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Safe Injection Unit Servicing Procedures

After recently hearing about an on the job injury I decided to post an entry on safety procedures and their importance.
My Thoughts
Whenever you are servicing a mold be sure to move back the injection unit from the clamping unit. Pressure can build up in the barrel when the nozzle is in contact with the sprue bushing. If a cold sprue is removed with the injection unit forward any pressurized plastic behind the sprue can shoot out resulting in serious burns or injuries. 
Remember, the heat shields around the machine barrel and heater bands can become very hot during operation and will stay hot for hours after the molding machine has been shut down. Take great care in determining the proper protective equipment needed when working on machines. Although the machine may have been turned off hours ago some regions of the injection unit may still cause serious burns. Even though heat resistant gloves may be common in your facility, take care in protecting your forearms and the rest of your body as well. I have seen many people burn their arms while wearing heat resistant gloves because they had short sleeves. 
High voltage components are enclosed within electrical cabinets, and are typically located on the front side of the molding machine. Anyone working on electrical machinery should be fully versed on the plant’s “lock-out / tag-out” procedures. Failure to follow the proper procedures can results in a serious shock or death. 
-Andy

Avoid Oversizing Your Micro-Molding Machines…

I was recently asked to determine if a specific machine is adequately sized for a specific job…

The Situation
The machine was 40 tons with a 1.5 oz barrel.
The part requires less than 5 tons with a 0.1 oz shot size.
My Response
The machine is much to large for molding a single cavity. The mold requires less than 25% of the tonnage, and the shot size is approx. 7% of the overall shot size. As a result, such a mold would result in a very inconsistent processes with a long barrel residence time and inconsistent mold clamping.
Since the mold was not yet constructed, the molder could create a two or four cavity mold which would better fit into the machine and better utilize the machine’s capabilities… though a smaller molding machine would still be better suited for a one or two cavity mold.
Additional Thoughts
Since larger machines use more energy, the closer you can match a mold to the machine’s capabilities… the more efficient the overall process will run.
-Andy

On-The-Job Training…

I was asked this question late last week…

John
How should I approach on-the-job training?
My Response
The best approach to on-the-job training is to structure the training and combine it with other forms of training.
Let’s assume you wanted to teach someone how to measure melt temperature, but you also want them to ensure they do this regularly as part of their job function. For the person to actually use the information, they must know why it is important to measure the melt temperature. As a result, you need to teach the person with three steps 1) explain why measuring melt temperature is important 2) instruction on how to properly measure the melt temperature safely 3) allow them to practice this test themselves.
Additional Thoughts
Basically, demonstration alone does not teach the concepts. You must also teach the employee why something is important… or they will never perform the function consistently.
-Andy

Using the Correct Cleaning Solutions…

Situation: I was recently at a molding facility with relatively new molding machines, but the safety window was all hazy, and the paint is already dulled. When I asked around, it turns out the technicians were using mold cleaner to clean the machines including the safety glass.

Cause: The technicians did not realize that the solution used to clean grease and residual volatiles from the mold surface was very caustic to the paint and plastic safety window.
Solution: In all cases, you should use the proper cleaning solution to protect the integrity and value of your equipment investment. Luckily, this company did not use equipment cleaner on the injection molds, but the lack of concern and knowledge is clearly evident. By not educating their technicians about the best method of cleaning the production equipment, the appearance of the production equipment makes a poor impression on visitors… especially their customers.
-Andy

Safely Removing Stuck Runners…

Last week, while at a molding facility, I had to instruct a molder on the safe way to remove a stuck runner…

Situation
When touring the plant, I witnessed a machine operator removing opening the door, reaching in with his bare hand, and pull a stuck sprue from the bushing.
Problem
This action by itself seems pretty routine, but the operator forgot a key element… YOU MUST BACK UP THE BARREL AND PURGE BEFORE REACHING INTO THE MOLD AREA DURING PROCESS INTERRUPTIONS. This will help prevent the possibility of pressure build-up and melted material being injected into the mold area while the operator reaches into the mold area.
I know hundreds of people who have either been burned or know someone who has been burned as a result of this oversight. Hot molten plastic will either burn your hand or actually become injected under your skin. In either case, the result is almost always disfigurement, amputation, or death. Never let your employees do this.
Recommendation
Please review your procedures and ensure that your employees are not making this dangerous mistake.
-Andy 

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