About Plastics
Do I need Injection Moulding?
Injection moulding is the preferred manufacturing process when you
want thousands or millions of the same plastic part/ product. The process
involves heating up the plastic raw material - small plastic beads or
pellets, usually to a liquid or near liquid state, and squirting it
under pressure into the cavity of a metal mould.
Once you have finalised the design of the plastic part you want to produce,
the first step in getting the part injection moulded is to build the
mould. The mould is normally made of steel, although softer metals such
as aluminium is used for moulds for some applications. The building
of a mould requires great precision using specialist design software
and metal working equipment. Moulds can be very expensive, the price
depending on:
-the size of the mould
-the number of cavities in the mould
-the material the mould is made of
-the texture if the finish required on the moulded article
-the complexity of the part - among other factors
I need Injection Moulding, how do I proceed?
You may need specialised advice at various stages in bringing your plasticware to market. For more information on how Africa Plastics can help with your project, please take a minute to contact us for an inquiry. Our target response time for genuine inquiries is within 5 working days.
As can be seen, the initial set-up cost (the design and manufacture
of the mould) to make an injection moulded part is quite high. That
is why the injection moulding process is the preferred method when you
want thousands or millions of the same part, not normally when you want
a few or even a few hundred. A well designed and built mould should
make several hundred thousand plastic parts before needing any major
refurbishment.
Moulds are built by specialist companies called toolmakers in South
Africa(or moldmakers in North America). Many injection moulding companies
will generally charge you a price per part or per thousand parts for
very small parts.
The price you pay
The price you pay will depend of course on:
- how heavy the plastic part is (injection moulded parts can be as
small as watch springs and larger than car bumper bars)
- what material the part is to be made from (there are dozens of different
types of plastic raw materials and dozens of grades
within each type)
- how thick the moulded part is
- how accurate the part has to be
- the number of cavities making the same part in the mould
- the quantity of your oder (there is normally a setup charge with every
moulding production run)
As a very rough guide, in a single cavity mould, the cost of the material
may be between 30% and 50% of the selling priceof the injection moulded
part. This will vary according to the cost of the material and the weight
of the article. The balance of the price that the custom moulder charges
you for the part is for machine processing time, labour, overheads and
a profit margin.
If the article being moulded is heavy or made of expensive material,
then the material proportion of the final price of the article is likely
to be higher. On the other hand, of the article being moulded is light
or made of inexpensive material, then the material proportion of the
final price of the article is likely to be lower.
The cost of the plastic material varies greatly according to the type
of properties needed for the application, to a lesser extent the quantity
of material needed for the job; and the part of the world in wich you
will be buying the material. For example, the material used to make
plastic buckets(pails) may cost R7-8 per kg; the material for clear
drinking tumblers may be up to R10-12 per kg; the material that is used
in the protective shields in taxi-cabs and banks may be around R60-70
per kg; and you would pay over R120-150 per kg for high heat and chemical
resistance material for technical and scientific applications.
Any prices and costs quoted in this article are in South African Rands
and are very broad estimates presented as guides only.