The term “lapping” stems from the acronym Loose Abrasive Process. Quite simply, the lapping process involves mixing water or oil with abrasive particles, which results in a slurry that acts as a liquid cutting tool. The liquid between the plate and workpiece creates an exact grinding and cutting action, leaving a rough, yet flat surface.
Single-sided lapping involves one lapping plate, while double-sided lapping has an upper plate that floats, a lower plate, a gear ring, and a sun wheel. Efficiency doubles with double-sided lapping as two surfaces are machined simultaneously. Clamping stress is also avoided when using double-sided vs. single-sided lapping.
What Is the Double-Sided Lapping Process?
The double-sided lapping process is as follows:
- The lap wheel is fixed to the upper and lower lapping disc.
- The workpiece is put in the differential gear (sun gear and ring gear).
- The cylinder pressurizes the upper lapping disc, which causes lapping pressure.
- The upper and lower lapping wheels are typically rotated at equal angles of opposite magnitudes.
- This rotation causes force to be applied to the workpiece.
Double-sided lapping can use either fixed abrasive or loose abrasive, depending on what is needed. Often, the components will also require double-sided polishing, but for other applications, only lapping is needed for completion.
What Is Double-Sided Lapping Used For?
Double-sided lapping can be used for a variety of components. However, double-sided lapping is ideal when:
- The design requires a high level of flatness and parallelism
- The sides have certain requirements for flatness
- Both sides of the component must be exactly equal and parallel in finish
Our specifications for double-sided lapping include:
Typical:
- Max size 13.3″ / 340 mm
- Flatness +/- 50 μm / 1.25 micrometer μm
- Parallel (same as flatness above)
- Roughness Ra <10 μm / <0.25 micrometer μm
Best:
- Same max size
- Flatness +/- 10 / 0.25 μm
- Parallel same as flatness
- Roughness <5 / <0.12 μm
Other applications for double-sided lapping include gears, robotics, and electronics. Double-sided lapping used in electronics applications can achieve tolerances to the next level of zero.
What Are the Pros and Cons of Using Double-Sided Lapping?
There are certain advantages when it comes to double-sided lapping. The better the lapping quality, the less time it takes to polish, which is a much slower process. When comparing double-sided lapping (and polishing) to the single-side process, it has these advantages:
- Faster processing (lapping both sides at once)
- Flatness
- Parallelism
Disadvantages of double-sided lapping vs. single-sided include:
- There is a size limitation
- Extreme aspect ratios
- Not optimal for small volumes
- Two sides can’t have different surface requirements
Double-sided lapping is a wise choice for larger pieces and larger volumes.
To learn more about polishing and our other capabilities, contact IRD Glass today to speak with a team member or receive a quote.