Polypropylene injection molding

Polypropylene injection molding

Polypropylene is one of common plastic resin which used for home appliance and medical plastic parts. It can be used for cup, washbasin, garbage can, basket and toys etc..  It can be also used for disposable medical vessel and box etc, sure you should use medical grade polypropelene. It is cheaper than ABS, PC, PC/ABS and nylon etc. resin. Also it is softer than them.  Polypropylene abbreviation is PP. PP with super folding resistance, so it can be used for lots of folding box such as  stationery and glass box etc. PP is not possible to do the painting process, but it is okay to do the printing.

Polypropylene injection moldingPP raw material is semi-transparent. Also you can pigment to have various semi-transparent color for PP injection molded parts.

To help you to save cost for PP injection molding, below we will talk about how to save cost on the prototype, mold making and injection molding.

Prototype making for Polypropylene

On the PP prototye making, generally it is not possible to carry out the folding performance. There is CNC machining, RTV casting and SLA printing to make PP prototype. You can also choose ABS resin to make the PP prototype.

Save your cost on Polypropylene injection mold

What is injection mold?

Injection mold is a tooling to form the Polypropelene or the other resin plastic product.

Choose right steel for Polypropylene injection mold

As you know PP is not so hard, generally it will use cheap steel such as P20, 2311 or 2312 to make the mold. If the injection mold core and cavity is lower than HRC 44, we call it prehard steel. For PP injection mold, we can use prehard mold. But for high volume injection mold, for example if the mold life is more 1000000shots, you need to consider through hard mold, it means you can choose H13 or 2344 for core and cavity.

If you do not know the quantities you are going to make based on your marketing, you can use prehard mold first.  If you purchase Polypropylene injection molding in China, you can always use prehard mold as mold maker will assure the mold life, anyhow you need to confirm with your mold manufacturer.

Define mold cavity for your injection mold manufacturer

If mold maker ask you how many cavity you need for your mold. It is like to ask you how many same parts you are going to put into your injection mold. This affect the production capacity. Generally the injection molding just take a few seconds to make one shot(cavity).  In case you are not professional, you can let mold maker know how many piece you are going to order each time, then you plastic mold manufacturer will carry out the mold layout.

Plastic injection mold manufacturing

Plastic injection mold manufacturing

Also there is family mold, it is to have different plastic parts in to cavity. If you do so, you need to let your mold factory know if you have different color for each parts, also the useage of each part into the cavity for your final assembly products.

Tips on Polypropylene injection molding

You should choose the right PP injection molding machine. Generally the high speed injection molding machine is more suitable to inject polypropylene. This is thanks to PP resin with high flow performance. This also need mold manufacturer to choose right mold manufacturing process and have reliable design for PP injection mold, otherwise it is easy to have flash. Please kindly noted the common standard injection machine is also suitable for PP injection molding, the difference is on quality and product capacity.

Clean room injection molding plant ChinaMold temperature will be used on the PP product structure. Cold water is widely used for PP injection molding to increase to product capacity.

Tips to purchase Polypropylene injection molding in China.

There are many injection molding factory in China. Some of them is mold manufacture, some of them is injection molding manufacture, also there is trading company. All of them can receive your orders. But if you face mold manufacture, you will have higher mold cost, you need to let them know your injection mold is to leave in the mold factory for production but not to have mold to import to your Country. If it is injection molding manufacturer, generally you can get reasonable mold cost.  But on the different location of China and even if it is different people to quote, there is difference on the mold price and unit price.

To have affordable price, you need to let injection molding manufacturer know below specification for PP plastic molding.

  • How many quantities you need to order each time?
  • Color for each of your parts
  • QTY for each part to assemble one your final product. If you have many parts to inquiry in one time, you have BILL OF MATERIAL form.
  • You need injection mold or you need to do the production in your molding manufacturers’ plant.

Once you have same specificaiton for your mold maker, then they use same specification for quotation, then it is easier to carry out which one with competition.


Ultimate strategy for clear plastic molding

Ultimate strategy for clear plastic molding

To make high quality and afford price clear plastic molding products, you should give importance on both injection mold and plastic molding.  We will talk about to control plastic mold quality first, then we will talk about the injection molding clear parts.

