A Basic Guide to 5 Axis Machining Center

1.What is a 5 axis machining center?

A 5 axis machining center is a precision CNC machine that uses a variety of cutting tools to remove material from a workpiece. It cuts along five different directional axes, either by positioning the workpiece or cutting along these axes simultaneously until the desired shape is achieved.

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To put it more specifically, an example of a 1-axis machine is a radial drilling machine, which has up and down motion (Z axis). By the same logic, a 3-axis CNC machine can move up and down (Z axis), left and right (X axis), and forward and backward (Y axis).

A 5 axis machining center has two additional rotary axes, which opens the door to endless machining possibilities. Types of rotary axes include rotary axes A, B, and C, which rotate around the X, Y, and Z axes, respectively.

Although these are three additional axes instead of two, they are still considered a total of 5 axes. The combination of additional axes depends on the machine and can be any combination of AB, AC, or BC.

With additional axes, the cutting tool can approach the part from all sides, allowing undercuts that are only possible on machines with fewer axes, provided the part is repositioned with integrated fixtures.

A 5 axis CNC machine avoids this time-consuming and error-prone process on machines with fewer axes.

2.How does a 5 axis machining center work?

The cutting tool on a 5 axis machining center can approach the workpiece from any of five sides. It moves on the X, Y and Z linear axes and rotates on the A, B or C axis.

Here are the corresponding axes and their movements:

1. X-axis – from left to right

2. Y-axis – from front to back

3. Z-axis – up and down

4. A-axis – 180° rotation around the X-axis

5. B-axis – 180° rotation around the Y-axis

6. C-axis – 180° rotation around the Z-axis

3.Difference between 3-axis and 5 axis machining

To better support the increasingly complex needs of advanced industries such as aerospace engineering, medical, defense, robotics and automotive manufacturing, CNC machine tool manufacturers continue to innovate and develop newer, more complex and at the same time more powerful machines.

A major milestone in this field was the development of 5 axis machining centers. The capabilities and flexibility of such machines are far superior to standard 3-axis machining centers.

The following table lists some key points:

4.How to set up a 5 axis machining center?

One of the advantages of a 5 axis machining center is that there is no need for complex clamping systems or fixtures to fix the machined parts. Therefore, setting up the workpiece on such a machine is quite easy.

The clamping device or workpiece component is preferably mounted in the center of the machine table. The clamping device can be a zero clamp, hydraulic clamp or simply a block to which the component to be machined is securely mounted.

More importantly, the part should have free access to the cutting tool from all 5 sides and be securely fixed so that it does not move or vibrate. The cutting tool and tool holder then need to be prepared, measured and loaded into the machine’s automatic tool changer (ATC) magazine.

By running a calibration cycle like this, all axes of the machine are freshly and correctly calibrated and there is no accumulated tolerance between each axis. This should be done at least once a month (preferably once a week) and certainly before every production run.

Unfortunately, many 5 axis machining centers are sold without this feature and necessary equipment, mainly to save money. While this can save initial money, it comes at the expense of accuracy. Over time, these costs can add up and result in substandard machining quality. This is certainly not part of industry best practices.

Another important thing to note is to double check for any potential collision areas before pressing the cycle start button. After this, let the entire program run step by step to ensure that every position is correct and every tool replaced is the correct one.

If you don’t take the time to check, collisions can occur. Not only will this take a lot of time to fix, it can also result in very expensive repairs and the need to readjust all the axes.

5.How to program a 5 axis machining center?

For part machining, a CNC program is required to position the axes and initiate drilling, tapping, and milling operations. For simple operations that are not too complex, you can do this directly on the machine with the help of the CNC control panel and various CNC macros/subroutines.

For machining more complex jobs or parts with more complex contours, a CAD/CAM system that is appropriate for the machine tool, the CNC control, and the overall configuration of the machine is required.

Most CNC programs today are written on secure and dedicated CAD/CAM systems, most of which can also check for errors.

The CAD/CAM system requires the right postprocessor from the CAD/CAM vendor – to ensure that all data is correctly converted into a format that the machine’s CNC control can use.

6.What tools can be used on a 5 axis machining center?

One of the advantages of 5 axis machining (or 3+2 / 4+1 machining) is that it allows the use of shorter, more robust cutting tools than 3-4 axis machining. This allows for faster feeds and speeds, less tool deflection, and better cutting conditions.

These combinations result in superior surface finish, greater accuracy, heavier cuts, and fewer setups, all of which result in shorter overall cycle times. This capability is very useful in recessed applications such as milling parts or deep cavities in molds.

