What is plastic mold polishing

Plastic mold polishing is a process used to improve the surface finish of plastic molds by removing surface defects and creating a smooth, even surface. The process involves the use of abrasives, buffing wheels, and polishing compounds to remove rough spots, scratches, and blemishes, resulting in a high-quality surface finish.

The goal of plastic injection mold polishing is to produce consistent, high-quality plastic parts, extend the lifespan of the mold, and improve production efficiency. The process is crucial in the manufacturing of plastic products and is typically performed by trained professionals using specialized equipment and techniques.

plastic mold polishing

plastic mold polishing

Why we need to do the plastic mold polishing?

There are several reasons why we need to do plastic mold polishing when make plastic mold:

  1. Improved surface finish: By polishing the mold, the surface finish of the molded plastic parts is improved, giving them a smoother and shinier appearance.
  2. Increased mold life: A polished mold surface is smoother and more durable, reducing wear and tear and extending the lifespan of the mold.
  3. Improved production efficiency: A polished mold can reduce production time, as parts are easier to release from the mold and require less post-molding processing.
  4. Enhanced product quality: Plastic parts produced from a polished mold are of higher quality and have fewer defects, such as surface cracks and flow marks.
  5. Improved production consistency: A polished mold can ensure that each molded part is consistent in size, shape, and surface finish, reducing the need for rework and increasing production efficiency.

Plastic injection mold polishing is a crucial step in the production of high-quality plastic parts, improving both the mold and the molded products.

How to Polish Plastic Molds

The process of polishing plastic molds involves several steps, including preparation, rough grinding, fine grinding, buffing, and polishing. Here’s an overview of each step:

  1. Preparation: Clean the mold surface to remove any dirt, grease, or residue. This will ensure a smooth and even surface for polishing.
  2. Rough grinding: Use a coarse abrasive, such as a grit sandpaper, to remove any large surface imperfections and rough up the surface of the mold.
  3. Fine grinding: Use a finer abrasive, such as a grit sandpaper or a grinding stone, to smooth out the surface and remove any remaining rough spots.
  4. Buffing: Use a buffing wheel and a cutting compound to further smooth out the surface and remove any scratches or blemishes.
  5. Polishing: Use a polishing wheel and a polishing compound to produce a high-gloss finish on the surface of the mold. Repeat the process with a finer polishing compound for a smoother and shinier finish.

It’s important to use the proper equipment, techniques, and abrasives for each step of the process to avoid damaging the mold or producing a poor surface finish. It’s also important to keep the plastic mold cool during the polishing process to prevent warping or other forms of damage.

How to handle the plastic mold polishing jobs?

There are normally two ways to do plastic mold polishing:

1. Do it in-house.

When we do the mold polishing in-house we could keep the time control.  And will be easy to communicate with your polishing department to keep the high-quality polishing job, this will prevent the issue happened by the over-polishing jobs.

2. Do it outsource.

  • You still can take control of the lead time easier by scheduling the polishing to an outside polishing company. Especially for some multiple cavities molds, because they have many polishing workers and can work on polishing cavities separately.
  • But when meet some issue that will be difficult to discuss with each other, if your polishing supplier is close to you, that will be much easy, you can go over there in minutes and explain to themPlastic mold polishing

Final suggestion to handle the mould polishing works

1. For some surface if your customer needs texture surface to cavity side, you can work this use EDM machine to make surface texture directly, This is my favourite method, because almost all the works are finished by EDM jobs,

The advantage on this is when the draft angle is very small and cavity side need some textured surface, use EDM you will never get any scratch issue, and this will be the only way to prevent the quality, we have been done this many times, at the first beginning we used the old way ( polishing and then texture), the was scratch issue on some area and never solved, finally we made a new cavity and made with texture by EDM machine, the result was perfect.

2. For some mold the cavity side needs high gloss surface polishing, which means this is high gloss plastic molding parts, so EDM machining is not possible to get mirror polishing surface even EDM machine can get the high gloss surface, but for some requirement are too high to meet, in this case we have to do the high polishing jobs, the best way to solve this is outsource, to find the professional polishing company to manage this hard task.

