The Basics of Gear Manufacturing

 

 

Gear Hobbing

Gear Hobbing is a machining process for gear cutting, cutting splines, and cutting sprockets on a hobbing machine, which is a special type of milling machine. The teeth or splines of the gear are progressively cut into the material (a flat, cylindrical piece of metal) by a series of cuts made by a cutting tool called a hob. Compared to other gear forming processes it is relatively inexpensive but still quite accurate, thus it is used for a broad range of parts and quantities.  The hob is basically a worm with gashes cut across it to produce the tooth face cutting edges. All motions in hobbing are rotary, and the hob and gear blank rotate continuously as in two gears meshing until all teeth are cut. Hobbing is one of the most fundamental processes in gear manufacturing. Its productivity and versatility make hobbing the gear manufacturing method of choice for a majority of spur and helical gears.

 

Gear Shaping

Gear shaping is a process for generating gear teeth by a rotating and reciprocating a pinion-shaped cutter.  The cutter axis is parallel to the gear axis. The cutter rotates slowly in timed relationship with the gear blank at the same pitch-cycle velocity, with an axial primary reciprocating motion; to produce the gear teeth. A train of gears provides the required relative motion between the cutter shaft and the gear-blank shaft. Cutting may take place either at the down stroke or upstroke of the machine. Because the clearance required for cutter travel is small, gear shaping is suitable for gears that are located close to obstructing surfaces such as flanges. The tool is called gear cutter and resembles in shape the mating gear from the conjugate gear pair, the other gear being the blank.

Gear shaping is one of the most versatile of all gear cutting operations used to produce internal gears, external gears, and integral gear-pinion arrangements. Advantages of gear shaping with pinion-shaped cutter are the high dimensional accuracy achieved and the less expensive tools. The process is applied for finishing operation in all types of production rates.

When the surface finish and dimensional accuracy are not accurate enough for certain applications, several finishing operations are available, including the conventional process of shaving, and a number of abrasive operations, including grinding, honing, and lapping.

 

How Gear Manufacturing Can Overcome the Backlash Problem

In some gear systems, too much or too little backlash can be a problem. Fortunately, there are a few techniques we can use when manufacturing gears to insure proper backlash.   Too much backlash and the gear mesh is sloppy, too little backlash and the gears have a potential to bind.  Because of this it is very important to know how the requirements for the gear system and optimize the backlash for the best performance.

In case you aren’t familiar, gear backlash refers to both an error in motion when two or more gears are moving, as well as the small spaces between gears that are responsible for those errors. Backlash tends to occur in all systems but is most critical in systems where gears reverse direction.  The more backlash, the more “slop” when a system reverses direction.

 

Imagining a System Without Backlash

It’s hypothetically possible to have a system with gears that reverse their momentum, with no backlash. In this system, the gears would need to be manufactured and designed absolutely perfectly. You wouldn’t be able to use any lubricant, and you wouldn’t be able to allow any kind of thermal expansion or retraction. Unfortunately, it’s practically impossible to construct such a scenario. So instead, we need to focus on optimizing backlash.

In some applications, backlash isn’t much of a concern. But for applications where minimizing backlash is a priority, there are some techniques we can use to reduce or eliminate the problem. For example, you can split some gears on a plane perpendicular to their axes, then use the two halves with springs to provide more torque to the system. We can also taper teeth in its axial direction, and then allow the system to take up slack by letting the gear slide in that same direction.

Ultimately, we can also reduce the impact of the backlash problem by doubling down on our commitment to producing top-quality gears.

 

We are a gear hobbing machine supplier. If you are interested in our products, please contact us now!

What Is Spline Milling?

 

What Is a Spline?

Typically made of stainless steel, carbon steel, alloy steel, or aluminum alloy, a spline is a shaft that features a series of equally spaced teeth that can be slotted into a mating piece for the purposes of transmitting torque or serving as a means of anti-rotation. They can be internal or external and comprise a variety of tooth shapes depending on function. Rotary devices such as gears can also be fitted onto the spline to serve a variety of functions. Splines are primarily found in rotating mechanisms such as drive shafts.

 

What Is Spline Milling?

