When Does a Filtering Chip Conveyor for CNC Lathes Make Sense?

Shops vetting potential new CNC milling machines or lathes to purchase commonly consider: how well they will fit into their current processes; if they have the capacity and versatility to change and grow with the business; how dependable and robust they are; and the availability of replacement parts, technical services and customer support.

LNS America says these same considerations should apply when selecting peripheral machining equipment such as chip conveyors as these devices can either optimize a machining process or become a weak link. The difference can come down to how well the conveyor matches current machining applications and if it can adapt to different requirements that might be encountered in the future.

Chip conveyors are available in a variety of designs and price points. In terms of the latter, filtering chip conveyors do represent a higher initial investment, but their return on investment might make them worthy of consideration to satisfy current needs and better enable machining equipment to more effectively accommodate new jobs and workpiece materials down the line, as the company explains here.

Chip Conveyor Choices

Hinge-belt chip conveyors are the most popular models and are often included with new CNC machine purchases. They are affordable and reliable when properly matched to specific machining applications, such as collecting a mix of coarse and stringy materials. However, they are not the best choice for operations that produce fine chips of aluminum, brass, cast iron or other materials as these smaller particles can contaminate the coolant and clog the conveyor, fluid lines and pumps.

Magnetic chip conveyors are appropriate for ferrous-only machining processes that produce broken chips. However, if the process creates stringy material longer than the conveyor magnet spacing, the long strings can cause a short in the magnets. In addition, using a magnetic conveyor when machining ferrous materials that create fines is not recommended, because of the same coolant delivery system issues mentioned above.

Conversely, filtering chip conveyors can evacuate virtually all chip materials, sizes and shapes, while removing particles as small as 50 microns that would otherwise damage pumps and reduce coolant life. Plus, they can be effective as shops push machine speeds and feeds to improve productivity and reduce cost-per-part. Doing so produces higher temperatures in the cutting zone which, in turn, requires greater coolant flow to reduce the heat. In some cases, this increased coolant volume overwhelms a conventional chip conveyor’s ability to efficiently remove chips and prevents contaminated coolant from recirculating. The result can be production slowdowns or stoppages and possible damage to the coolant pumping system. Recirculating chips can also reduce cutting tool life and mar machined workpiece surface finish. These attributes can prevent shops from implementing reliable lights-out production or limit unattended machining time, too.

Filtering chip conveyors can evacuate virtually all chip materials, sizes and shapes, while removing particles as small as 50 microns.

In addition, modern machine tools can process a wide variety of operations and materials that might range from aluminum and basic steel to exotic alloys. When new job orders come in that require changing a production process, the ability of a machine to adapt might be hampered by a chip conveyor that can’t handle the new workload. In these situations, it might be necessary to replace the existing conveyor with a more efficient model. Therefore, the chip conveyor type that is most capable of efficiently handling the widest range of CNC machining challenges is one that successfully filters virtually all chip materials, types and shapes, from coarse and stringy to very fine, which LNS says is the filtering chip conveyor.

What to Look for in a Filtering Chip Conveyor

There are a number of filtering chip conveyor designs available. Some use replaceable filter media, while others have permanent, self-cleaning filtering drums made from stainless steel or other materials that might also employ scraper systems or perforated box filters.

Chip conveyors that have replaceable, self-cleaning filter boxes are said to greatly reduce maintenance and can be easily modified to accommodate different machining applications. For example, the LNS MH Series of filtering chip conveyors has interchangeable filtration boxes that eliminate chips as small as 250 microns, while the SF compact filters chips as small as 50 microns. In addition, these conveyors offer hardened tracks, especially in curves, to reduce wear; reinforced belts for longer life and reduced maintenance; a footprint no greater than non-filtering chip conveyors (compact units that use even less floor space without sacrificing performance are available); and discharge-point customization.

In fact, upgrading to a filtering chip conveyor enabled Flotec in Indianapolis to meet increased demand in response to the COVID-19 pandemic. Flotec manufactures regulators and other essential components for medical equipment used by hospitals, neonatal ICUs and EMS services. The company, which started in 1983, provides parts for both OEMs and end users around the globe, and these products are almost all custom created. At last count, its regulator line alone boasted over 4 trillion unique items.

As the coronavirus pandemic spread, the demand for Flotec’s products pushed the company to maximize its output and rely even more heavily on lights-out production for its twin-spindle, twin-turret Swiss-type lathe. As is often the case, successful overnight production required that every part of the manufacturing process be trouble-free. When inefficient chip management caused interruptions, Flotec brought in LNS to help solve the problem.

The Swiss-type machine came equipped with a standard hinge-belt type chip conveyor. However, Flotec uses this machine to machine 6061 and T651 aluminum, some 350 brass alloy and 303 stainless steel. The process creates very fine chips that passed through the chip conveyor into the recovered coolant and flowed into the coolant tank filtering system.

The machine has four high-pressure filter baskets and an additional basket that catches the fines before they get into the coolant pumps. These materials filled the filtering baskets, causing lower coolant levels. Meanwhile, chips accumulated in the coolant tank, thus displacing coolant volume. This loss of volume triggered low coolant alarms that reduced coolant flow through the high-pressure delivery system. As a result, the parts being machined and the cutting tools were insufficiently cooled, leading to shorter tool life as well as degraded part finishes.

The LNS solution was to replace the existing hinge-belt chip conveyor with the LNS Turbo MH 250 filtering chip management system. The self-cleaning filter box design enables the MH 250 to remove virtually all sizes and types of chips, including fine aluminum and brass such as those produced by Flotec’s milling process, while filtering coolant to 250 microns.

According to Flotec President Brian Davidson, “Before replacing the original chip conveyor with the LNS filtering model, we were getting about 75 units of production during the day and 40 when running lights-out overnight. We now produce 75 units per 9-hour day and 125 units from 5:30 PM when we turn off the lights until 8:30 the next morning. As a result, we’ve more than doubled the output of this CNC machine from approximately 2,875 production units per month to 6,000 units per month simply by replacing the original chip conveyor with the LNS MH 250 filtering chip conveyer.”

He says there also is less maintenance. “We now clean out the coolant tank only once per month. Before switching to the filtering chip conveyor, we were cleaning out the machine’s two filter baskets three to four times per day. Now we only clean them twice weekly. Likewise, we’ve reduced the high-pressure filter basket cleanout from daily to once per week.”

Flotec also found that without the fines displacing and degrading coolant, the high-pressure system is able to perform properly, which protects critical part finishes, reduces tool wear and extends coolant life.