Automation of Materials Handling Systems Is Key to Cost Savings

By treating raw materials handling equipment as an afterthought, or as a secondary expense to primary machinery, plastics processors are missing out on costs savings and productivity enhancements.

“Auxiliary equipment is often given short-shrift because it does not cost as much as the primary equipment,” said Patrick Smith, vice-president of marketing and sales for the Aston, Pa.-based Maguire Products Inc., a supplier of raw materials management equipment and software. “You can have the absolute best Husky machine, which is state-of-the-art, but if your blender is messing up, or your dryer is not properly drying materials, you can destroy any productivity gains you may have counted on when you invested in the primary equipment.”

Smith, along with many other raw materials management and equipment suppliers, say it is often shocking to see how inefficiently plastics processors uses raw materials handling equipment, and how poorly resin is moved about a plant.

For example, it is not uncommon to find an injection molding machine hooked up to a piece of auxiliary equipment that it is not compatible with. Either the device cannot handle the necessary workload to keep the molding machine operating at peak efficiency or it allows contaminants into the system. On some shop floors, resin is moved manually from dryers and blenders, slowing down production and increasing the chances of resin being inadvertently mixed with other materials.

Also, it’s not unusual for a rushed employee to take resin that has spilled onto the floor and dump it into a nearby gaylord without checking for wood chips, nails or other debris. Machinery suppliers also say, despite traditional common sense, too often that same person does not even bother checking if the resin picked up off the floor is the same as the resin in the gaylord. The resulting contaminated resin can spoil a production run, or in the case of a foreign object, damage an expensive molding machine.

AUTOMATION TO KEEP THINGS RUNNING SMOOTHLY, CLEANLY

Preventing contamination or damage to a molding machine can be achieved, however, through automation. Suppliers of raw materials management systems and auxiliary equipment recommend plastics processors automate many or all materials handling functions. Automation not only cuts down on the possibility of operator error, but can produce cost savings by allowing for better monitoring of the amounts of resin used in a manufacturing process.

Maguire’s Smith said his company’s Weigh Scale Blenders (WSBs), introduced in 1989, provide automation that can help produce such cost savings.

For use with injection molding, blow molding, extrusion coating or cast film production, the WSBs can be mounted over the throat of an extruder or molding machine, and can blend and meter batches of resins and additives in a variety of ratios. The WSBs dispense resin and additives from separate hopper bins into the weigh chamber and funnel the raw materials into the processing machine in the exact amounts and ratios needed.

Smith said this gives processors greater control over the quantity of resins and additives used, thereby allowing for improved cost control.

Since between 40 and 70 per cent of the cost of a plastic product is materials, ensuring the blender is feeding the processing machine just the right amount is crucial. An improperly calibrated blender, or one that has been allowed to ‘drift,’ can cause a plastics processor to use more materials than necessary, thereby increasing overall costs, Smith added.

“We had an automotive supplier that saw a payback on the (auxiliary) equipment in three months because it discovered it was overdosing on colour but had no idea it was doing so,” Smith said.

This automotive supplier used the blender’s controls to discover the problem and to set the right levels, and they were locked them in to prevent any drifting or accidental changes. The result was more efficient use of resin and consequently, cost reductions.

OPTIMAL DESIGN FOR MATERIALS HANDLING

Further efficiencies and costs savings are possible if plastics processors also take the time to better layout the shop floor so auxiliary equipment can be used to its full potential.

It is common for some processors to have resin dryers in different parts of the plant, away from the location of the molding. This means dried resin is often manually transported to the molding machines, wasting time and increasing the possibility of the dried resin re-absorbing moisture during transportation.

And operations don’t necessarily improve if dyers and other auxiliary equipment are kept close to molding machines.

“I’ve seen molding machines with a dedicated dryer sitting on, or next to, that machine, then a gaylord of material and blender beside that machine as well,” said Chuck Thiele, senior consultant with Conair in Pittsburgh, Pa.

