5-axis machining is milling on a machine that has the three straight-line axes (X, Y and Z) plus two rotary axes, so the cutter can reach a part from many angles. The rotary axes tilt or turn the part, the spindle or both. A machine can use them only to position the part for each cut, called 3+2 machining, or move them while it cuts, called simultaneous 5-axis machining.
This guide explains what the five axes are, how 3+2 differs from simultaneous machining, the four ways builders arrange the rotary axes, what the control has to do and which builders make these machines. It ends with how to tell what kind of 5-axis machine you own and what to note about it.
Machine Tool Exchange buys used 5-axis machining centers directly from the shops that own them, so the guide closes with the details an owner needs on hand.
What Is 5-Axis Machining?
Wikipedia's article on multiaxis machining says typical CNC tools move in three axes, while multiaxis machines also rotate around one or more axes. On a 5-axis machine the two extra axes are rotary. Modern Machine Shop notes that on most machines they are named by the straight axis they turn about: the A axis pivots around a centerline parallel to X, the B axis around one parallel to Y and the C axis around one parallel to Z.
A 5-axis machine adds those two rotary axes to the three straight axes of a mill such as a vertical machining center. For the other machine families, start with our guide to types of CNC machines.
Each rotary axis is built into either the table that holds the part or the head that carries the spindle. Wikipedia says each axis of movement is implemented either by moving the table or by moving the tool, so machines with the same number of axes can differ in the movements they can perform. That is why the layout matters as much as the axis count, and why this guide covers both.
What Is the Difference Between 3+2 and Simultaneous 5-Axis?
Carr Lane, a workholding maker, separates three modes. In 3+1 machining one rotary axis is positioned and locked before each operation. In 3+2 machining a second rotary axis is added, so the part or the tool can tilt and rotate into virtually any orientation, but the rotary axes are held fixed during cutting. In simultaneous 5-axis machining, all the straight and rotary axes move together in real time under coordinated control.
| Feature | 3+2 (positional) | Simultaneous 5-axis |
|---|---|---|
| Rotary axes during the cut | Positioned and locked | Move together with the straight axes |
| What the tool does | Ordinary three-axis moves on each face | Keeps re-orienting toward the surface |
| What it asks of the machine | Positioning and locking two rotary axes | Per Carr Lane, advanced programming, control and exceptional structural rigidity |
| Parts Carr Lane says it suits | Prismatic parts with several angled features | Complex freeform surfaces, or work that needs uninterrupted multi-axis motion |
Carr Lane adds that true simultaneous motion almost always requires the trunnion or rotary assembly to be fully integrated into the machine casting.
How much of a 5-axis machine's work is simultaneous varies by shop. Modern Machine Shop's case study of one contract shop, General Tool Company in Cincinnati, says its continuous five-axis work is about one job in five of those that call for a five-axis machine. In the other jobs the rotary axes only reorient the tool or part outside the cut. That lets the spindle reach opposing faces in a single setup, and lets a standard milling cutter, held at an angle, machine an angled surface. It is one shop's mix, not an industry figure.
How Are 5-Axis Machines Built? Table, Head and Trunnion Layouts
Where the two rotary axes sit changes what a machine does well. The same Modern Machine Shop article describes four layouts. The shop's engineer says none of the designs is inherently better than another: each makes that machine the best in the shop for a particular workpiece geometry. The last column is that shop's view, not a rule for every machine.
| Layout | Where the rotary axes sit | What the shop says it suits |
|---|---|---|
| Rotary table plus pivoting spindle head | One in the table, one in the head | Tall workpieces, and cylindrical parts with holes around the outside |
| Double rotary table | Both in the table | Long tools or extensions, and a ring of holes in one face |
| Double pivot spindle head | Both in the spindle head | Parts that are not round, such as long aerostructure parts with odd-angle holes |
| Rotary table plus table trunnion, in a compact machine | Both under the workpiece | Smaller parts, and relatively deep cuts for its size, since the spindle head does not pivot |
A trunnion is a rotary axis built into the table instead of the spindle head. In the article's fourth design, a 360-degree rotary table is combined with a 180-degree trunnion. Wikipedia's table of multiaxis machines lists the same four layouts under slightly different names.
What Does 5-Axis Machining Change in the Shop?
Wikipedia lists what multiaxis machines can offer over other CNC machines. A better surface finish can be obtained by moving the tool tangentially about the surface. More complex parts can be made, particularly parts with curved holes. Tool life can increase because the tool can meet the surface at optimal angles. And what once required multiple setups can now be done in only a few, if not one, which reduces steps and the chance for error.
Those are general statements about the technique, not claims about any one machine. The trade-offs sit in the machine and the control. Carr Lane says a tilting table on a vertical or horizontal machining center often reduces the usable workspace and limits part size, and that simultaneous motion places significantly higher demands on the stiffness of both the machine and its positioners.
What Does the Control Have to Do?
When the spindle head pivots, the position of the cutting edge changes in every straight axis as the angle changes. Modern Machine Shop explains that on such a machine the tool offsets in X, Y and Z must all change every time the spindle angle changes, and that some CNCs for five-axis machines can do this math automatically. If the control cannot, the offsets have to be built into the program, which limits the shop to tools that were measured before the program was written. On a machine where only the workpiece pivots, the tool offsets stay fixed.
