“Green” Injection Molding, a Molder’s Path.
The recent popularity of green thinking can be embraced by a wide range of steps that fit with minimizing costs in the molding environment. For instance, saving energy reduces electrical costs. It does go far beyond that, and here at Recto Molded Products we have experimented with a lot of them.
On the material side of the discussion, there are a wide range of materials that are considered green for a number of reasons. Way back in time Henry Ford experimented with thermoplastics made from soybeans. Even before that, billiard balls have been made from not only thermosets, but also Cellulosics (from trees) that were a favorite material in the 1950’s as an impact material, before polycarbonate became popular. Even today Cellulose Acetate is the favored choice for screwdriver handles because people just love to hit them with hammers.
A recent arrival is PEK, polyetherketone, that is polymerized with 50% greenhouse gases. This material falls property wise between 6/6 Nylon and Acetals, with reduced friction than either.
Popular biodegradable materials like PHA and PLA are suitable for non-demanding applications and are more expensive than the normal choices like HIPS and Polyethylenes.
Can PEEK be considered green? With a cost of $40+ per pound every ounce is cherished in the manufacturing and design steps. A stretch perhaps, but arguable.
During manufacturing, green can be focused on using every ounce of material, recycling, reusing, and even using purchased previously used materials. Every pound that is diverted from landfill and has a productive life, then reused again is a benefit for all.
During manufacturing, green can be energy efficient processes of many forms. All electric or servo pump molding machines are equally efficient. Servo pump machines cost less so the cost savings can be utilized for other aspects of the operation. That is green in the more meaningful, financial sense. Recto Molded Products has more all-electric than servo pump machines because while they are 30-40% more expensive, they process faster, and are more precise. That is another factor in green thinking that is harder to quantify. Servo pump machines also use hydraulic oil where all-electric machines do not. Not using petroleum products is a positive gain, especially during third shift when a hose splits and oil squirts all over the place. It is important to shut off all equipment when not being used. Granulators and mold heaters tend to get left on when production is complete.
Having an efficient facility is also green. Solar panels of sufficient output to offset peak demands are beneficial, although the incentives to install them make payback periods extremely long. When roofing needs to be replaced, a white TPO membrane(with 2” of foam) will reduce interior summer temperatures by 10-degree F. Collecting rain water for cooling towers saves a very small (but increasing) amount of money, but the true value is the lack of chemicals that get left behind on the cooling tower itself. The “purer” water seems to evaporate slightly faster making the tower more efficient especially on very hot days. If the building is a bare ground build, installing a layered system of 1” PEX tubing around the perimeter of the foundation, then circulating 90F process water around system will help keep the building warmer in the winter, but also supplement the cooling tower’s efforts to cool the process water. Using a water-cooled chiller and using water cooled heat pumps for areas of the building that need conditioned space is very cost effective. Planting trees that only grow to 25’ produces a cool region around the building, without the inconvenience of significant leaf removal needs in the fall. Trees are especially appreciated if they are used in an area that will keep employee’s cars cool in the summer.
The molding area can get quite warm in winter, even with all electric molding machines. Reverse an air extractor fan and install a variable speed control for use in cold weather. Low fan speed on Monday morning start-up or when temperatures are very cold, higher speeds when things warm up. Having the extractor fan near the peak in the building mixes the warm air near the ceiling like a ceiling fan. Also use a fan combination in far areas of the building to “drag” the heated air from the molding area to other locations in the building. At Recto Molded Products during Covid, this constant supply of fresh air I believed resulted in zero employee Covid experiences. After the epidemic, we saw more cases due to people socializing during periods away from work.
LED lighting is the real deal, and recent new designs are quite surprising. Good lighting seems to improve productivity and quality.
Green environmental, and green financial are not mutually exclusive, being more profitable means greater efficiency which reduces the demand on resources.