As the core transmission components of aircraft seat shoulder belt tensioning mechanisms, ratchet parts directly impact the safety and comfort of pilots seated in their seats.
These components regulate seat belt tension, securing pilots safely while preventing overly loose or tight restraints.
Aircraft seat safety relies on ratchet components, which demand high machining precision and surface quality.
Manufacturers still manually machine most ratchet components, resulting in low efficiency and inconsistent quality.
To overcome manual machining issues, ratchet components require improved efficiency and quality via process optimization.
This paper develops an optimized machining solution for ratchet components and guides manufacturing of similar precision parts.
Analysis of Technical Challenges
Current methods mainly use milling for gear cutting, but ratchet teeth with pointed bases require custom or self-sharpened tools due to angular constraints.
Horizontal milling is common, but low spindle speeds cause rapid tool wear, preventing ratchets from meeting surface roughness standards.
CNC tools cannot reach tooth roots, causing rounding that fails aviation standards, making CNC unsuitable for ratchets.
Engineers reconsider electrical discharge machining (EDM) as an alternative given these limitations.
Taking wire EDM as an example, this process can significantly reduce tool-induced rounding compared to CNC milling.
Operators machine ratchets with single-pass wire EDM, achieving Ra 1.6 and eliminating oxide scale for chrome plating.
In practice, wire cutting achieved only Ra 3.2, requiring extra polishing and oxide removal.
The gear-like outer contour prevents conventional tools from reaching tooth roots, requiring manual polishing to meet specifications.
In actual production, the numerous teeth requiring polishing consume substantial labor.
Difficult tooth-root processing lowers quality and efficiency, so operators must optimize machining methods.
Geometry limits traditional ratchet milling, requiring custom tools; low spindle speeds cause rapid wear, and the process produces Ra 3.2 instead of the required Ra 1.6.
Wire cutting reaches the root corners, but operators must manually polish for quality, extending cycles and increasing costs.
In aerospace manufacturing with small, diverse batches, current processes fail to ensure consistent quality, efficiency, or cost control.
Process Technology Improvements
Before examining the material properties, it is essential to review potential process improvements that can enhance machining efficiency, surface quality, and overall performance of ratchet-type components. These improvements form the basis for selecting appropriate materials and processing parameters.
Material Properties
30CrMnSiA has high hardness, strength, toughness, and corrosion resistance, with HRC 50+, 1600 MPa tensile strength, and 10%+ elongation after heat treatment.
30CrMnSiA is widely used in aerospace, military, and other special wear-resistant components due to its outstanding material properties.
Selection of Improvement Solutions
In the field of precision gear manufacturing, broaching—as a quintessential traditional forming process—continues to hold significant technical importance.
This process efficiently machines 0.5–12 mm gears using coordinated spindle linear motion and workpiece rotation with involute broaches.
This broaching method efficiently mass-produces gears but involves high tool wear, difficult changeovers, and surface finish issues.
Ratchet components are complex and varied, requiring specialized fixtures, precise equipment, and high initial investment.
Furthermore, numerous uncertainties persist throughout the part manufacturing process.
In the aerospace manufacturing sector, the characteristics of multi-variety, small-batch production are particularly pronounced.
This model requires frequent part changes to meet diverse aerospace demands.
However, purchasing dedicated broaching equipment solely for ratchet-type parts would significantly increase production costs.
On one hand, the specialized broaching equipment itself is costly, representing a substantial acquisition expense.
In small-batch, multi-variety production, specialized equipment often sits idle, wasting resources and limiting aerospace manufacturers’ efficiency and growth.
Wire cutting and magnetic grinding efficiently shape complex ratchets, cutting costs and avoiding equipment underuse.
Building upon the advantages demonstrated by wire cutting, attention now shifts to the subsequent manual machining stage.
Optimizing manual machining with wire cutting integration advances ratchet manufacturing to a higher standard.
Exploring ratchet manual machining can overcome traditional limits and boost component processing efficiency.
Roll grinding processes multiple parts simultaneously, offering higher efficiency and stable, high first-pass quality.
Ratchet tooth roots’ tight, curved geometry limits conventional abrasives’ reach during roll grinding.
Poor abrasive contact at the root causes uneven material removal, high roughness, and unmachined zones, reducing ratchet accuracy and reliability.
Given this, in-depth exploration and research into grinding process methods have become an urgent priority.
Only by overcoming this challenge can grinding play a greater role in ratchet component processing, thereby enhancing overall part quality.
Within grinding process methods, abrasive selection plays a decisive role in machining outcomes.
Conventional abrasives cannot fully reach ratchet roots, causing incomplete machining, poor surface quality, and reduced performance and lifespan.
