SAFETY

Bernards' Injection Molding Tips, Techniques and Technology for Shop Floor Technicians and Supervisors | home

THE FOLLOWING IS MEANT TO SHOCK YOU

INTO THINKING ABOUT SAFETY

In 1989, a 40 year old male supervisor died as a result of being crushed by the clamp force of an injection molding machine. This person bypassed or removed the safety interlocks to work on the mold. Another person noticed that the machine was not in operation and proceeded to start the machine on an automatic cycle. As the machine cycled, it crushed the head of the supervisor using a "Pinch Point Action" (OSHA, 14 August 1989). For this accident, the company was issued violations for standard 95012901 - General Duty Clause and standard 19100212 - Machines, General Requirements. These violations cost the company $19,000.00 in fines and penalties.

The principal hazards associated with injection molding machines include: (1) crushing injuries due to clamp mechanism, (2) burns due to hot plastic, (3) limb amputation due to clamp mechanism or plastic feeding mechanism, (4) slips, trips and falls due to loose plastic pellets on the floor and (5) electrocution due to failure to de-energize circuitry prior to maintenance operations.

Other hazards exist in an injection molding company due to auxiliary equipment. These hazards include: (1) contusions and abrasions, (2) limb amputation due to scrap grinders, (3) being pinned by a robot or (4) burns from a hot mold.

The above information is from an OSHA report. There is so much that I could say about safety that it is overwhelming. Instead I will limit this discussion to some very basic elements of Injection Molding Safety.

1) LOCK OUT PROCEDURES

By law, your company is required to establish very detailed lock out procedures and by law, you are required to comply. Simply put, when ever you work on a piece of equipment and a "power hazard" exists, you are required to lock out the power source.

Below are a few of the basic elements for lock out procedures. Please realize that this is not a complete lock out procedure, it simply demonstrates some of the elements.

SUGGESTED ELEMENTS OF A LOCK OUT PROCEDURE

It is the policy of ______________ to maintain and enforce a written Lock Out Procedure. This procedure is to be applied at any time when unexpected motion or electrical or other energy release may cause injury.

The purpose of this procedure is to protect all employees from unintended release of energy or unintended machine motion which could result in injury when they set up, adjust, repair, service, install, or perform maintenance work on equipment, machinery or processes. This procedure and its' enforcement are mandated by Federal and State law.

EMPLOYEE AND MANAGEMENT RESPONSIBILITY

1) Each supervisor is to train new employees and periodically update current employees as to the requirements of this procedure is to document said training.

2) Each employee will be provided with an individually keyed lock which will be their responsible to maintain.

3) Managers, Foremen and Maintenance Department Supervisor are responsible for the enforcement of this policy including the use of appropriate disciplinary action.

4) The is to be notified of any failure to comply with any safety rule.

5) It is the responsibility of all plant employees to consult with their supervisor or the___________________ when ever they have questions regarding their protection or this policy .

UTILIZATION PROCEDURE

1) The power source of any equipment or machine shall be locked out before it is adjusted, setup, repaired, serviced, installed, etc. if unintended motion or release of energy could cause personal injury. Other sources of energy such as hydraulic, air pressure, etc. should be evaluated for the potential of personal injury the person doing the repair, etc. as above. Such energy sources shall then be relieved.

2) Each person who is making the repairs, etc shall apply personal safety locks.

3) The employee shall retain one key for every lock, the other key will be retained by the __________________.

4) Power is to be turned off at the main control only after the control at the point of operation is turned off.

5) If a machine connected by plug to a 110 Volt power supply a "Do Not Start" tag shall be affixed either at the 110 Volt plug or conspicuously near the start switch.

6) A machine connected to a power source greater than 110 Volts shall have the plug locked in an isolating device and a "Do Not Start" tag shall be applied.

7) Repair to a press or mold in a press shall not begin until the press motors (hydraulic pumps) are turned off and the press is locked out.

8) Before a granulator is cleaned the power shall be disconnected from the power source and an isolating device installed over the power plug and physically locked.

TO DOWNLOAD A PRINTABLE VERSION (MS Document 8k)

OF THE ABOVE LOCK OUT ELEMENTS

CLICK DIRECTLY BELOW

FOR FREE OSHA COMPLIANCE SOFTWARE CLICK

BELOW TO GO TO THE DOWNLOAD SITE

(click "back" on your browser to return here)

THE FOLLOWING IS NOT MEANT TO FRIGHTEN YOU. IT IS, HOWEVER, MEANT TO SHOCK YOU INTO THINKING ABOUT SHOP FLOOR SAFETY. I GUARANTEE THAT IF YOU READ ALL OF THE BELOW, YOU MAY VERY WELL SAVE YOURSELF OF SOMEONE ELSE FROM SERIOUS INJURY OR A PREMATURE TRIP TO THE STARS.

