The goal of modern CNC milling is to convert materials such as metal castings into finished, usable parts. This can only be achieved with extremely precise CNC milling machines.
Computer software is the brain of a CNC (Computer Numerical Control) milling machine, controlling the machine and automating production to increase output and maintain consistent quality. It's this repeatability that makes CNC machining so efficient and so valuable to the customer and the machinists themselves
Final result? Custom machined parts in high volume to exact specifications while achieving extremely tight tolerances. Highly skilled machine operators understand that CNC milling machines are not only important to their jobs, but also to manufacturing and its impact on the world economy.
What is the role of CNC milling machine?
The thrill of being a CNC machinist is turning castings into usable and trusted parts, often in larger products. These parts often require tight tolerances that are not available in unfinished castings until the CNC mill completes the operation.
Plane - CNC face milling places a plane on the workpiece. Face milling creates a flat sealing surface that virtually eliminates potential leakage problems.
Drilling - Drilling creates a hole, tapping adds threads. Through and threaded holes are the most common ways to assemble parts. Drilling focuses on the diameter and depth of the hole.
Drilling - Enlarge existing holes using drills and rigid boring bars with single point cutting tools to create precise cavities in the workpiece. Drilling allows parts to be assembled correctly and tightly (to very tight diameter tolerances), or to allow valves to consistently control the flow of air, oil or gas.
When talking about "tight tolerances", how tight do we really mean? CNC machines can cut 0.001 inches (in the single-digit micrometer range) or about 1/4 the width of a human hair. This is done with incredible speed.
In CNC mills, 2-axis, 3-axis, 4-axis and full 5-axis options are included.
CNC-Machine-Axis-1
2-Axis Machine - for manual jig builds; movement is only in the x and y axes; not a lot of repeatability
3-axis machine - often used for end milling; moves in x, y, and z axes
Four-axis machine - most common CNC mill; uses an additional b-axis to move in the x, y, and z axes to allow the table to rotate, allowing access around the workpiece; usually limited to horizontal machines, but also used by premium shops 4-axis vertical machine (normal vertical is 3-axis)
5-axis machines - move on x, y, z, and b axes, plus an additional a-axis; these are specialized milling machines; not suitable for mass-producing parts
Vertical and horizontal machines
CNC milling machines have two spindle orientations. In a vertical CNC machine, the main axis, called the z-axis, is oriented vertically. In the c-pillar configuration, the spindle moves in this direction, while the table holding the workpiece moves in the x and y horizontal directions. Vertical machines are ideal for high-volume, fast-paced projects such as covers and brackets that are milled from one side.
In a horizontal CNC machine, the spindle z-axis is horizontal, usually parallel to the length of the machine. The main axis travels along the vertical y-axis and horizontally along the x-axis. Pallets and fixtures hold the workpiece and move along the z-axis and rotate along the b-axis. Horizontal machining has several advantages: machining from four sides, multiple operations on the same fixture, milling of more complex parts, and better chip evacuation.
Can CNC milling be combined with other operations?
With computer automation and an engineer's imagination, CNC milling machines are capable of milling just about anything imaginable. These incredible machines also allow additional operations to be added to the milling process, providing even more functionality.
For example, a lathe can first remove most of the part material (which is faster than contour milling), creating any desired circular turning. The part can then be milled, drilled, tapped, and more. A single operator controlling two milling machines in one cell or work center can create a complete part. Efficiency can be improved without multiple work centers and operators.
A Machinist's Perspective - Being able to multitask back-to-back not only gives CNC machine operators a sense of accomplishment, but cements a reliable and valuable position on the shop floor.
What are the capabilities of Stecker's CNC milling machines?
No two machine shops are alike, each finding a unique market niche and developing its own manufacturing strengths.
Stecker Machine is an example of a modern high-end shop capable of handling many CNC milling projects. While equipment is regularly updated to meet customer needs, at the time of this writing, Stecker's CNC mills consist of 61 horizontal and 14 vertical mills.
Depending on production needs, 95% or more of these may run during a typical first shift, while the rest are available for setup. There are more than four times as many horizontal CNC mills as vertical, which shows Stecker's focus on complex parts that demand tight tolerances.
In addition to standard milling cutters, use specialized tools when needed. For example, a tool is custom made with all three diameters on it, which is usually done with three separate drill bits.
Another less common tool is an indexable head on a CNC milling machine. Rather than a drill that comes straight out of the spindle, this tool allows the spindle to be rotated 90 degrees to be able to punch holes in the side of the part without additional work.
We hope that you have a deeper understanding of CNC milling machines and look at it. More than just a job. The benefits are numerous and stable employment is appreciated by thousands of CNC machinists across the country.