The problem with machining today is simple: it's costly and takes up too much time. Time from a skilled operator. Time on an expensive machine. Time to set up. Time to get a part in hand.
This problem becomes extremely painful when it comes to machining custom tooling — the production of fixtures, jigs, molds, and patterns. Tooling is traditionally one of the most time-consuming and costly portions of the machining process. Again, why is tooling so painful?
It’s time consuming and costly.
The typical process to get a set of custom milling jaws in hand is:
Design jaws in computer-aided design (CAD) software
1. Draft blueprint/drawing of jaws in CAD
2. Approve design of jaws
3. Program CNC
4. Schedule jaws on CNC
5. Machine jaws on CNC
7. Deliver jaws
By the time the jaws are delivered, as many as five different people have touched it in the process. A design engineer to design the jaws. A manager to sign off on the blueprint/drawing. A programmer to program the CNC. A skilled machinist to machine the jaws.
Now, what happens when the part the jaws were designed to hold iterated from Rev 1 to Rev 2 and, eventually, to Rev 3? Each revision results in a revision to the jaws, and the whole process begins again from step one.
At low-production volumes, manufacturers either refuse production or charge a premium per unit cost. The inherent problem with tooling is they don’t generate revenue. For example, the cost to a manufacturer for machining a set of milling jaws on a CNC is machine downtime, labor, and overhead. Machining milling jaws does not help a manufacturer's bottom line. If the jaws are never used again, in order to recuperate the initial, upfront cost and its successive iterations, the cost of the jaws are gambled and spread across the final, production-run milling jaws or the end-use, revenue-generating parts being machined.
This is where additive manufacturing — colloquially known as 3D printing — steps in.
In addition to allowing more freedom in design, additive manufacturing drastically shifts tooling from time-consuming and costly to hands-off and affordable. For one-off tooling, additive manufacturing opens the door for manufacturers to improve their bottom line by reducing CNC machine downtime, labor, and overhead to just material cost. As shown in Figure 1, it is extremely affordable to 3D print one-off tooling compared to conventional manufacturing.
Additive manufacturing streamlines the production of end-use, revenue-generating parts by drastically decreasing their time to market. With additive manufacturing, the jaws can be printed immediately after design, completely disrupting the tooling manufacturing paradigm.
Gone are the arduous days of design, draft, approve, program, schedule, machine, inspect, and repeat; gone are the days of tying up a revenue-generating CNC to machine one set of jaws; gone are the days of consuming CNC programmers' days programming to machine one set of jaws. The quicker the tooling is available, the quicker the end-use, revenue-generating parts can be machined.
How to 3D Print Milling Jaws
When designing milling jaws for 3D printing, the three prerequisites are understanding milling jaw design, CAD, and Continuous Fiber Fabrication (CFF). The first and second prerequisites are self-explanatory. For the last prerequisite, 3D printing milling jaws is a matter of orienting and reinforcing with CFF. So, what is CFF?
Continuous Fiber Fabrication (CFF)
Additive manufacturing technologies of the past print thermoplastics too weak to withstand the harsh environments of CNC machining. With the introduction of Continuous Fiber Fabrication (CFF), Markforged has disrupted the additive manufacturing industry by printing with continuous fibers (carbon fiber, Kevlar®, and fiberglass) to reinforce thermoplastic printed parts. The strength of the continuous fibers are shown in Figure 2.
For example, the needle bearing workpiece shown in Figure 3 requires a face milling operation on one of its faces. The milling jaws used for that operation are shown in Figure 4.
The continuous fibers are printed on the XY-plane parallel to the build plate making orientation critical! When considering how to orient a set of milling jaws for printing, the keys to success are understanding how the clamping pressure will be applied to the jaws, and how to route continuous fibers to counteract the clamping pressures. For example, the jaws shown in Figure 4 are designed to clamp on the workpiece for a face mill operation. The clamping pressures are at the contact points conformal to the workpiece. At the contact points, the jaws experience the clamping pressures as a compressional force caused by the workpiece and the vice as shown in Figure 5.
In order to optimally route continuous fiber to counteract the compressional forces, it is important to understand that fibers are strongest in tension. When reinforcing the milling jaws with continuous fiber, route the fiber to maximize the number of fibers can be put in tension. In Figure 6, continuous fibers are routed concentrically around the outer walls of the part and will be put in tension due to the compressional forces.
Continuous fibers put in tension resists the compressive forces to keep the jaws dimensionally stable. It is important to note, using the vice to sandwich the jaws and reinforce it against the shear forces across the printed layers plays a key role. When considering jaw design, maximize the amount of surface contact to the vice.
Advanced Milling Jaws for 3D Printing
The next step in 3D printing milling jaws is creating a modular milling jaw. For example, instead of printing the entire jaw shown in Figure 4, consider using a set of hard jaws as the "blanks" and 3D printing soft jaws as the "inserts." As shown in Figure 7, the machined, metal jaw is the "blank" shown in purple, and 3D printed, composite soft jaw is the "insert" shown in green. Since the conformal geometry changes between different workpieces, one blank can serve many inserts.
Although CFF jaws are great for replacing aluminum jaws because of parity in strength and non-marring nature of composites, what happens when there is a need to replace steel jaws? Leveraging the same idea of modularity, the “blank” can be machined aluminum or 3D printed CFF, while the “inserts” are 3D printed on the Metal X System by a process known as Atomic Diffusion Additive Manufacturing (ADAM). With the current release of 17-4PH Stainless Steel and H13 Tool Steel, the Metal X System preserves all the advantages of 3D printing, such as conformal geometries, quick turn-arounds, and reduced costs, and meets the material properties required to replace steel jaws.
Transitioning from shelves of tooling to a quick, interchangeable solution, the modular milling jaw is the future of manufacturing. Additive manufacturing further shifts manufacturing tooling from time-consuming and costly to even more hands-off and affordable.
How to best 3D print milling vise jaws
3D printing milling vise jaws isn’t rocket science, but it does require a fundamental understanding of milling vise design, CAD, and CFF. The important steps to remember are:
(1) determine the clamping pressures on the milling vise jaws between the workpiece and the vice;
(2) choose a print orientation that maximizes fibers in tension against clamping pressures; and
(3) reinforce with continuous fibers in tension.
Interested in learning more? Talk to one of our product specialists to discover where 3D printed parts fit into your business.