CNC Milling

A milling machine or mill for short, functions by spinning at very high speeds, a cutting tool (eg- a mill or drill) relative to the work piece (or part to be converted from raw material into finished good) which is held stationary. In some cases the work piece is moved in very slow relative motions in coordination with the cutting tool. When the high speed cutting tool comes in contact with the raw material it starts to shave away the surface layer of the material in small chunks or chips. A good analogy for this would be the way a chisel works on wood, or even a knife through butter. As the cutting tool takes more and more material off, the automated controller continues to extend the tool into the part until the desired shape or dimension is achieved. The speed at which the spindle (the element that holds the cutting tool) spins is referred to as the Spindle Speed or often just Speed. The rate at which the tool moves relative to the work piece (movement along an X, Y or Z axis) is referred to as the Feed Rate or just Feed. The Speed and Feed rates are very critical and need to be highly controlled to conform to the unique characteristics of different materials, cutting tool types, and features being machined. In a CNC this process of material removal is automated and therefore highly controlled and very repeatable.

Metal is perhaps the most common material type to be machined on a CNC Milling Machine, but these machines can also process various plastics, woods, composites and ceramics along with myriad other elements and compounds. Metal machining ranges from carbon and stainless steels to aluminum alloys to brass and copper to a variety of specialty and exotic metals like Inconel, Hastelloy, etc.

While there are several different configurations of CNC milling equipment, in general there are a number of common elements used in each. The diagram below highlights some of the common components of a machine. The spindle is the moving element of the machine that holds the cutting tools (mills, drills, etc). The spindle rotates at very high rates of speed, often up to 20,000 RPM, but some machines can reach speeds up to 60,000 RPM or higher. The part to be machined is held in a workpiece holder or vice. The vice clamps and holds the part in place either through a manual crank or some external force, such as hydraulic or pneumatic vices. Multiple vices can be mounted in a stack to the worktable. The worktable is a flat tabletop often with grooves for mounting accessories like workholding equipment, or rotary axes. The base of the machine is the large frame that supports the entire payload and dynamic forces exerted from the equipment. The user interface houses the machine controller, and can be programmed to enable CNC automated control of the machining process.

In the diagram below there are three different axis of motion to move the workpiece relative to the spindle and cutting tool. In some cases it is the spindle moving, in other cases the workpiece is moving. This varies greatly from one machine design to the next and some machines have as many of 5 separate axes of motion allowing for machining of complex geometries. These would include 3 linear axes of motion (X, Y, Z) and two rotary axes. In some machine designs the spindle axis moves in and out relative to the work piece (typically referred to as the z-axis), while the worktable moves side to side and in and out (the x and y axis. In some designs the spindle moves in 2 axes and the table only moves in one, along with a variety of other designs. Additionally designs vary based on whether the machine is a vertical mill or a horizontal mill as discussed further below. CNC mills will also a tool changing system. This component can house multiple different types and sizes of tools and can index through the tools for quick and automated change-over during the machining process. As a practical example, imagine a project where we need to machine a tapped hole into a square plate. Once the plate is mounted in the vice and the machine is programmed for the operations to be done, the spindle axis will retract to its home position, the tool changer will index to the appropriate tool, in this case a drill to drill the hole for the tap. The size of the drill and the particular tool number in the index will have already been programmed into the CNC. Once the hole is drilled the spindle will retract again, the tool changer will move to the correct tap tool and then replace the drill with the tap, and then the machine continues the operation.

There are several different machine construction styles of CNC Milling Equipment. Three of the most common configurations used in industry today are highlighted below:

Vertical Milling Technologies

A vertical mill is what is shown in the diagram above. In this configuration, the spindle is oriented vertically relative to the worktable. The worktable is almost always parallel with the floor. This means that when the spindle moves to the part it is moving up and down inside of the machine. Typically the worktable moves around under the spindle in the X and Y axis and will sometimes house rotary axis. The spindle either moves up and down to the part or sometimes the worktable will move up and down relative to a fixed spindle.

This configuration is ideal for plunging type machining operations, and also lends itself to larger potential workpiece sizes than horizontal technologies. This is because the work piece size is typically limited to the size and travel of the worktable and not the travel of the spindle.