Ultimate strategy for clear plastic moldingNo. 1 Choose right mold steel for clear plastic molding mould.

As you need to reach mirror polishing on cavity and core of injection mold for clear plastic parts. You have to choose high quality stainless steel for core and cavity. Based on different request for the polishing, you have different choice for the mold steel, then you have affordable price.

To choose your steel for core and cavity based on the polishing request. If you need above SPI A3 polishing, you have choose ASSAB S136  or NAK80 steel. At the same time, if the mold life or production capcity is more than 300000shots, you have to consider ASSAB S136 through hard steel.  If you need the polishing is around SPI A3 or lower than this, then you can choose FINKL 420 or China LKM 420 steel. Anyhow if the mold life is less then 300000 shot, you can choose prehard LKM 420 steel too.

NO. 2  Choose right injection mold factory to make the mold for clear plastic molding.

The plastic mold manufacturer should have experience for injection mold manufacturing for clear plastic product. On purchasing process, you need to have your mold factory to show you study case for clear plastic mold manufacturing. The best practise to have reference customer to prove it.  On the polishing process, it is very important to control the polishing method. In China most of mold maker is outsourcing for mirror polishing. There is professional mold polishing shot to finish the mirror polishing processs.

No. 3. Have the right draft angle for clear plastic product

If there is not enough draft angle for clear product, then it is easier to have scratch during clear plastic product injection molding.  If this is happen, you have to have mirror polishing again, if it is not solved. Then you have to chane your product design with big draft, it is terrible. So during design for manufacture process, your injection mold maker should have enough experience to carry out which draft should be suitable.

No. 4. Have less ribs as possible on the design if you need mirror polishing.

It is diffcult to polish the plastic ribs due to it small gap for polishing operators. It is diffcult to work. Please try to optimize your plastic product design as possible to reduce the ribs. Also for the clear plasit product, you also need to consider to have insert for the thin rib, then there is venting for the ribs, then it is easier to have the resin to fill into the gap to form ribs.

No. 5 Choose right plastic injection machine.

Lots of China injection programmer do not know the injection screws affect the injection result. For clear plastic parts, generally it is PC or PCTG resin. There is PS, SAN and PMMA etc. Generally smaller injection screw is easier to have good result. Nowdays, the injection machines guys will suggest right injection machine to shot different resin and product.

For thin wall and thick wall clear plastic molding, it is different to choose right injection machine. For thin wall clear plastic molding, you should consider high speed injection machine, generally in Japanese injection machine, it is electronic injection machine. For thick wall clear plastic molding, you can choose hydraulic injection machine, but you need to choose higher servo motor with smaller injection screw, then it is easy to shot thick wall clear plastic molding parts. In SEASKYTOOLING, we customize both kinds of injection machine to shot thin wall clear plastic parts and thick wall plastic molding parts.

No. 6 To get high quality clear plastic molding parts.

For common clear plastic molding parts, you can produce in generall injection plant. But for high quality clear plastic parts such as lens and light guide, you have to injection molding clear parts in clean room. SEASKYTOOLING have ISO 8 clean room for clear plastic molding.

If you need to know more about SEASKYTOOLING China plastic molding manufacturer, please kindly watch below video.

family plastic injection mold

Drawing format for quotation


  • If you offer STL drawing, it is okay to quote the SLA prototype.
  • Also it is possible to offer the casting prototype. If you need to make casting prototype, the quantities should be more than two sets, otherwise there is no advantage compare to SLA and CNC machining prototype.
  • If you offer STL to let us to offer casting prototypes, it is too expensive. We will not offer this.

STEP, IGES, X_T, UG9.0, Solidworks 2014

  • One of these drawing format is the best to input into SEASKYTOOLING for :
  • CNC machining prototype,
  • SLA prototype,
  • Plastic casting prototype,
  • Mold quotation,
  • Unit price,
  • Mold design,
  • Mold manufacturing,
  • Silicone mold quotation,
  • Silicone parts unit price,
  • Silicone mold manufacturing,
  • Silicone parts manufacturing,
  • Compression molding,
  • Extrusion,
  • Machining etc.

