Mold Polishing Tips For Injection Molds

 

Mirror polish injection molds

 

What is mirror polishing?

Mirror polish injection molds refer to molds that have a highly reflective and smooth surface finish, similar to a mirror. This is achieved through a polishing process that removes any surface imperfections and creates a high-gloss finish.

Mirror polish injection molds are often used in applications where the final product requires a high level of clarity, such as in medical devices, optical lenses, and consumer electronics. The mirror-like finish helps to reduce the amount of light scattering and distortion, resulting in a clearer and more precise image.

The polishing process for injection molds is typically done using a series of abrasive compounds and polishing tools, starting with a coarse grit and gradually moving to finer grits until the desired level of mirror finish is achieved. The process can be time-consuming and requires a high level of skill and expertise to achieve the desired result.

Overall, mirror polish injection molds are a valuable tool for producing high-quality products that require a clear and precise finish.

[caption id="attachment_4629" align="alignnone" width="300"] Mold Polishing[/caption]

Mold Polishing Tips For Injection Molds:

① Surface after the rough polishing process by milling

EDM, grinding, etc. You can choose the speed at 35 000-40 000 rpm rotating surface polishing machine or ultrasonic grinding machine for polishing. Commonly used methods using diameter Φ3mm, WA # 400 wheel removing layers of white sparks. Then hand Whetstone grinding, strip Whetstone plus kerosene as a lubricant or coolant. The general order of use is # 180 to # 240 to # 320 ~ # 400 ~ # 600 ~ # 800 to # 1000. Whetstone polishing method. Which is the most important job a difficult job processed according to different specifications? And an angle of approximately 70 degrees a balanced cross lapping position? Ideally from a range of about 40 mm to 70 mm. Whetstone jobs will vary according to the material processed. Many mold manufacturers in order to save time and choose from # 400 to start.

② Semi-fine polishing semi-fine polishing mainly used sandpaper and kerosene.

After Whetstone's job is job sandpaper, sandpaper when the job. Pays attention to die Jen rounded edges, rounded corners, and orange peel generation. So try to make the finest Whetstone flow processing. Sandpaper polishing focus. Sandpaper with a hard stick like a stone like a job for about 70-degree angle to cross grinding. Polishing sandpaper side number about 10 times to 15 times. If the grinding time is too long, the grinding force of sandpaper will reduce. Which would lead to the machined surface uneven phenomenon? Which is also produced one of the reasons orange peel?

When jobs are generally used bamboo sandpaper grinding. Low stretch material actually used a small stick or rod hardness of about 45-degree angle grinding is the most ideal. The polished surface cannot be used as a rubber or a material with high elasticity. And cannot be polished with a 45-degree angle may be an acute angle shape. Numeral sandpaper as follows: # 220 ~ # 320 ~ # 400 ~ # 600 ~ # 800 ~ # 1000 to # 1200 to # 1500. Actually, # 1500 sandpaper only suitable for hardened tool steel (52HRC above) does not apply to pre-hardened steel. This may lead to pre-hardened steel surface burns.

③ Fine polishing diamond polishing paste mainly used.

If the powder or mixture of diamond abrasive grinding wheel pastes for polishing a polishing cloth. Then the order of the normal polishing 9μm (# 1800) ~ 6μm (# 3000) ~ 3μm (# 8000). 9μm diamond polishing paste and polishing cloth wheel can be used to remove the # 1200 and # 1500, leaving hair like sandpaper grinding marks. Then with sticky carpets and diamond polishing paste for polishing. The order of 1μm (# 14000) ~ 1 / 2μm (# 60000) ~ 1 / 4μm (# 100000).

Accuracy requirements in 1μm above (including 1μm) polishing process in the mold processing workshop in a clean polished interior can be carried out. If a more precise polishing an absolute necessity to clean the space. Dust, smoke, dandruff. And saliva Mo is likely to be scrapped after a few hours of work to get a high-precision polishing surface.

Cn-moulding is a reusable china injection mold company. We focus on high glossy mold manufacturing. One strong point of us is polished mold mirror and glossy, with short cycle time and competitive price.

Why injection molds use hot runner?

 After years of development, injection molds have become one of the preferred molds for manufacturing in all walks of life around the world, especially in the developed countries of Europe and the United States, which have advanced in the industry. The most important thing to mention is the use of hot runner technology in injection molds.

hot runner

1， Hot runner technology shortens the injection molding cycle

Because there is no limitation of the cooling time of the main channel and the secondary flow channel, the injection mold can be ejected in time after being solidified. Many thin-walled product molding cycles produced with hot runner molds can be completed in less than 8 seconds.

2，Eliminating subsequent processes is conducive to production automation.

