Machining is a set of industrial processes performed on raw materials by which material is removed in a controlled manner. Generally, it is done on metallic material, yielding the desired shape and size for various applications across all kinds of industrial sectors.
At CLR, the processes applied for gear machining are chip removal, and abrasion to a lesser degree.
In this article we will learn how gears are manufactured at CLR and what kinds of parts we can manufactured to obtain the best results.
What is gear machining?
Gear machining is the set of industrial processes by which different gears are manufactured and shaped from a raw material that is subjected to different treatments.
To accomplish this, the material (which is generally metallic, but may also be some other raw material such as plastic , which is becoming increasingly widespread) is filed and sculpted in a controlled manner until the desired size and characteristics are attained.
Nowadays we can claim that gears of the most diverse shapes are used across all industrial sectors; it is common for all – or almost all – machines used within manufacturing processes to include gears. They are especially used in machines that have heat or electric motors.
The fact that there is a great need for gear machining means that this process – which used to be done by hand – experienced major technological advances, both in regard to machines and to the tools used for machining, milling and grinding gear teeth.
- The gear hobbing machine can hob splined shafts with few splines or a dividing mechanism, even though the latter is in disuse.
- In the industry, each hobbing machine has a specific purpose within production, which is why each machine has a specific transmission programming and operational constants.
- Mass production hobbing machines are used to machine normal bevel, helical and spur gears.
Depending on the different types of machining that they perform, they yield different types of gears, such as straight-toothed gears, worm gears, bevel gears (both straight and spiral toothed), helical gears and hypoid gears.
Gear hobbing stages
The main stages are:
1. Raw material
The raw material used as the basis for the gear machining is usually steel of different types (cast, malleable, etc.), ferrous metals, die cast, super-alloys or hardened materials.
However, synthetic materials of all kinds may also be used, or even wood. As for the type of surface of these raw materials, they may be curved or flat, with slats, notch cuts, etc.
2. Turning (gear blank)
The gear turning process is based on the rotation of the part on which we want to work.
The machine performs a forward motion, fastening the part between the centers or securing it at the chuck. The tool also performs the cutting motion.
Turning yields a part called the gear blank, a cylindrical part that is obtained through chip removal.
There are different types of lathes at a machining center, such as:
- Frontal lathe designed for short, large diameter parts
- Vertical lathe, called this way because the main shaft is positioned this way in relation to the ground
- Bench lathe, which adjust the cutting motion to the rotating part
- The CNC, which is the most advanced of them all, uses numeric control. This is the type used by CLR for our part machining.
- The automatic lathe which does not require an operator and works based on a program. It is particularly used with metallic parts and has the purpose of producing high numbers of parts with the same dimensions and specifications.
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3. Milling (pinion)
Milling is the stage of machining that yields the gear pinion with different shapes.
While in traditional milling machines, different shapes are obtained by moving the areas to be machined toward the tool, in advanced milling the entire process is performed by a CNC machine (also known as numerical control).
The ISO programming code is responsible for guiding the operations, which ‘command’ the machine to follow certain paths. The numerical control of the entire process guarantees the best results.
Drilling is the process by which holes are made in the tools. It consists of performing a cut in the material as the result of a rotating bit, which makes a hole in the material through chip removal.
The shape and diameter of the material, among other specifications, are programmed into the drill.
The various types of drilling include:
- Specific, central or deep drilling.
- Micro drills are used for small holes.
- Drill interpolation, high-speed drilling and vibration drilling are used to
address specific needs.
What are the pinion and gear machining processes?
The two main pinion and gear machining processes are abrasion and chip removal.
1. Abrasion machining
Abrasion machining consists of the removal of material from the surface of the raw material as the result of the friction of the bit.
The bit is made up of tiny, hard and abrasive glued particles.
One of the great advantages of this process is that it offers a high precision and an excellent finish.
As for its drawbacks, it requires high production times.
2. Machining by chip removal
The chip removal technique includes grinding processes. This is based on coarsely removing a significant amount of material, as well as removing material with extreme precision in the finishing process, whose purpose is to give the different faces of the material a surface finish.
A successful chip removal requires both a main (or cutting) motion and a forward motion.
- The main (or cutting) motion is responsible for the removal of material from the part as per the desired finish
- The forward motion leads the trajectory while the main motion is performed.