If you have other drawing format, we should discuss if we can input for production.

2D drawing format in DWG, JPG, JPEG, PDF etc. with dimensions.

It is okay to offer quotation for export mold.

If you can offer part weight, we can offer mold cost and unit price. Please pay attention have your drawing to show all of structure of your product.

What drawing we will offer to you after production

All of drawings including production parameter used for production, we can offer to you to assure you can do:

  • modification,
  • correction,
  • move mold out of SEASKYTOOLING,
  • input production in your own plant,
  • build new mold etc.

Just let us know what drawing format you prefer, we can offer.

You can also review below page to know more for our quotation process:

Plastic product manufacturing based your draft

Copy plastic products with plastic samples

New injection mold

Moving molds to SEASKYTOOLING for injection

Can SEASKYTOOLING accept to move molds for production?

Yes, we can.  To prevent the misunderstanding and both of us are happy for the cooperation, we should have close communication for the mold moving.New injection mold

How to move molds to SEASKYTOOLING for injection?

Before you move the molds to SEASKYTOOLING, we should understand your situation.

1, If your supplier have no ability to finish the mold making for your product? Also you have lots of trouble on the mold making and cooperation.

There will be following things may happen:

1, Have cost to repair the mold or correct mold,

2, Remake the mold if the quality is too bad,

Please try to have following things from your current supplier:

  • 2D mold drawing,
  • 3D mold drawing,
  • Electrode,
  • Mold modification your supplier did on your molds,
  • Final molding parameter report,
  • Final inspection report for your product,
  • Final samples from the latest mold trial,
  • Mold trial video if it is possible.

Your supplier may have ability to offer this, please try what you will have to offer to us.

You should also offer following information:

  • Final part drawing include 2d & 3d for the mold making,
  • Specify what the problem you faced on the engineering of mold making & injection molding,

If it is possible, please arrange following things, you had better arrange a mold trial in your current mold factory, and have us to present the mold trial.

You may not arrange above due to bad cooperation, but anyhow we can support you to solve the issues.  But before mold moving, SEASKYTOOLING have to understand if we have ability to solve the issues. If not, we will tell you first to prevent unhappy things happen again.

SEASKYTOOLING want to be honesty to support you.

2, If your supplier have just no capacity to do injection molding, but for mold quality is good.

If so, then it should be easier to arrange the things on point 1.  SEASKYTOOLING  want to be honesty to cooperate with you.

Before moving molds, SEASKYTOOLING will offer the unit price based on your demand and mold layout.

Regarding moving molds, please kind noted below:

SEASKYTOOLING will not undertake cost to repair the mold due to bad quality caused by your supplier.

SEASKYTOOLING did not undertake the additional cost caused by less lacking document.

You should undertake the cost for mold trial to verify the mold quality.

The most important for moving molds cooperation between you and SEASKYTOOLING.



Plastic injection mould steel

Choose right mould steel for injection mold makingPlastic injection mould steel

Last year I wrote a post for how to choose the mold steel. Today we will have a few example to help you to choose the mould steel easily.

For the plastic resin such as PP, ABS, HIPS, PS, PC, Nylon and PBT etc.  and mold shot lower than 3,000,000shots.

For export mold, mold in your country for production.

Small common mold core and cavity steel:

For general products such as electronic product enclosure, plastic cup, plastic bottle and plastic bracket etc.We can choose P20 (1.2311) or P20+Ni or P20 Mod, P20 modified.etc. Based on economic consideration and smaller molds( core and cavity block lower than 500x500x200), you can choose LKM 738H.

Large exprot mold core and cavity steel:

If it the core and cavity is too big, especially the mold size is close 1 meter and core and cavity is solid on A, B plate,  you can choose more economical mold steel such as Baosteel SWP20, WY 718H or Baosteel SW718H. If it is nylon with glass fill products without lots of ribs, you can choose the economical steel and chrome plate the steel.

Production mold in China

SEASKYTOOLING take responsibility for the mold core and cavity steel to assure your mold life.

