Safety aspects at injection molding plant
It would be fairly safe to say that, if all aspects of good housekeeping were strictly observed , there would be very few accidents in the molding shop.
Unfortunately，good housekeeping is often sacrificed in the cause of keeping production going, sometimes with disastrous results.
Spillage of granules on the floor has already been mentioned, along with leakages of oil. The combination of granules, oil, and water often met in the molding shop.
the floor can be almost lethal. Oil spillages are sometimes soaked up with rags and sawdust which are then left on the floor for hours, or even days at a time.
It only requires a cigarette end or a spark to start a serious fire.
Proprietary materials are available for soaking up oil and rendering it almost non- inflammable but it really is best not to spill it in the first place.
Early attention to leaks and the use of a drip tray during maintenance work will do much to avoid this hazard.
If an accident does occur, resulting in a spillage of oil, it is best to soak it up, clear the floor, and wash with a suitable detergent solution.
Observation indicates that very few floors in injection molding shops are ever washed!
Flexible pipes and leads
One often sees flexible air, water，and electrical connections draped in festoons around the machines.
This cannot be thought of as good housekeeping and could easily be a safety hazard.
A forklift truck or a mold lifting gantry can easily foul the pipes and wires.
At best，there might be a water leak with not much danger, but a fractured electrical lead could cause a severe or even fatal accident.
All flexible leads should be clipped into neat positions and mold temperature controllers should be arranged as near to the machine as possible.
Obviously，if any of these connections can be run over on the floor by trucks and barrows there is an additional hazard. Even treadling on such leads could be the cause of trouble.
It is a good plan to colour-code all auxiliary connections to the machine with distinctive markings so that they can be easily and quickly traced.
Machine guards are particularly important. If there is any possibility that hot plastic could be sprayed over an operator there should be a guard made of a robust transparent plastic such as Perspex acrylic sheet or polycarbonate sheet.
These materials can be shaped quite readily in most small workshops.
Expanded metal guards which are often fitted to machines are no real safeguard if hot material is being sprayed out.
Hot water, hot oil, or glycol circulating through a mold can present a safety hazard and frequent checks should be made to ensure that flexible connections to the mold are not being abraided during mold opening and closing.
The sheet plastic guard already mentioned will help to reduce the danger should one of the leads be fractured.
Disposing of purgings and hot material
Good housekeeping dictates that purgings and hot material should not be allowed to stay on the machine.
They can cause unpleasant burns which take a long time to heal.
Remember that plastics have very high heat capacities and keep hot for a long time.
Purgings of acetal are best put straight into water, especially if they are decomposing.
Although unpleasant and toxic in large doses, formaldehyde,the decomposition product of acetal plastics is lachrymatory and is liable to drive the personnel out of the factory long before it can do any lasting damage.
Ventilation is an important aspect of safety in housekeeping.
Some plastics contain additives that can have a slight toxic effect and some might contain minute quantities of suspected materials.
One such plastic is PVC. Stringent precautions are observed in its manufacture because of the suspicion that the monomer VCM might have certain physiological effects.
There is virtually no chance that VCM could be liberated during the injection molding of PVC but no risks should be taken and a special extractor system is very desirable over machines used for this purpose.
All plastic mold shops should be very adequately ventilated,not simply by the opening of windows and doors but by means of extractor fans in the roof above the machines.
Adequate and efficient lighting is of importance,particularly from the point of view of safety.
Lamps，tubes，and reflectors need regular cleaning and faulty lamps should be replaced as soon as possible,even though they may be in inaccessible places.
Of course, faulty switches should be taken out of service immediately and replaced as quickly as possible.
Although as much energy as possible should be saved by switching off unnecessary lights, this should never be done to the extent of jeopardizing safety.
The desirable levels of lighting for various industries are laid down in factory legislation and should be strictly adhered to.
Some operations which take place in connection with the molding of plastics require the provision of safety glasses to be worn when using grinding equipment, etc.
It is also desirable to provide them to operators working on granulating machines because the small particles which sometimes tend to fly out of the feed throat can be harmful to the eyes.
Lifting tackle，including slings, A-frames hoists, and fork-lift trucks, needs to be regularly inspected to ensure continued safety in operation.
Each item should be clearly marked with the safe working load, and all plastic molds, especially larger ones, should have their weight stamped on them.
Accidents with fork-lift trucks are possible if too heavy a load is slung from a position to far along the fork.
Each mold should，for preference, be supplied with its own lifting eye and make-shift slings of any description should never be used.
It is unwise to sling any mold with a piece of ordinary rope and the proper equipment should always be used.
As an additional safeguard where heavy pieces of equipment, such as molds, are being regularly handled, it is wisest for the operator to wear safety shoes or boots.
These have a strong steel toe-cap and can be instrumental in saving broken bones in the feet if an accident occurs.
Ladders and scaffolds need to be of robust and firm construction.
Some of the portable steps often seen in molding shops are somewhat unstable,having castors and spring-loaded steadies which come into contact with the floor when anyone mounts the steps.
Until the weight is actually on the steps they are free to move, and this can be disconcerting to the operator carrying a 25 kg sack of plastic granules on his back.
Strong wooden steps, suitably designed for each machine,having a hand-rail, platform and non-skid steps are much to be preferred.
Where there are bridges over pipes on troughs on the floor,they should be given a non-skid surface.
Ladders should be securely fixed and two persons should always be employed when long ladders are being used.
Air lines and hoses should be regularly inspected, water traps blown clear at intervals and filters renewed.
If water from air lines is inadvertently blown on to electrical equipment, particularly printed circuit boards，a great deal of damage can be done.
The practice of blowing dust off the clothing by means of an air line can be extremely dangerous and should on no account be allowed.
It is all too easy for air to penetrate the skin, and air embolisms can prove fatal.
Fire-fighting equipment should always be accessible and all persons working in the molding shop should know where it is and how to operate it.
One of the best safeguards is a sprinkler system, the installation of which can save enough on insurance premiums to pay for itself in a very few years.
However, the damage to material in the event of its operation can be considerable and it is wise to take extra precautions in its storage.
Asbestos fire blankets are very useful, particularly if clothing catches alight or if the fire is small and can be easily confined.
It is also a good plan to have a static water tank or fire buckets available at strategic points in the building.
Noise in the molding shop is a hazard to health and safety and should be prevented or reduced as much as possible.
Sometimes panels are removed from machines during maintenance and are not properly replaced.
Without them，the machine is not only more susceptible to the entry of dust and dirt, but it is also often noisier.
With very noisy machines, thick block- board screens can do much to reduce noise and to make for more pleasant working conditions.
If portable granulators have to be used in the molding shop, a strong blockboard cabinet surrounding each one will help to reduce noise and will also eliminate dust- Where an operator is using a large granulator for several hours at a time, ear muffs must be provided.
Of course,the greatest single step towards the reduction of noise in the molding shop (and to the better utilization of energy) will be taken when machines no longer have individual power sources,but are supplied from a central hydraulic fluid reservoir, with the motors and pumps in a separate sound-proof room.
This used to be the situation in the days of compression molding when many machines operated from a central supply system and the only noise was the gentle hiss of steam from a steam trap.
Minor accidents are bound to happen and the provision of proper equipment for treatment may prevent them from developing into something worse.
Trained first-aid personnel should be available on each shift and should be responsible for ensuring that the equipment is complete at all times.
An eye-wash bottle is a useful additional item in case of an operator getting dust or other foreign matter in the eye.