Tool changes can be easily automated with modern automation solutions on 5 axis machines. These systems can transform the machine into an FMC (Flexible Manufacturing Cell) system. This makes “high mix – low volume” production a reality.

Larger ATC magazines offer significant advantages when machining very complex parts, both in terms of tools and the number of tools used. Standard magazines with 30-40 stations quickly become limiting.

Therefore, a 5 axis machining center with 60 tool stations is recommended. If the part is very complex and automation is added to the machine, an ATC with 60 stations is a must, although 120 stations would be better.

This feature not only provides a sufficient number of different tools, but also allows the integration of “sister” tools. Such tools have precise dimensions and specifications for specific operations and wear out faster than other tools.

Sister tools are automatically replaced as soon as other tools with the same specifications reach the end of their life. This will avoid working with weakened or broken tools.

The main advantage of a multi-axis machining center is probably that more surfaces and sides of the part can be machined in the same setup/clamping than a simple machine. It is also possible to perform multiple operations such as milling, drilling, tapping, etc. without re-clamping the part to a secondary position or even moving the part to another machine.

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Not only does it save time and avoid fixture costs, it also eliminates errors. This reduces the need for additional machines or manpower.

7.What are the advantages and disadvantages of a 5 axis machining center?

Now that you understand how a five-axis machining center works, you may ask what are the advantages and disadvantages of this type of machine tool. Let’s take a closer look.

Advantages of 5 axis machining centers

1) Minimized machine setup

With a single setup process (aka “one-stop completion”), you can significantly reduce preparation time and improve manpower and machine efficiency. This can also reduce human and machine errors, which are caused by multiple setups for each machining stage.

Simpler clamping equipment used to place parts in the required position in the machine can also save time and cost and reduce potential errors.

2) Machining complex shapes

With 5 axis machining, complex shapes and designs can be easily processed. This may include: hydraulic system components, water pump housings, gearbox housings, gears, injection molds, oil and gas equipment, medical or blood transfusion equipment, etc.

3) Higher machining accuracy

By reducing the number of manual setups required, 5 axis machining centers can help improve the overall accuracy of produced parts.

4) Better surface finish

With a 5 axis machining center, the cutting tool can not only be close to the workpiece, but also positioned at a 90° angle to the part surface, so that optimal cutting conditions can be achieved at all times.

The 4th and 5th axes (rotary axes) allow for shorter cutting tools with less vibration, which improves surface finish. The main purpose of the additional axes is to allow the cutting tool to reach all 5 sides of the part with greater precision.

5) Faster Material Removal

Designed to remove the toughest materials quickly and efficiently, 4+1 or full 5 axis machining centers significantly reduce any manual operations. This improves machining efficiency and stability.

6) Significant Time Savings

With rising labor costs, a lack of trained manpower, and the need to increase factory productivity, it is becoming increasingly important to consider operational and labor costs.

Because such machines are set up in an integrated manner, operators do not need to re-clamp parts and move them to other machines for the next operation. Instead, they can focus on managing additional machines, which improves productivity.

7) Significant Cost Savings

Increased tool life reduces the frequency of changing to new tools. Improved accuracy reduces the risk of costly mistakes or scrap.

5 axis machining centers further reduce floor space requirements, increase flexibility and spindle utilization, reduce the need for expensive fixtures, and reduce overall inventory investment, all of which can save costs.

8) Expanded Plant Capacity and Production Flexibility

For both part manufacturers and contract manufacturers, investing in a 5 axis machining center increases production flexibility. With its multitude of applications, this type of machine tool allows you to maximize the machine’s use to meet both large and small manufacturing orders.

These features may not be present in low-cost standard machines with significantly limited functionality. 5 axis machining centers are also ideal for today’s high-mix, low-volume manufacturing environment, where large-scale production is not as common as delivering machined parts in small batches that can be delivered repeatedly if needed.

9) Reduced Competition

Five-axis machining centers can significantly increase your productivity and profitability. They put your manufacturing capabilities several levels above your competitors because they are able to take on a wider range of complex jobs, improve product quality, and meet upcoming production needs.

Disadvantages of 5 axis machining centers

Of course, there are some disadvantages to 5 axis machining centers. Here are some common disadvantages:

1) Cost

Five-axis machining centers and the prerequisite software generally require a higher initial investment. The total investment cost is usually higher than that of a standard 3-axis machining center. In addition, the required maintenance is usually more complex.