On August 11, 1992, a 20-year-old production worker at a plastic injection molding company contacted 220 volts (ac) in an uncovered electrical box, housing the on and off buttons. The OSHA investigator was notified of the fatality by the county coroner on August 12, 1992. The OSHA investigation was initiated on August 13, 1992 with an interview with the employer and tour of the incident site. Also interviewed was the county coroner. The company involved had been in operation for five years and six months. At the time of the incident 17 persons were employed, 12 of which had the same job title as the victim. The victim had been employed by the company for approximately five weeks. The employer did not have a designated safety officer or written safety plan at the time of the incident. Employee training was accomplished on the job. The employer provided hearing and eye protection to the employee.

This plastic injection molding company manufactures small furniture fixtures, toy items, and plastic funnels. This operation runs three shifts, the victim was working a 2:55 pm to 11:10 pm shift. At the time of the incident, approximately 9:30 pm, there were 4 employees present. The victim was operating the Cumberland brand 8x10, serial #39006180, plastic grinding machine. It was plugged in to a 220 volt ac outlet in the area where it is used. The outer cover for the on/off buttons was missing. Apparently the victim went to activate the off button and missed. Her fingers slid by the button and contacted the energized part of the switch. The victim was electrocuted by the 220 volt power source.

According to an interview with the co-worker, she normally works with her back to the victim and the grinder. She heard a noise coming from the victim, as if she was trying to speak. She turned to see the victim lying against the machine with her right hand inserted into the switch box housing the on/off buttons. Sparks were being emitted around her hand. The co-worker immediately pulled the plug on the grinder and summoned help. The victim fell to the floor following the de-energization of the machinery.

The emergency medical service was summoned to the incident site. The plant employees had no CPR training and the victim was offered little assistance until the EMS arrived. Upon their arrival victim was found lying on her left side. The victim had no pulse, no respiration and no blood pressure. CPR was initiated as well as Advanced Cardiac Life Support (ACLS). Attempts to resuscitate the victim were continued in route to the local hospital where she was pronounced dead shortly after arrival.

During an interview, Gary Bean related a story of a 22 year old female that was burned via a purging. She was standing nearby while the supervisor purged her machine and made it ready for production. After purging, the supervisor went to place the hot, melted plastic on the floor. As he turned to place it on the floor, carefully using a large screwdriver to maneuver the plastic, he inadvertently threw it on the arm of the operator. She suffered third degree burns on her arm as a result (Bean).

John Jarrells told of a person that lost the sight in one of their eyes due to hot plastic splashing on them. This person was setting the machine up for production, during which he purged the degraded plastic out of the barrel of the machine. As he was purging, the plastic sputtered and splashed. A nearby operator called out to the supervisor and as he turned to talk with the operator, the plastic splashed again. His eyeglasses did not have side shields on them and some of the hot plastic splashed into his eye, thus causing the loss of sight (Jarrells).

Burns can also occur due to the heat of the injection unit itself. To melt the plastic, the steel "barrel" of the injection unit must contain an equal portion of heat. A representative accident involving the barrel could be that a person has started to slip and reaches out for support. In place of holding the bed of the machine, they grab the barrel. A first or second degree burn would then ensue.

Electrocution can also occur due to contact with the barrel of the machine. The barrel is surrounded by heating elements that are electrically powered. Should one of these elements become ungrounded, shocks would be possible. This hazard is remote, but possible. Injection molding machines draw power from hydraulics and electricity. Contact with electrical circuits are another danger in dealing with these machines. This particular hazard falls to personnel during a repair operation. Electrocutions occur as a result of leaving the machine energized while attempting a repair. Many accounts detail experiences with electricity, ranging from simple "jolts" (110 volt power) to death from the 440 volt circuitry.

The facility that contains the injection molding machines also offers the "opportunity" for electrocution. To power the plant, it is necessary to run "bus bars" of electrical power to all of the machines. These bus bars contain wiring that carries tremendous (up to 10,000 amperes) of current. Coming into contact with any of these bus bars could easily be lethal.

An example of electrocution comes from NIOSH (1987). A "set-up" man was killed while attending to a quality problem. As he closed the safety gate on the machine, he was also in contact with a grinder. The grinder had a ground fault and the machine provided a grounding route via the man. Thus, the 270 volts powering the grinder went through the body of the man, stopping his heart. No one at the company knew cardiopulmonary resuscitation and help was 16 minutes away.

Slips, trips and falls occur in many ways within injection molding companies. The most common slip transpires because of plastic pellets on the floor. Plastic is transported to molders as pellets contained in bags, boxes, truck load or rail car. In truck load and rail car quantities, the pellets are stored in large, grain-style silos. The plastic enters the plant via pipes directly connected to the molding machines, thus preventing most spills. But, for companies that use bags or boxes, spills are common. With these pellets on the floor, it is nearly impossible to prevent slips. Fortunately, most of these slips are minor.

