Plastics Molding & Manufacturing/Operator Roles
A machine operator is by far the most important of all the various components that come together to make up the injection-molding process. The injection moulding machine can be fine-tuned and monitored to run flawlessly from cycle to cycle. BUT the operator is the only component with the capacity to actually think, and therefore can adjust his or her activities whenever needed from cycle to cycle. This attribute can be extremely beneficial to an employer because the operator can make on-the-spot observations regarding how well (or poorly) a job is running.
Focus on the operator role
editConsistency
editOperator must make sure that every cycle is run exactly the same as every other cycle by operation of the machine gate. For the semi-auto machine, the gate is simply a large sliding door that the operator opens at the end of a cycle to remove plastic parts, and then closes to begin the next cycle. On some machine,the gate opens automatically but it still must be closed by the operator. The timing of opening and closing the gate controls the consistency of the cycle. The operator must make sure that the opening and closing activities take exactly the same amount of time each cycle. A difference of as little as 1 second from cycle to cycle can make a difference of $10,000 or more a year in lost revenue to a company.
Solutions: Practices as counting time while performing the activity, or reciting a poem that has been created to finish at the exact second the activity is completed.For new operators, pair up with experienced operators to learn the tricks of the trade. |
Inspection of Parts
editOperator had little things to do when a molding job is running well. But in reality this is not the case. For instance, the molded part may not drop off the ejector pins when the mold opens or there may be a small amount of flash present on the molded part. This requires operator action to identify the errors and quickly corrects them. Even when the job is running almost perfectly, the operator must visually inspect the parts to make sure there are no defects. It is important to understand one major economic fact. Someone pays for every part molded, whether good or bad. The customer pays for good parts, the molding company pays for bad parts. It is imperative that bad parts be discovered quickly so corrective adjustments can be made to the machine settings. It is the responsibility of the operator to make those discoveries and immediately notify the supervisor to make changes to the settings. Regardless of whom are making the change, it must be recorded. This record should include pertinent information such as what change was made; what happened to require the change; the result of the change; and shift information including operator, supervisor, time, and date.
Solutions: Each job should have some detailed inspection information and boundary samples posted at the operator’s station so it can easily be seen what is acceptable and what must be rejected. The operator must constantly compare every molded part with that information. It soon becomes second nature for the trained operator to spot defects in a short period of time while inspecting parts. Veteran operators can spot these defects in a fraction of a second, while an untrained person may take several minutes to find the same defect. |
Inspection of Mold
editOperator must understand that mold is an expensive but necessary tool. The cost for one mold can be from tens of thousands of dollars to hundreds of thousands. Molds also takes from a few weeks to many months to be built. Some forms of damage may actually ruin an entire mold to the point of requiring total replacement. So, again, it is important to understand that damage to a mold is costly in terms of time and production that is lost while the mold is out of commission. Usually the customer is paying for building the original mold but the molding company pays for mold repairs.
Solutions: An operator can help minimize the amount of damage to a mold by simply looking at it every time it opens at the end of a cycle. Some common things to look for are flash, broken pieces of metal, missing components, water leaking from the mold, and part of a plastic part stuck or broken away. Basically an operator should get a good idea of what the mold should look like at the beginning of a job and notify a supervisor immediately if anything at all looks different at any time during the run. If anything does change, the operator should not close the gate, but wait until a supervisor has inspected the mold to determine if it is all right to close it. |
Inspection of Machine
editA molding machine consists of many parts that must work together. If any parts breaks down, the machine will not operate properly and may produce defective products, causing damage to the mold and become a safety hazard that can cause injury.
Solutions: The machine operator becomes the company’s eyes and ears for detecting any changes in machine operations. The changes can be subtle, such as simple clicking or whining noises. Or they can be very obvious, such as sudden oil leaks or clanging noises. As with the other inspection exercises, an operator must be aware of the normal sounds and appearances of the molding machine operation, and be ready to notify a supervisor immediately of any changes in those normal events. When the machine is operating properly, the sounds it makes eventually become background noise to the operator. They are there, but not really noticed. When a change in those noises occurs, it is like cold water in the face to the operator. The change is very obvious and the operator notices it immediately. At that point, the operator should notify the supervisor for immediate attention. |
Housekeeping ( 5S )
editProper housekeeping at the operator’s workstation is important for at least two reasons.
The first is safety. If items are left lying around where they do not belong, or if tools are not replaced in the proper area, there are high chances untowards incidents such as someone may inadvertently be cut with a trimming knife, or trip over a cables on the floor,may occur.
Solutions: Keep the immediate molding machine station area orderly and cleaned up, with all tools properly stored and loose items packed away or tied down. |
The second is contamination. This is the second most common cause of defects in molded parts (second only to moisture, which is also a form of contamination). These defects can be caused by potato chip salt getting into the plastic material before it reaches the hopper, or by empty soda cans carelessly deposited in material containers by people who thought they were trash barrels. It can even be caused by touching freshly molded plastic parts with hands that are oily or otherwise dirty.
Solutions: Wearing of gloves will help prevent hand oils from affecting parts and will also help to protect the skin from hot plastic. A small central vacuum will make it easier and more efficient to keep the immediate area clean and less dusty. Good lighting will help illuminate the area, making it easier to notice housekeeping problems. |
Attitude
editThe final area of responsibility for the operator to be concerned with is attitude. At times, the job of operating a molding machine can seem boring and tiresome. The job is mostly repetitive, and sometimes the operator feels that no one is paying attention to him or her. In a good productive company, this is not the case. Actually, the company wants to listen to the operator because it is aware that the operator knows better than anyone else how well or poorly a job is running and how to improve the efficiency or productivity of a job.
Solutions: Make sure the operator is part of the decision-making process, and will encourage the operator to make recommendations. Management should keep a bright outlook and cooperative attitude will go a long way toward ensuring satisfaction in the position of machine operator. Operators must realize that they are a vital link in chain that makes up the molding company. No one knows better than the operator the type of quality that goes into the products being molded. The molding company and the final customer both rely heavily on the operator to keep that quality level high, and the production costs as low as possible. |