why cleanliness important at a moulding shop
It does not always follow that the cleanest factory is the most efficient, nor that the dirtiest one is the least.
It is, however, quite clear that good housekeeping aids efficiency and that bad housekeeping can be detrimental to profitability, to safety, and to health.
At the present time, when job satisfaction plays such an important role in industrial management and relationships it would seem that clean and pleasant working conditions have their part to play.
A person occupied in keeping the moulding shop clean may be just as gainfully employed as a machine operator, but there is also a great deal to be said for encouraging all persons working in the shop to have good housekeeping in mind.
With an individual fitter/technician or a team of fitters made responsible for a group of machines, competitions can be held for the best kept section; and this, with an attendant productivity bonus, certainly has the effect of increasing overall efficiency.
Not only is a clean machine in clean surroundings easier and more satisfactory to work on; it enables the operators, setters, and maintenance staff to see and rectify troubles before they reach unmanageable proportions.
Ideally, working a 120 h weekly shift scheme, the time from 6 a.m. or 8 a.m. on Saturday until midday should be devoted to cleaning and minor maintenance jobs.
If this cannot be arranged, cleaning and maintenance staff should attend to machines as they become idle at the end of a project, before setting up a new job.
Dirt, dust, and granules
Some of the treatment that injection moulding machines receive is not calculated either to improve performance or to prolong the life of the machine-
Starting where the material starts, in the feed hopper, there is often a spillage of granules or powder on to the machine when filling the hopper.
This falls on to the hot heater bands around the cylinder and tends to stick. After some time, virtually the whole of the cylinder begins to look in poor condition.
Powder and dust fall on other parts of the machine, settling on cams and microswitches and penetrating into cracks and spaces.
If not removed, this dust can penetrate into other working parts of the machine and, where the oil tank is not totally enclosed, it has been known for Plastic granules (and even mouldings) to be found in the oil.
Purgings from the cylinder are another source of trouble.
If left until solid on the shelf below the nozzle they may be difficult to remove, and where an unattended machine is allowed to dribble at the nozzle by being left with heaters switched on, there is the possibility of wires becoming encased.
While hot, this can be removed, although with difficulty, but when allowed to cool a hacksaw is needed to free the wires, and not without some hazard to the safety of the insulation.
Sometimes the weight of plastic is great enough to pull thermocouples out of their pockets and to cause wires to break when the carriage is moved.
Disposal of mouldings
etc. Especially when starting up a machine or after fitting a new mould, a considerable number of mouldings have to be made and examined-
Often there is nowhere to put them except on any flat surface of the machine, which quickly becomes festooned with mouldings in various stages of completeness.
If a table or trolley is provided, the danger of leaving the mouldings on the machine is avoided and a step is made towards a tidier shop.
Tools, nuts and bolts, mouldings, purgings, and even cigarette ends all get mixed up on top of the machine, and some even end up in the granulating machine.
This sort of situation can rapidly develop unless a constant watch is made on housekeeping and cleanliness.
Who, for example, has not seen odd nuts and bolts, washers, and perhaps even a spare nozzle put inside the control cabinet of a machine “for safety”.
The provision of proper tool cabinets on trolleys and a spare parts box attached to each machine avoids this sort of trouble.
Care of packages
Most plastics, except those provided in bulk, are packed in paper sacks, generally with a polythene film interlayer.
Although fairly tough, the occasional sack ruptures and a trail of granules on the floor marks its travel through the moulding shop.
This should be avoided, if only to minimize waste, because of the cost of the material. The dust and dirt and the hazard of granules on the floor can all be avoided by using adhesive tape as soon as the tear in the sack is seen.
A frequent cause of dirt in the moulding shop is the small granulator placed by the machine so that the operator can de-gate the mouldings and re-grind scrap on the spot, ready for recycling.
There are two objections to this, and to the practice of drilling, machining, or otherwise treating mouldings while waiting for the next cycle.
- (1) dust is generated near to the machine and this, as has already been explained, can be detrimental to the control system;
- (2) by recycling scrap in this way a true material balance and machine utilization is difficult to obtain.
Turning to the machine itself: containing oil, circulating oil, and being lubricated with oil, the machine and all its surroundings all too often become an oily mess.
Oil on the floor is a hazard, making it slippery and attracting dirt and dust; oil on the tie rods or too much oil and grease around the machine makes mould setting and maintenance very dirty work.
If mechanically actuated lubrication systems are set to give too much lubrication, all parts of the machine where oil can accumulate become awash and it is then very difficult to keep mouldings clean.
Although lubrication is important, so is the cleanliness of the machine.
Coolant fluid and hydraulic oil
Another hazard to cleanliness in the factory is the cooling system When moulds are disconnected from the temperature controller there is nearly always some spillage of water or coolant.
Operators should be trained to use a bucket or container to catch the water and to drain the mould, using a low-pressure air line to clear all the channels in the mould.
Water drained from a mould often contains some rust and if an antifreeze material is included in the coolant, it should be saved and returned to the system after filtering.
Leaks from the hydraulic system, particularly from flexible hoses, are another possible source of dirt in the moulding factory.
They should not be allowed to develop because, if a flexible pressure line fractures, the whole moulding shop can be showered with oil.
Often overlooked, but nevertheless a fruitful source of dust and dirt in the moulding shop and a common cause of contamination of material, is the dirt lodging on roof supports, beams, pipelines and electrical trunking.
On a dry, windy day in summer with windows and doors open and ventilation systems working, the factory can soon be full of air-borne dust.
Regular cleaning can reduce this hazard and small birds can be excluded by means of wire screens. If birds build their nests in the factory roof they become a very mobile source of dirt and contamination.