For resin with glass fill (export or non export)

If your production quantities is lower than 10000 shots, you can consider to use China local P20 for core and cavity.

If you could choose H13, 2344 from LKM for core and cavity.

If it is long term production mold and too much glass fiber, you could choose S7 for core and cavity and use P20 for A, B plate, ejection plate of mold base.

For transparent product but it not lens:

You could choose LKM 420(h) for core and cavity. Even if it is SPI A3 finishing, you could choose LKM 420 through hardness steel.

For transparent lens:

SEASKYTOOLING suggest to use stainless trhough hardness steel for core and cavity such as S136(HRC 48-52).

For PVC mold core and cavity:

SEASKYTOOLING suggest to use LKM 2316 (h) for core and cavity, this steel is developed for PVC injection mold.

If you consider the economical selection,  you could choose LKM 2083 with chrome plate.

For very low volume mold core and cavity, lower than 1000shots,

You could choose S50C/1050/1.1730 for core and cavity, but your product should not be mirror polishing.

If it is small mold, please do not mind what steel you could choose, it will not affect a lot of mold cost.

Silicone keypad manufacturer

Silicone rubber parts manufacturing solution

What silicone rubber parts manufacturing solution SEASKYTOOLING have?Silicone rubber keypad manufacturer

  • SEASKYTOOLING use the compression molding process to manufacture silicone rubber parts.
  • This is simple mold with lower cost, which should be about 1/5 cost of injection even lower.
  • Generally the mold is like two plate with cavity and core on the two plate. During the production, the solid silicone will be put into the cavity. Then heat the mold to form the silicone rubber part.

Quick answers for silicone rubber parts manufacturing:

Is there samples charge cost?

There is no sample charge if you already pay the production mold, our mold cost normally include 10 sets of samples, if you have more, please specify before quotation.

Why there is no sample charge?

If you paid the mold cost, we should offer samples for your approval, samples is free till to your approval. Anyhow normally we can get your approval in one time based on our quality.

There is supplier did not charge me mold cost, can you offer mold with free charge?Silicone rubber part manufacturer

Your supplier already spreaded the mold cost to the unit price, also they have requirement for large MOQ and strict advance payment term.

What kind of payment term does SEASKYTOOLING offer?

SEASKYTOOLING accept hire purchase, you can pay 50% of mold cost to start to build the mold, once the mold is finished you pay balance.

For the production it is same. 50% of product cost as deposit, balance before shipment.

Can SEASKYTOOLING ship the parts to my warehouse in my Country?

Yes, we can ship to your warehouse.

Can I make different color for my silicone rubber parts?

Yes, you can make different color, the advantage of compressiona molding is to make different color without set up charge compare to injection molding.

 Is there any MOQ?

No MOQ, but you had better to produce 5000pcs to have price advantage. Sure, we also have a few order as 1000pcs.

Anyhow SEASKYTOOLING do want to support your sucess.

Choose molded logo or printing logo for plastic parts

What is molded logo ?

Molded logo manufacturing process is to engrave the logo on plastic injection mold. Then molded plastic parts with logo directly without secondary process.

What is printing logo?

The printing logo manufacturing process is to have pad printing or silk-screen printing or painting process to manufacture the logo on plastic molded parts. It is the secondary process.

Molded logo VS printing logo

Molded logo is cheaper than the printing logo thanks to molded logo is the process to injection the plastic parts with logo without the secondary process.

With printing process, you can print various color for your own logo. If you need to have different color for your logo compare to your plastic parts, you had better to choose the printing logo.

On the molded logo, you can also choose the different color for your logo, you have use the two shot color injection or over molding process what is too expensive.

You can also use molded logo with printing logo to have your beautiful logo, you can engrave your logo first, then you can painting your logo or printing your logo on the logo engraving area. Sure this is more expensive.

Till now you should understand the molded logo is the cheapest solution to make your logo on mass production.

During your production, you can choose the logo manufacturing process based on your purpose. There is more logo manufacturing process, you can inquiry your molding supplier. Anyhow SEASKYTOOLING offer the solution based on your demand for the logo manufacturing. Also we can be your consultant to choose the logo manufacturing process even if the whole products manufacturing.

