LASER CUTTING ACRYLIC AND MULTIPOLYMER SHEET
Lasers are user-friendly, powerful and cost effective tools for cutting acrylic and multipolymer sheet. Small complex parts, parts with clean, sharp inside corners and parts of any size that require cutting tolerances of less than .005-in./ft. can be laser cut and finished with a near flame-polished edge. Because of their extremely narrow kerf (.001-.020-in.) and multidirectonal, non-contaminated, dust-free cut, lasers are the premiere choice for critical applications. "Designing for and cutting with a laser offers many advantages and is as easy as working with other CNC machines," states John Korney, CYRO Industries Marketing Manager for Sheet Products, "Clear and complete instructions are available to fabricators for every step of production through our comprehensive technical service support staff, at our facility or theirs." Getting Ready - The three basic variables involved in laser cutting are the power of the laser, the feed rate, and the pulse rate. Each affect the quality of the cut and the resulting level of stress in the laser cut edges. These can all be adjusted to allow for different materials, material thickness, and edge finishes. A laser as small as 40 watts can be used for thickness up to 1/4", at a rate of approximately 20 inches/minute. With thicker sheet or faster feed rates (approx. 80 inches/minute), a larger laser is needed. Increasing the power of the laser at a given rate usually results in a glossier finish, but also increases the stress in the edge of the sheet. A faster feed rate with a more rapid pulse rate will generally result in an edge with lower stress and a less glossy surface. Put Your Finger on the Pulse - The pulse rate of a laser (measured in pulses per second - pps) is the rate at which a laser fires. The beam in actually a series of small bursts or pulses, not a continuous stream. It can be controlled two ways: proportionally to time or proportionally to d9stance traveled. While the pulse rate proportional to time is more common and easier to initially program, it usually results in burned inside corners. The x-y controller takes longer to cut a corner than a straight line so the corners (particularly the inside corners) may absorb too much energy, tend to melt, and become over-stressed. This is an important consideration when cutting notch sensitive materials like acrylic, multipolymer, and polycarbonate sheet. The solution: make the pulse rate proportional to distance traveled. As the controller slows the feed rate at corners, the pulse rate slows down, keeping constant the amount of energy emitted at a given point on the cut. Stress Reduction - Edge stress is always a consideration when laser cutting certain applications. Whenever acrylic is heated, the possibility of stress exists. This is at its greatest when only part of the sheet is heated. Edge stress can be reduced by adjusting the feed rate, pulse rate, and power, and can be further minimized by annealing the sheet after cutting. Lowering the power and slowing the pulse rate, combined with a rapid feed rate, reduces the amount of heat absorbed by the sheet. This reduces the amount of stress and the distance that the stress extends into the sheet. These conditions will result in a less glossy edge finish. For high gloss and low stress, adjust the above parameters to obtain the gloss desired, then anneal the part. To Mask or Not To Mask - Acrylic can be laser cut with the masking in place, but one should consider that the laser may fuse polyethylene masking to the edge of the sheet, making it difficult to remove. However, if there are a number of additional fabrication steps performed after cutting, the fused-on poly masking is recommended for laser cutting. New, specifically developed polyethylene maskings that provide ease of removal after laser cutting are now available. Lasers are high-powered sophisticated tools that are no more or less dangerous than any other piece of shop equipment. When properly installed and operated, lasers can provide the most accurate acrylic cut. CYRO also operates a Technical Center in Orange, CT, where highly skilled tech service engi- neers work closely with customers to recommend appropriate acrylic materials, as well as offer acrylic-related solutions. CYRO serves the North American Market with the aid of CYRO Canada, Inc., its Canadian subsidiary, headquartered in Mississauga, Ontario.

For more information, contact CYRO Industries Technical Service, 203-795-6081. Headquartered in Rockaway, NJ, CYRO Industries is one of the world's largest manufacturers of acrylic sheet, and acrylic molding and extrusion compounds. Formed in 1976, CYRO continues to expand existing markets and develop new uses for high-quality acrylic products.