After the workpiece is formed by the hot runner mold, it is the finished product. There is no need to trim the gate and recycle the cold glue lane. Conducive to production automation. Many foreign manufacturers have combined hot runners with automation to significantly increase production efficiency.

3， Hot runner technology saves plastic raw materials

In the traditional mold injection, the nozzle material is produced. The high plastic product is not allowed to use the water material (recycled secondary material). Because the reuse of the nozzle material will degrade the structure and performance of the plastic part, the reuse will affect the product quality. There is no cold runner in the hot runner mold. So no nozzle material is produced (fees are required). This is especially significant for applications where the price of plastics is expensive. In fact, the major hot runner manufacturers in the world have experienced rapid development in the world. When oil and plastic raw materials are expensive. Because hot runner technology is reducing materials and reducing materials. Fees, an effective way to save costs.

4，Expand the application of the injection molding process

Many advanced plastic molding processes have been developed based on hot runner technology. Such as PET preforming, multi-color co-injection in the mold, a variety of materials co-injection process

5， Reduce the defective products of injection molds and improve product quality

During the hot runner mold forming process, the plastic melt temperature is accurately controlled in the runner system. The plastic can flow into the cavities in a more uniform state, resulting in a consistent quality plastic part. The hot runner molding plastic parts have good quality, low residual stress after demolding, small deformation of plastic parts. And greatly improved the surface appearance of injection mold products. Therefore, many high-quality products on the market are produced by hot runner molds. Many familiar plastic parts, such as telephone casings, mobile phone cases, printer cases, computers, and automobiles, are produced using hot runner molds.

The factors affect the percentage of regrind materials

 

The factors affect the percentage of regrind materials

The factors affect the percentage of regrind materials

1, The purpose: In order to control and improve the quality of plastic parts, reduce the cost of plastic parts and injection molding plant regrind materials management, to meet customer technical requirements.

2, The scope: for the injection of all of the Company ABS, PA66, PA6, PP plastic parts, and workshop back to powder, processing, storage, labeling, and other management regulations.

3, Regrind material recovery and grade classification

1, Recyclable materials:

A.Defective products produced during injection molding (such as scratches, incomplete, burr) and other defective products.

B, injection molding process generated in the runner compound (nozzle material).

C, other (such as: engineering testing and other models can not be shipped demolition of plastic pieces or scrap pieces).

2, Regrind materials level:

A, The first regrind materials: the new material produced by the first injection of plastic.

B, The second regrind materials: after the second injection of plastic produced.

C, The third regrind materials: the second or more (including three) after injection of plastic and scrap.

The bulk density of the regrind is probably the single biggest factor affecting how much regrind one can use.

If you are using a recycled film scrap that hasn’t been densified then you pay a tremendous penalty in your rate. There are densifiers like a Munchy that will compact the film scrap to something close to a virgin pellet. In this case, then you can use quite a bit of scrap – 20 – 30%.

Another thing affecting your percentage of regrind is the use of grooved feed sections for extruders. They really are not designed for anything but pelletized material. It is best not to use more than 5% regrind if you have a grooved feed otherwise the grooves will clog and production rate will drop significantly and product quality will also suffer.

In blow molding, for instance, it is not uncommon for bottlers to use 35% regrind as the moels and tails comprise a considerable amount of material in relationship to the end product. That stuff is usually compressed and put back in the hopper.

Pre-hot runner systems had a lot of regrind as dense material sitting in the runners and gates was recycled. Those rates were quite high. I have seen that as high as 50%.

The other points are quite well such as contamination from streams and other things that need to be considered. In the end, I would say there is NO rule of thumb it greatly depends on so many factors.

There is no 1 rule of thumb. It will depend on several elements;

What type of Polymer and how they degrade (heat stability and moisture content)

whether filled and type of filler. Glass length will degrade making more brittle, lower modulus

whether it is a blend, PC: PBT interact with each other (transesterification)

can you add heat stabilizers, can increase the level of regrind

what kind of shear are you putting into the mix

you won’t try to color match or all bets are off on color stability

Ultem PEI is great, but high heat, I’ve seen >50% regrind work fine, unfilled PP of PE can go a long way with the addition of phosphate/phenol stabilizers.

 

plastic injection molding sink mark

 

The reasons for sink mark in plastic products are as follows:

Reasons for injection molding sink mark

Sink marks in injection molding are common defects that occur when the surface of a molded part shrinks and creates a depression or dimple. This typically happens because the inner part of the material cools and shrinks faster than the outer surface, pulling the surface inward. Sink marks are most noticeable on thicker sections of the part or near ribs, bosses, or other features that create variations in wall thickness.