Falls can be much more dangerous. Prior to entering the injection unit of the molding machine, the pellets are stored in large hoppers attached to the top side of the injection unit. A vacuum system moves the plastic from box or silo to the hopper. This vacuum system contains a piece of equipment (the loader) that sits on top of the hopper. It is often necessary to construct platforms for personnel to attend to these loaders. These platforms require ladders and can be as high as 20 feet in the air. Falls transpire when a person attempts to maneuver the loader while either on the ladder or the platform.

The auxiliary equipment around an injection molding machine contain several hazards. The first piece of necessary auxiliary equipment is the mold itself. A mold consists of a minimum of approximately 1000 pounds of steel and assorted other metals. This chunk of metal must be positioned in the molding machine. Positioning the mold involves lifting it up and over the framework of the machine. This is done either by overhead cranes or by fork trucks with chains. Either of these methods have some inherent dangers of their own. Should the mold be mishandled, it can lead to crushed and/or severed limbs.

Scrap grinders present dismemberment perils to operators and setup personnel. The rotating blades contained in these machines can either directly amputate a body part, or it can trap loose clothing or jewelry. Glenn Looper recounts a story of a maintenance person that got a finger cut off by one of the blades. While sharpening the blades of a grinder, his hand slipped and he severed his finger. Fortunately, he was hustled to a hospital where they were able to reattach the finger (Looper).

Since grinders granulate material, it is possible for some of it to fly into the eye of a person operating the grinder. Gary Bean related an account of one such accident during his interview. The person was operating a grinder, granulating off quality pieces. As the machine chewed up the pieces, small, ground fragments of plastic flew into the air. Several of the bits of plastic ended up in the operator's eye. It took several minutes at an eyewash station to remove the plastic (Bean).

Dryers offer burn hazards to all personnel that work around molding machines. The dryer is connected to the material hoppers via hoses that carry the hot air to the material to eliminate the moisture. As these hoses are generally insulated, the danger is not great. Looper relates an account of a person that slipped and fell on some loose pellets on the floor. As they fell their hand and arm became entangled with the dryer hose. After sorting himself out and getting up, the only true harm was to his pride. No burn had occurred due to the dryer hose (Looper).

Machine mounted robots contain the second most prevalent source of hazards in injection molding companies. The major concerns with machine mounted robots are: (1) trapping, (2) falls and (3) electrocution. An example of trapping was related by Gary Bean during his interview: A maintenance employee was in the process of setting up a manufacturing work cell. This involved installing two molds into two molding machines, after which the automation equipment was put into place. The final step was to assure that the robot would pick the parts out of the mold and then place them correctly onto the conveyor system of the automation. The mold and automation installations went according to plan. When the maintenance employee cycled the robots, he was standing too close to the conveying system. As the robot descended to drop the parts, it trapped the man by pinching his head between the robot arm and the conveying system. As the robot would not ascend until reaching its full downward position, the man's head prevented this, the man was trapped until power could be cut from the robot. This was to be accomplished by hitting an emergency stop button. The man could not reach the button to kill the power. Finally, the man was unable to scream out, as the robot had him pinned from the top of his head and his chin rested on the conveyor. Fortunately, a person saw the condition and cut the power switch off. The maintenance man suffered some bruising and a laceration on his head that required 8 stitches to close (Bean interview).

The first hazard discussed earlier refers to the ability of the clamp unit to either dismember or kill. Mechanical guarding is an effective means of preventing these injuries. All three of the standards require that the clamp unit have fixed guards surrounding the "rearward" half of the clamp (ANSI 1990; SPI 1992; SPI 1996). These fixed guards prevent two types of clamp related injuries: (1) getting pinched/caught by the "knuckle" part of a clamp and (2) being caught by the gear that sets the amount of stroke for the machine. These fixed guards should also contain electric interlocks to avoid their being removed and the machine actuated.

The front half of the clamp unit calls for moveable guards (ANSI 1990; SPI 1992; SPI 1996) on the front and back of the machine. Placing molds and retrieving product from within the mold necessitates the ability open a guard. Also, during setup or due to quality issues, it is necessary to adjust the process of the machine. The ability to retrieve parts from within the mold is critical during processing. To protect the operator and all other personnel, a safety door is installed. The safety door blends three separate systems to prevent the mold from closing on a person. The first system used is an electrical interlock. When the door is open, the electrical power circuit for the machine opens and will not allow power for closing the clamp. Oftentimes, the machine will have more than one electrical switch attached to the safety door. The second system is a hydraulic interlock. As the clamp moves via hydraulic power, this interlock prevents the flow of hydraulic fluid into the mechanical cylinders that actuate the clamp unit.