2) CAD/CAM Programming

Five-axis machining involves two rotational motions in addition to three linear motions, so it is more complex than three-axis machining and requires consideration of the coordination of the motions of each axis, avoiding interference, collisions, and the appropriate amount of interpolation motion.

Complex programming can be a challenge to optimize the required machining accuracy and surface quality, which may require the services of a qualified programmer.

3) Advanced operator skills are required

5 axis machining is an advanced technology in which programming, setup, and machine operation require more highly skilled technicians.

As can be seen from the above points, the advantages of using a five-axis machining center often outweigh the disadvantages. However, you should still consider the range of challenges you face when purchasing a five-axis machining center. To avoid making costly mistakes, consider a comprehensive review of your machining requirements before investing in such a machine tool. In today’s challenging production and manufacturing environment, the lack of such a highly flexible machining center will put your machine shop at a significant disadvantage.

While many CNC’ers have gotten in the habit of always specifying climb milling, there are times to climb mill and there are times where conventional milling is preferred. Before we get into when to use each, let’s look at a quick definition of the differences. First thing to note is terminology.  Some will say “Climb milling versus conventional milling” while others say “Down milling versus up milling.” They’re one and the same:

• Climb milling = down milling
• Conventional milling = up milling

Climb milling is when the direction of cut and rotation of the cutter combine to try to “suck” the mill up over (hence it’s called “climb” milling) or away from the work. It produces the best surface finish. Here is a diagram showing climb versus conventional milling for a number of orientations: Arrows show workpiece motion, not spindle motion! Keep in mind that for this illustration, it is the workpiece that moves, not the spindle. On some machines, like a gantry router, the spindle moves, so the labels would reverse. I keep it straight by thinking of the spindle as a pinch roller that can either help move the workpiece in the direction it was already going (climb milling), or that might fight that movement (standard or conventional milling). Try the experiment on your mill of cutting both ways and you’ll see that climb milling is a lot smoother and produces a better surface finish (most of the time; there are times when conventional gives a better finish — see below). Note that depending on which way you are milling, you will need to make sure your workpiece is supported well in that direction.

Advantages and Disadvantages of Up Milling and Down Milling (Conventional vs. Climb)

Advantages of conventional milling (up milling):

• The width of the chip starts from zero and increases as the cutter finishes slicing.
• The tooth meets the workpiece at the bottom of the cut.
• Upward forces are created that tend to lift the workpiece during face milling.
• More power is required to conventional mill than climb mill.
• Surface finish is worse because chips are carried upward by teeth and dropped in front of the cutter. There’s a lot of chip recutting. Flood cooling can help!
• Tools wear faster than with climb milling.
• Conventional milling is preferred for rough surfaces.
• Tool deflection during conventional milling will tend to be parallel to the cut (see the for more).

Advantages of climb milling (down milling):

• The width of the chip starts at maximum and decreases.
• The tooth meets the workpiece at the top of the cut.
• Chips are dropped behind the cutter — less recutting.
• Less wear, with tools lasting up to 50 percent longer.
• Improved surface finish because of less recutting.
• Less power required.
• Climb milling exerts a down force during face milling, which makes workholding and fixtures simpler. The down force may also help reduce chatter in thin floors because it helps brace them against the surface beneath.
• Climb milling reduces work hardening. It can, however, cause chipping when milling hot rolled materials due to the hardened layer on the surface.
• Tool deflection during climb milling will tend to be perpendicular to the cut, so it may increase or decrease the width of cut and affect accuracy.

Climb Milling Backlash

There is a problem with climb milling, which is that it can get into trouble with backlash if cutter forces are great enough. The issue is that the table will tend to be pulled into the cutter when climb milling. If there is any backlash, this allows leeway for the pulling in the amount of the backlash. If there is enough backlash, and the cutter is operating at capacity, this can lead to breakage and potential injury from flying shrapnel. For this reason, many shops simply prohibit climb milling on any manual machines that have backlash. Some machines are even equipped with a “backlash eliminator” whose primary purpose is to enable climb milling and its advantages. One way to think of it is to consider the concept of chip load. This is a measure of how much material each tooth of the endmill is trying to cut. Typical values for finish work would be 0.001 to 0.002 inch per tooth. For roughing work, that might increase to 0.005 inch. Now, in the worst case, climb milling may grab the table and slam the work into the cutter by the full amount of backlash during the instant when a single tooth is cutting. You can therefore add the backlash to the chip load to see what your new effective chip load might be in this worst case. Suppose you are roughing 0.005 inch per tooth and have 0.003 inch backlash. In the worst case, your chip load will soar to 0.008 inch. That’s probably not the end of the world, but it is a strain. Now suppose you have an older machine with 0.020 inch of backlash and are running a 0.005 inch chip load. If the worst happens there, your chip load will soar to 0.025 inch, which is probably going to break the endmill and is very dangerous. The second thing to consider is whether cutting forces are strong enough to pull the table through the backlash in the first place. A lot will depend on the exact cutting scenario together with your machine. If you’ve got a fancy low-friction linear way machine, it can grab easily. If you’ve got a lot of iron in the table, and maybe you’re running with the gibs tightened a bit, it’ll be harder. There are ways to calculate the cutter force, but in general, smaller end mills, less depth of cut, lower feeds, and lower spindle speed will all reduce the cutting force and make it less likely the cutter will drag the backlash out of your table and create a problem. In general, CNC machines shouldn’t have any noticeable backlash, so these are more for manual machines.

