Laser Machining Yields Manufacturing Enhancements for Speed
Laser machining introduces many possibilities
during the design process for changes or evaluation of processes that
may be too time-consuming or costly to consider.
Rapid prototyping (RP) processes have proven to be very effective as visualization tools for fit and function and, sometimes, as the final production process. Cases in which RP processes do perform well in development through production, they become effective for defining the intent of a process for prototyping and for production, but material limitations in RP processes do not yet meet the same physical property requirements of many design materials.
FEA tools can be most effective for uncovering design flaws, but they cannot reach into the heart of many manufacturing processes and expose troublesome inherent process limitations. Actual physical components that are produced from the parent process, parent material, and in suitable numbers that show stability or robustness of the process are what is needed to expose process limitations in many cases. However, this route traditionally takes time and can involve substantial cost, depending on the complexity of the component. Additionally, meteorology data must be obtained from the process and material to validate the reliability, robustness and compatibility of the component and process. The bottom line is that obtaining this early processing knowledge can make a big difference in product reliability, development time and in weeding out potential problem processes that might creep in much later.
Traditional prototyping processes are good at yielding an early visual, ergonomic or even physical working instrument and are most effective in obtaining design feedback; but they provide little understanding of the downstream potential problems that may be lurking in this early design/process compatibility. We cannot separate the design of a component from the process used to make it. Speed for knowledge and speed-to-market are really what it is all about. Regardless of the type of component - whether it is metal, plastic or fabricated - knowing process limitations now, not later, can make all the difference.
New technologies emerge yearly and have the potential to meet various manufacturing needs. Identification of the right technology is critical, because it must meet certain identified up-front criteria to be effective. Also, one size does not fit all components. To be effective in selecting the most effective technology, developing a business plan that will target process development enhancements can be very beneficial in identifying the right process technology. It also is useful in identifying any up-front, high-end technologies that can drive speed for knowledge. Establishing criteria for technology selection, such as simplification, automation or replacement of traditional methods, is beneficial. Specialization of processes, e.g., standardizing tooling, can have an impact on reducing time and cost as well as using CAD technology to its fullest, not only for design, but also manufacturing.
Laser Machining
Laser machining with the DML40 SI brings to the table several very important manufacturing enhancements for speed (see Figure 1).
The process is truly directly CAD-driven. Data input into the machine
is in the same .stl format used on many RP machines. The data input
into the laser machine is the exact shape to be produced in the tooling
that is similar to EDM machining. We refer to this data as an
electronic electrode. With laser machining, no actual physical
electrodes are made, and there are no intermediate offline CNC
programming steps required for driving the technology. Once the data
are read into the machines, Lasertec (Kanagawa, Japan) - a provider of
laser and LCD inspections and measurement systems - software options
are then available to determine the desired outcome of the machining
process, but the actual NC data used to drive the machine are
automatically generated by the machines software program. This in
itself is a huge time-saver and opens up the possibility of disposable
tooling, i.e., tooling that easily can be recreated from totally new
data with minimal effort. Another big benefit of this technology is
that no cutting tooling is used. The laser does all of the machining by
laser ablation in thin layers from one to five microns, starting in
depth from the top of the workpiece down (see Figure 2). One
can machine any material that can be ablated by the laser from full
soft to extremely hard. Tool steels, graphite, and ceramics all can be
machined. Even though the process, in effect, machines from light, the
accuracy achievable in X, Y and Z is comparable to existing CNC
manufacturing processes (see Figure 3). Finishes are comparable also with existing standard RAM EDM finishes (see Figures 4a, 4b).
We find this finish in the unpolished state to be adequate for
development components. This high degree of accuracy and finish is
attributable to the machine's real-time measuring system built into the
machining process. (see Figure 5).
Laser Enhances MIM, CNC and Casting Possibilities
Considering a small metal component used in a medical device (see Figure 6),
several processes could be identified for manufacturing: CNC machining,
metal injection molding (MIM) and precision casting. Each has the
possibility to be effective as a final production method, provided it
is cost- and time-effective. Each could be used as a prototyping
method, provided it is time-effective; however, with traditional
manufacturing methods, none is truly a disposable process (i.e., a
process that could be easily and cost-effectively changed for a totally
new component or design, with the component then quickly manufactured
over again in the parent material). In many cases, the effort to
produce design iterations is time-consuming; and any design changes can
have an impact not only on delivery, but also on the quality of the
component.
All three processes for development and production have limiting factors. CNC machining requires extensive programming and machining time and is not very flexible for changes. MIM is a two-step process, requires extensive tool design and build time for the green part, consisting of CNC machining and EDM machining. The MIM process is not very flexible for changes and requires a postfurnace operation to sinter the components to full density. Precision casting is a two-step process, requiring a reliable master to be reproduced in large quantities, with the master tool being manufactured by CNC machining and EDM machining; it is not very flexible for changes and requires ceramic tooling created from the masters for the actual casting process. With these difficult hurdles to overcome, the real challenge is to identify, integrate and manage processes that are very time-effective in the development processes in providing prototype components. At the same time, taking advantage of this early processing begins to establish and validate the process in being robust enough to be used in production. Additionally, producing the component during the prototyping phase is to be done in a relatively short time and at low cost.
In today's world, CAD drives the manufacturing process and shares a large responsibility for time and cost by leveraging downstream processes effectively. The integration of laser machining technology in the downstream processes as a key element in the overall reduction of time and cost starts with CAD (see Figure 7). To be truly effective, the overall CAD design process must include at least the design and layout of tooling inserts for the component design and manufacturing process chosen (Figures 8a, 8b) show tool inserts laid out in CAD for a casting master. The tooling inserts also could be for a MIM tool. The CAD design for laser machining should be a fully valid solid model of the tool inserts. With solid modeling, electronic electrode shapes for laser machining are extracted easily from the insert designs and transferred to the laser machine. What makes the overall laser machining process excel is that electrode manufacture and long RAM EDM machining times are eliminated or greatly reduced from the tool manufacturing process. As an example, two to four RAM EDM electrodes each would be required for the core and cavity details. Each electrode requires design, CNC programming, and CNC machining before being placed in the RAM EDM machine and individually burned into the tool insert. Laser machining, in contrast and in many cases, only needs one electronic electrode shape designed in CAD of the entire shape to be produced. The electronic electrode data then are transferred to the laser machine and processed on the laser machine, which then automatically creates the NC program. Then, the NC program is activated, and laser ablation takes place to produce the shape into the tool insert.
Laser machining provides the end user with a dramatic contrast to traditional processes. Because no real physical electrodes are produced when laser machining, many possibilities open up during the design process for changes or evaluation of processes that may be too time-consuming or costly to consider. Dual paths of possibilities for evaluating similar processes also are benefits, because tool machining and build times can be reduced by 50 percent to 70 percent from traditional tool build methods. R&D is the ultimate benefactor of this technology through time and cost reduction. This time and cost savings can be more effectively used by R&D in speed for knowledge by providing the ability for early refinement of the product/processes to better understand the design requirements and meet customer needs. In addition, noncompatible processes and design requirements are identified early.