The final system is a mechanical device that physically prevents the mold/clamp from closing. The device can either be a drop bar that actually blocks the mold from closing or a system of pawls and ratchets that engage to prevent movement. These physical devices differ on each model of machine, as the size and strength necessary changes. These devices must also be adjusted for each of the molds placed within the machine, particularly as the stroke of the clamp unit changes. The back side of the clamp unit also has two separate guard systems. The rearward half again has fixed guards. The front half has a semi-fixed gate. This gate is only used for installation of molds, not for part removal. The back gate protects via an electric interlock (similar to front gate) and a hydraulic interlock (also similar to the front gate). It does not, however, have the mechanical device. These systems "should be inspected at each eight hour shift to ensure proper operation (NSC Data Sheet I-454, 1988)." The stroke of the unit can sometimes "slip." Also, it is possible for the switches to become loose and less effective.

The injection unit can also be controlled via guards. All three of the standards (ANSI 1990; SPI 1992; SPI 1996) again call for guards to protect the front, rear and top of the purging area. An electrical interlock insures that the guard is in place during the automatic running of the machine or during the purging cycle. Should viewing of the purge area be necessary, a window should be provided that will with stand the splashing of the plastic material without failure.

As an added precaution, safety glasses, with side shields, or face shields should be worn to avoid injury due to splashing of the hot plastic into a person's eyes. The standards (ANSI 1990; SPI 1992; SPI 1996) require that the company provide these personal protective equipment items to all employees.

To prevent electrocution hazards, the company should establish an adequate lockout/tagout procedure. The company should also provide the means for positive lockout. For example, the company provides individual locks to all employees. This policy should be enforced vigorously, with discipline when necessary. Molding machines (and auxiliary equipment also) should be readily equipped with adequate lockout allowances. For example, holes should be put in the main power switches for the machine so that a lock can easily be mounted when the switch is in the off position. Another example would be to put holes in the contacts of the electric cords for auxiliary equipment, again allowing ease of insertion of locks.

There are three standards that directly apply to injection molding machines. These standards are:

ANSI/SPI B151.1: Safety Requirements for the Construction, Care, and Use of Horizontal Injection Molding Machines, Revised 1990.

Recommended Guideline for the Safety Requirements for the Manufacture, Care and Use of Single Station Vertically Clamping Injection Molding Machines. 1992.

Recommended Guideline for the Safety Requirements for the Manufacture, Care and Use of Multiple Station Vertically Clamping Injection Molding Machines. 1996.

All of these standards are comprehensive in nature. They cover the molding machines and all auxiliary equipment, except for robots. Standard (1) & (2) are very similar in nature. There are no discernible differences between the two. The third standard is different in that it adds some clauses related to having multiple stations.

The injection molding industry is making great strides, but, there are two glaring weaknesses. The first weakness is the general level of training at most companies. The other is enforcement of policies. Many of the 5500 companies are small "mom and pop" type places that do not emphasize safety training or enforcement. As roblematic as the "mom and pop" places are, there is also a lack of training and enforcement at some of the larger companies. Upon reviewing the OSHA data for this report, it was discovered that one of the ten largest injection molders in the world had been given a violation (out of 11 violations given to the company) for lockout / tagout. To ensure that this industry keeps improving its safety record, the managers that have started to see the value in their people must accelerate the pace of improvements. We must not only make the machinery safer, we must force the people themselves to be safer. Gary Clubb, formerly of A&E Products Group, related the story of a person crushed by a molding machine (Clubb interview; OSHA, 14 August 1989). The person that was killed bypassed the electrical and hydraulic interlocks on the machine while working inside of it. All of the needed safety devices were in place, the person was the unsafe factor. With this in mind, we must compel everyone in the industry to understand and fulfill their obligations to safety.

Bean, Gary (Technimark Plant Manager). Personal Interview. 12 March 1998.

Clubb, Gary (United Southern Industries Quality Manager). Personal Interview. 14 April 1998.

Griffiths, J.C. "Plastic Injection Injury of the Hand." Injury 8 (1978): 143-144.

Jarrells, John (Technimark VP of Engineering). Personal Interview. 12 March 1998.

Looper, Glenn (Technimark Plant Manager). Personal Interview. 14 March 1998.

Raafat, HMN. "Comparative Strategy for the Safety of Horizontal Injection Moulding Machines." Safety Science 16.1 (1993): 67-88.

Raafat, HMN. "Effectiveness of Standards for the Safety of Horizontal Injection Moulding Machines." Journal of Health and Safety 8(1992): 5-22.

Society of the Plastics Industry. Recommended Guideline for the Safety Requirements for the Manufacture, Care and Use of Multiple Station Vertically Clamping Injection Molding Machines. Washington, DC: SPI, 1996.

State of Wisconsin. Department of Industry, Labor and Human Relations. Analysis of

United States. Bureau of Labor Statistics. Fatal Occupational Injuries by Industry