- THE MAGAZINE
Computer-driven machine tools, like computerized numerical control (CNC) machining, ultrasonic machining and laser cutting technologies, have revolutionized the way precision components are machined. However, these advanced equipment systems often come with high price tags, time-consuming setup requirements and increased labor costs.
A new alternative has recently been developed. Called the Photo-Machining Process (PMP),* it provides a lower cost alternative to conventional machining for many applications. PMP can selectively remove material or coatings from a variety of dense, hard or brittle materials, and it can also scribe or mark metal surfaces for labeling identification numbers and logos with pinpoint accuracy.
In addition, PMP can be used to roughen surfaces to promote better adhesion between adjoining parts. This process can reduce setup and machine time, as well as operator skill level. It also benefits ceramic engineers striving for improvements in design capabilities.
*Developed by IKONICS Corp., Duluth, Minn.
Process SpecificsPMP combines the precision and accuracy of a photoresist with abrasive etching to selectively remove materials. Key steps include the photoresist imaging operation and the abrasive etching process. First, the design is printed on a transparency-like film with a standard inkjet or laser printer. This film becomes the working tool, or phototool, for the photoresist masking operation.
The phototool allows the transfer of the desired pattern onto the photoresist mask by limiting the ultraviolet (UV) exposure to the selected pattern (see Figure 1). An abrasive-resistant mask that changes physical properties when exposed to UV light, the photoresist mask does just what its name suggests-it resists or repels the abrasive to protect the surface being machined.
Proprietary photoresist technology is the key to PMP. Photoresist technology has been around for many years, particularly in the electronics and decorative etching industries. The films used in PMP have vinyl or rubber-like properties that repel the impact of abrasives, allowing them to survive aggressive etching by fine particulates in a precision sandblasting environment.
CapabilitiesBrittle materials like ceramics are notoriously difficult to machine because of their high level of hardness and propensity to chip or crack. The benefits realized with PMP vary depending on the size and type of patterns or features that are required. However, detailed patterns and shapes, such as channels, surface pads, blind holes and/or markings, can be created with high accuracy and repeatability, with relatively deep etching on lower density materials (see Figure 4). With film resolution of up to 50 µm (.002 in.), fine detail machining is easy to achieve.
PMP is effective for drilling holes in thin wafer materials, and the process enables hole array patterns to be drilled quickly. All holes are made simultaneously, which is much faster than the one-at-a-time laser or ultrasonic drilling methods. Other uses include individually and indelibly engraving hard-to-mark parts, texturing surfaces for subsequent coatings or to promote adhesive bonds, and selectively removing coatings from surfaces. Where etch depth control is required, an automated etching system can be used to maintain 50 µm (.002 in.) depth variation over a 50 cm (20 in.) length.
Although metals and plastics can be surface engraved or marked, they cannot be machined deeply with PMP due to their inherently ductile nature. However, PMP does work well to selectively remove thin layers (<.005 in.) of these materials, such as copper-clad substrates or metal encapsulated ceramics.
Many of these operations can be accomplished through traditional machining techniques, but PMP often reduces setup and production times. In fact, PMP provides several advantages over conventional machining methods when modifying hard/brittle surfaces or when selectively removing coatings from these surfaces. PMP enables the removal of large amounts of material quickly, with little need, if any, for special tooling fixtures or jigs. The system requires no expensive cutting tools to wear out or replace, and the reduction in localized heat eliminates the need for coolants. PMP also has a reduced tendency for "chipped" edges, causes no pitting or stray markings, and does not require a subsequent deburring step.
Due to the buildup of abrasive in the etched cavity, PMP produces a tapered side wall as the etch deepens. This buildup causes the sides of the feature to etch more slowly than the center, leaving the bottom of the etch area with a slight radius.
Photo FinishPMP combines proprietary photoresists with fine particulate abrasive etching to create a variety of precisely machined parts. The process is simple, quick and less expensive than many conventional machining methods. While PMP does not entirely displace the need for conventional machining, it opens up opportunities as an excellent alternative in a wide range of applications.
For additional information regarding PMP, contact IKONICS Corp. at 4832 Grand Ave., Duluth, MN 55807; (800) 643-1037; fax (218) 628-2064; or visit www.ikonicsindustrial.com.
SIDEBAR: PMP PossibilitiesBelow is a partial list of materials and coatings that have been tested with PMP:
- Alumina Silicate
- Aluminum Nitride
- Anodized Aluminum
- Boron Carbide
- Carbon Fiber
- Ceramic Composites
- Plated/Painted Materials
- Silicon Carbide
- Silicon Nitride
- Titanium Nitride