliance injection mold processes, the change of materials is important. Even when there is already a designed plastic household appliance, its respective mold built and everything ready to start production.

Moreover, we decide that the household appliance does not come in ABS, but in Nylon. And the new material comes from the manufacturer and the new resin is common.

Changing the plans, in this case making a variation of the resin to be common, is not at all recommended prior to the start of production unless it is absolutely necessary, there are some important considerations that must be taken into account to carry it out in the best possible way.

What do you need to know to make household appliance injection mold?

To ensure that an injection molding project for household appliance injection mold produces components within specification. It is necessary that both the technical area and the household appliance design. Further, mold manufacture takes into account the following indications if they decide to change resin:

1. Shrinkage rates: Different resins will have different shrinkage rates. For example, materials like ABS and polycarbonate shrink in the range of 0.4% to 0.6% per linear dimension. Others like nylon and acetyl have shrinkage rates of around 2.2% to 3% per linear dimension.

How to make a change in household appliance injection mold?

Consequently, making a change from ABS to Nylon will result in a smaller final component than the original. In many cases, this may not be an inconvenience. However, if this new component is a household appliance injection mold of a pre-existing assembly, it is possible that its dimensional change could cause problems in the final coupling.

2. Specific injection points and relief surfaces: injection points and degassing surfaces are usually designed specifically for each type of resin. Switching from one material to another can cause burr problems.

Otherwise, if the point originally designed for Nylon is too small to inject ABS, defects such as burns will be seen on the product due to high shear rates, as well as unwanted flow marks around the injection point.

Use of Additives in household appliance injection mold

Some manufacturers think that the use of additives to modify properties of household appliance injection mold. Fiberglass will not have a major effect on the manufacturing process. However, in this case, the fiberglass will significantly reduce the shrinkage rate of the final component.

Likewise, fiberglass is very abrasive for mold.

Why is the change of material necessary?

The lesson is that you should make material changes if you are fully aware of the implications. This decision will have on the household appliance, its associated components, and the mold.

Having a baseline of the laminating unit’s performance allows you to understand how much wear and tear it has over its life and maintain your productivity from household appliance injection mold.

What are the tips to monitor and control the performance injection unit?

Therefore, here are major five tips to monitor and control the performance of the injection unit:

Control on the transformation process

In polymer transformation processes, mass flows are crucial. Being clear about the kilograms per hour that our process transforms is essential to evaluate costs in terms of energy consumption, productivity, heat flows, or for any estimation and performance evaluation.

In extrusion, any revision comes to this value. In injection, it is more common to talk about the number of:

• household appliance
• cycle time
• among others

Therefore the first recommendation is that in household appliance injection mold the mass flow is also appropriated as the main performance indicator.

Injection capacity of machines

Injection machines are specified for an injection capacity. This normally comes in units of volume per unit of time and, in some cases, in units of mass per unit of time, but the most common is that they refer to units of mass in polystyrene.

Moreover, there are two points to consider here. The first is that if you process a resin other than polystyrene, you have to do a density conversion at process temperature. And the second is that the data is for a back pressure that in a few cases specify.

 

Further, here is the second recommendation. At the time of starting the machine, carry out a validation of the plasticizing capacity, with the different resins that will be common at different back pressures and also at different revolutions per minute. This will serve as a zero base for your team.

Monitoring of the condition of the check valve

It is also very important to monitor the condition of the check valve throughout its service life for household appliance injection mold. As already mentioned, this is a household appliance responsible for consistency in shot-to-shot weight.

Moreover, recommendation number three is to develop a test. You can raise the pressure, simulating the pressure important for injection or even higher. It is to evaluate how much material the non-return valve allows to be returned to the screw dosing zone.

Furthermore, this comes by evaluating the forward travel of the injection unit, at maximum pressure, without letting material escape. It will depend on the resin and the process temperature. Similarly, it is also good to carry out the zero-base evaluation with different materials. It is in order to then have points of comparison in the monitoring moments.

Location of the measuring elements

The condition of the heating bands and of the temperature measuring elements for household appliance injection mold located in the barrel should also be evaluated periodically.

Further, their condition can significantly affect the stability of the process and, therefore, the consistency and efficiency in terms of mass flow and product quality.

Operation of the household appliance injection mold

As a fifth recommendation, the metrological verification of the main geometric variables of the screw and barrel present; the correct operation of the injection unit will depend on the clearances between these two elements.

Summary household appliance injection mold

In addition, collecting a history will allow refining maintenance strategies and will even provide feedback to the optimization process of designs that in the future represent greater efficiencies.

As always, the resin processed, the working conditions, the product specifications, and the production levels will make the household appliance injection mold represent a greater or lesser relevance. However, do not lose sight of the evolution of the injection unit over time.