Plastic injection molding color pantone book

Plastic injection molding color quantities affect the unit pricePlastic injection molding color pantone book

During the plastic part development, if you choose the plastic injection molding process to manufacture plastic parts. You should understand  the more plastic injection molding color on the same production quantity is more expensive than one color production.

Why more expensive to order more colors?

Because there is additional cost during the multiple color production based on same quantity such as:

Mold set up charge include:

  • Labor cost to clean the plastic injection machine barrel to change color,
  • Pigment cost (inclue the labor cost to deploy pigment and pigment cost),
  • The labor cost and machine cost to shot samples to match your color samples.

Based on above to change color is silimar thing to set up the mold again to have production, this is the reason most of injection molder calculate the plastic parts unit price based on production quantities on each color but not the total quantities for whole colors.

How to optimize the plastic injection molding color to have competitive price?

  • Obviously, you can have less color. You can choose the best color to start our market and have more market inquiry to get what color will be best to start.
  • If it is family mold, you can put the same color on the same mold and consider the cavity quantites based on your dosage for the final assembly product.

You can understand more technique information on our below page:

Plastic parts color affect the injection mold layout

Plastic injection molding color

Plastic injection mould manufacturing China

Plastic parts color affect the injection mold layout

To consider the plastic parts color before mold layout will reduce the production cost and mold cost.

Why plastic parts color affect the plastic injection mold layout?Plastic injection mould manufacturing China

  • The common injection machine just shot one color and one kind of resin in one shot,
  • If you are going to make family mold, then you had better to consider to have same color plastic parts in one mold.
  • If you put different color plastic parts in one mold, this means that you should use the runner switch to shut off the different color plastic parts. This means that it is to build big mold but on the injection molding it can not be used for injection molding in one shot. If you just make hundreds of shots, this is a solution to reduce mold cost, but this solution is not good to reduce the production cost on mass production.

How we should consider the plastic parts color for injection mold layout?

Plastic injection mold multiple-cavity

Plastic injection mold multiple-cavity

  • Have same color plastic parts in one shot, sure it should be the same resin.
  • If you have possible color change, please let your mold maker or your mold layout designer know this, have them to optimize the mold layout.
  • You can review our injection mold cavity page and family mold page to understand more technique information to optimize the mold layout.



family plastic injection mold

Family mold to reduce the mold cost

What is family mold?

family plastic injection mold

Family plastic injection mold

Family mold is multiple cavity mold, but the plastic parts are different.

Why you need family mold?

  • Save mold cost and plastic unit price.
  • To shot different parts at one shot.

What you need to pay attention to purchase family mold?

If you need to have all of the parts at one shot:

  • Please make sure that all of your parts are same color and same resin.
  • Make sure there is no big difference on the height of the plastic parts, otherwise it maybe more expensive compare to the multiple cavity mold or single cavity mold.

Even if the plastic parts resin and colors are different. you can also consider to use family mold.Family injection mold

  • If so, you need to consider to use the runner switch to control the runner shut off or open.
  • Use the runner switch, you can control to produce one of the plastic parts or combine the parts whatever you want to produce or produce all of them.
  • But please noted that just same color and same resin plastic parts can be produced in one shots.
  • At right picture, you can see the runner switch in purple color.

Custom service in SEASKYTOOLING to make the family mold for you:

You will have no responsibly or risky to make the family mold thanks to we will optimize the family mold and control the quality.Family plastic mold

Also we can help you to make a decision what kind of family mold you need, you just need to tell us the demand of your plastic parts,  part usage per your one sets of products, colors and resin. You can also let us know know your marketing situation, then we will know how many parts you need to order each time and demand for recent 5 years, it is very useful for us to design and offer most suitable injection mold and price for you.

Compression mold advantage to make family mold:

Compression mold  can be used to produce silicone, NPR, EPDM and natural rubber etc. thermoset plastic parts.

It is also possible to make family compression mold. The advantage difference compare to injection mold to make family most is that you do not mind if you need to put same color parts in one shots, even if you have different colors for family compression mold, you still have the unit price advantage.