What is plastic blow moulding?
Blow moulding is based on extrusion. In a blow moulding, a tube of warm plastic is lowered between the halves of a mould. The mould is closed, and air is led into the tube at a suitable pressure, moulding the plastic tube into the contours of the mould. The piece is then cooled down, the tube is cut, the mould is opened, and the piece is ready for finishing.
The process is quick, which makes a blow-moulded piece very competitive in terms of pricing. What makes blow moulding an excellent mass production method is its good repeatability and because it is very controllable to produce identical results between repetitions.
The benefits and properties of blow moulding
Blow moulded pieces are seamless, vessel-shaped or sinusoid, most often round. Blow moulded pieces can be very long or channel shaped. There are no real restrictions to shape. Different kinds of evasions or include several inserts, such as metal threading, hose clamps, support struts or fastener ears.
“Especially in machining and appliance industries, our clients struggle with cramped spaces in ever-shrinking machining spaces. With blow moulded pieces, we can utilize the tight spots, because the pieces can take many shapes and the thickness of the pieces is controllable.”
The blow moulding method enables equal and thin thickness in the pieces. In blow moulding, the thickness of the pieces can be determined in a very detailed manner, because the method ensures good viscosity. Thus, it is possible to optimize the weight of a piece, because the thickness does not need to be increased to reach required stiffness.
The thickness of the piece’s wall affects material expenditure and thus the price per unit of the pieces. Material choices also enable transparency, enabling for example seeing how full of liquid a piece is without opening it.
Production of dimensionally accurate plastic products is possible, because the range in blow moulding is easy to control.
” The range of two fastener ears at the opposite ends of a piece that is over a meter long can be kept under a millimetre.”
Strong flat and thin pieces can also be blow moulded. The capsular structure ensures a stiff enough piece but is lighter than a solid structure.
The plastic used in blow moulding is chemical resistant and is thus safe in even challenging targets.
Blow moulding mould
The moulds for blow moulded pieces are very resilient and last almost forever. A yearly yield of 100 000 moulded pieces can be easily done with a single mould. Resilience and a long life are visible in the price of the moulds but is compensated quickly, if the volume of the moulded piece is expected to grow.
” Our oldest moulds are from 2003, and they are still in complete working order. We do basic maintenance and slight adjusts to our moulds from time to time. “