Cutting Aluminum Faster
Sometimes high-speed CNC machinery with the latest software can cut much faster, requiring less EDM work.
To better take advantage of high-speed spindles, aluminum prototype molds can be designed with inserts that allow deep ribs to be cut without hesitation. This aluminum mold was cut with a high-speed CNC machine. Images courtesy of Phoenix Proto Technologies.
No EDM was used to produce these 1.1-inch-deep ribs with 0.5-degree draft. They were cut with a 0.031-diameter cutter.
Technology, speed, quality, timing and price are essential deciding factors for establishing appropriate manufacturing processes. When it comes to building prototype aluminum molds, the right software, hardware and machinery help to determine the best method. This can mean heavy investment in cutting more detail rather than adding detail through the EDM process. EDM is still a necessary option, but sometimes using high-speed CNC machinery with the latest software can cut aluminum much faster. Here is a look at two key factors that can influence process efficiency in cutting aluminum.
Mold design. Designing more inserts in molds decreases material costs by allowing the mold builder to order thinner pieces of aluminum and less graphite. It also speeds polishing time, as such designs yield better access to certain details, including those that might require a more delicate approach when the machine is cutting them. Inserting specific areas of a mold also permits the addition of more vents in the tool, which yields a better processing window for molding the parts.
At Phoenix Proto Technologies, we previously used EDM 65 percent of the time to add detail in cavities. Today, we use it only 20-25 percent of the time. We commonly use a 0.031 ball cutter to cut ribs with a 1/2 or 1 degree of draft, and the depth will vary from 1 to 1.75 inches. We also frequently use 0.02 ball cutters to cut ribs with 1 degree of draft as deep as 0.50 inch. The smallest tool we use is a 0.010 ball cutter with 1 degree of draft at a 0.25-inch depth.
High-speed spindles. We consider high-speed spindles our most important investment to date. They have enabled us to reduce costs, build a better tool and achieve quick turnaround, but most importantly they have changed our way of thinking. We have experienced a 30-percent decrease in cut times, which permits us to push more jobs through the machine. The higher spindle speeds also produce a better surface finish, which in turn reduces polishing time. Machine accuracy is also key, as it helps reduce the time it takes to complete final fitting of the parts that come off the machine.
Our main CNC machines have high-speed spindles that run to 42,000 rpm and employ a pallet system that integrates with the machine’s controller to exchange workpieces around the clock. This plays a vital role in our ability to hit lead times of three weeks or fewer, allowing a trade of inefficient (or interrupted) man hours for efficient (or uninterrupted) man hours. If a programmer can set up several pieces in the pallet changer at one time, he can spend the rest of his day uninterrupted at the computer, designing and programming the next job.