Horizontal Milling Technologies

Picture taking the spindle of the vertical mill and flipping it 90 degrees on it side, and you will be left with a Horizontal Mill. Here the spindle is oriented parallel to the worktable and thus the floor. The spindle moves in and out rather than up and down. The in and out motion is called the Z axis, just as with the vertical mill, and in some cases the spindle moves in the Z, sometimes the table moves and in some cases both both in the Z. The X motion is made moving side to side (parallel to the floor) and the Y motion is up and down (perpendicular to the floor). X and Y can be performed on the worktable or the spindle depending on the design. There is also typically a rotary axis, often referred to as the B-Axis, on the worktable making this a 4 axis machine. This rotary axis often includes a workholding fixture referred to as a tombstone or clamping pillar. These tombstones sit on top of a pallet, which is on the rotary table. There are typically multiple pallets on a horizontal mill, allowing for changeout of the workpiece on one tombstone, while the other is undergoing machining. This makes for a highly efficient process.

Horizontal Mills are ideal for machining grooves, slots and facing off a part, as well as parts that have multiple sides or faces that need to be machined.

Boring Mill Technologies

Like traditional milling equipment boring mills can be segmented into vertical and horizontal configurations. Horizontal boring mills functions much like a horizontal milling machine as highlighted above. Vertical boring mills (sometimes referred to as a VTL- Vertical Turret Lathe) are more similar to vertical turning equipment and will thus be covered under the Vertical Turning Technologies section. Probably the largest differentiating characteristic between boring equipment and standard milling machinery is the size and scale. Boring mills are generally much larger in size, allowing them to machine much larger work. As the name indicates, boring mills are designed to bore or enlarge large holes in materials. They are also ideal to face off (machine the entire surface on a single plane) material. The orientation of a horizontal boring mill is set-up exactly like the horizontal mill, with the Z-axis being the in and out motion of the spindle relative to the part, the X-axis moving side to side and the Y-axis moving vertically. Any rotary axis would be referred to a the B-axis.

Our CNC Milling Process and Approach

At Alle-Kiski CNC Machining is the backbone of our business. We have 17 modern CNC centers to serve a variety of different unique machining requirements. We are constantly reinvesting in our business and adding new machine tools to our equipment portfolio. We have predominantly standardized on Mazak systems, as we have found that the durability, performance and ease of use is unmatched. Additionally, we have a number of high performance Haas systems to maximize our range of capabilities.

For a current list of all of our equipment see our Equipment List.

Our milling equipment includes both horizontal and vertical machinery, which we leverage to ensure that we can cover a broad range of applications and requirements and do so as cost-effectively and efficiently as possible. Our machines are all staffed with our experienced team of journeymen machinists. The pool of talent and experience in our machining area is the secret to our success. Their combined know-how allows us handle complex machining challenges along with giving us a great deal of flexibility to program parts right at the machine and adapt to changes or unique needs from our customers.

Our approach is focused around flexibility. We thrive in projects that range from low volumes or even single piece such as prototyping, to high volume production runs. We can support a variety of materials, from steel to stainless steel to aluminum to plastics to exotic metals and everything in between. We cover industries from medical, to energy to defense to instrumentation and robotics and more.From small high precision parts to large part requirements, our goal is to service a wide range of needs for our customers. To supplement our internal capabilities, we have built out a strong partner network that allows us to fill in any gaps, and maximize response time.

Have a current or upcoming project? Have a member of our team contact you to discuss.

CNC Milling Applications

Generally speaking any milling operation, whether CNC controlled or manually operated, is optimal for industries and applications that require removal of metal from a raw material to reshape it into a specified dimensional footprint or with specific dimensional features. Some example operations include but are not limited to:

  • Drilling of holes for mounting- eg screw holes, clearance or access holes, ports, etc
  • Threading of holes
  • Boring or opening up holes- eg- enlarging a hole in a casting to a specified dimension
  • Milling of a planar surface (referred to as face-milling) to achieve a flatness or straightness specification
  • Milling of slots or grooves- eg. bearing seats, keyways
  • Surface contouring- to achieve unique surface geometries
  • Gear cutting

The Advantages of CNC Milling

Because of the automation that CNC equipment provides CNC mills are generally more ideal for larger production runs (greater consistency through automation) and parts with greater complexity in shape and contour. Conversely small run volumes of parts with limited complexity may be more ideal for a manual process as the time to program the machine is eliminated, making overall run time shorter and therefore more cost-effective to produce.

