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.


About Hedy Yeh

Major in machinery and tooling in university from 2001 to 2004; Worked for plastic mold design, mold manufacturing and mold and production project management from 2003 to 2008; Working for mold marketing and mold project management from 2008 till now My facebook page  

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