We’ll explain some of the most impactful equipment available for supporting multi-axis work and shares advice on how to best match it to your new machine and the work you plan to do. Learn different ways to optimize tool and workpiece setups, maximize spindle uptime and preserve performance.
GET THE MOST OUT OF YOUR 5-AXIS MACHINE
What we’ll cover
The purchase of a 5-axis machining center, or even one that works on multiple axes, is a big deal for any metalworking operation. Apart from the financial commitment, it changes how jobs move through the shop and the way people work—and there are a lot of adaptors out there right now. According to the Association for Manufacturing Technology (AMT), orders for 5-axis machining centers grew 22 percent year over year, in the midst of COVID. Machine shops represent nearly half of the buyers, followed by aerospace and transportation sectors, which tend to invest in larger 5-axis machines. To get the most out of such a significant investment, making smart decisions when choosing the equipment that supports the new machine, and the team using it, goes a long way. We’ll explain some of the most impactful equipment available for supporting multi-axis work and share advice on how to best match it to your new machine and the work you plan to do. Read on to learn different ways to optimize tool and workpiece setups, maximize spindle uptime and preserve performance.
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Setting up tools
In order to realize the return on your investment as soon as possible, a multi-axis spindle needs to be spinning as much as possible. In other words, measuring, adjusting, inspecting or any general fidgeting with tools is best done away from the machine while the machine continues making chips. One of the first things a shop needs to maximize 5-axis performance is accurate 3D models of every tool holder for your CAD system. The tooling assembly has to be modeled as close as possible to how it will be put into the machine—body diameters, gage lengths, etc. There is so much movement and rotation that the chances of a collision are real and costly. The problem is, not all STP files are created equal. Imprecise models aren’t uncommon, especially for cheaper tools. Not only are these difficult to simulate accurately, but it makes adjusting and verifying more time consuming; worst case scenario, the programmer fingers through a catalog and draws the tools himself. Accessibility can also be an issue—how easy are the files to access and acquire? As with tool quality, you get what you pay for when it comes to models. Carefully consider model accessibility and accuracy before purchasing and consider ease of use on future projects. With models and tool lists done, the next important step is accurate measuring and verification of the predefined tool specs. The simultaneous actions of 5-axis machining require more strict control of gage lengths, as measured from the face of the spindle and body diameter. This is where offline presetters become indispensable.
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Setting up tools Tap into digital for help
Using a ruler with 1/16 increments, trusting every spec or using inconsistent in-machine probes are not effective ways to measure when a couple thousandths of inch can make a difference. Tool presetters serve primarily as measuring systems for verifying tool geometries match the programmer’s specs—offsets, body diameters, etc.—offline before putting them into a machine’s spindle. This essentially eliminates any of this work at the machine tool, so that valuable multi-axis spindles can work while verification is done at the presetter. Depending on how and where you prefer to perform setups, there are a variety of presetter options. Vision-based presetters allow for much more than just verification. They are the perfect place to assemble tools and compare directly to the catalog, DXF or STP model that was given to the programmer. Last but not least, consider the tools themselves when thinking about setups. Digital heads are a great option for efficient 5-axis tooling setups. Their on-tool digital readout makes it easy for operators to see and make extremely precise diameter adjustments in just about any situation—even if it must be done in the spindle. A corresponding mobile app allows you to look up tool speeds and feeds on the spot. The next generation of digital boring heads is already on the way. These allow for more interactivity and control via an app for even faster setups and data mining.
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Holding parts
Most of the 5-axis machines come with a round, square, or rectangular table or plate. They don’t, however, come standard with quick-change workholding ready to go. There are different bolt hole patterns and pins used to locate and stabilize the workpiece. Having to match these locations with each different workpiece adds another cumbersome step in a process that needs to be closely controlled—before cutting even starts. Add the fact that 5-axis machining is rarely used for processing the same part over and over, and the right workholding can be a difference maker.
Specifically, the ability to use a zero-point system as a primary datum locator for all workholding, regardless of if it’s a vise, magnetic clamping or a dedicated fixture, is indispensable for setup reduction.