CNC Turning

CNC turning is an operation that is performed by a CNC Lathe. Similar to a milling machine a lathe uses a spindle which is a high speed rotary device. The major difference between the two machine tools is that the lathe holds the workpiece in the spindle and therefore rotates the material to be machined relative to a stationary cutting tool. The inverse is true with a milling machine. Like a milling machine, a lathe is designed to remove material from the workpiece by moving the cutting tool in to contact the workpiece (which is spinning at high speeds), and thus chipping away material from the surface until a desired outer dimension is achieved. The speed at which the spindle (the element that holds the workpiece) spins is referred to as the Spindle Speed or often just Speed. The rate at which the tool moves relative to the work piece (movement along an X or Y axis) in one given revolution is referred to as the Feed Rate or just Feed. Once the spindle is in motion and spinning at a high rate of speed, a static tool (eg. cutting tool) will come in to make contact with the surface of the workpiece and then traverse slowly (feed) along the surface of the part removing material and bring to a desired dimension. In a CNC this process of material removal is automated and therefore highly controlled and very repeatable. Because of the design of the lathe it is best suited for manufacturing round parts, however some accessories features on lathes can provide additional functionality and enable milling like capabilities within the same machine.

Metal is perhaps the most common material type to be machined on a CNC Lathe, but these machines can also process various plastics, woods, composites and ceramics along with myriad other elements and compounds. Metal machining ranges from carbon and stainless steels to aluminum alloys to brass and copper to a variety of specialty and exotic metals like Inconel, Hastelloy, etc. 

Generally speaking Lathe Equipment can come in one of two design configurations, Horizontal Lathes or Vertical Lathes. Both are described in further detail below. The functional elements of the lathe are fairly uniform between the configurations and the diagram below calls out some of the common components of the machine. In a standard lathe the Main Spindle, which is the rotary element powered by an electric motor. The Headstock assembly houses the spindle along with the bearing set, gearing and other elements required to support and drive the spindle. The Spindle houses a Chuck which functions the same as a vice does on a milling machine and clamps on the workpiece to be machined. The spindle sits opposing the Tool Turret, which is an tool holding device that houses multiple different tools (cutting, drilling, etc) and can index around in a rotary fashion, to quickly change-over from one tool to another without any manual intervention. For example, once an initial operation is complete, let’s use the example of a cutting operation with a cutting tool to turn the outside diameter of a round bar material to size, then the turret indexes (rotates around) to the next tool in the program, lets say a drill bit to drill out an inside diameter of the part. Some CNC Lathes have an option called Live Tooling. With this feature a lathe can function like a milling machine. In this case the spindle will stop spinning and hold the work static. Then the tooling on the turret will start spinning and come in to the part to machine away material. A good example of how this would be used is putting a flat on a round surface. The OD would initially be created through a traditional turning process, and then the live tooling would turn on and machine the flat on the part. This provides a lot of additional functionality and mitigates the time and cost of having to perform some operations on a lathe and then moving to a mill to finish the work. 

The Bed of the lathe is base where the other main components are mounted and tied together. This is a rigid, structural member that connects the Headstock with the Tailstock and the Carriage, and makes sure that are remain aligned. The Carriage is the moving member that holds the tooling and moves in and out on the x-axis to engage the main spindle chuck and workpiece. The Tailstock is used to support the opposite end (or free end) of the workpiece to stabilize the part as it rotates. Imagine a long bar that needs to be machined. If one end is held in the chuck on the spindle, and the other end sticks out more than multiple inches, once the spindle starts spinning the unsupported end will whip, and prevent accurate machining as well as creating damage. To prevent this the tailstock is positioned into place near the free end of the part and a tailstock quill, which has a tapered end, is extended to come in contact with the free end of the part. Now when the spindle starts to spin, the quill spins with the part and keeps i supported. 

Another common accessory on a CNC Lathe is a Dual Spindle Feature. There are multiple different configurations have multiple spindles on a lathe, but a Dual Spindle refers to the addition of a secondary spindle that sits mirrored to the main spindle. In some cases the chuck size, spindle speed limitation and horsepower may be different between the two, but ultimately the Dual Spindle enables additional automation within the machine. Imagine a cylindrical part that requires machined features in both ends of the cylinder. In a traditional lathe design, you would machine the one end, and then remove the part from the chuck, flip it around and then machine the opposite side. With a dual spindle design, the first operation can be performed in the main spindle and then the machine transfers the part to the secondary spindle to perform the second operation, without any human intervention. This can dramatically improve downtime and productivity, and is ideal for high volume production projects.

