I often hear machinists complain about the difficulties in milling acrylic. Their problems range from chipping, melting, “bird nesting” (the gathering of material around the cutting edge of the tool) and not being able to achieve clear, see-through surfaces and edges. Even seasoned manufacturers who have perfected the milling of acrylic, often through the use of diamond-coated tools, still complain about the cost of these expensive acrylic cutters. I’m always pleased to mention to these frustrated folks that DATRON has a solution that is amazingly efficient and surprisingly inexpensive. In fact, DATRON offers a complete line of solid carbide acrylic milling cutters – from single-flute end mills to form end mills in lots of different variations – all with polished flutes that make them superior to any other acrylic tools on the market.
The advantage of DATRON acrylic tools is two-fold. First, the tool geometry is designed with aggressively acute cutting angles that are much sharper than conventional cutting tools. Second, the flutes are polished. These two elements work synergistically to achieve virtually transparent acrylic milling results at a fraction of the cost of diamond-coated tools. But the cost savings is not solely based on the upfront purchase price. What our customers have found, is that they can eliminate secondary polishing applications because parts come off the machine with a glossy, transparent appearance.
Groove Milling in Acrylic
So at this point in my blog, some of you may be ready to simply download our Acrylic Cutting Tools Catalog. For others who are interested in learning about some acrylic milling strategies, I’d like to expound on this topic a bit more. While Groove milling in acrylic can be performed with any number of single-flute end mills and double-flute ball nose end mills, the strategies are perhaps too diverse for this blog. So, I’ll focus on more specialized milling processes.
How to Face Mill Acrylic or Plexiglas
In general, use tools with a high positive or high shear cutting geometry. Plastic material that is fixtured properly, either with pneumatic clamps or a vacuum chuck, can be face milled with high speeds and feeds. The DATRON double flute end mill with edge radius and polished flute is designed with an advanced face geometry and a polished flute for added transparency in machined acrylic parts. One face milling strategy that we have used employs a roughing pass with a 5mm single-flute end mill at 15,000 RPM and a 197 inch per minute feed rate (3.75mm XY infeed, 0.9 mm Z infeed) followed by a face milling/finishing pass with a 3mm double-flute ball nose (spherical) end mill at 40,000 RPM and a 118 inch per minute feed rate (0.08mm XY infeed, 0.02mm Z infeed). Of course, materials and applications vary so please call or email email@example.com for tool suggestions that address your specific application.
Edge Chamfering Acrylic
As I mentioned earlier, DATRON has a number of form end mills including tools for external radius milling, countersinking and chamfering. These come in a range of different cutting angles. Our countersinks for acrylics feature a large flutes for added chip room, as well as a 15° spiral to guarantee optimum chip evacuation. While the milling strategy would depend on your application and desired results, I can share the specifications for a recent sample that we machined. In this case we used a 3mm double-flute countersink tool, 90° at 15,000 RPM and a 20 inch per minute feed rate for edge chamfering in acrylic with 0.2mm XY infeed and 0.2mm Z infeed.
Drilling Threaded Holes in Acrylic (using helix drilling and thread milling)
One strategy that we’ve found to be effective for milling threaded holes in acrylic consists of a one-two punch – helix drilling first and thread milling second. As an example, we recently helix drilled an acrylic part with a 2mm single-flute end mill at 20,000 RPM and a feed rate of 10 inches per minute with 1.0mm Z infeed. Then we used a M2.5 – M4 thread mill at 25,000 RPM and a 31 inch per minute feed rate with 0.75mm Z infeed.
The acrylic milling strategies detailed above are associated with specific applications and the applications for milling acrylic are diverse. So, please feel free to contact us with your tooling questions at firstname.lastname@example.org or 603.672.8423.