At family-run Paul Precision Machine, Inc, a Tulsa, OK machine shop specializing in oil and gas equipment, the heavy machining of cast iron was creating a recurrent and costly problem.
"Every 80-100 hours, our big machining centers were going down, due to filter clogging from cast iron fines," company founder and president Chuck Paul explains. "We'd need to stop production, completely break down the system, clean and replace parts, reassemble, and get back to business. This process usually took anywhere from 8-12 hours and that represented substantial loss of revenue, in addition to pushing back our production scheduling, every two weeks or so."
Then, son Kevin Paul attended the machine tool show in Chicago, looking for an answer to this challenge, and made a discovery: a magnetic chip disc filtration system specifically designed to handle the fines from cast iron machining. On his return to Tulsa he began the process of further investigating the system, manufactured by Hennig, Inc of Machesney Park, IL.
Making the Decision
Within 60 days of conversation and drawing exchanges, a decision was made and the first Hennig Cast Iron CDF Filtration System (CICDF) was installed on one of Paul's 600 mm Okuma machining centers. Through the first four months of operation, not a single instance of machining center downtime occurred as a result of a canister filter clogging.
Machining of cast iron, as Chuck Paul explains, causes a large volume of small particles, known as fines, to be produced. These particles are often in the 25-100 micron range, well below the typical machine tool filter system's capabilities. This results in a sludge accumulating in the chip conveyor's coolant tank as well as the filter vessel. When clogging occurs, the machine requires substantial downtime with accompanying loss of production, as the sludge is literally shoveled out of the system.
On the Hennig CICDF, the dirty coolant is channeled to the conveyor, where the big chips and larger particles are conveyed up the incline and discharged into the chip hopper. Next, smaller cast iron fines are collected by a magnetic drum that rotates across a stainless steel scraper blade. As the sludge accumulates on the scraper blade, it drops the fines onto the conveyor incline with the chip load for delivery to the chip hopper. Finally, the smallest particles that escape the magnetic field of the drum migrate to a disc filter medium, made from a micronic weave of stainless steel mesh, which intercepts particles as small as 25 microns. A continuous backwash of coolant blasts the particles collected on the disc back to the magnetic drum, where they are likewise scraped off as sludge, eventually dropping onto the conveyor incline and carried out with the chip load. The disc filter is sealed with an inverted lip seal on the clean side of the conveyor wall, where the fines and contaminants do not interfere, ensuring a consistently tight seal and long seal life. Paul reports longer coolant life and less heat buildup as other benefits of the system. Only clean coolant returns to the reservoir for continuing duty on the machine tool or is diverted to the system's self-cleaning spray nozzles.
Quick ROI Leads to Additional Purchases
Chuck Paul admits he experienced some "sticker shock" at the cost of the first system, until he calculated the payback time to be 14-16 months on a machining center running one 10-hour shift per workday. And that calculation only took the billing rate for the machine tool into account. With the additional uptime and better predictability on his work schedule, Paul was able to improve turnaround time on jobs and not make the almost bi-weekly adjustments caused by the former system's excessive and costly downtime.
As a result, an additional Hennig CICDF has been installed and a third is scheduled soon for installation on the shop's Daewoo machining center. Compared to the alternatives of a vacuum cleaning system or the changeover and hazmat disposal problems of conventional paper media, Paul notes there are substantial cost and other benefits to the magnetic drum system selected at his shop.
Installation of the Hennig CICDF was a relatively low-impact process for Paul, as the system utilizes the machine tool controls, interconnected to a manual autoswitch, so the system runs whenever the machine tool is in operation.
Chuck Paul cited Jeff Nau and Susan Block at Hennig for their particular assistance in the engineering, delivery, installation, setup and training on the Hennig CICDF systems at his shop.
"They made the entire process a satisfying experience for Paul Precision, especially as we began to see the benefits of the system on our shop floor were exactly what they promised," he says.
