How long do injection molding machines last?

Today, injection molding is one of the most popular and effective manufacturing processes for producing plastic parts in large volumes. You should, however; note that the tooling costs that are associated with injection molding can be expensive and thus, they should be considered as an investment. Mold development is an expensive segment in injection molding that is responsible for giving shape and form to molten plastic and requires the utmost precision and accuracy.

DENICE are exported all over the world and different industries with quality first. Our belief is to provide our customers with more and better high value-added products. Let's create a better future together.

The life expectancy of plastic injection molds can range between hundreds to over a million cycles and the durability depends on its environment, maintenance, materials, structure, molding conditions, structure design, and other factors. It's also imperative to optimize injection molding processes to avoid defects such as sink and burn marks, flow lines, and surface delamination since these defects impart damage to the mold. 

Injection molds can be maintained to extend their lifespan by inspecting, maintaining, and coating the mold, as well as ensuring that the mold operates under appropriate conditions. In this article, we explain in detail the basics of injection mold lifespan, the factors that affect injection mold life expectancy, and what should be done to increase the longevity of the mold to achieve the best results. 

You can maintain injection molds to extend their lifespans by making sure the mold meets the part's requirements, using appropriate operating conditions for the mold, periodic cleaning of the mold, periodic inspections of the mold, and using coatings for the mold.

• Make Sure the Mold Meets the Part's Requirements: This means the core and cavity of the mold should have appropriate hardness (greater than 52HRC, as a reference), so it can be used in the processing of plastic materials.
• Use Appropriate Operating Conditions for the Mold: Make sure to use the mold in the environment and in the processes it was originally planned to operate to ensure there are no additional stresses and wear sources. Using SPI classification will help with determine the appropriate operating conditions of the mold.
• Periodic Cleaning of the Mold: Exact cleaning and maintenance can vary based on the type of mold, but the most common activities include periodic cleaning, finishing, coating, and greasing of the mold. The frequency of maintenance also depends on the resin used in the injection process.  For instance, when injecting abrasive resins, such as glass-filled variants, more frequent cleaning and maintenance should be expected.
• Periodic inspections of the Mold: Related to maintenance, visual inspections of the mold in question is the bare minimum when talking about inspections. This can be done as frequently as once every few days. Checking for wear and detecting it in its early stages will save both money and future headaches.
• Using Coatings for the Mold: Coatings can help limit wear and damage to the mold. Using mold coatings has the effect of reducing the need for mold maintenance, reducing part downtime, and improving performance of the mold. Carbon-based coatings are a quite common option, especially for moving parts, due to the lubricity they add to the part. Besides the sliding wear resistance (very useful in the case of ejector pins for example), coatings can help protect against corrosion and seizure.

Mistakes That Reduce the Lifespan of Injection Molds

Injection mold damage can be indicated and in some cases increased by mistakes in the parts being made. These mistakes include sink marks, surface delamination, flow lines, burn marks, and flash. In more detail:

1. Sink Marks

Sink marks are a source of further damage that can be inflicted on the mold, further reducing lifespan. These are small depressions localized in the thicker areas of the mold and are caused by incorrect cooling time. The plastic does not cool sufficiently while it is inside the mold, an issue that is usually related to inadequate pressure inside the cavity or too much heat.

2. Surface Delamination

Surface delamination can decrease mold lifespan by increasing wear over the long term. This issue involves thin layers of materials that appear on the part surface and is caused by contamination with unintended materials or release agents. Adjusting the ejection mechanism may remove the need for the use of release agents.

3. Flow Lines

Flow lines indicate either flow rate problems or bad mold design. Flow lines are patterns or lines that appear on parts. Usually caused by varying flow rates which cause the molten plastic to solidify at different rates, this issue is fixed by adjusting injection speed and pressure in order for the cavity to be filled evenly. In more serious cases, this issue can be a sign of bad mold design, in which case the mold must be redesigned.

4. Burn Marks

Burn marks reduce injection mold lifespan over the long term with the burned material, though the overheating won't directly damage the mold. As the name suggests, burn marks are rust-colored discolorations that appear on injection mold parts and are caused by either the degradation of the plastic material (excessive heating) or inappropriate injection speed.

5. Flash

Flash introduces wear to mold clamps around where extrusion occurs, which can lead to the need for replacement clamps. Flash is a defect that occurs when molten plastic escapes the cavity, creating extrusions that stick to the finished product. Injection speed, pressure, and mold temperature should be adjusted to avoid this. Mechanical inspections of the extrusion part should also be conducted to ensure the problematic region is not permanently deformed.

If you are looking for more details, kindly visit automated Bakelite moulding machine.

SPI Mold Classifications Used to Estimate the Expected Life of a Mold

SPI (Society of Plastics Industry) mold classifications estimate the expected life of a mold by indicating how many cycles a mold can perform. The SPI Mold classification encompasses 5 classes of injection mold:

1. SPI Class 101 Mold ' Extremely High Volume

SPI Class 101 molds are expected to be used in over one million cycles, which is the case in extremely high production activities. Molds in this category are also the most expensive since they are manufactured with the highest quality material. Some properties of this class are:

• Minimum hardness of tool structure components 28 RC (RC refers to the Rockwell scale, also known as Rockwell Hardness. It's used as a unit of measure for hardness.)
• Minimum hardness of cavity and cores of 48 RC
• Guided ejection
• Slides (or sliders) should be equipped with wear plates

Note: Wear plates are used to reduce the friction caused by slider movement. Not all injection molding processes involve a sliding mechanism though. A slider (or slide, as these terms are used interchangeably) refers to a sideways movement in the injection molding process used to form complex geometries.

A more complete explanation of how and where wear plates are used can be found here.

2. SPI Class 102 Mold ' High Volume

Class 102 molds are expected to be used in medium to high production manufacturing. The number of cycles is expected to be in the range of 500,000 ' 1 million. Most properties of class 101 apply here too, with some differences such as plated cavities and corrosive resistant temperature control channels not being mandatory.

3. SPI Class 103 Mold ' Medium Volume

Class 103 handles medium-volume production manufacturing activities with cycles under 500,000 and not very stringent requirements, such as:

• Detailed tool design is recommended
• Cavity and cores must have minimum 28 RC
• Tool structure components should have a minimum hardness of 18 RC

4. SPI Class 104 Mold ' Low volume

Class 104 is aimed at molds expected to last less than 100,000 cycles, characteristic of low-volume manufacturing. The base of these molds can be made of aluminum and mild steel. The same can be applied to cavities and cores.

5. SPI Class 105 Mold ' Prototypes

Reserved for less than 500 cycles, class 105 usually refers to mold prototypes, which are the least expensive type out of this list. They can be manufactured out of cast metal or even epoxy, the focus being the manufacture of mold in the least expensive way possible.

Remember that SPI mold classifications indicate, but do not guarantee, quality. Aluminum molds could last for years and even decades while it is possible for class 101 molds to rapidly decay, due to inappropriate maintenance. Activities that seek to prolong lifespan are of such vital importance to the injection molds regardless of the classification of the molds.

Contact us to discuss your requirements of precision Bakelite injection moulding system. Our experienced sales team can help you identify the options that best suit your needs.