While zero-point workholding was initially developed and has long been used for setup-time reduction, the system has had great success in 5-axis machining for another distinct reason: access. A standard vise will block the sides of a part and low-profile vises leave sides more open, but grips only along the part’s lower edge. Alternatively, the option to use a zero-point system to clamp exclusively on the underside of the part leaves the workholding hidden—concealed from all these interferences by the workpiece itself—for a freer state of machining. Pulling a part down is also better than squeezing it, because the squeezing process puts stress on the raw material and the material removal process can compound the negative effects of this stress. What’s more, the closer the part is to the table, the higher the risk of collision with the tool or tool body. Solutions include using a longer holder, which only tickles the part, or raising the part off the table. There are many dedicated workholding solutions dedicated to this, even in confined work zones. 5-axis table adapters, for example, allow 5-axis base chucks to be mounted anywhere they are needed to access the table T-slots or grid holes, all while providing a strong foundation. Another example, the UNIFLEX System, is made up of a clamping ball and collar that are attached to the underside of the part or fixture. The part and fixture are then lowered on to either a clamping base or a clamping extension. The clamping collar is then rotated to tighten the six bearing balls on to the main ball. If the part or fixture is warped or needs to be set at an angle, the clamping ball can pivot up to 15° in any direction.
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Holding parts Choosing the right workholding
The benefits of 5-axis machines are greatest when workholding is chosen based on the size and shape of the workpiece instead of the limitations of the table interface. Now, some quick advice on choosing the right workholding for a new 5-axis machine. Find a balance between stability and access. The fixture may be large and provide rigid holding but may limit access to the workpiece—and vice versa. If a part is too small for your fixture, consider palletizing multiple parts. If a part is too big for your fixture, consider upgrades if you have a modular system, or add custom pieces, if possible. Know what parts are coming down the line. If the parts are prismatic, most often a vise will do just fine. If the part is round, you’ll need to hold onto an outer or inner diameter on the part. Whether the part will be raw material, a casting or partially finished is also an indicator what the workholding will have to accommodate. For example, a round raw bar from the mill may have an OD tolerance of ±.005 " , but if a part is cast, then the size may be ±.02 " —could be better, could be worse. If a part has already been machined, then the size is not a variable—it’s a known controlled value. Choose the right chuck and lay it out carefully. Depending on the material of the fixture plate, the part or fixture should not extend too far beyond the diameter of the chuck. With a steel plate that’s at least 20mm thick, you can generally go 40mm off diameter without losing stability. If it’s an aluminum plate 25mm or thicker, 20mm off the diameter should be about the limit. Thicker plates are an option, but material costs start getting a little higher than most customers want to bear. When it comes to multiple chucks, plate material and thickness are key. General guidelines for maintaining accuracy and rigidity: if the diameter is less than a 138mm chuck, spacing should max out at about 200mm; for bigger diameters, we recommend a maximum spacing of about 350mm.
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The machining process
A common misconception is to always look first to square or rectangular billets for parts that will ultimately resemble that shape when finished. Sure, in most cases this will save a few minutes, but, because of all the movements that you can make accessing five sides, there are more options. Bar stock is less expensive, more readily available and easier to hold than more frequently used billets. And yes, while there will be slightly longer machining time, the material savings and ease of access will far outweigh the cost in the big picture. The right mill, with an HSK or BIG-PLUS interface, will allow very aggressive material removal. A shorter stickout helps too. Indexable mills are usually longer once assembled because a straight shank must go into another tool holder. Alternatives like our FULLCUT MILL are capable of high performance in ramping, helical-, shoulder- and plunge-milling operations. Sharing a similar compact design, the C-CUTTER MINI can quickly finish jobs—chamfer, back chamfer and even some light face milling. Often times with a standard solid carbide end mill, you’ll see a helix cutting tool used in the Z-direction to get down to a specific height, and then it’s moved in the X and Y to make a pocket. With FULLCUT MILL ramping, you’re able to move simultaneously in the X, Y and Z directions in order to ramp down and around the workpiece, rather than having a whole series of steps that are then followed by X and Y movements.
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The machining process Reaching difficult pockets: hydraulic or shrink fit?
The ultimate goal is to make every tooling assembly as short as possible, 5-axis machine or not. The shorter the tooling, the less room for error. That said, the unusual angles, sizes and shapes of the parts that require multiple axes don’t always allow for that. We’ve talked about some workholding solutions for this challenge, but you have options in tooling selections too. The choice often comes down to hydraulic chucks and shrink-fit holders. Compared to collet chucks, shrink-fit holders and hydraulic chucks have a smaller nose diameter relative to the tools they hold. This is critical, as these holders allow a further reach into mold cavities or other tricky work envelopes without interference. Let’s quickly explore what to consider when choosing between the two holder types.