The main advantages of this gear machining system are:
- Versatility, since it offers the possibility to create a wide range of shapes.
- The fact that it allows the raw material to preserve all of its mechanical properties.
- In addition, a good finish can be accomplished.
- This machining process is easily automated with the proper machinery.
Conversely, the drawbacks of this technique include the great amount of wasted material, a greater energy use and certain limitations to the finish and precision. The size of the parts that can be worked on is limited, since it has to adjust to the characteristics of the machine-tool.
Part machining machines
For part machining, the industry uses a series of specific machine tools that may be manual, semi-automatic or automatic. The following see the most use at CLR:
A lathe is a set of machines and tools that can remove chips from geometrically shaped parts until the target finish is attained.
It works by rotating the part to be machined, which is affixed to the chuck, while one or several cutting tools perform a controlled forward motion against the surface of the part at the same time.
Sometimes the lathe can work with moving rotary tools while the part is fixed, allowing for operations such as off-center drilling, keyways, seams and others.
One could say that one main difference between lathes is whether they are bench lathes or vertical lathes:
- For the former (bench), it uses a rotating part for chip removal.
- For the vertical lathe, the machine is controlled by a CNC and is usually employed with very large parts. A CNC numerical control lathe is better for rotating parts, due to its functional structure.
In the event that the machining of parts with several levels is required, a lathe copier is used, which combines an electronic and an hydraulic device.
Together with lathes, milling machines are the most multi-purpose and universal tools.
They work by removing chips from the semi-finished part through the use of a rotary tool with several cutting edges, called a bur or milling cutter.
Milling machines are characterized by the forward motion taking place at the base of the machine, where the part is fastened, while the rotary tool performs the cutting motion.
At CLR we have both conventional milling machines and numerical control milling machines. Milling machines are highly useful when making rollers, prototypes, supports, spherical joints, valve assemblies and screws.
Related reading: The use of rapid prototyping in mechanical engineering projects
The morticer, also known as mortiser and mortising machine, is a machine that manufactures parts through chip removal, just like the lathe and milling machine.
The difference in this case is that the cutting motion is caused by the tool, which moves longitudinally and vertically; meanwhile, the forward motion is performed by the base of the machine, where the part is affixed.
The morticer can be used to obtain geometric shapes by copying the profile of the tool.
This type of machinery is heavily used to shape levers, shafts or sheets, as well as to machine slats.
The broaching machine is a machine tool that allows for the machining of the keyway of fixed gears, with the purpose of affixing them to a keywayed shaft instead of using a fastener.
The tool that is used for this purpose is called a broach, and its design allows for each tooth to make small cuts into the material.
The broaching machine can machine surfaces that are parallel to their generatrix moving in a straight line.
It is used to make slats using multi-edged cutting tools. Broaching is used when the goal is to obtain polygonal shapes starting from cylindrical holes, though it is also used for the manufacture of helical surfaces, since it is highly precise and can accomplish this in little time.
A broaching machine is composed of the base, which is the main support; the work table, where the part to be machined is affixed; and the pull bar, which transfer the power in a straight line.
The morticer and the broaching machine are very similar. People usually refer to them as if they were the same machine.
Types of numerical control machines
Throughout this article we have already mentioned that there are machines that can be numerically controlled. This means that those machine tools are automated and operate via commands programed into storage media.
There are three types of numerical control machines based on the motion that they perform:
- Point-to-point controlled: they do not control the motion, speed or path, but rather the starting and ending points. A spot welder and a driller would fit this type.
- Interpolating controlled: these are the most versatile. They allow for machining across different paths.
- Paraxial controlled: such as lathes. These allow for the programming of both motions and speeds during the entire path, through the latter must be parallel to the axes.
Machined products that can be provided by CLR
Through the various machining processes, CLR can manufacture a wide range of parts and components, which include:
- Screws: Machining of screws made of tin, aluminum and all kinds of steels. With a pitch of 0.10 up to 2.
- Gears: shaping of helical, globoid and spur gears of up to 120 mm (4.72”) and a module of 0.10 up to 2.
- Custom products: made using a CNC lathe, made out of steel and various alloys. Up to a maximum diameter of 200 mm (7.87”) and a length of 400 mm (15.75”).
Do you want to make your engineering project come true? Do you need custom parts? Contact us and we will assist you!