A milling machine is one of the basic metalworking machines and perhaps the most widely used one. Your milling machine is only second to the lathe machine, in terms of versatility and importance.
- How Milling Machine Works?
- Types of Milling Machines and Their uses
- 1. Bench Top Milling Machine
- 2. Column and Knee Type Milling Machine
- 3. Horizontal Milling Machine
- 4. Vertical Milling Machine
- 5. Ram-Type Milling Machine
- 6. Fixed Bed Type Milling Machine
- 7. Simplex Milling Machine
- 8. Duplex Milling Machine
- 9. Triplex Milling Machine
- 10. Turret Mills
- 11. Rotary Table Milling Machine
- 12. Planer Type Milling Machines
- 13. Tracer Milling and Pantograph
- 14. Tracer-Controlled Milling Machines
- 15. 3-Axes CNC Milling Machine
- 16. 5-Axes CNC Milling Machine / Machining Center
How Milling Machine Works?
The milling machine works by feeding the workpiece fixed on the bed of the machine against a revolving milling cutter that removes material from the work to create flat, curved and or complex 3D surfaces. Depending on the type of machine, this is achieved by either moving the bed, ram, or a combination of the two. You can also use a milling machine to drill holes, boring, reaming, thread cutting etc.
On a simple conventional machine the ram is fixed and the movement of the Z-axis is usually to give depth of cut. During the actual milling process only the X-a and Y-axis moves. The exception would a hole making process such as drilling or boring where the X and Y-axes movements are arrested and the Z-axis moves up and down.
On a 3-axis milling machine, all the three axes can move simultaneously to create any sort of complex and irregular shapes on the workpiece. On a 5-axes machine you also have the rotational and angular motion in addition to the three axes. There are several other non-conventional milling machines that are designed for specific uses.
Let us explore the world of Milling Machines.
Types of Milling Machines and Their uses
Here is a list of different types of milling machines that are commonly used in metalworking.
|01||Bench Top Milling Machine||09||Triplex Milling Machine|
|02||Column and Knee Type Milling Machine||10||Turret Mill|
|03||Horizontal Milling Machine||11||Rotary Table Milling Machine|
|04||Vertical Milling Machine||12||Planer Type Milling Machine|
|05||Ram-Type Milling Machine||13||Tracer Milling and Pantograph|
|a) Universal Ram-Type Milling Machine||14||Tracer-Controlled Milling Machine|
|b) Swivel Cutter Head Ram-Type Milling Machine||15||3-Axes CNC Milling Machine|
|06||Fixed Bed Type Milling Machine||a)||Horizontal Machining Centers|
|07||Simplex Milling Machine||b)||Vertical Machining Centers|
|08||Duplex Milling Machine||16||5-Axes CNC Milling Machine / Machining Center|
1. Bench Top Milling Machine
Your Bench Top Milling Machine, also called Mini Milling Machine is of simple construction and can be mounted on a work-bench or table. You can use this machine for milling wood, metal, plastic, and engage in your hobby creating projects or as a professional lab technician or optician.
Your Machine is of cast-iron construction, has two-speed ranges, R8 spindle taper to hold up to ½ inch drill, 5/8 inch end mill, and 11/8 inch face mill. You can precisely move the table longitudinally or transversely and the spindle up and down using graduated handwheels. You can even swivel the spindle head to your right or left up to 45 degrees to do taper milling. If you want a cheaper machine, you may get it at less than half the cost of this machine, but they are smaller in size with fewer features.
2. Column and Knee Type Milling Machine
If you see a Column and Knee Type Milling Machine, you will understand why they are so named. If you sit on the floor with the knees of your folded legs protruding outwards, well, that is how the Column and knee machine looks.
The structural parts of your Column and Knee Type Milling machine are of cast-iron material and the reason is the good shock absorption capability of cast-iron.
Your Column and Knee Type Milling machine has the following major parts.
The base of your machine acts as a foundation, and the complete machine structure is built on it.
The hollow column of your machine is mounted vertically on the base and supports the knee, saddle and table; it houses the spindle and all its drive mechanism and provides movement to the knee, saddle, table, spindle, etc.
The knee of your machine is mounted on the column guide-ways and can be moved vertically, up and down.
The saddle of your machine is mounted on the guide-ways of the knee and has transverse movement.
The table of your machine is mounted on the saddle and can move to and fro longitudinally. You can clamp the workpiece directly on the table using the T-slots or with the help of a machine vice.
The overarm and brace of your machine is mounted on the top of the column and supports the arbor (fitted into the spindle as an extension). You have the overarm and brace arrangement only in Horizontal Column and Knee Type Milling Machine.
Your Column and Knee Type Milling Machine has a pressurized cooling system consisting of a coolant tank filled with coolant, coolant pump, and piping to direct the flow of coolant on the cutting area.
