【Knowledge】Control Knob – Introduction and Application

Knob is a part which can transmit order to the device by spinning, and the mechanical transmission could control thermal, volume and other features. Such knobs are widely used in washers, audio equipment, car AC control and others.

The control knob mainly consists of housing and shaft hole. Knob housing can be designed for different purpose. According to the shape of housing, it can differentiate into various types like wedged knob, pointer knob and others. Shaft hole is a critical part for mechanical transmission so the dimension and types of shaft is a key determinant of knob selection.

Compare with buttons and touchscreen, the control knob is an intuitive design. Users can even take their eyes away and still control the device. Besides, only one knob can control multiple functions just turning the knob. For example, the knob on washers can control different ways of washing for various fabric rather than many buttons. By this design, it can minimalize the space of products and lower the cost as well.

The Materials of Control Knobs

Aluminum Control Knobs

Compare with other metal, aluminum is lighter. Compare with plastic material, aluminum has metallic luster which the plastic parts don’t have. Such luster shows high quality and suitable for audio products and consumer electronics. Aluminum control knobs include full aluminum and aluminum shells.

Full aluminum：It is one-piece aluminum knob so it has better strength. Since it’s made by cutting aluminum bar, its MOQ will be lower compare with plastic knobs. Another advantage is handy control. However, the price is higher than plastic knobs.

Aluminum shell：Literally means aluminum shell with plastic insert. This kind of knob is cheaper than full aluminum. Besides, the plastic part can be made into various shaft types.

Q：Why the MOQ for full aluminum knobs is lower than aluminum shell knobs?
A：There’s fewer process to manufacture full aluminum knobs because we just cut the aluminum bar and surface treatment. However, when it comes to aluminum shell knobs, we not only cut the bar but also do stamping and heat treatment. Besides, there is a plastic part which needs manufacturing and assembling. Due to it is more complicated, the MOQ jumps to more.

Plastic Control Knobs

Compare with aluminum knobs, the price for plastic control knobs is lower. Besides, the shape and the color of knobs can be various. For the shaft hole, the shapes varied depending on different requirement.

ABS

ABS is commonly used for plastic control knobs because it’s easy to get and the price is not that high. This material is widely used in consumer electronics parts.

Pros.
It is easily painted so it can fulfill different color requirement. Also, there are many types of ABS according to its heat resistant degree and strength degree for selection.
Cons.
It’s not suitable for outdoor.

Nylon

Pros.
High-impact resistance. Oil resistance. Better heat resistance than ABS. It’s suitable for cookers.
Cons.
It tends to absorb moisture so its dimension may be affected.

PBT

Pros.
High abrasion resistance. Better heat resistance than Nylon. Low water absorption. Easily painted. Oil resistance. Widely used in cookers.
Cons.
Its notch sensitivity reduces toughness. PBT is an anisotropic material so it will cause warpage easily.

Phenolic

Phenolic (Bakelite) is a common thermoset material for knobs.

Pros.
Moisture and electrical resistance. Heat resistance. It’s widely used in consumer electronics.
Cons.
Less selection of colors. The MOQ will be higher for other color except for black. Besides, Thermoset material is too hard and the shaft might be detached after assembling. Thus, it’s fixed by a screw or inserts a brass.

Types of Shaft Hole

Round Shaft

Round shaft is the most widely used type in knobs. There is no horizontal and vertical mounting consideration but this type needs a side screw to fix in case of the shaft could not be driven by the knob. If the shaft is short, the way of screw fixing can still work even the height is not enough.

D-Type

Literally speaking, the shape just looks like a half of circle. The flat part varies by different width and depth of flat side. The most common size is 6 * 4.5mm.

18-Tooth

It’s one of widely used types. The common size is 6mm. Not like round type, this type cannot easily matchup because there will either be a "peak" or a "valley" in the knurl at the top of the shaft. This means a 10-degree difference if you get the wrong matchup.

Surface Treatment for Knobs

Anodizing

The common surface treatment for aluminum is anodizing which can avoid oxidation. The common color while anodizing is black and silver (aluminum color)