Cost – When it comes to the holders themselves, shrink-fit is generally a slightly lower cost. Where the major difference in expense lies is in the equipment needed to heat shrink-fit holders.
Maintenance – Because shrink-fit heating temperatures can approach 600° Fahrenheit, we recommend using dry cutting tools without oil on them. From there, diligent attention must be paid to the holder bores and tool shanks. Any contamination will be baked onto the metal and progressively deteriorate performance. Hydraulic chuck maintenance is straightforward as long as the hydraulic chamber stays sealed. Training, handling and safety – Hydraulic chucks are infinitely simple. A turn of a wrench locks the tool in place. When it comes to shrink-fit systems, there are a few more factors to consider when getting the team up to speed, including safety considerations. Setup – Hydraulic chucks use a simple wrench to lock in the tool, providing the option to swap tools at the machine or offline. Shrink-fit setups must be done exclusively offline where the heating and cooling can be powered. Most heating cycles can be as fast as 15 seconds. Vibration – Potential out-of-balance issues due to a hydraulic holder’s one-sided set screw design are a worry of the past. A good-quality hydraulic chuck has some natural damping characteristics that run every bit as true as a shrink-fit holder, with more consistent clamping tolerances and forces over the life of the holder. That’s not to say shrink-fit holders are ineffective in terms of vibration management. Their runout is five times better than side-lock holders.
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More than 150 machine tool builders are licensed to use and make BIG-PLUS on original equipment, so there’s a good chance a new 5-axis machine is built to achieve its peak performance with BIG-PLUS tooling. If you aren’t sure about your machine’s interface, the easiest way to figure it out is to place a standard tool into the spindle and see how much of a gap there is between the tool holder flange face and spindle face. Without BIG-PLUS, the standard gap should be visible, or about .12 " . If it is BIG-PLUS, the gap is half of this amount, or only .06 " . These values change depending on 30 taper, 40 taper or 50 taper sizes, but the gap is visibly less than usual. For those who don’t know, dual contact refers to the shank contacting the spindle taper and the spindle face simultaneously. The torque (or moment) exerted by the cutting forces is maximized at the point where the holder and spindle meet. When the holder contacts the spindle face via BIG-PLUS, the effective diameter would be the larger diameter of the v-flange, since this is the new anchoring point of the holder and spindle. You are essentially beefing up the diameter at the point where the reactionary force is greatest. The truth about dual-contact tooling
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All BIG-PLUS tools are dual contact, but not all dual-contact tools are BIG-PLUS—and this really matters when choosing tooling. Only a licensed supplier of BIG-PLUS has master gages that are traceable to the BIG DAISHOWA grand master gages and have the dimensions and tolerances provided to do it right. Non-licensed dual-contact tool makers are guessing or using a sample BIG-PLUS tool holder as their own master gage—a practice that any quality expert will advise against. Unless the tools are marked “BIG-PLUS Spindle System-License BIG DAISHOWA SEIKI,” the use of tooling not made by BIG DAISHOWA or its licensees may result in inconsistent performance or damage to the machine. So, what are the consequences of using unlicensed dual-contact tooling on an expensive 5-axis spindle? If the distance between flange face and gage line diameter are more than specification, little or no face contact occurs; tool holders provide only taper contact and no benefit of BIG-PLUS. If the distance between flange face and gage line diameter are less than specification, there’s face contact only; tool holders float in spindle taper with no positive radial location. Large cutter runout and fretting corrosion on spindle face occurs immediately. Severe spindle damage can occur.
If the gage line diameter is less than the specification, there will be face contact with only minimal or no taper contact. Severe spindle damage can occur.
If the gage line diameter is more than the specification; there will only be taper contact, eliminating all benefits of BIG-PLUS.
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The quickest path to ROI
A 5-axis machine is not purchased in a vacuum. The addition will have ripple effects across a business that need to be prepared for. You can’t simply assume that because a 5-axis machine is a large investment that it will make up for every operator error or up/downstream inefficiency. Similarly, don’t assume the way things were done on an older machine is the best way. Getting creative and seeking out the inventive solutions designed uniquely for 5-axis work can accelerate all-important ROI; choosing the equipment to support the machining center will empower the team to succeed and unleash the full capabilities of the business.
How can we help?
Visit us at bigdaishowa.com.
Explore our High-Performance Tooling Solutions catalog here.
Find a local representative, get a quote or ask us anything here.
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