With the above arrangement, you can move the table up and down, longitudinally (left and right) and transversely (back and forth).
Your Column and Knee Type Milling Machine can have a manual operation or power control for all the movements (including rapid movement) and you can adopt your machine for automatic cycles using the stops and other control devices.
3. Horizontal Milling Machine
Your Horizontal Milling Machine has all the features of a Column and Knee Type Milling Machine and comes with a horizontal spindle. Your Machine is generally bigger than vertical Milling Machine and comparatively heavy and larger work-pieces can be machined.
You can directly mount a face milling cutter and do face milling of work-pieces clamped on the table.
You can also use an arbor for mounting one or more cutters and do plain milling, slab milling, straddle milling, slotting, etc. You need to support the other end of the arbor using the overarm arrangement.
Your Horizontal Milling machine is classified as a universal type, if you are able to swivel the table in the horizontal plane, normally up to 45 degrees to your left or right.
4. Vertical Milling Machine
Your Vertical Milling machine is a Column and knee type Milling Machine minus the overarm arrangement and has a vertical spindle head at the top of the column. The milling head of your Vertical Milling Machine may be the fixed head, sliding head or swiveling head, or a combination of swiveling and sliding head. You can move the quill of the spindle up and down.
Your Vertical Milling machine is suitable for milling operations like face milling, slotting, keyway milling, and form-milling using a form cutter.
You can mount the work-piece on a rotary-table (mounted on a machine table) and cut circular slots or slots at equal angular locations.
You can mount indexing head arrangement on the machine table and do operations such as gear cutting, keyways etc.
5. Ram-Type Milling Machine
Your Ram type Milling Machine has all the features of the Column and Knee Type Milling Machine except that you have a movable ram (with a vertical milling head) mounted on the top of the column. You can move the ram in the transverse direction both manually and with power.
Universal Ram-type Milling Machine
Your Universal Ram-Type Milling Machine is a smaller version of Universal Horizontal Milling Machine with an arbor and an addition of movable ram (with vertical milling head) mounted at the top of the column. The horizontal and vertical milling heads of your machine are driven by independent motors. You can support the other end of the arbor of horizontal milling by adding a brace to the ram when needed. Thus you have the flexibility of a horizontal and vertical milling machine with a swiveling table.
There is another version of your Ram-Type Milling machine, which has all the features explained as above minus the horizontal spindle.
Swivel Cutter Head Ram-Type Milling Machine
Your Swivel Cutter Head Ram-type Milling Machine has a movable Ram (with a vertical milling head) mounted at the top of the column. The Milling head is mounted on the ram through a single or double swivel joint and you can swivel the milling head around the horizontal and vertical axes up to an angle allowed by the manufacturer. There is no horizontal spindle in your Swivel cutter head Ram-type Milling Machine
In addition, you may be able to swivel the Ram of your Machine around the vertical axis.
Your Machine is very versatile and helps you to machine components of tools, jigs, and fixtures. You can do face milling, end or slot milling, drilling, fine boring and many other operations.
You can add a DRO (Digital Read Out) to your Machine for precise control of the work-piece movement and feed.
6. Fixed Bed Type Milling Machine
Your Fixed Bed Milling Machine is similar to a Knee and Column Milling Machine; however, here the knee is replaced by a fixed bed, hence the name Fixed Bed Milling Machine. The table of your machine is mounted on the fixed bed and you can move the table to and fro in the longitudinal direction.
Your Fixed Bed Milling Machine can be of vertical or horizontal type depending on the spindle orientation.
The horizontal milling head is mounted on the column guide-ways and you can move it up and down, and the transverse movement is obtained through a spindle quill unit. Your Fixed Bed Milling Machine is as versatile as your Knee and Column type and has the advantage of 50 % more rigidity.
Your Machine is used for high production work and may be equipped with the automatic cycle for spindle head or both spindle head and table.
7. Simplex Milling Machine
Your Simplex Milling Machine has all the features of a Fixed Bed Milling Machine. As the name implies, your Simplex Milling Machine has only one milling head and can be of vertical or horizontal orientation.
You can move the spindle head of your Machine in the upward and downward direction and the table moves to and fro longitudinally. You will get the transverse movement by the spindle quill unit.
Your Simplex Milling Machine is easy to operate, reliable, and suitable for high production.
8. Duplex Milling Machine
Your Duplex Milling Machine has all the features of a Fixed Bed Milling Machine but with two major differences. Your Machine has two columns instead of one and has two horizontal milling heads, one on each column. Your machine name ‘Duplex Milling Machine’ implies that there are two milling heads. You can move the milling heads vertically up and down and the table to and fro longitudinally. The transverse movement in your machine is obtained by the spindle quill unit.