Bar feed systems are another lathe accessory that is used to increase productivity of the machine. A bar feeder sits adjacent to the headstock end of the machine, and can be used to feed raw material into the machine. After a part is completed it is dropped off from the spindle chuck and then the bar feeder will extend more raw material into the chuck and keep the machine running with minimal downtime and with no manual intervention. 

Horizontal Turning Technologies

The diagram above represents a horizontal lathe. In this configuration the relative motion of the carriage and tailstock happen side to side or right to left in front of the machine operator and the spindle sits parallel to the floor. Horizontal are more common in industry than Vertical lathes, but both have their place. For example horizontal lathes are able to turn much larger materials, as they are not restricted to ceiling height as in a vertical lathe. Additional, optional accessory equipment like bar feeders and dual spindle designs are readily available for horizontal turning equipment, but not vertical systems. For this reason horizontal lathes are generally more flexible and optimal for large volume production runs.

Vertical Turning Technologies

Vertical and Horizontal Lathes are essentially the same equipment with the same components, however the vertical lathe has been essentially flipped up on its end. In this case the spindle sits perpendicular to the floor and the carriage traverses up and down inside the machine. One major advantage is that because the workpiece is oriented to take advantage of gravity, vertical lathes can often support much larger and heavier projects. Consider that in a horizontal orientation, a large heavy part, will be fighting gravity as it turns and will naturally want to deflect down and create a whipping effect. A downside of vertical equipment is that because the worktable and workholding sit below the tooling, it is more difficult to keep the part clean during machining. As the part is being machined, chips will inevitably rest on top of the part. In a horizontal lathe gravity works to your advantage here and the chips fall off to the chip pan which sits below the working area of the machine.

Our CNC Lathe Process and Approach

CNC machining is one of the cores of our business at Alle-Kiski Industries. We have a vast assortment of CNC equipment consisting of 17 modern CNC centers to serve a variety of different unique machining requirements. We are constantly reinvesting in our business and adding new machine tools to our equipment portfolio. We have predominantly standardized on Mazak systems, as we have found that the durability, performance and ease of use is unmatched. Additionally, we have a number of high performance Haas systems to maximize our range of capabilities.

For a current list of all of our equipment see our Equipment List.

We have a mix of CNC and manual lathe equipment including both horizontal and vertical configurations. Our machines are all staffed with our experienced team of journeymen machinists. The pool of talent and experience in our machining area is the secret to our success. Their combined know-how allows us handle complex machining challenges along with giving us a great deal of flexibility to program parts right at the machine and adapt to changes or unique needs from our customers.

Our approach is focused around flexibility. We thrive in projects that range from low volumes or even single piece such as prototyping, to high volume production runs. We can support a variety of materials, from steel to stainless steel to aluminum to plastics to exotic metals and everything in between. We cover industries from medical, to energy to defense to instrumentation and robotics and more.From small high precision parts to large part requirements, our goal is to service a wide range of needs for our customers. To supplement our internal capabilities, we have built out a strong partner network that allows us to fill in any gaps, and maximize response time.

Have a current or upcoming project? Have a member of our team contact you to discuss.

CNC Turning Applications

As with milling equipment, turning equipment or lathes, are ideal for any application where a material (commonly metal, wood, plastic, etc) needs to be reduced in size on one or multiple surfaces, by removing material (commonly referred to as subtractive manufacturing). With lathe equipment this removal of material usually occurs on a round surface or feature given the nature of the operation. Some example operations include but are not limited to:

  • Drilling of holes- eg clearance or access holes, ports, etc
  • Threading of holes
  • Boring or enlarging holes- eg- opening up a hole to a specified dimension
  • Machining of grooves in a round part- eg. bearing seats, seal seats, etc
  • Surface contouring- to achieve unique surface geometries
  • Tapering of a round part

The Advantages of CNC Turning

Some of the same advantages that exist for other CNC equipment also exist for CNC Lathes. The machines are generally more advantageous for production runs of parts, given some of the advanced automation on CNC lathes, eg- bar feeding, dual spindle, live tooling, which are all designed to reduce downtime on the machine, and allow the machine to run virtually unattended, reducing overall cost. Conversely small run volumes of parts with limited complexity may be more ideal for a manual process as the time to program the machine is eliminated, making overall run time shorter and therefore more cost-effective to produce.