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Kevin Brown Method: How a random orbital affects your polishing performance

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A random orbital and its different settings can affect your performance in a great way. A couple of big issues that influence the polishing performance are the speed, stroke size and pressure. But first some general information about the machine.

Machine information

Machine stroke is the distance between the driveshaft axis and the backing plate axis multiplied by two. Machine manufacturers also refer to machine offset: the distance between the driveshaft axis and the backing plate axis. An orbit is one rotation by the machine driveshaft. This means that the backing plate will travel once around the driveshaft axis.

Speed

Depending on the job, you choose different speed setting on your machine. Select the right speed setting for your goal, it can be the difference between a good or a stunning result.

High or low speed setting?

As we know paint will be removed faster when using a higher machine speed, which means more orbits per minute. The levelling ability also increases when the pad is moving faster. Levelling is the minimization of height variations on the paint surface, which makes the paint look smooth. When we accomplish a sufficient result in levelling of the surface, there’s no benefit for continued use of a high speed.

The preference for (heavy) defect removal is a high speed setting, because it increases cutting power and can save a lot of time. But that doesn’t mean that you can’t use a slower speed setting, because a high speed setting also increases the risk of pigtail marks. This results in a decrease in smooth paint levelling and increase the level of refining that needs to be done. A low speed setting can give us many benefits:

  • We don’t have to control the machine by a heavy hand.
  • When used at lower speeds a pad will maintain a higher level of pliancy, which causes the pad to better contour a complex shape.
  • The heat caused by friction is kept to a minimum when using a low speed.
  • The material of the pad can be damaged at high speed movement. The buffing cycle will be shortened when the material is damaged.
  • The motions that the random orbital makes are more aggressive when the speed is increased.

Another variable that can affect your polishing session is stroke size. Stroke size is the difference between a full inwards position and the full outward position of an excentric movement (also called “throw”).

Stroke size affects polishing efficiency

A refined finish can be accomplished by a smaller stroke. For polishing you will have to minimize the backing plate motions when a soft buffing pad is used. A small stroke machine is great for working on small or confined areas and easy to control.
A more consistent levelling of the surface will be easier accomplished by a large diameter pad than a small diameter pad.

The following factors are important for choosing an ideal stroke size:

  • The machine’s motion can be affected by cushioning from the buffing pad, this can affect the paint polish.
  • If the stroke diameter increases, it travels more distance at the same speed as with a smaller diameter. It has to travel a longer distance in the same period of time.
  • A small diameter pad is perfect for small or complex areas. A larger diameter pad is better for a large area or when a lot of material has to be removed.
  • A large stroke machine causes much more vibration

In relation to the stroke of the machine or pad, pressure is another variable that we have to take into consideration.

Pressure

A small diameter pad delivers more pressure per square inch than a larger diameter pad of a similar type. It’s important to note that an increase in downward applied pressure is often required when buffing pads are used (not when you use a sanding pad).

Different opinions

There are a lot of opinions when it comes to pressure. The amount that should be applied is dependent upon different factors, like buffing pad, buffing liquid and pad rotation. When you want to remove defects and you have to press down hard to notice an improvement, try these steps:

  • Use a smaller diameter pad
  • a pad from different material
  • Change the stroke diameter of the machine.

If an increase in pressure is necessary, remember that it is not the only factor when using the Kevin Brown Method. Adjusting other factor might help to prevent the use of increased pressure. Priming your pad properly is very important, also consistent pressure across the pad, because the pad should rotate at all times. If there is insufficient removal of defects, consider a pad that is more aggressive or smaller in diameter. But when heavy defect removal is the intention, more pressure is a good thing.

Speed and pressure when using a foam pad

If you remove defects with foam, you need to drop the speed to minimize a quick increase in temperature because of pad velocity. After that, downforce should be increased. This causes the paint to heat more than light pressure, but helps to better remove the defect.

The random orbital and the Kevin Brown Method

The Kevin Brown Method uses a random orbital machine for polishing. In this method a couple of variables are taken into consideration. First of all: speed. Although it seems tempting to use a high speed setting (because the job is done faster), you should use a lower speed settings. A low speed settings has a couple of benefits;

  • the pad can contour the defect better,
  • the heat is kept to a minimum,
  • the motions are smoother and
  • there is lesser risk in damaging your equipment.

Second variable is stroke size. Hereby it’s more your own opinion that matters, but it is important to take the factors into consideration when choosing an ideal stroke size. At last; pressure. There is no need in the Kevin Brown Method to use a lot of pressure. Because priming your pad properly and continuous rotation of the pad ensures that you can use a lot less pressure for this procedure.

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