Your Duplex Milling Machine is sturdy and suitable for production work and you can machine two parallel faces of the work-piece (I-beam or rectangular block) simultaneously.
9. Triplex Milling Machine
Your Triplex Milling Machine has all the features of a Fixed Bed Milling Machine but with three major differences. Your Machine has two columns and a cross beam instead of only one column; each column is mounted with one horizontal milling head, and one vertical milling head is mounted on the cross beam. Your machine name ‘Triplex Milling Machine’ implies three milling heads.
You can move the horizontal milling heads vertically up and down and the vertical milling head has up and down as well as cross-wise movement. You can move the table to and fro longitudinally. You will get the spindle movement through a quill unit.
Your Triplex Milling Machine is sturdy and suitable for production work and you can use a combination of two or three milling heads for simultaneous machining of work-piece.
10. Turret Mills
Your Turret Mill is a vertical milling machine with most of the features of a Colum and Knee Type Milling Machine. You can move the work-piece (mounted on the machine table) longitudinally, vertically as well as transversely. You can use the quill unit of the spindle during machining.
Your Turret Mill is comparatively smaller than the regular vertical milling machine; highly versatile, making it suitable for the production of automobile components. The advantage of your Turret Mill is that it is relatively cheaper and you have a clear view of the whole machine during working with all the controls reachable by your hand.
11. Rotary Table Milling Machine
Your Rotary Table Milling Machine is a fixed bed type milling machine and has two columns, each mounted with a vertical milling head with independent motors. You can move the milling heads up and down on the column. The circular table on the fixed bed of your machine can rotate in the vertical axis and traverse on the bed guide-ways towards the columns.
You can use one milling head for rough milling and another milling head for finish milling. You can arrange the position of your work-piece and the two milling heads in such a way as to achieve rough and finish milling of the work-piece in one revolution of the table (when material removal is minimum). You have to ensure minimum ‘idle or non-cutting time’ of the milling head during the operation. Your Rotary Table Milling Machine is suitable for batch production of components.
12. Planer Type Milling Machines
Your Planer Milling Machine is a fixed bed type milling machine albeit bigger in size. Your machine has a fixed bed mounted on the base, two vertical columns connected with an overarm support at the top, and a cross rail.
The table of your machine is mounted on the fixed bed and has longitudinal to and fro movement. Your machine has two horizontal milling heads one on each of the columns and two vertical milling heads mounted on the cross rail. All 4 spindle heads have their own motors.
You can move the horizontal spindle heads up and down on the columns and your vertical spindle heads move up and down as well as across the cross-rail. You can use all these movements to locate the work-piece with respect to the milling heads. In addition, you may be able to swivel the vertical milling heads for angular milling. You may also use the quill unit for all the spindles.
You can mount the work-piece on the table using the T-slots and position it for milling. You can use one milling head, or a combination of 2, 3, or 4 milling heads for milling. You achieve the milling by setting a suitable feed rate for the table.
Your Milling Machine is suitable for heavy work-pieces and batch production.
13. Tracer Milling and Pantograph
Do you know what a pantograph is? Your pantograph is a mechanical linkage connected in a manner to facilitate copying and proportionate scaling of the template.
One end of your pantograph has a tracer to trace the template and transfer the two-dimensional movement to the rotating milling cutter mounted on the other end of the linkage. You can set the required ratio on the pantograph such as the proportionate size of the copied item is 50% of the template.
The construction of your manually operated machine is very simple. Your machine has a base, one movable table for the work-piece, a fixed table for the template, and an arrangement to mount the pantograph and drive for the milling cutter.
You have to trace the template by holding the tracer in your right hand and hold the rotating cutter-head in your left hand for cutting on the workpiece. Your pantograph will transfer the two-dimensional coordinates of the template to the cutter end in the proportion set by you. You can engage and disengage the cutter from the work-piece using a lever on the cutting head.
You can use your Pantograph Milling Machine for engraving letters on a metallic or non-metallic surface, copy intricate shapes, etc.
14. Tracer-Controlled Milling Machines
Your Tracer-Controlled Milling Machine is capable of two-dimensional tracing of the template and transfers the coordinates to the milling head through an electronic, optical, or hydraulic system.
Your Machine has a work-table with longitudinal and transverse movement, two columns, and a cross rail. You have a tracer head with a stylus and milling head, both mounted on the cross-rail and can be moved/positioned on the cross-rail.
You can clamp the work-piece on the table, below the cutter and the template below the tracer. During working, your tracer head stylus traces / copies the profile and transfer the coordinates to the milling head by the controlled movement of the table. You can mill various intricate two-dimensional shapes on this machine including cams.
