If you work in injection molding, you know what happens after the mold opens.There is the finished product.And then there is the sprue.
Depending on the mold design, runners and other solidified plastic pieces may also need to be removed from the finished parts. They are not part of the product, but they are still valuable plastic material that has already passed through the production process.
Instead of leaving these pieces in a corner of the workshop, many factories collect them for recycling.The first step is often size reduction.
In this customer's factory, a Longhe 【plastic crusher】 is being used to crush plastic sprues generated during injection molding.The application is simple: take the relatively large, rigid sprues and reduce them into smaller pieces that are easier to collect, transport and send into the next recycling or regrinding process.
A sprue is the solidified plastic remaining in the main passage through which molten plastic enters the mold.After the injection molding cycle is completed, the sprue is separated from the finished part.
Depending on the mold structure, the production waste may also include runners and gates.For a factory running injection molding machines continuously, these pieces can accumulate surprisingly quickly.
One molding cycle may produce only a small amount.Multiply that by hundreds or thousands of cycles, and the sprue becomes a regular production waste stream.
That is why 【plastic sprue recycling】 is not just a waste-management issue. For many manufacturers, it is also a material-handling and production-cost issue.
The original sprue is usually not in a convenient form for storage or further processing.It may be long, thick and irregular.Crushing changes its size and shape.After passing through the crusher, the material becomes smaller plastic pieces that are easier to collect and handle.
The basic process looks like this:Injection molding → sprue separation → crushing → collection → regrinding or further recycling
The crusher performs the mechanical size-reduction step.What happens afterward depends on the plastic material and the factory's recycling process.For suitable thermoplastic materials, the crushed sprue may be processed into regrind and potentially returned to production under controlled conditions.
There is one thing worth emphasizing before putting a pile of sprues into any recycling machine:Know what plastic you have.
A factory may run several types of resin, such as PP, ABS, PC, PA or other engineering plastics.If different materials are mixed together, crushing them does not magically separate them afterward.The crusher makes the pieces smaller. It does not identify the resin.
For this reason, injection molding factories normally benefit from separating production scrap by material before crushing.Color can also be important when the recycled material will be reused in production, particularly for products where appearance matters.A clean, well-separated sprue stream is much easier to manage than a mixed pile of unknown plastic.
This is where the customer's actual production process becomes important.Crushed sprue can be collected as plastic regrind and then processed further.
For some injection molding applications, properly controlled regrind can be mixed with virgin material and reused.For other applications, the crushed plastic may be sold to a recycling company or sent to another processing line.
The appropriate route depends on:
Plastic type
Product requirements
Material cleanliness
Previous processing history
Required regrind size
Factory recycling procedures
So when selecting a 【sprue recycling machine】, it is useful to know what the crushed material needs to become afterward.
There is no single answer.This is one of the most important points when selecting a crusher.A factory does not necessarily need the smallest possible particle size.Instead, the output should match the requirements of the next process.
If the crushed sprue will go through another recycling machine, the downstream equipment may determine the required size.If the material is going to be reused as regrind, the factory's feeding and processing system will determine the suitable particle size.
The screen therefore needs to be selected according to the application.Smaller is not automatically better.The right size is the one that works efficiently with the next step.
These terms are often used together because both can become injection molding scrap.A sprue is the main channel connecting the injection molding machine nozzle to the runner system.A runner carries molten plastic from the sprue toward one or more mold cavities.
After molding, both become solidified plastic waste.Both can potentially be crushed for recycling, but their dimensions can be quite different.A small runner system may produce relatively thin pieces, while a large sprue can be much thicker.
That difference matters when selecting the feeding opening and cutting configuration of a plastic sprue crusher.
A common mistake is to choose the machine based only on the plastic name.For example:“We use PP, so we need a PP crusher.”
That information is useful, but it is not enough.Two factories may both process PP and have completely different crushing requirements.One may produce thin, short runners.Another may produce large and thick sprues.One may generate 30 kg of scrap per day.Another may generate several hundred kilograms.
The machine selection should therefore consider:
Material: PP, ABS, PC, PA or another plastic
Maximum size: largest sprue or runner that needs to enter the machine
Shape: short runner, long sprue, molded parts or mixed scrap
Capacity: amount generated per hour or day
Output: required particle size after crushing
This is why Longhe can carry out material testing with customer-supplied material.Testing the actual sprue gives a much clearer picture than looking at a generic sample.
The value of crushing plastic sprues is not complicated.The machine does not need to perform ten different processes.Its job is to reduce the size of the plastic.But that one step can make everything afterward easier.
Smaller material is easier to collect.It takes up less space.It is easier to transport.It can be more convenient to feed into downstream recycling equipment.
And when the material is clean and compatible with the production process, the crushed plastic may become a useful source of regrind rather than simply being treated as waste.For an injection molding factory, that makes a plastic recycling machine part of the production workflow rather than something sitting separately from it.
FAQ
What is the best way to recycle plastic sprues?For clean thermoplastic sprues, a common approach is to separate them by material, crush them into smaller pieces and then send the material into a regrinding or recycling process. The appropriate recycling route depends on the resin and the requirements of the final product.
Can injection molding sprues be reused?
Yes, many clean thermoplastic sprues can potentially be reused as regrind. Whether they can be returned directly to production depends on the plastic type, product requirements and the factory's processing conditions.
Can sprues and runners be crushed together?Yes, if the materials are compatible and their dimensions are within the crusher's feeding and crushing range. Sprues are often thicker than runners, so the largest piece should be considered when selecting the machine.
What machine is used to crush plastic sprues?A plastic crusher or granulator can be used to reduce the size of injection molding sprues. The suitable model depends on the sprue dimensions, material type, processing capacity and required output size.
Can a plastic crusher crush large injection molding sprues?It depends on the size and hardness of the sprue and the specifications of the crusher. The maximum feeding size should always be checked against the actual sprue dimensions. If your sprues are large or thick, sending a sample for testing is a practical way to determine the suitable model.
What size should plastic sprues be crushed to?There is no universal output size. The screen should be selected according to the requirements of the next recycling or regrinding process. If the downstream equipment requires a particular particle size, that requirement should be used when selecting the crusher screen.
Can crushed sprues go directly back into an injection molding machine?Not necessarily. Crushing only reduces the physical size of the material. The regrind still needs to meet the requirements of the injection molding process, including material compatibility, cleanliness and product-quality requirements. The factory should determine the appropriate regrind ratio and processing conditions.
Should PP, ABS and PC sprues be mixed together?Generally, they should be kept separate when the material is intended for recycling or reuse. Different resins have different properties and processing requirements. Once different plastics have been mixed and crushed together, separating them becomes much more difficult.
How do I calculate how much plastic sprue waste my factory produces?A simple starting point is to collect the sprues generated during a known production period and weigh them. For example, measure the total sprue weight from one shift or one day. This gives a practical estimate of the scrap volume that the crusher needs to handle. Production conditions can then be used to estimate the required hourly or daily capacity.
Is a small plastic crusher enough for injection molding sprues?It depends on the sprue size and production volume, not simply on the fact that the material is called a sprue. Small runners and small sprues may require a relatively compact machine, while thick sprues or large quantities of scrap may require a larger model. The actual material should be evaluated before making the final choice.
Can I test my own plastic sprues before buying a crusher?Yes. This is particularly useful when the sprues are unusually large, thick or irregular. Longhe can test customer-supplied plastic sprues and evaluate the crushing effect, feeding behavior and suitable screen configuration before recommending a machine.