“All you are causing is a lot of unnecessary congestion around the machine,” he explained. “If this is a molding operation where materials have to be changed often, in order to change those materials, the hopper has to be emptied, cleaned, refilled and then the new materials have to be dried. This can take up to four-and-a-half-hours.”

This downtime costs money — quite a lot of money.

If a molder has to change materials up to 10 times a week, that means there would be 40 hours of machine downtime. If that machine’s time is worth $50 per hour, then it adds up to $2,000 a week of lost productivity. Spread over a year and possibly multiple machines, lost productivity could accumulate to tens of thousands of dollars, even though initially it seemed logical that placing the raw materials handling equipment close to molding machine would help keep costs down.

Thiele said the goal is to use raw materials handling equipment in such a way as to reduce, or possibly eliminate, downtime and to prevent molding machines from receiving the wrong mixture of resins or contaminated materials during changeover from one batch of resin to another.

Conair’s ResinWorks System is made to do just that by combining drying, blending and conveying into one system that can be customized to fit the particular needs of any plastics processor.

ResinWorks includes measured airflow to each hopper, integrated airflow and temperature controls, protection from over-drying and automatic line purging and dry-air conveying to reduce the chances of resin contamination and rehydration.

Brian Da Silva, vice-president of research and development with Mould-tek Industries Inc. in Toronto, said his company recently installed an integrated materials management system for a plastics processor that molds components for the automotive industry. This system combined under-press drying and loading, cell operations, and central blending and conveying into a single, logical process to provide greater control over the amount of materials moved to the molding machines.

“We were able to streamline operations, decrease the amount of waste and improve the quality of the final product,” Da Silva added. “All of this came about because of better control and a more rational approach to the drying, blending and conveying of material.”

Da Silva said the key to successfully using auxiliary equipment is for plastics processors to work closely with suppliers and manufacturers of raw materials handling equipment. Suppliers must first take time to understand the processor’s needs, how its operations work and its end products, in order to design the right materials management system. A one-size-fits-all approach or simply dropping a dryer, blender or conveyer into an operation will not provide any productivity enhancements or cost savings, he said. Each materials management system will be unique for each plant.

Joe Sharma, maintenance manager for Woodbridge, Ont.-based Royal Injection, a division of Royal Alliance Inc., said his company’s work with Markham, Ont.-based Nucon Wittmann Inc. to put in an integrated materi
als handling system for its new plant has helped improve efficiency and productivity.

The current facility has 72 molding machines running 24 hours and 365 days a year.

In the old plant, machines would have to be loaded manually from gaylords set beside the machines, Sharma said. This manual system was just not efficient for the amount of product Royal Injection wanted to produce, and the system was prone to errors.

“At that time we had 50 machines and we realized that the old system was not going to work,” Sharma added. “With the old (manual) system, we had to be very careful not to make any mistakes such as bringing the wrong gaylord to the machine. Now everything is automated right down to the (resin) weight, mixture and the amounts that are delivered and go into each machine.”

Nucon Wittmann got involved early on in the design of the new plant, making sure there was a central drying and conveying system that could take materials to each machine without interruptions. At the same time, the materials handling system is flexible enough to accommodate additional molding machines.

Baltimore, Md.-based Novatec Inc., recently developed for Tory, Mich.-based Delphi Corp., a conveying, blending and drying system for Delphi’s new facility in Vienna, Ohio. The system is designed to convey, blend and dry more than 90 different resins and materials and move them to 124 injection molding machines using a dry-air and line purging system.

Moisture is managed using Novatec’s Moisture Manager control technology, and other controls ensure the right materials reach the right machines without contaminating other lines.

Tom Spangler, manager for technical services for Novatec said an added feature of the control technology is built-in remote access so technicians can remotely connect and track problems from any computer terminal in the plant or from an off-site location.

“If a customer says their dryer seems to be acting a bit funny, we don’t have to get a service person on an airplane anymore [fixing the problem in two days],” Spangler added. “We just go in via the modem and we can check the dryer and even upload and download information. We had one customer call saying that a dryer was out of whack, and via the modem we had that customer back up and running in 20 minutes.”