Paintless dent repair
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Paintless dent repair (PDR), also known as paintless dent removal, describes a method of removing minor dents from the body of a motor vehicle. A wide range of damage can be repaired using PDR as long as the paint surface is intact. PDR may be used on both aluminum and steel panels.
The most common practical use for PDR is the repair of hail damage, door dings, minor creases, large dents and bodylines damage.
The method can also be utilized to prepare a damaged panel for repainting by minimizing the use of body filler. This technique is currently known as "push to paint" or "push for paint".
Limiting factors for a successful repair using PDR include the flexibility of the paint (most of today's refined automotive paint finishes allow for successful PDR) and the extent to which the metal has been stretched by the damage, which depends on the thickness of the metal, the curvature or flatness where the damage occurred and the intensity of the impact. Generally speaking, the shallower the dent, the greater the likelihood of paintless dent repair being a suitable option. Even dents several inches in diameter can be repaired by this method as long as the metal and paint are not stretched. Most experienced technicians can repair a shallow large dent or crease to an acceptable level, but very sharp dents and creases may not be suitable for PDR.
Paintless dent removal was invented by Oskar Flaig in February of 1960 during the "International Motor Sports Show" in New York City, USA.
Oskar Flaig was an ordinary member of staff at Mercedes. His job was to take care of the paintwork of all the show cars presented at trade fairs. Damage, scratches on the paintwork and small dents, produced by the public during the day, needed to be re-painted at night, so the vehicles would be in perfect condition on the next day. At the trade fair in New York City, Oskar Flaig used a hammer handle to push out a small dent, so he would need to apply less filler before painting. Nevertheless, the result already looked perfect after pushing. This was the beginning of paintless dent removal.
The most common PDR techniques utilize metal rods and body picks to push out the dents from the underside of the body panel. Glue and specially designed tabs may be used to pull out the dents from the outside of the panel. Fine tuning the repair often involves tapping down the repair to remove small high spots. Quality technicians can blend high spots to match the texture of the paint called orange peel. Pushing too hard can create high spots that cause the clear coat and paint to split or crack. Experienced technicians can avoid cracking or chipping with the use of heat, although a re-painted surface has a greater likelihood of cracking. Furthermore, it is unwise to "glue pull" a repainted panel, because you risk also pulling non factory paint off. When damage is so great that body filler is necessary, a PDR technician may "push to paint", resolving most of the damage before minor filling, sanding, and painting, thereby saving time and cost.
The process of paintless dent repair requires a technician to manipulate precise locations of metal to the correct height, which can only be observed by the use of a PDR reading instrument such as a paintless dent repair light. Fluorescent or LED lighting, or in some cases a reflection board, may be used to visualize the deformation of the dent and to aid the technician in locating the tip of the tool being used to push the metal. Without a reflection from a light source or board to read the dent, the fine detail of the process may not be suitable for the technician. 
Advancements in PDR techniques are constantly being updated and improved. One of the greater advancements of Paintless Dent Repair has been with the advent of Dentology.
Dentology, is a branch of auto body repair, dealing with the removal of minor pressure blemishes to metal, through a scientific method, commonly referred to as paintless dent repair. It deals with, but is not limited to, the process of restructuring metal on a vehicle to its original state, after a minor impact or push. Dentology primarily deals with two types of dents, perforated and protruding, with two primary causes dynamic denting and quasi-static denting; together, they contain endless subcategories and varieties. This branch, defines a dent or ding as any discontinuity to a panels resistance and stiffness from its original factory setting. Which is typically created by hail damage (dynamic denting), or by structural frame resistance caused from "door slamming" to the outer shell (quasi-static denting).
Mapping Micro and Macrodynamics: Dents are further defined by size factor mapping: breath, length, depth, location, metallurgical alloys, paint, structural obstructions, and environmental variations. The size factor mapping of a dent, is primarily focused on the shape and form of this discontinuity. Perforated dynamic denting is by far the most common, defined as pushes from the outside in, and caused by a number of factors that a vehicle will encounter, from the outside world. Protruding dynamic denting is far more rare, at least as a stand alone: often accompanying large dents when bracing is struck from pushing the outer shell into the bracing. That is to say, together these two types of dents create macrodynamics, which is the study of complex dented structures as it relates to dentology and microdynamics, which deals with simple dented structures.
Mapping the Origin: Microdynamics deals with the most basic shapes encountered within dentology: namely, triangles and circles. Since triangle dents are by far the most complex of the two, lets briefly touch on their structure. The contour of the origin both laterally and diagonally, is the deepest point of the origin; its caused by the shape of object that struck the panel, in this case triangular. The path of the object which struck the panel affects the depth of the dent and angle of the strike vertically and laterally. This is important because it helps up reverse engineer the damage at least in theory. The process of reverse engineering a dent is known as reversing the origin, while the entire process of identifying the contour of the origin is called mapping the origin or simply, mapping. Either way, mapping's entire purpose is to reverse the origin. When dealing with triangles we start with the trench.
The Trench: The trench or "path of the origin" of a crease is the lateral origin along its length and includes any and all damage attached along its line. The trench does not refer to the bottom of the crease as a whole, but rather the entire damage to include the teardrop or point of entry. These trenches have walls which are attached to the undamaged portion of the repair surrounding the crease. This is referred to as the bank or simply the embankment. The embankment, although relatively flat is still affected by the crease due to the displacement of metal, which we will not be covering here. Perforated and protruding creases are vertical structures defined by the origin and its relation to medial embankment angles. A crease has two separate origins. 1) the lateral origin which is the trench or lowest point that runs with the direction of the impact. 2) medial origin, which starts on one side of the trench and runs to the other high side of the trench through the origin. The vertical mean is always cut in half and creates two right angles cutting through the center of the crease. This allows us to mathematically determine the exact angle of the origin, based upon the medial origin and hypotenuse embankment. The medial origin has two medial embankment angles on each side determined by the angle of the origin, for brevity sake we call them alpha/bravo banks. As a result we can begin to define rules, such as: 1) Do not fold the embankment over the origin. 2) Always open the embankment instead of closing. 3) Make passes on the lateral origin along the path of the origin. Just to name a few.
- What is Paintless Dent Repair? National Alliance for Paintless Dent Repair Technicians
- Lockdall, Randy (2016). A Complete Guide to Starting a Paintless Dent Repair Business. AuthorHouse. pp. 118–. ISBN 978-1-5049-8207-8.
- Meredith, Mike. "Paintless Dent Repair - Skilled technicians remove dents without repainting". MSN Autos. Archived from the original on 2008-01-04. Retrieved 2011-07-14.
- Materials for Automobile Bodies by Geoff Davies