Causes of Sink Marks:

1. Insufficient Cooling Time:

• If the cooling time is too short, the outer surface solidifies while the inner material is still cooling and shrinking, causing sink marks.

1. Inadequate Holding Pressure or Time:

• Holding pressure helps pack additional material into the mold to compensate for shrinkage. If the pressure or time is insufficient, the material shrinks excessively, leading to sink marks.

1. Excessive Wall Thickness:

• Thicker sections cool more slowly, increasing the likelihood of shrinkage and sink marks.

1. High Material Shrinkage Rate:

• Some materials, such as semi-crystalline plastics (e.g., polypropylene or nylon), have higher shrinkage rates, making them more prone to sink marks.

1. Improper Gate Location or Size:

• If the gate is too small or poorly located, it can restrict the flow of material, preventing adequate packing and leading to sink marks.

1. High Melt Temperature:

• Excessive melt temperature can increase material shrinkage as it cools, contributing to sink marks.

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How to Prevent Sink Marks:

1. Optimize Wall Thickness:

• Design parts with uniform wall thickness to ensure even cooling. If thick sections are unavoidable, use coring or ribbing to reduce material volume.

1. Increase Holding Pressure and Time:

• Apply sufficient holding pressure and extend the holding time to pack more material into the mold and compensate for shrinkage.

1. Adjust Cooling Time:

• Ensure adequate cooling time to allow the entire part to solidify uniformly.

1. Use Low-Shrinkage Materials:

• Select materials with lower shrinkage rates, such as amorphous plastics (e.g., ABS, PC) or filled resins.

1. Optimize Gate Design:

• Use larger gates or position them near thicker sections to ensure proper material flow and packing.

1. Control Melt Temperature:

• Avoid excessively high melt temperatures to minimize shrinkage.

1. Add Mold Features:

• Incorporate mold features like gas vents or cooling channels to improve cooling efficiency and reduce shrinkage.

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Corrective Actions for Existing Sink Marks:

• Increase holding pressure and time.
• Reduce melt temperature.
• Extend cooling time.
• Modify part design to reduce wall thickness or add coring.
• Adjust gate size or location.

By addressing these factors, you can minimize or eliminate sink marks and improve the quality of injection-molded parts.

Plastic Thermoforming company in China

 

Vacuum Thermoforming in China

Vacuum thermoforming is commonly used for various plastic packaging china but has many applications from plastic

toys to aircraft windscreens to cafeteria trays.

Thin gauge (less than 0.060 inches) sheets are mostly used for rigid or disposable packaging. While thick gauge (greater than 0.120 inches) sheets are typically used for cosmetic permanent surfaces on automobiles.

Shower enclosures, and electronic equipment. A variety of thermoplastic materials can be used in this process, including the following:

Acrylic (PMMA)

Cellulose Acetate

Polystyrene (PS)

Low-Density Polyethylene (LDPE)

High-Density Polyethylene (HDPE)

Polypropylene (PP)

Acrylonitrile Butadiene Styrene (ABS)

Polyvinyl Chloride (PVC)

 

 

	Typical	Feasible
Shapes:	Thin-walled: Cylindrical The Thin-walled: Cubic Thin-walled: Complex
Part size:	Area: 0.04 in² - 300 ft²
Materials:	Thermoplastics
Surface finish - Ra:	60 - 120 μin	16 - 120 μin
Tolerance:	± 0.04 in.	± 0.008 in.
Maxwall thickness:	0.015 - 0.15 in.	0.002 - 0.25 in.
Quantity:	10 - 1000	1 - 100000
Lead time:	Days	Days
Advantages:	Can produce very large parts High production rate Low cost
Disadvantages:	Limited shape complexity Limited to thin-walled parts Scrap cannot be recycled Trimming is required
Applications:	Packaging, open containers, panels, cups, signs

 

Thick-Gauge Thermoforming in China

Thick-gauge--or "heavy-gauge"--thermoforming, manufacture parts with a thickness in the range of .060 to .310. This thickness creates sturdy, rigid enclosures. Perfect for enclosing things like electronic equipment in supercomputers. Materials used in thick-gauge thermoforming include flame-retardant ABS, polycarbonate, and a PC-ABS blend. Low volume orders are common, and a quality thick-gauge thermoforming company can do economical low-volume runs.

In addition, thick-gauge thermoformed must consider aesthetics. How the enclosure looks--since the enclosure is not going to be discarded like the packaging but is actually part of the product itself. For customers concerned with branding, the look of these enclosures. From color to logo placement.Is an important part of the thermoforming process. what to find a good thermoforming company that can meet your volume requirements and deadlines is critical in China. At CN-MOULDING, our award-winning thermoforming process takes your 3D injection files to finished parts in just 2-4 weeks.