Tips to improve your plastic mold polishing
  • Cleanliness. Keep your polishing area away from grinding dust and chips. Do not allow it to become a disorganized mess of loose stones and accessories.
  • Separate your stones. It is amazing that people dump a 220 gritstone in a box or can with a 600 grit stone. Sometimes they even mix up polishing sticks with different grits of the diamond. Let’s see, if you think you are polishing with a fine finish diamond and you get a coarser diamond piece mixed in, what do you think will be the result?
  • Move your polishing area away from grinders and bead blasting equipment. For some reason, many shops just keep polishing away, right next to the surface grinders. All it takes is one stray piece of grinding grit to ruin your finish.
  • Use a microscope. Even though it is disheartening to see your work under a microscope, this is the only way to see the tiny scratches and imperfections. Plus, you can avoid rolling edges and damaging critical molding details
  • Don’t use unskilled help to do skilled work. Polishing is an art that takes a lot of time to learn. Don’t expect everyone to have the same ability when it comes to fine finishes or detail. Yet this often happens when owners view polishing as a nuisance.
  • Make a chart of the diamond paste colors. For some reason, some shops never write down which diamond is which grit and injection mold makers are left trying to figure out the same problem over and over again. Figure it out and make a copy near the diamond compound!
  • Don’t think that “cross-hatching” is some kind of religion. Sometimes you see people who think you must only polish in one direction for each grit. Horizontal with a 400 grit and vertical with a 600 grit, for example. You can and should go back and forth in any direction you need to, just make sure you end up with the lines in the direction of the ejection-draw polish it. Your speed will dramatically increase once you get over this misconception.

Hope this information is helping you on how to do better plastic injection mold polishing, in this case, you could have a better idea on your project what kind of surface will be the best option, any question welcome to send us an email

At Sincere Tech, a leading China mold company, we are committed to maintaining our industry-leading position through constant innovation and a forward-thinking approach. Anticipating future trends and embracing advancements, we actively explore novel materials and composites that promise enhanced performance and sustainability. Our continuous investment in research and development ensures that we deliver cutting-edge solutions, addressing the evolving needs of our esteemed customers. Renowned as one of the premier injection mold suppliers in China, we take pride in our unwavering commitment to excellence.

Aligning with our dedication to sustainability, we prioritize environmentally friendly practices, including the incorporation of sustainable alternatives such as biodegradable polymers. At Sincere Tech, we actively implement recycling initiatives, minimizing the environmental impact of our manufacturing processes. By choosing our custom injection molding services, your brand aligns with sustainable manufacturing practices, contributing to a greener and more eco-conscious future.

Quality remains paramount in our operations, and we enforce stringent quality control measures throughout the entire manufacturing process. Our state-of-the-art facilities and skilled technicians ensure that each product undergoes rigorous inspection and testing, guaranteeing exceptional performance, reliability, and customer satisfaction.

Choosing Sincere Tech as your preferred plastic mold polishing partner ensures you benefit from the highest level of professionalism, expertise, and innovation. We are committed to helping you bring your ideas to life, delivering superior products that excel in performance, durability, and cost-effectiveness.

Our expanded capabilities include:

  1. Plastic Mold Polishing:
    • Sincere Tech specializes in meticulous plastic mold polishing, enhancing the surface finish of your molded products to meet the highest aesthetic standards. Our skilled technicians employ advanced techniques to achieve impeccable results, ensuring your products stand out in terms of visual appeal.
  2. Rapid Prototyping:
    • Transform your concepts into tangible prototypes swiftly with our rapid prototyping services. This allows for iterative design improvements and accelerated product development, ensuring you bring your ideas to market faster.
  3. Precision Tooling:
    • Benefit from our advanced tooling capabilities, creating high-quality molds with tight tolerances. This ensures consistency and precision in your injection-molded products.
  4. Overmolding:
    • Specializing in overmolding, we combine multiple materials or components, resulting in enhanced functionality, aesthetics, and durability in your products.
  5. Insert Molding:
    • Expertise in insert molding allows us to securely encapsulate inserts within molded parts, facilitating efficient assembly and enhancing product performance.
  6. Two-Shot Molding:
    • Utilizing two-shot molding, we produce complex, multi-material components in a single operation, reducing assembly requirements and expanding design possibilities.
  7. Value-Added Services:
    • Beyond injection molding, we offer a range of value-added services, including product assembly, packaging, and logistics support, streamlining your supply chain and reducing costs.

Partner with Sincere Tech for your plastic mold polishing and custom injection molding needs. Benefit from our comprehensive capabilities, unwavering commitment to quality and sustainability, and our determination to exceed your expectations at every step of the process. Together, let’s bring your innovative ideas to life with impeccable plastic mold polishing.