Net weigh filling machines have their disadvantages
Ocme has just supplied a complete line to PZ Cussons that incorporates net weigh filling. Installed at the company's brand new facility in Agecroft, Manchester, the high-speed line fills shampoos and conditioners, of various viscosities, into a range of bottle sizes up to a maximum of 500ml.
Ocme has also just developed a new net weigh Oil Filling machine incorporating a two-part tank, which is capable of filling two products into one container - either simultaneously or one after the other. This allows companies to create ‘shake and mix' products with two components or package two products in one container that is split down the middle.
"It's a system we've been working on for some time for which we were hoping there might be take-up," says Mayhew. "At the moment a lot of companies are looking at it but nobody is going into it in a big way."
Net weigh filling machines do have their disadvantages, though. One downside is that their load cells and electronics make them quite complex. Secondly, the equipment is expensive, and therefore only makes economic sense for companies filling hundreds, rather than tens, of containers a minute, says Nick Osborne, director of packaging systems supplier ACO Packaging.
ACO Packaging serves the lower-volume end of the market and says for these customers, volumetric or vacuum oil filling machines tend to be more suitable. The difference between the two is that volumetric or ‘piston' fillers fill to a preset volume, whereas vacuum fillers fill to a level.
According to Osborne, where vacuum systems come into their own is filling glass bottles. "The wall dimensions of glass bottles can vary wildly so if you put 250ml into a glass bottle and stand 10 bottles next to each other, your levels will all be different. That's where vacuum filling comes in because it fills to a level."
Volumetric water filling machines , on the other hand, are the method of choice where accuracy is important, says Osborne, for example, when filling expensive products like essential oils. ACO says that its piston fillers are particularly accurate thanks to a custom-designed cylinder that is more accurate than off-the-shelf pneumatic cylinders, as well as being constructed entirely from stainless steel INOX 316 grade.