Spline milling is one of the processes of machining grooves into a chunk of raw material to create the teeth of a spline. The following steps outline the process of spline milling:

• The chunk of raw material that will become the shaft of the spline is fitted into the indexing fixture of the milling equipment.
• Side milling cutters are mounted onto the arbor of the fitting equipment with a spacer and shims inserted between them, depending on the desired width of the spline.
• The arbor is mounted onto the spindle of the milling machine, and the cutters are centered over the raw material that will become the shaft of the spline.
• The splines are cut into the shaft by a process called straddle milling. The indexing fixture holds the shaft of the spline steady while a groove is cut by the rotating milling cutters along its length. Depending on the depth of the spline, multiple passes along the same groove may be needed. Multiple passes also help to guarantee uniformity throughout the spline.

 

How to Cut Splines on a Shaft?

Spline milling is one of several processes of spline cutting, which is the process of machining teeth into internal or external splines. Spline cutting can be used to create shafts, gears, and other mechanical components that mesh into one another and allow power to be transferred throughout a mechanical system.

There are four main spline cutting techniques:

• Broaching
• Hobbing
• Milling
• Shaping

 

Know about Geepro Machinery YK631 CNC Spline Milling Machine

 

 

YK631 CNC spline milling machine is five-axis linkage machine tool with the movement form of workshaft, tool spindle, servo feed (X axis), servo feed (Z axis), tool lift (Y axis). Mainly use rolling and milling processing straight slot spline shaft, inclined tooth spline shaft, tooth shaft and straight gear, and can process cone spline and step spline shaft.This machine tool is suitable for the machining of automobile, tractor industry and machine tool manufacturing industry, hydraulic parts manufacturing industry, lifting machinery, construction machinery and other industries.This function realizes the rolling for two or more splines with the same number / analog of teeth on the workpiece.

Rob speed range of this machine tool: from 100-1500 turn CVT adjustable, can double improve the cutting efficiency.The machine tool can select air-cooled and wet cutting according to the tool and production process.

Know The Difference Between Gear Shaping And Gear Hobbing

 

Just like any sheet metal is fabricated to form the right mold, shape, size, and so on, gear manufacturing has certain machining processes such as shaping, hobbing, and so on. Gears are required to be set in motion, rotate, and raise the speed of any machine, industrial equipment, automobiles, and so on. So, how are these gears made? CNC machining methods are widely applied in the last stages of gear manufacturing, and milling, casting, forging, and so on are some of the methods used. Gear shaping and hobbing are also two important processes of gear manufacturing. The process to be used depends on gear specifications such as the shape and size required, among other parameters. This post discusses and compares the two methods- gear shaping and gear hobbing.

 

What is Gear Shaping?

Shaping is almost a subset of the milling process. This process helps form the gear teeth with the help of a rotating cutter tool, wherein its axis is parallel to that of the gear. The rotating speed and velocity of the cutter must match with the gear blank for teeth formation. A train of gears helps achieve the relative motion between the cutter shaft and the gear blank. Here the cutting may happen either at a downward or upward stroke. This is suitable for shaping of gears closely located toward the flanges or other obtrusive surfaces. This is widely used process for making internal and external gears. High dimensional accuracy is one of the major benefits of the shaping process apart from its cost-effective tools. After this process, surface finishing may be required depending upon the application.

 

What is Gear Hobbing?

Hobbing is a method also used for teeth formation in gear manufacturing. This teeth formation is done on the gear blank with the help of a hob on CNC gear hobbing machines. This machine is a type of special milling equipment. It could be an index hob or a master hob. There are various other types of hobs such as spline, spur, helical, chamfer, roller chain sprocket, straight side, and so on. The gear blank and the hob rotate simultaneously and produce continuous cuts on the blank gear which gives the required depth to the teeth. As mentioned above, the machining processes chosen are largely based on the shape and size of the gear. Likewise, hobbing is applicable for gear shapes such as helical, straight bevel, crowned, worm, face, and chamfering. Also, it is suitable for medium to high production volume. This cost-effective yet efficient process is useful to make several parts irrespective of the quantity.

 

Accuracy

There are benefits that come with each gear production. For example, the movement accuracy of gear hobbing is high. While that is not the case for gear shaping, gear shaping is more accurate in the surface finish. This is because the mechanic gear shaper is more complex. When comparing the two even further, the manufacturing process is simpler and easier to manufacture more accurately.

 

Productivity

In most scenarios, gear hobbing is more productive than gear shaping. This is because, in gear hobbing, there is not a large number of redundant metals. There is an instance, however, where gear shaping can compete with gear hobbing in terms of productivity. That scenario occurs when the gear is smaller in size and the teeth have a large and small-tooth width.

