Robot/auxiliary/molding machine supplier Wittmann Inc. (Torrington, CT; www.wittmann-ct.com) offers the following advice on how to conserve and reuse materials, evaluate energy efficiency in dryers and injection molding machines, and how to make the most with your automation. Plus, see how advances in screenless granulators are allowing medical molders to realize energy and material savings by using regrind in a closed-loop cleanroom setting. These tips apply to a wide range of machinery, and more information on the specific products offered by Wittmann is available on its website.
Sustainability in material handling
• Eliminate spillage—use silos, surge bins, and totes instead of open gaylords. Use conveying systems instead of manually handling gaylords.
• Eliminate material contamination—same as above.
• Reduce labor and forklift use—use a central material area and efficient multimaterial conveying systems to deliver material to the processing machine.
• Reduce floor space requirements—reduce the number of gaylord boxes in inventory by purchasing in bulk; reduce the number of brands and types of similar materials; use silos and surge bins.
• Reduce energy consumption and increase machine utilization with efficient just-in-time (JIT) material conveying systems. These systems use quick cleanout, minimum-inventory vacuum loaders and machine hoppers, and line purging functions to eliminate wasted material. They support faster material changes, multimaterial central drying systems, and quick-change manifolds.
• Use a central drying system in lieu of individual press-side dryers to reduce floor space requirements, gaylord handling at the machines, and press downtime waiting for material to dry. Conserve energy using one larger dryer instead of multiple small units.
• Reclaim scrap material by using grinders, proportioning valves, and blenders.
• Increase the amount of regrind used in new parts utilizing precise weigh-scale-type blenders that exactly control material ratios as well as documentation of product material composition.
Sustainability in dryers
For any discussion on energy consumption to be useful, the processor needs a standardized test method and common units for comparison. When it comes to drying, energy consumption is quickly becoming a key factor in the decision-making process for one technology over another. However, drying energy consumption has several elements and key factors that affect the overall energy usage of a dryer. The combination of heat-up energy and sustainable drying energy are the elements that will, in the end, affect how much it costs to dry your resin on an annual basis. A uniform industry test standard would define the air capacity, basic load, and kWh/unit of material, allowing the processor to enter the given material, throughput, and local energy rate to calculate the true annual energy cost.
Sustainability in injection molding machines
As high energy prices increase manufacturing costs, molders are looking to reduce consumption. In addition, many energy providers offer rebates for reductions in energy consumption or investment in energy-optimized machinery. This has prompted molders to look at new ways to minimize their reactive load (which peaks several times during the molding cycle) at the machine to realize savings.
Published data indicate recently introduced electronic real-time control devices at individual injection molding machines can offer substantial savings. Actual results with these devices indicate reductions of 12.4-45.9% in reactive power and 22-61% in current are achievable.
Other measures to improve efficiency of a molding cell can be examined using a best practices review of process settings, mold construction and insulation, and energy efficiency of auxiliary equipment associated with the molding cell.
Automation efficiency: Using robots for advantage
One of the least expensive but potentially most beneficial steps a processor can take to ensure its robots and other automation are operating to its best advantage is an audit of current operations. Improving automation efficiency based on what already exists may seem obvious, but many processors often don’t have the time or staff to determine if the equipment is performing at its best or if it could do more. The ultimate goal is to identify minimal cost enhancements to an existing process or equipment in return for additional savings over the life of the project.
The use of part removal robots and automation can reduce scrap and labor, along with increasing product output and quality. Automation gives a molder more options for quoting on new types of projects such as insert molding, multicomponent products, or inmold labeling, thus setting one’s capabilities apart from "ordinary" molders.
Regrind in medical market?
The medical market has not traditionally seen as many applications for regrind as other markets, but this is changing with the increased use of low-speed, screenless granulators for cleanroom applications. Material is cut only once, producing uniform regrind with fewer fines. A major contributor to fines from conventional granulators is the unnecessary cutting of material due to excessive rotor speed sweeping sufficiently size-reduced particles past the screen holes.
Another cause is a plugged screen, a problem eliminated by screenless granulators. Significantly less horsepower is required for a low-speed/high-torque screenless granulator than for a conventional granulator. Not only do these units use less energy, but the elimination of fines and dust opens up new applications for cleanroom medical processors that use closed-loop systems to convey material from the granulator to the processing machine.
The processor not only cuts material costs by using regrind, but there is also less chance of material contamination in a closed-loop process. There is also energy saved when dried regrind can be reintroduced directly into the processing machinery without further drying, and let’s not forget eliminating any risk of resin degradation.
Clearly, if medical molders are experiencing cost savings and benefits using regrind, then one would expect molders in other markets where material price pressures are equal or even greater to review what they are doing (and look at new applications) to see if they could benefit from using screenless granulators.—[email protected]