Thick Gauge Thermoforming has cost an effective way

Whether for new products or updating existing products. Thick Gauge Thermoforming is cost an effective way to achieve the function, style. And durability is required for many applications. Chinese thermoforming companies have experience producing parts for a wide range of industries such as Communications, Search and Rescue, Construction, Automotive. And various military applications. Plastic thermoformed parts can be both lighter weight and offer greater impact resistance than comparable parts in metal. The Thick Gauge Thermoforming process allows for the material to be formed into more complex. And smoother shapes than traditional metal forming techniques can produce.

Plastic thermoformed parts also offer a nice appearance without additional surface finishing. Though color matched painting is an option. The benefit of plastic coloring is that it goes all the way through the material. So if the part is scratched it won’t show a different color below the surface. Special properties can be incorporated into materials. Such as UV protection, flame retardance, electrical conductivity, solvent resistance, food-grade, etc.

Reference for plastic packaging by CN Moulding.

Precision injection molding characteristics

 

Precision injection molding characteristics

Precision injection molding characteristics

     The Precision injection molding is generally referred to as the precision of forming parts and surface quality is demanding high technology, some people think that precision injection is the size of plastic parts to achieve the accuracy of 0.01 ~ 0.001 mm injection molding process. In recent years, with the electronic, medical, communications, automotive, and other industries. With the rapid development of people’s plastic products, high precision, high-performance requirements. The traditional plastic molding process has been difficult to meet the current high standards. Is one of the most important plastics molding methods. Therefore, precision injection molding technology more and more people’s attention. Making precision injection molding technology continues to progress, new technology continues to emerge. Factors that affect precision injection molding require high dimensional accuracy, low warpage, excellent transfer characteristics, and excellent optical properties.

Therefore, it is on the injection molding machine, injection mold, molding process, raw material properties. And formulations have special requirements, affecting the many factors of precision injection molding. According to the current actual production point of view, the impact of precision injection molding factors are the following aspects:

1. Plastic shrinkage design of precision plastic products, plastic shrinkage should be considered.
2. The shape and size of the product The shape and size of the plastic parts have a great impact on the accuracy of the parts, the production practice shows that the more complex the shape of the product and the larger the size, the lower the accuracy
3. Mold structure The accuracy of plastic parts and mold cavity number and production volume are closely related. It is also shown that the accuracy of the single-cavity mold structure is higher than that of the multi-cavity mold, and the accuracy of small-mass production is higher than that of large quantities.

Plastic mold manufacturer

 

Plastic mold manufacturer

When you develop a new plastic model, you need to find plastic moulding china to make the mold.
Since the company size, location and history are different. They will quote you different prices.at the moment lots of trading companies pretend to be a plastic mold manufacturer to dealing with you. They will take at least a 30% profit from you and do nothing. Just think about it. If your competitor finds a true plastic mold manufacturer but you find the trading company to develop the same project. They will have a 30% price advantage compared to you. Do you think if you have any chance to win the market?

 

How to find a reliable plastic mold manufacturer?

I think it’s better to spend some time to get to know one or China injection molding several plastic mold manufacturer really well. Visiting them is the best idea once you get a good feeling about it (after discussions about mold engineering or making a small test mold). When you have a good relationship with a plastic mold manufacturer. And you will know how they think about the technologies and use the same language to discuss mold engineering, more effective. You can move on to your project very fast. That’s where the profit is along with the life of the project. Steel is steel and CNC machines are the same for every shop. In the end, it counts on the people who work with you and if someone does a value stream analysis of a project, the mold quality will be different.

 

Visit the plastic mold plant

 

Visit the plastic mold plant and check the facility available with them. Injection molding company asks about his existing customers and main marketing. Check the molds which are in construction in the shop, see the project management system. Look at the sample components they made in the past. All this will give you an idea of the capability and the quality levels of plastic mold manufacturer.
Then check which is your most concern like, lead time of mold building, the finish of the samples, dimensional criticality, quality of steel. After-sales service like modification of mold based on the change in design change during the mold life, the durability of the product.

 

Know injection mold cost

The cost of mould includes： material fee + design fee + processing fee and profit + VAT + trial fee + packaging transportation fee. According to material cost calculation, mold price =(6~10)* material cost.

Visible, the cost of the mold is mainly in the technology and processing costs above, the material ratio is smaller. The more complex the structure of the mold, the greater the difficulty of production, the higher the cost of course. In addition, the higher the precision of the mold requirements, the greater the difficulty of processing, the greater the effort spent. Of course, the cost of mold production will go.

The most important is: find many plastic mold manufacturers for price and quality checks. Choose the best and proper one as your business partner.