 

The conclusion

Looking at the accuracy and productivity allows you to better see the difference between gear shaping and gear hobbing. These two gear producing systems are alike, yet have their differences. Hopefully, this explanation gives you a better foundation to understand that.

If you notice, the difference between these two methods is really in the way the gear teeth are formed.

If you happen to be searching for a company that can create custom made gears, look no further. Not only do we have skilled professionals who can create exactly what you need, but we will provide you with insight on all things gears as well.

A Short History of Gears

 

 

Gears are considered as one of the oldest equipment known to mankind. The origin of gears goes down to the Chinese South-Pointing Chariot in the 27th Century B.C. This chariot was known to pointing to the south no matter how it was turned.

Aristotle has the credit to his name of giving the earliest description of gears in the 4th century B.C. According to his definition, the direction of rotation is reversed when one ear wheel drives another gear wheel. Gears have been used by the Greek Inventors in water wheels and clocks. The sketches of various types of gears of this time can be found in the notebooks of Leonardo da Vinci.

Even after these ground-breaking discoveries, no major development concerning wheels was made until the 17th Century. In this time, first attempts were made to provide constant velocity ratios. These attempts utilized the involute curves. This was just the beginning of something that changed the world for all the good reasons. However, in the 19th century, form cutters and rotating cutters were first used and it was then in 1835 when the English inventor Whitworth patented the first gear hobbing process.

Various other patents followed until 1897 when Herman Pfauter of Germany invented the first hobbing machine capable of cutting both spur and helical gears. Through the 20th century, various types of machines developed. But, the next major step came in 1975 when the Pfauter Company in Germany introduced the first NC hobbing machine and in 1982 the Full 6 axis machine was introduced.

 

Today

Gears or Cogs are in just about everything containing a spinning part, that is, from cars to clocks. Car's transmissions and engines contain lots of cogs that help in reducing the gear in motorized equipment. There're other lots of important jobs performed by these simple machines.

Besides being used in the industry, gears are also being used in different toys and they are one of the major components in toy cars and other toys to help them move. Even in smaller toys, gears are used in different sizes to ensure the proper functionality of them.

Gear manufacturers primarily use CNC machines to cut gears from blanks, and our level of precision is driven by sophisticated design software and advanced engineering theories. Modern gears are exceptional pieces of work, capable of lasting centuries (or longer, if cared for properly), and technology continues to advance to bring us better ways of producing gears.

 

If you have a custom made gear to order, or need a quote for a large project, be sure to contact us today!

What is Gear Hobbing Machine Process?

 

 

Hobbing machines provide gear manufacturers a fast and accurate method for cutting parts. This is because of the generating nature of this particular cutting process. Gear hobbing is not a form cutting process, such as gashing or milling where the cutter is a conjugate form of the gear tooth. The hob generates a gear tooth profile by cutting several facets of each gear tooth profile through a synchronized rotation and feed of the work piece and cutter.

 

As the hob feeds across the face of the work piece at a fixed depth, gear teeth will gradually be generated by a series of cutting edges, each at a slightly different position. The number of cuts made to generate the gear tooth profile will correspond to the number of gashes of the hob. Simply put, more gashes produce a more accurate profile of the gear tooth.

 

The hobs several cutting edges will be working simultaneously, which provide significant potential for fast cutting speeds and/or short cycle times. With this realization, one can see the hobbing process’s advantage over other cutting processes.

 

All gear hobbing machines, whether mechanical or CNC, consist of five common elements.

1. A work spindle to rotate the work piece

2. A cutter spindle to rotate the cutting tool, the hob

3. A means to rotate the work spindle and cutter spindle with an exact ratio, depending on the number of teeth of the gear and the number of threads of the hob

4. A means to traverse the hob across the face of the work piece

5. A means to adjust the center distance between the hob and work piece for different size work pieces and hobs

 

 

While the hob and work piece are rotating, the hob normally feeds axially across the gear face at the gear’s tooth depth to cut and produce the gear. In conventional hobbing, the direction of feed matches the direction of the cutting motion. Alternatively, in climb feeding, the feed is opposite to the direction of the cutting motion. Generally, conventional hobbing produces a better finish, whereas climb hobbing yields better tool life. For either method, the cutting forces of the hob should be directed towards the work spindle and not the tailstock.

 

Gear Hobbing Basics

Gear hobbing is a diverse and wide-ranging process that can be used to create several different gear types: Helical, worm and spur gears are some of the most common, but others are possible as well. It's carried out using a special form milling machine, one that contains a tool known simply as a hob.