The principal of tracing with a stylus can be extended to three dimensions for the milling process like ‘die sinking’ (creating die cavity for moulding) in the manufacture of dies.
15. 3-Axes CNC Milling Machine
In your 3-Axes CNC Milling Machine, 3-Axes machining refers to the ability of the CNC Milling Machine to perform the movement in three different axes simultaneously. Your three axes are X, Y, and Z. Z-axis is always parallel to the spindle axis of your machine, and X and Y are the other two movements.
All of your milling machines seen earlier like Horizontal Milling Machine, Vertical Milling Machine, Fixed Bed Milling Machine, and Ram-Type Milling Machine has X, Y and Z axis of movement and can be designed as 3-Axes CNC Milling Machine.
Your CNC Milling Machine is operated using CNC systems where the Machine follows the step-by-step instructions given by the CNC system. You can feed the instructions into the CNC system either by directly using the system keyboard or design it offline on a Computer Aided Design (CAD)/ Computer-Aided Manufacturing (CAM) system and transfer it to the CNC system. Your CNC Milling Machine can start production, once you establish a trial component, and will run automatically without needing much of your attention.
The tool change in your CNC Milling Machine may happen through a tool changer, which picks the pre-selected tool from the tool-magazine and loads it on the spindle or you can do it manually.
The CNC system on your Milling Machine has closed-loop feedback and monitors the program continuously in real-time and implements corrections to ensure repetitive mass production of components.
When your 3-Axes CNC Milling Machine is made more automated and suitable for operations beyond milling, they are called machining centers. Your machining center can be Vertical or Horizontal Type, depending on the orientation of the spindle.
Vertical and Horizontal Machining Centers
When you refer to X, Y and Z axis, they mean slightly different with respect to Vertical Machining Centre and Horizontal Machining Centre.
Vertical Machining Centre (VMC): Here the longitudinal movement of your machine table is X axis, transverse movement of the table is Y axis and vertical movement of the spindle is Z axis.
Horizontal Machining Centre (HMC): Here the longitudinal movement of your machine table is X axis, vertical movement of headstock / spindle head is Y axis and transverse movement of the spindle is Z axis.
Main features of your VMC and HMC are- fixed column, precision LM guide-ways, and Ball Screws on all axes, dynamically balanced spindle supported on high precision preloaded angular contact ball bearings, tool magazine, and high positioning accuracy and repeatability. Your machine has a high-pressure cooling system and may have a chip disposal system. The CNC system of your machine can be Siemens or equivalent make.
Your VMC has a spindle speed range of 60-6000 rpm and 60-8000 or more rpm.
Your HMC has a spindle speed range of 20-3600 rpm with 1 rpm increment.
You can program your VMC and HMC to do milling, drilling, reaming, boring, etc. on the workpiece with the simultaneous movement in X, Y, and Z axes.
Your Machining Centers VMC and HMC are very versatile and highly productive machines.
16. 5-Axes CNC Milling Machine / Machining Center
Now, you have understood the working of a 3-Axis CNC Milling Machine or Machining center. So, what is this 5-Axes CNC Milling Machine?
Your 5-Axes CNC Milling Machine is a Machining Center with movement in X, Y, Z, and additional two axes.
Before proceeding further, you have to understand the additional axis designated as A, B, and C. A, B, and C axes are related to the work-piece.
In CNC language you call the X, Y, and Z as linear axes and A, B, and C as a rotary axis.
Now consider your vertical Machining center with 5-Axes.
The three axes of your machine are:
X– Longitudinal movement of the machine table.
Y-Transverse movement of the machine table.
Z-Vertical movement of the spindle.
.Your A, B, and C axes are
A-Your work-piece has provision to rotate around the X axis, and this axis of rotation is designated as A-axis.
B– Your work-piece has provision to rotate around the Y axis, and this axis of rotation is designated as B-axis.
C– Your work-piece has provision to rotate around the Z axis, and this axis of rotation is designated as C-axis.
Your 5-Axes Machining Center has X. Y, Z, and normally B and A axes of movements. This means you can program your 5-Axes machine, to mill complex, intricate geometry and shapes by simultaneous movement in 5-axes. 5-Axes Machining Center is more productive than your 3-Axes Machining Centers and gives a better surface finish.
Milling machines are the next best versatile machines after Lathe and you cannot imagine any production shop without a milling machine. Your CNC Milling Machine and Machining centers are an advancement of the basic milling machine and its versatility helps to produce complex and intricate components faster with a high level of repeatability.
Apart from the types of milling machines you have seen above, there are many milling machines for custom milling operations like key-way milling, spline shaft milling, and die sinking machines.
You can add a DRO (Digital Read Out) to any of your non-CNC machine for precise control of the work-piece movement and feed.