Pads -some observations Clean and / or replace pads as often as is necessary; a clean seasoned pad will enhance the abrasive abilities of the compound / polish and make the process not only more efficient but less time consuming. Kinetic (or dynamic) Friction Kinetic friction induced heat is an often misunderstood concept of polishing / compounding; abrasives require friction to breakdown, not heat; heat is just a resultant of friction between two surfaces. Polishing a paint surfaces transfer’s kinetic (or dynamic) friction induced heat to the paint surface, thermoplastic polymers have both tensile strength and elongation (elasticity) which allow the surface to flex, expand and contract in accordance to surrounding temperatures, solvents, resins and other ingredients in polishes will expand causing the paint film surface to expand. As the metal substrate expands the paint moves with it, due to its elasticity, thereby becoming elongated (thinner) this is part of the cause of friction induced ‘burn’, you’re applying pressure and an abrasive to a less dense (‘thinner’) paint surface. The smaller the contact or surface area of the pad the more kinetic (heat) energy is transferred to a given paint surface area. (Area = π (r2) - 6-inch = 28.26 sq.ins - 4-inch = 12.46 sq.ins. The amount of applied pressure will also affect the kinetic friction (heat) energy transferred Foam Pad Design a) Non-reticulated [:foam membranes are completely sealed to prevent fluid absorption or air penetration] (closed-cell) which means less product absorption, and less air flow, reticulated foam are relatively less abrasive and less dense than polymerized foam; due to this density the polish provides the abrasive ability as opposed to the foams composition (use when thoroughly dry as they tend to retain water) With polymerized foam your polish stays wetter for longer, which extends the products work time This pad design is relatively firm so that none of the machines action (rotational or orbital) is lost, as is the case with soft foams. Due to their lack of airflow the foam doesn’t drain that well they are harder to clean, and take longer to dry b) Reticulated [: foam which is a linked network or matrix of small squares or shapes] its composition varies with pore size. Their open-cell construction allows heat to dissipate and fluids to permeate the pad to a greater degree than closed-cell materials, such as non- reticulated foam and their lower tensile strength allows them to conform to contours more easily. Reticulated foam, which is a less dense than polymerized foam, therefore your polish provides the abrasive ability as opposed to the foam. Porosity is typically 95%, but can be as high as 98%, typically resistance to compression is decreased while tensile properties like elongation and resistance to tearing are increased. This pad design is relatively soft so that some of the machines action (rotational or orbital) is lost An open cell pad has slightly stiffer foam, which can act like a squeegee cleaning any polish or paint oxidation residue and exposing fresh abrasives. This type of pad construction has less resistant to compression, allowing you to ease up on the pressure slightly while maintaining an even surface contact area. Compression / Rebound - compression load deflection is the measurement of how long the foam takes to regain shape after under certain pressure, foam pads should be compressed to no more than approx 50% of its thickness Tensile strength – the strength of a material refers to the materials ability to resist an applied force Density - provides a protective cushion allowing foam compression to maintain constant surface pressure and it also lessens machine vibration. It also affects the amount of polish the pad will hold; foams that hold a high volume of product allows the polish to do the cutting, as opposed to the abrasiveness of the foam. Velocity - pad velocity is substantially increased with a larger diameter pad, increased velocity will increase abrasive capability at the outer edge of the pad. Foam Pad Thickness Standard foam pads - 1.25 inch pad thickness was set as an industry standard because it prevented solvent residues and provided insulation from friction heat from reaching the backing plate, either of which could compromise the Velcro® (delaminate from the backing material). They have a rounded outer edge for easy transitions over seams and edges, and there is also a safety margin between the edge of the baking material and the foam with a ‘standard’ foam pad. This foam density provides a protective cushion allowing foam compression to maintain constant surface pressure and it also lessens machine vibration. OEM-style 7/8-inch foam pads - due to the reduced foam thickness tilting a 7/8 inch pad will change the polishing pressure on the surface. These foam pads are flat cut on the top edge, as opposed to a standard 1.25-inch, which have a rounded outer edge for easy transitions over seams and edges and the backing material is cut back 3/8 of an inch around the perimeter of the pad to ensure a safety margin. On the 7/8-ich foam pads the backing material extends to the edge of the pad where it could scratch the paint when working in close corners or around mirrors and wings. OEM-Style pads are designed for high volume pad users where cost is a significant factor Like all things related to tools, pad thickness comes down to personal preference. Pores per inch (PPI) As an example you could purchase two seemingly similar pads based upon their PPI rating, but one pad may have thicker walls between each pore, be made of softer material, feature a reticulated or non-reticulated foam structure (basically open or closed cell), or simply be a thicker (1.25 or 0.75-inch) foam, which can affect the machines movements. Compressible, open cell polyether polyurethane reticulated foam is usually specified by pores per inch (PPI).The greater number of pores per inch generally equates to foam that is softer; and has less abrasive ability, less density, more porosity and easier compression. There is no recognisable standard for the abrasive abilities of foam, other than a colour assigned; most foam manufacturer’s that supply foam to detailer’s product vendor assign their own colours to donate abrasion. On this basis a PPI rating allows abrasive ability comparisons between different foams Remember the flatter and more uniform you make the surface, the greater the light reflection .While most enthusiasts understand this principle when applied to polishing, the same is true of finishing. The more uniformly you apply the final wax or sealant, the greater the shine Scale 30 – 100 PPI • Abrasive Cutting Foam (40 pores per inch) • Medium Cutting Foam (50 pores per inch) • Light Cutting Foam (60 pores per inch) • Finishing Foam (70 pores per inch) • Fine Application (80 pores per inch) • Ultra-Fine Finishing (100 pores per inch) The thicker consistency products (i.e. a hard wax) seem to work best with a more porous pad; a very tight pad used with these types of products seems to load up and clog the pad, which in a turn leads to product clumping. When applying light consistency products (i.e. liquid polymer) a more porous pad will absorb and waste product Soft flexible foam (60 PPI +) is ideal for polishing complex curves, allied with a flexible packing plate it transfers rotational movement on vertical panels and easily compresses to conform to contoured body panels. Some kinetic energy is absorbed by the foams horizontal movement across the backing plate, which reduces its levelling ability somewhat
Posted on: Fri, 12 Sep 2014 18:47:24 +0000
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