Under Certain Conditions, Climb Milling Produces Negative Cutting Geometry

So far, you’ve probably gotten the idea that maybe you should always climb mill. After all, it leaves a better surface finish, requires less energy, and is less likely to deflect the cutter. Conversely, manual machinists are often taught never to climb mill because it’s dangerous to do on a machine that has backlash. The truth is somewhere in the middle. AB Tools, makers of the popular Aluma-Hogs and Shear-Hog cutters, point out some worthwhile rules of thumb:

• When cutting half the cutter diameter or less, you should definitely climb mill, assuming your machine has low or no backlash and it is safe to do so!
• Up to 3/4 of the cutter diameter, it doesn’t matter which way you cut.
• When cutting from 3/4 to 1x the cutter diameter, the preference is for conventional milling.

The reason is that cutter geometry forces the equivalent of negative rake cutting for those heavy 3/4 to 1x diameter cuts. It seems that Dapra Corporation first discussed this phenomenon way back in . G-Wizard now reminds you with a little hint which one you should use:

G-Wizard’s hints tell you what to do: “Use Climb Milling.” If you’ve never played with our G-Wizard Speeds and Feeds software, take a moment right now to sign up for the 30-day trial.

Tool Deflection and Cut Accuracy in Climb vs. Conventional Milling

How does climb versus conventional milling affect tool deflection and accuracy? The following illustration contains small arrows (often called vectors) showing the direction of tool deflection as the cutter moves along the toolpath:

The arrows show where the cutting force is attempting to deflect the cutter.

Conventional cut at top, climb cut at bottom. Note how the deflection force vector is more nearly parallel to the cut with conventional milling (albeit the arrows are longer, showing there are higher cutting forces). With climb milling, the arrow is nearly perpendicular to the cut. If your cutter deflects 0.001 inch, wouldn’t you prefer it to be nearly in the direction of travel? The alternative is for the cutter to plow deeper into the wall or pull away from the wall. Either case will introduce more error in the part being machined. The counterpoint is that the lengths of the vectors are longer when conventional milling. That’s telling you that the cutting forces are heavier and the tool is more likely to deflect. Try climb for roughing, because you can rough faster and the tool deflection effects on accuracy don’t matter – the finish pass will deliver the accuracy. You can rough faster because cutting forces are lighter and the thick-to-thin chip profile carries the heat away on the chip. That thick-to-thin + carrying the heat away is particularly crucial for tough work-hardening materials like stainless. It also results in a nicer surface finish if you can afford to climb for the finish pass.

Consider Conventional Milling for Finish Passes

This one is counterintuitive for a lot of machinists who were trained for most of their careers that climb produces a better finish than conventional. All other things being equal, that’s true, but all other things are seldom equal! The problem is that deflection affects surface finish, too. If the vector is nearly parallel to the path, you can consider that the portion of the vector that pushes it “off parallel” is very small. Therefore, the tool will have little tendency to deflect and put waves on the wall you’re finishing. Note that this may be particularly important in thin wall work where the walls are weak! Therefore, you should switch to conventional milling for the finish pass if you’re at all deflection challenged (use G-Wizard to see if your tool diameter and stickout result in small enough deflection for your finish pass). At the very least, avoid too much depth of cut when climb milling lest it invite deflection. The same article suggests that when deflection is to be minimized, use no more than 30 percent of the diameter of the cutter for conventional milling and 5 percent for climb milling. Of course, here again, if you have G-Wizard, you’ll know what kind of deflection to expect and whether it’s a worry. Climbing to rough and conventional to finish is inline with the consensus over at Practical Machinist as well. Properly managing deflection can help you avoid the need for an extra spring cut, which saves time and money.

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Consider Conventional Milling When Micromachining