In previous articles in On Machines and Tools we already briefly mentioned pneumatic tools when describing rotary hammers, riveters, belt sanders and socket wrenches, and we even published an article especially dedicated to pneumatic riveters.
In this installment we are going to address the subject in greater depth and present the multiple applications that we can find in the market and that make use of this increasingly used technology.
As can be easily inferred from their name, these tools they work thanks to the pneumatics. This is a branch of technology that employs compressed air (a way of storing mechanical energy) to produce useful work, for example, for the purposes of printing a force and / or moving objects.
The technology pneumatics it’s used on industrial systems such as, among others, lifting platforms, opening and closing of doors or valves, packaging and packaging, forming machines, drilling of parts, industrial robots, labeling, logistics systems, presses and machine tools.
In either case, a pneumatic system It consists of various components designed to fulfill three fundamental functions, which are the following:
one. Production, conditioning and distribution of compressed air: this stage includes,
- a air compressor.
- a Deposit to store compressed air.
- a maintenance unit to condition compressed air, consisting of:
- filters– Remove airborne solids and liquid contaminants that can affect equipment performance.
- regulators: they provide a controlled and consistent air pressure, which ensures the adequate supply of air to maintain relative torque and speed control, in addition to conserving compressed air.
- lubricators– Helps to ensure that equipment receives the lubrication required for optimum performance, reduce wear, and extend the life of the tool.
- distribution pipes of compressed air.
two. Compressed air control: this stage includes valves that monitor the operation of the pneumatic circuit, allowing, interrupting or diverting the passage of compressed air according to the operating conditions of the circuit.
3. Use of compressed air: the final part of the circuit is made up of the actuators pneumatic, either cylinders or motors that operate using pneumatic technology.
It follows from this that Neumatic tools They bring together a series of advantages and disadvantages that we summarize in the following table.
Focusing specifically on the machine tools who use technology pneumatics, we can prepare a long list that includes, among others: drills and / or screwdrivers, pneumatic hammers, impact wrenches, ratchet wrenches, nailing guns, fixing and staplers, airbrushes, blow guns, reciprocating saws, pneumatic jacks, sprayers ( paint, cement, plaster, insecticides, molten metal, plastic fibers, etc.) and abrasive tools such as straight and angle grinders, orbital and belt sanders, polishers and grinders.
It should be added that this type of tools They can not only be powered by compressed air, but also by gas, specifically carbon dioxide. Therefore, they can be much more practical and simple to transport, since they only incorporate a small gas cartridge. However, to avoid confusion, the tools that use interchangeable cartridges are called gas tools and not Neumatic tools, which make use of compressed air exclusively.
Typical circuit. How does a Pneumatic Tool work?
As we already expressed previously, the Neumatic tools They must be connected to a circuit in order to function, the components of which are described in the following figure.
2. Air storage tank
3. Drain the condensate
4. Main filter
5. Main pipe
6. Supply line
7. Draining the condensate
8. Lubricator regulator filter
9 and 10. Coupler
12 and 13. Coupler
The compressor fulfills a function similar to that of an electric generator and, depending on its design, it can run on both electric power and fuel. The purpose of the compressor is to supply high pressure air through a hose that connects to the pneumatic tool. Success in using a pneumatic tool depends heavily on the choice of the right compressor, therefore this machine is key in any operation based on the pneumatic technology.
The compressed air travels through the hose and is subjected to various control and conditioning operations through drains, filters and couplers, until it reaches the pneumatic tool using another coupler.
As we see in the figure below, inside this tool you will find a series of air tubes, a piston or anvil, and a spindle that turns the cutting element, be it a drill bit, a screwdriver, an abrasive disc, a saw, etc.
The high pressure air coming from the compressor flows in only one direction of the circuit, pushing the piston so that it impacts on the spindle and put in motion the cutting element. The movement of the cutting element, in combination with the vibration of the tool that impacts on the work surface causes the inversion of a valve inside the air tube, which in turn, reverses the direction of air circulation and therefore the piston moves away from the spindle. This process is repeated over and over again, and it occurs very quickly, with the piston striking the spindle more than 25 times per second, which means that the pneumatic tool it strikes about 1,500 times per minute.
Parameters of pneumatic tools
As in all tool, there is a series of parameters important factors that define the design and, therefore, the application of Neumatic tools According to the need. In fact, these parameters will also serve when choosing the tool suitable for our work. Those parameters are:
Maximun working pressure: is the one that needs the tool for its operation and is measured in atmospheres, bars, or pounds per square inch (psi). Most of the Neumatic tools They operate at a pressure of 90 psi (6.2 bar). Some impact wrenches and ratchets work best at 100 psi. It is important to note that higher pressures do not improve performance. For example, in some tools, performance drops at pressures above 120 psi.
Air flow or consumption: is the amount of air that should feed the tool and is measured in cubic meters / minute or liters / minute or cubic feet / minute (cfm). The tools rotary machines tend to use more air volume, followed by tools oscillating and finally the fixing guns, which are, in general, those that consume less air.
Power: It is measured in watts or HP and it is the determining factor to keep the level of revolutions stable under load. The load results from the material to be worked, the aggressiveness of the tool and work pressure.
Torque: measures the clamping force and is expressed in foot-pounds, Nm, or kgm. The Neumatic tools they are capable of producing maximum torque even under overload. They consume more compressed air under low torque load conditions (free speed) and less under high torque load conditions.
Other considerations such as free speed, no load or empty (determined in rpm), the number of strokes per minute, the diameter of the hole for air inlet hose (measured in mm or fractions of an inch), the type and size of the accessories the maintenance unit, the location of the air exhaust, the levels of noise and vibration, and the incorporation of silencers, among others, are also essential for a correct choice of the pneumatic tool more suitable.
The following table summarizes the ranges of values of some of these parameters according to the tool offered in the market, as well as the main applications of each tool.
Virtually all materials can be worked with Neumatic tools, be it wood, metals, fiberglass, plastic, concrete, stone, marble, ceramic, coatings and a vast etcetera.
In many cases, there are Neumatic tools specially designed for the material in which they are to be applied and in future articles we will address these cases in greater detail.