The hob is the tool that directly generates the teeth for both gears and splines, and it does so with relative simplicity compared to other gear manufacturing types. It allows for high-volume production of these gear types.

 

The final words

To cut a helical gear, a standard hob cutter can be used. Mechanical hobbing machines provide a differential motion through a series of change gears to generate a gear tooth helix. Today, CNC hobbing machines electronically provide this necessary differential to produce helical gears. Contact gear hobbing machine supplier for a quote!

How Gear Hobbing Works

 

 

A gear hobbing machine contains two skew spindles. One of these spindles houses the hob, while the other houses the gear blank. The angle at which these spindles are placed relative to each other depends largely on the type of gear being manufactured.

 

Once the spindles are placed at the proper angle, the machine is set up to begin rotating the shafts at a speed ratio that suits the gear type. As the shafts rotate, the hob gradually cuts the teeth into the gear with the proper depth. To facilitate faster production, manufacturers can stack multiple blanks on the spindle together, allowing the hob to cut teeth into multiple gears at once.

 

Just like there are multiple different angles, speeds, and techniques manufacturers can use to customize the process, there is also a wide variety of hobbing machines available for use. Most hobbing machines specialize in distinct applications. Hobbing machines are built to handle gears of a particular size and come in two different varieties: single-threaded and multi-threaded hobs. Multi-threaded machines allow for increased production, but they aren’t as precise as single-threaded machines.

 

 

Hobbing is one of the most fundamental processes in gear manufacturing. Its productivity and versatility make hobbing the gear manufacturing method of choice for a majority of spur and helical gears.

 

One of the most important concepts  to understand about gear hobbing is that it is a generating process. The term generating refers to the fact that the shape of the gear tooth that results is not the conjugate form of the cutting tool. Rather, the shape of the tooth is generated by the combined motions of workpiece and cutting tool. During hobbing, both the hob and the workpiece rotate in a continual, timed relationship.

 

For a spur gear being cut with a singlestart hob, the workpiece will advance one tooth for each revolution of the cutter. When hobbing a 20-tooth gear, the hob will rotate 20 times, while the workpiece will rotate once. The profile is formed by the equally spaced cutting edges around the hob, each taking successive cuts on the workpiece, with the workpiece in a slightly different position for each cut. Several cutting edges of the tool will be cutting at the same time.

 

During this rotation, the hob is typically fed axially with all the teeth being gradually formed as the tool traverses the work face.

 

The hob itself is basically a worm with gashes cut across it to produce the cutting edges. Each cutting tooth is also relieved radially to provide chip clearance behind the cutting edge. This also allows the hob face to be sharpened and still maintain the original tooth shape. In its simplest form, the hob tooth takes on the shape of a straightsided rack tooth. The final profile of the tooth is created by a number of flats blending together. The number of flats corresponds to the number of cutting gashes which pass the workpiece tooth during a single rotation. Thus, the greater the number of gashes in the hob, the greater the number of flats along the profile, which improves the “smoothness” of the tooth profile.

 

Geepro Machinery

WUXI GEEPRO GEAR HOBBING MACHINE has been one of the professional gear hobbing machine manufacturer and supplier in China since 2007.

Benefits From Our Advantages:

• Professtional Sales Engineers

• Stable Performance of Machines

• Reasonable Price For Users

• Long Life After-Sales Service

We provide high speed high accuracy gear machinery and other workpieces solutions with premium quality service to global users. Contact us now!

Gear Hobbing Machine: Everything You need to Know about Gear Hobbing

 

 

Gear hobbing has been an integral part of gear making. Whereas milling would be used to produce the basic gear shape, gear hobbing performs the much more intricate task of shaping the gear. Various facets of gear teeth emerge once hobbing is complete, including its thickness, profile and addendum.

Gear hobbing is a specialised process of gear cutting, spline cutting and sprocket cutting. The central equipment in the gear hobbing process is the milling machine. This gear hobbing machine does the task of cutting the spline or teeth using a series of cuts using a hob. Gear hobbing is often used for spur gear and helical gear making, because of its ease of use and cost effectiveness.

 

Construction Of Gear Hobbing Machine

Hob– In this process, the gear blank is rolled with a rotating cutter called a hob. Gear hobbing is done by using a multipoint cutting tool called gear hob. It looks like a worm gear having a number of straight flutes all around its periphery parallel to its axis. These flutes are so shaped by giving proper angles to them so that these work as cutting edges.

