Different Polishing Procedures: A Guide

Table of Contents

Introduction
Materials: There is a Wide Variety of Materials for Ferrules and Connectors, Plus a Variety of Connector Styles
Equipment: The Type of Polishing Machine – as well as the Condition of Equipment and Accessories – are Key Factors
Methods: Product Specification Requirements Dictate the Polishing Methods
Environment: Temperature and Cleanliness are Often Overlooked Environmental Factors that Impact the Polishing Process
In Conclusion

Introduction

In an idyllic world, there would be just one polishing process. In this idyllic world, users could follow a basic “recipe” to implement fiber optic polishing process – and following this recipe would ensure that implementation is quite quick and easy. Unfortunately, because of a lot of factors influencing the polishing procedure, it is difficult to provide a step-by-step “instruction sheet” that could accommodate all.

The positive news is that there are some customary practices to follow. For instance, it is common to clean between each polishing step, and it is common to meet specific geometry and visual appearance needs. Also, while there may not be one polishing process specifically, there are a few standard ingredients for every recipe: pressure, time, and speed.

The correct recipe for a polishing process depends on specific factors in a fiber optic cable assembly process: materials, techniques, equipment, and environment. Furthermore, it depends on the goals. What does one want to accomplish in the polishing process? Which specifications does one need to meet?

The following paragraphs look at some of the variables that impact the polishing process – and help to understand why there is no one-size-fits-all, universal polishing process.

Materials: There is a Wide Variety of Materials for Ferrules and Connectors, Plus a Variety of Connector Styles

Here is a main reason why there is no standard polishing process: Single-fiber and multi-fiber ferrules are made up of different materials and have various shapes, hardness, diameters, and tolerances. Here are two examples:

  • Single-fiber ferrules are typically pre-shaped with either a conical tip or a flat surface (with numerous conical angles like 45-60°) and pre-domed, or even pre-angled and pre-domed.
  • Zirconia ferrules are available in a number of diameters: 2.5 mm, 1.58 mm, 1.25 mm, and 1.0 mm

Compounding this, there are a number of different connector components with considerations such as dimensional tolerances and spring force. For single-fiber connectors, the most frequently used material is ceramic; however, stainless steel is also used. Multi-fiber ferrules are composed of a type of plastic (a glass-filled polymer).

Equipment: The Type of Polishing Machine – as well as the Condition of Equipment and Accessories – are Key Factors

Normally speaking, in the case of polishing machines, there are certain commonalities. For instance, every polishing machine has to apply pressure to the ferrule for a specific amount of time. The polishing medium has to be in motion to abrade the surface (to polish away material). All polishing machines operate in a series of steps, beginning with a rough grit of polishing film and moving to a finer grit.

The particular polishing machine used will greatly influence the process. Why? Because different manufacturers employ different philosophies concerning how they approach polishing. Machines utilize different approaches to apply pressure, various patterns of motion to use the full area of the film, and different lengths of time:

  • Pressure – Techniques to apply pressure include mechanical clamps, pulling, pneumatic pistons, and pushing
  • Different motion of the abrasion film – Certain polishing machines employ a circular motion, some employ a figure-eight motion, and most use a two-axis spinning-and-rotation motion (fundamentally, a continuous spiral moving over the surface)

In case one is aware of the polishing process, it would be known that the lapping film is positioned on a flat surface – typically a glass pad or rubber pad. The quality and condition of those pads are crucial. Also, it is important that ferrules accurately align with the machine’s polishing surface; this guarantees a steady and equal amount of material is removed from each ferrule.

Any decent polishing machine will have precise integrated dimensional tolerances. However, over time, there will be wear. This is one reason why it is crucial to continually watch and monitor a polishing process.

Additionally, the recipe for a polishing process relies on a polishing film (aka lapping film). Different manufacturers have various types and qualities of film, offering numerous levels of consistency and durability. Every film cuts at a diverse rate. Obviously, all these different materials influence the polishing process.

Methods: Product Specification Requirements Dictate the Polishing Methods

What are the requirements? Certain applications need a PC finish, some need a flat finish, some need angled PC, and others need angled flat. A majority of fiber optic cable assemblies have very specific geometry needs – yet some needs are wide open. Certain specifications allow scratches on the fiber’s core while others do not allow any scratches on the core. Also, there are various end face finish needs that determine how rough the surface can be. Certain specifications require an extremely rough surface. For some, it does not matter if the surface is rough. All these factors, combined, will dictate the polishing techniques desirable to accomplish the end goal and meet the requirements.

Environment: Temperature and Cleanliness are Often Overlooked Environmental Factors that Impact the Polishing Process

In case one uses rubber pads for a polishing process, it is useful to keep in mind that pads wear over time due to UV exposure. Also, they are sensitive to changes in temperature. Ambient temperature will alter the hardness of the rubber pads and, thus, alter the results of the process. The aging process of rubber pads is not homogeneous and begins with hard spots in the rubber. Consequently, the average ferrule Radius values stay acceptable, but the Apex values weaken.

Cleanliness is another factor that influences a polishing process. Remember that all polishing processes contain several steps. Between steps, one needs to clean the polishing material away from the ferrules so as to transition from a rougher-grit to a finer-grit polishing film. Furthermore, remember the environment. The polishing process causes contamination when the material is ground from the ferrule. The level of cleanliness in the polishing environment will influence the amount of cleaning required on the product and films between each step.

In Conclusion

The article is not meant to excessively confuse or frighten those wanting to enter the fiber optic ferrule polishing world, but to explain the variables at play that will impact the polishing process – and to enlighten why a one-size-fits-all, universal polishing process is not available. It is vital for those who are thinking about entering the polishing world to understand that, in all cases, there will be a certain level of process development investment required to “dial-in” a process that matches specific product and production requirements.

For implementing a polishing process, it is helpful to know Fiber Optic Center Polishing Instructions, which offer acclaimed polishing machine settings. These published machine settings are meant to act as a basic reference for an ideal starting point for a polishing process development. It is expected that slight changes to some suggested machine parameters will be required so as to meet specific product requirements.

Fiber Optic Center has always assisted the customer to ensure their manufacturing procedures create the highest quality jumpers cost-effectively. Soon they will add this to long available benefit by launching new tiers of service.

This will include:

  • On-site polishing process development (reducing film cost, tighter control on geometry, and increase capacity)
  • Calibration, preventive maintenance, and verification of purchased equipment
  • Purchase discounts on equipment purchase to be applied on lapping film and epoxy
  • On-site repair or priority on available loaner equipment to guarantee production continuation
  • Final inspection on manufactured cable assemblies (comprising overall appearance, connector geometrical, optical and visual inspection connector as well as cross sectioning.)

This information has been sourced, reviewed and adapted from materials provided by Fiber Optic Center, Inc.

For more information on this source, please visit Fiber Optic Center, Inc.

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