Precision grinding assures fast, compliant repairs
How advanced grinders facilitate rapid turnaround for vital MRO services like aircraft brake rotor resurfacing.
September 16, 2024 | By Mike Anderson
Close-up of an aircraft landing gear Photo: DCM Tech Inc.Precision grinding using semi-automated grinders has a variety of maintenance applications across several industries, from automotive to military. For the purpose of this article, we’re going to look at one specific and important application of precision grinding, and that’s aircraft maintenance, specifically brake rotor resurfacing.
As critical components of an aircraft’s braking system, these rotors are subjected to significant wear and tear due to extreme conditions of heat and friction during landing and braking. Uneven rotor surfaces can cause wear on brake pads, which adversely affects braking performance and can lead to vibration and even noise during braking. The high temperatures generated can cause the rotor to warp, a condition that must be corrected by restoring it to a true, flat state. Contaminants and debris that accumulate on the rotor surface must also be removed.
When brake rotors show signs of damage or deformation, precision grinding can remove a thin layer from the surface of the rotor to eliminate irregularities such as scoring, uneven wear, corrosion, and brake pad deposits to restore the rotor to required specifications.
However, imprecise grinding can lead to serious issues that can compromise the safety and performance of the aircraft, including uneven brake wear, increased heat, vibration, and noise, or lead to premature replacement. Slow grinding can also impede repair turnaround time. As a solution, advanced precision grinders can speed rotor resurfacing by leveling surface irregularities to improve performance, safety, and longevity.
Benefits of precise grinding operations
When aircraft rotors are sent in for grinding, they often have deep scores or grooves. Since grinding off enough material to completely smooth out these deep grooves would be impractical, most maintenance professionals will grind the rotor surface until about 60 per cent of the material is removed or until most of the imperfections are gone. This method helps to improve the rotor’s surface and extends its usable life.
Semi-automated rotary surface grinders (often referred to as “Blanchard-style” grinding but not always exclusive to that brand) are designed to outperform conventional reciprocating surface grinders by efficiently removing larger amounts of material to tight tolerances in much less processing time. What’s more, semi-automated solutions allow less-skilled operators to run parts with less time, attention and labor involved.
Conversely, conventional reciprocating surface grinders (with a reciprocating table and a horizontal spindle that spins the grinding wheel) have a slow material removal rate. That’s because it requires multiple table passes and a skilled operator to continually monitor the grind process.
While conventional rotary surface grinders without technological enhancements are a faster option than reciprocating surface grinders, they can also be problematic in the hands of less experienced operators. With limited control of spindle speeds as well as manual 3-axis traverse controls, the equipment requires sophisticated operators with considerable expertise that can sense optimal machine performance.
Today, semi-automated rotary surface grinders are designed with advanced sensors and control technology that allows for an interface with easy-to-use touchscreen HMIs. These surface grinders outperform conventional surface grinders (both manual rotary and reciprocating) by more efficiently removing large amounts of material, maintaining close tolerances, and reducing process time.
Features such as variable feed rate and spindle speed, single or multi-step grinding, and easily programmable grind processes make these machines an ideal platform for processing a wide range of materials.
A semi-automated surface grinder holds the workpiece firmly in place on a rotating table underneath a vertical spindle. Unlike conventional grinders, the grinding is not performed by the peripheral edge of the wheel, but by the entire diameter of the abrasive surface. This is similar to a lawn mower blade that can cut a wide swath of grass versus a blade run on its end, which will only cut a narrow strip. The eight-inch abrasive wheel more than covers the cross section of the rotor between its ID and OD for complete grinding of the rotor surface.
To expedite the maintenance or overhaul, the grinder provides an automatic feed system, so the machine can continue running without further operator oversight once it is started. A unique demagnetization function on the electromagnetic chuck ensures that before the brake rotor is released from the machine, any residual magnetism is dissipated. This is valuable because if any magnetism remains in the rotor, it might attract magnetic material that could have a negative effect on the brake pads once installed.
Whether for fast and easy aircraft brake rotor resurfacing or for other industrial components, by opting to utilize more efficient, precise grinding equipment, MRO professionals can expedite necessary repairs and maintenance while facilitating safety and productivity.
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Mike Anderson is a technical specialist at DCM Tech, Inc. (www.dcm-tech.com), a company that designs and builds industrial semi-automated rotary surface grinders.For more information, visit www.dcm-tech.com; or email info@dcm-tech.com.
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