Therefore, identifying a specialized abrasive capable of meeting the machining demands of ratchet component root areas holds significant practical importance.
To achieve effective root-area machining of ratchet components, grinding media used in roll grinding must possess the following characteristics:
First, the abrasive should exhibit excellent shape adaptability to facilitate entry into the confined root-area space.
Second, it must possess sufficient hardness and wear resistance to ensure effective removal of excess material during processing.
The abrasive must minimize surface damage to ensure a high-quality finish.
Comparative tests on ratchets were conducted using silicon carbide, zirconia, resin-bonded, and magnetic rod abrasives.
Tests showed traditional abrasives struggled to reach ratchet roots, causing high roughness and unprocessed areas.
Magnetic rod abrasives smoothly entered narrow roots, enabling thorough tooth root processing.
The surface roughness of the root area is significantly reduced after processing, and dimensional accuracy is markedly improved.
Magnetic rods self-sharpen during roll grinding, boosting efficiency and quality, overcoming traditional abrasives’ root-area limitations.
Determination of Improvement Plan
Grinding machines using magnetic fields are suitable for ratchet components, but only small-diameter metal rods can access the root areas.
Magnetic grinding rotates magnetic needles via pole switching, which polish the part by removing oxidation and surface defects.
Tests showed rods <Φ0.33 mm lack force to remove oxidation, while rods >Φ0.5 mm cannot reach roots and may damage surfaces.
Through repeated experimental verification, magnetic rods with diameters ranging from Φ0.3mm to Φ0.5mm were found to meet practical processing requirements.
Using a magnetic grinder with Φ0.3–0.5 mm rods meets ratchet component processing requirements.
Determination of Part Processing Parameters
Two primary factors influence magnetic grinding of ratchet-type parts: the diameter (Φ) of the magnetic rod and the magnetic grinding time (s).
Thirty parts were ground for 30 minutes to find the optimal magnetic rod diameter for ratchets.
Using Φ0.5 mm magnetic needles for 30 minutes, 22 of 30 parts had bright luster, 8 showed thread marks, and 6 had under-ground radii.
Using Φ0.3 mm needles for 30 minutes, 12 of 30 parts had bright luster, 18 had thread marks, and 20 had under-ground radii.
Test data indicates that the Φ0.5mm magnetic rod can process all areas of ratchet-type parts without causing surface damage through over-processing.
While the Φ0.3mm magnetic rod also meets processing requirements, it requires significantly longer grinding times.
Therefore, the Φ0.5mm magnetic rod achieves the highest processing efficiency when used as an abrasive.
Four sets of parts were ground with Φ0.5 mm rods for 20, 30, 40, and 50 minutes to study grinding time effects.
Using Φ0.5 mm needles for 20 minutes, parts showed minor surface change with significant oxidation residue.
Using Φ0.5 mm needles for 30 minutes, parts showed minor surface changes with much oxidation residue.
The surface condition of ratchet-type parts changed somewhat, but oxidation layer residue still remained.
Using Φ0.5 mm needles for 40 minutes, parts had significant surface improvement with most oxide removed, but machining marks remained.
Using Φ0.5 mm needles for 50 minutes, parts achieved smooth, mark-free surfaces.
Processing shows slight change at 20–30 minutes with residual oxide, while 50 minutes yields smooth, mark-free surfaces.
Extending grinding to 50 minutes caused surface darkening due to increased oxidation from prolonged magnetic rod impact.
Excessive tumbling can distort dimensions, compromising accuracy and surface finish.
To remove oxide without harming ratchets, tumbling time should be 40–50 minutes.
Rolling 150 parts confirmed smooth, pattern-free surfaces, meeting aerospace standards with a 100% pass rate.
Optimizing the process cut ratchet component machining time from 30 to 13 minutes per piece, boosting efficiency by 17 minutes per part.
Conclusion and Outlook
This study focused on optimizing the machining process for ratchet-type components, employing magnetic roller grinding for in-depth investigation.
Experiments show Φ0.5 mm magnetic rods with 40–50 minute grinding time give optimal results.
Under these conditions, the processed ratchet components exhibit a smooth, pattern-free surface quality that nearly perfectly meets design requirements.
The optimized process cut 17 minutes per component, greatly improving ratchet manufacturing efficiency.
This research supports ratchet production optimization and informs machining of similar complex parts.
Looking ahead, substantial research potential remains in further optimizing magnetic roller grinding processes.
Studying factors like magnetic field strength and grinding speed could refine process control.
Moreover, given its broad applicability, magnetic roller grinding technology warrants exploration for processing other complex components like gears and splined shafts.
Adjusting magnetic roller grinding for different parts can validate its versatility and effectiveness.
Combining magnetic roller grinding with EDM or laser processing enables efficient, high-quality machining of complex parts.