In gear hobbing operation, the hob is rotated at a suitable rpm and simultaneously fed to the gear blank.

The gear blank is also kept as revolving. Rpm of both, gear blank and gear hob are so synchronized that for each revolution of gear bob the gear blank rotates by a distance equal to one pitch distance of the gear to be cut.

The motion of both gear blank and hob is maintained continuously and steady. A gear hob is shown in Figure and the process of gear hobbing is illustrated in Figure

The hob teeth behave like screw threads, having a definite helix angle. During operation the hob is tilted to helix angle so that its cutting edges remain square with the gear blank.

Gear hobbing is used for making a wide variety of gears like spur gear, helical, hearing-bone, splines and gear sprockets, etc.

 

Types Of Hobbing Process :

The process of gear hobbing is classified into different types according to the directions of feeding the hob for gear cutting. The classification is described as given below.

• Hobbing with Axial Feed

In this process the gear hob is fed against the gear blank along the face of the blank and parallel to its axis. This is used to make spur and helical gears.

• Hobbing with Radial Feed

In this method the hob and gear blanks are set with their axis normal to each other. The rotating hob is fed against the gear blank in radial direction or perpendicular to the axis of gear blank. This method is used to make the worm wheels.

• Hobbing with Tangential Feed

This is also used for cutting teeth on the worm wheel. In this case, the hob is held with its axis horizontal but at the right angle to the axis of the blank. The hob is set at full depth of the tooth and then fed forward axially. The hob is fed tangentially to the face of the gear blank.

 

 

The process of gear hobbing is as follows:

• The gear hobbing machine is checked for any mechanical issues. This includes the synchronisation of the rotating gears for the workpiece and the hob.

• The gear hobbing machine has two skew spindles, one of which has the gear blank while the other one has the hob.

• The spindles are set at an angle from each other, depending on the type of teeth to be set on the gear blank.

• The two spindle shafts are then rotated proportionally with the hob cuts on the gear blank. Having them properly rotating is the key to making the right gear teeth on the gear blank.

• The hob would then be applied to the gear blank until the correct tooth depth has been reached.

• The hob is then run through the gear blank’s axis of rotation as a final step.

• The process is repeated for each gear blank, which is often stacked one atop another. The rotation ensures identical gear spindle depth and a consistent number of teeth on each gear blank.

• The completed gears are removed from the milling machine.

• The central tool to gear hobbing is the hob, a worm-shaped cutter. The hob makes successive cuts on the gear blank to create the gear teeth. In order for the cutting to be precise, the gear blank and the hob must be synchronised in the rotation.

 

The 5 Advantages of Gear Hobbing

Gear manufacturing gives us lots of options. There are a handful of different processes we can use to make dozens of different gear types from dozens of different materials. Accordingly, when we choose a gear manufacturing method, it’s because it’s the best one for the job.

Gear hobbing is just one way we can manufacture gears. It relies on a special form milling machine with a tool known as a hob, which generates the teeth in both gears and splines. So what are the advantages of this process?

• Speed. Some gear manufacturing processes take a long time, but gear hobbing is relatively fast. The machine is simple, so it doesn’t require as much operational attention, and for some gears, we can stack multiple units to hob them all at the same time.

• Precision. That said, not just anyone can operate a hobbing machine. With the right expertise, hobbing can be highly precise, resulting in high quality gears.

• Flexibility. There’s more than one type of hob—and more than one type of hobbing machine. There are countless variations that cater to specialized applications, so you always have options available.

• Applications. While hobbing is often used for spur gears, the process can be used for a variety of other gears, such as cycloid gears, helical gears, worm gears, ratchets, splines, and sprockets (as long as you have the right tools for the job).

• Related processes. One of hobbing’s only weaknesses is that it does not work for internal gears (with inward-facing teeth). However, there’s a related process called shaping that can be used instead—with all the same advantages of hobbing.

 

Geepro Machinery

WUXI GEEPRO GEAR HOBBING MACHINE has been one of the professional gear hobbing machine manufacturer and supplier in China since 2007.

Benefits From Our Advantages:

• Professtional Sales Engineers

• Stable Performance of Machines

• Reasonable Price For Users

• Long Life After-Sales Service

We provide high speed high accuracy gear machinery and other workpieces solutions with premium quality service to global users. Contact us now!