It’s not unusual to hear the terms CNC machining center, CNC milling machine, and CNC machine tools when talking about the high-precision machinery of the modern machine shop. And then, there are Horizontal Machining Centers (HMC) and vertical machining centers (VMC). Is it any wonder a newly-minted machinist would be confused when many of these terms are being used interchangeably?
Since the term machine tool refers to machines that are power-driven, non-portable, and use cutting tools to remove material, all of these are machine tools. Horizontal and vertical concerns are the position of the spindle relative to the worktable. And that leaves the matter of the difference between a CNC milling machine and a CNC machining center.
What is a Horizontal Machining Center?
Like any form of milling, horizontal milling relies on various cutting tools to remove metal from a workpiece. The machining occurs on a horizontal machining center (HMC) with a spindle parallel to the worktable and the floor. With this arrangement, the tool sticks out of the side of the tool holder and machines across the side of the workpiece, allowing chips to drop away and avoiding having to clear chips from the table.
Horizontal machining centers also accommodate two pallet changers, allowing unattended production work and reducing part cycle times. The time saving occurs because work is loaded on one pallet of the HMC while machining is happening on the other pallet. After one part is machined, the pallet will index, and the next workpiece is ready.
CNC Milling Machine vs. CNC Machining Center
The machining center typically functions like all milling machines. However, the CNC machining center has an automatic tool changer, while the milling machine does not. A CNC machining center is controlled by a CNC controller to drive the X, Y, and Z axes and also includes the tool changer for increased efficiency.
The horizontal machining center does not get as much recognition as its vertical counterpart, so we’ll take an in-depth look at it, determine its uses, cost, and why a machine or fabrication shop should buy one.
How Does a Horizontal Machining Center (HMC) Differ from a Vertical Machining Center (VMC)?
Both machines have advantages, and choosing them depends primarily on your machining needs. Each is a high-performance, multi-axis machine tool with high spindle speeds, high-pressure coolant, and CNC control systems to enable high-speed machining.
VMCs are by far the more popular of the two for several reasons. They are the least expensive of the two machines and operate in a way that’s more familiar to the average machinist. VMCs are versatile machines available in numerous types and sizes, and they have a reputation for being multi-use machine tools that have proven themselves over the years.
Although vertical machining centers have excellent qualities, they also come with a few limitations. They only have one work plane, meaning the workpiece must be flipped five times to reach five sides of a square block. This process increases handling and spindle downtime, requiring a skilled operator.
Horizontal machining centers are better suited for workpieces requiring machining on multiple sides. HMCs are typically built with two integrated pallets, on which fixtures are often attached, allowing the operator to stage a part in the setup station while the piece on the other pallet is machined. As a result, the spindle is utilized more frequently, and production is much higher.
Other advantages of the HMC include its larger tool capacity and a better chip flow that sends them away from the worktable, eliminating the need for operators to stop the machine for an occasional chip cleanup. And you can have a fourth axis with the addition of a rotary table.
When Would You Use a Horizontal Machining Center (HMC)?
Job shops might not reap all of the benefits of a heavy-duty horizontal machining center since they probably won’t make enough parts to keep the machine occupied. However, HMCs are suitable for production shops able to keep it running continuously with large orders that require the following:
- Slot cutting
- Gear cutting
- Groove cutting
- Parts with detail work on the side
- Blocks that require machining on multiple sides
- Projects with sizable or heavy parts
What are Five-Axis Horizontal Machining Centers?
5-axis machining centers are becoming more prevalent and are a step up from the typical 3-axis horizontal machining centers. In addition to the X-axis, Y-axis, and Z-axis, the 5-axis machining center add two rotary axes from the A-axis, B-axis, and C-axis.
Five-axis machining involves moving CNC cutting tools across five different axes simultaneously. This machining is a high-efficiency, high-precision process during which the workpiece is entirely machined by clamping it once. Five-axis machining is ideal for machining complex and intricate parts in aerospace, automotive, high-precision medical devices, and the military.
Companies that produce five-axis horizontal machining centers include Makino, Kitamura, Okuma, and Mazak. The pallet size and work envelope for these machines could vary.
How Much is a New Horizontal Machining Center?
HMCs are productive machines that can be a game-changer for your business, but no one claims they are cheap. For example, a Haas EC-630 four-axis horizontal machining center with 50-tool capacity and twin pallets starts at $350,000, and five-axis models from Okuma and Kitamura can run over $500,000. Even off-brands from DMG Mori cost in the hundreds of thousands.
How Do Companies Justify Paying for a Horizontal Machining Center?
Some companies realize that the heavy-duty HMC has the rigidity to enable faster speeds and feeds and lower cycle times. They believed that an HMC could lead to business growth since the ability to do so many more types of work would open avenues to previously impossible work. Shops become more competitive in their quotes, knowing they will produce high-quality parts faster thanks to fewer setups and unattended operations.
You Don’t Have to Spend Several Hundred Thousand Dollars to Improve Your Bottom Line
Most shops don’t require a pallet changer or need the ability to machine five sides of a workpiece simultaneously. For them, machining one or two sides of a workpiece are sufficient, and they can get that with a CNC vertical knee mill at a fraction of the cost.
CNC Masters is the manufacturer and distributor of some of the finest Bridgeport-type CNC vertical knee mills and desktop CNC milling machines on the market. And these high-quality machines are produced right here in the USA with ball screws, a warranty, excellent service, and a competitive price!