Tool-center-point functions are one place the control matters when a machine changes hands. On some controls they are software options. The Heidenhain TNC 640 manual, for example, lists its FUNCTION TCPM, which maintains the position of the tool tip when positioning with tilted axes, as Option #9. So when you describe a used 5-axis machine, say which control options are enabled, not only which control it has.
How Is 5-Axis Milling Different From a Multi-Axis Lathe?
The starting point differs. A 5-axis machining center starts from a mill: a spinning cutter, with two rotary axes added to X, Y and Z. A multi-axis lathe starts from a turning machine: a spinning workpiece, with milling added. Our guide to multi-axis lathes covers the turning side.
The two families overlap at the top end. Mazak lists turning capability on its VARIAXIS i-700T, i-800T and i-1050T, and the machines called mill-turn or multi-tasking machines do both jobs in one setup.
Who Builds 5-Axis Machining Centers?
Several builders list 5-axis lines. This table shows what each builder's own page or a reference source names. It is not a ranking or a full list.
| Builder | Line named | What the source says |
|---|---|---|
| Mazak | VARIAXIS i (models i-500, i-700T, i-800T, i-1050 and i-1050T) | Mazak's page lists multi-face machining and simultaneous 5-axis machining with one chucking, a wide variety of table sizes, spindles and automation systems, and automatic measurement of the centers of rotation of the C and A axes |
| DMG MORI | DMU series | DMG MORI calls them universal milling machines for 5-axis machining up to 5-axis simultaneous machining, with a rigid swivel rotary table that has a swivel range up to 135 degrees |
| Haas | UMC | Wikipedia describes Haas's universal machining centers (UMC) as 5-axis vertical machines |
Our page on used 5-axis machining centers also covers machines from Makino, Okuma and Doosan, among others. Our builder pages cover Mazak, DMG MORI, Haas, Makino and Okuma machines.
How Can You Tell What Kind of 5-Axis Machine You Have?
Look at these together, because an axis count alone does not settle it:
- Where the rotary axes sit. A tilting table or trunnion under the workpiece, a pivoting spindle head, or one of each. These are the four layouts above.
- What the control calls the axes. Rotary axes are usually named A, B or C by the straight axis they turn about.
- Whether it moves them while cutting. A machine may be used for 3+2 positioning only or for simultaneous motion. The control, its options and the program decide. Carr Lane says true simultaneous motion almost always requires the rotary assembly to be integrated into the machine casting.
- Whether it also turns. A 5-axis machine with a turning table, such as Mazak's VARIAXIS i-800T, sits closer to mill-turn.
- The builder's description of the model. Read the model plate and the builder's page. An axis count in a listing is not enough, because machines with the same number of axes can differ.
What to Note on a 5-Axis Machine You Own
To describe a 5-axis machine accurately, collect these details from the machine:
- Model and serial number, from the data plate. A photo of the plate is more reliable than memory.
- Build year, or your best estimate.
- Control name and generation, and which options are enabled, including simultaneous 5-axis and tool-center-point functions.
- Layout and mode: table, head or trunnion, and whether it runs simultaneous or 3+2.
- Table size and the largest workpiece it takes.
- Spindle hours, if the control tracks them.
- Pallet changer or pallet pool, and any robotic loading.
- Tool magazine capacity, probing, and through-spindle coolant.
- Last calibration or service date, especially on the rotary axes.
- Tooling and attachments that come with the machine.
These are the same things we look at when we buy a used 5-axis machining center. Machine Tool Exchange buys them outright from the shops that own them and arranges the pickup. A bill of sale or other proof that the company owns the machine outright, rather than still holding it under a lease, speeds up closing. Request a quote or call 517-514-5190.
Frequently Asked Questions
What are the five axes in 5-axis machining?
Three straight-line axes (X, Y and Z) and two rotary axes, usually named A, B or C. The rotary axes tilt or turn the part, the spindle or both, depending on the machine's layout.
Is 3+2 machining really 5-axis?
It runs on a machine with five axes, but the two rotary axes are positioned and held fixed during each cut, which Carr Lane describes as 3+2 machining. In simultaneous 5-axis machining all the straight and rotary axes move together while the tool cuts.
What is a trunnion on a 5-axis machine?
A trunnion is a rotary axis built into the table, beneath the workpiece, instead of into the spindle head. In one machine Modern Machine Shop describes, a 360-degree rotary table is combined with a 180-degree trunnion under a spindle head that does not pivot.
Is a 5-axis machine the same as a multi-axis lathe?
No. A 5-axis machining center starts from a mill and adds two rotary axes to X, Y and Z. A multi-axis lathe starts from a turning machine and adds milling. They overlap on machines such as Mazak's VARIAXIS i-700T, i-800T and i-1050T, which add turning to a 5-axis machine.
Does Machine Tool Exchange buy 5-axis machining centers?
Yes. Machine Tool Exchange buys used 5-axis machining centers directly from the shops that own them, with or without pallet systems. We buy outright and arrange the pickup. Call 517-514-5190 or use the quote form on our sell page.
Have a 5-axis machining center you want to sell? Machine Tool Exchange is a direct buyer, so the offer comes from the buyer. We buy outright and arrange the pickup. Get a quote or call 517-514-5190.