Page 34 - MetalForming April 2020

Fabrication: Laser Cut Metal Parts
complexity, which can increase produc- tion cost.
3Avoid crowding the parts nest with repetitive parts. When preparing a nest for cutting, a fabricator or experienced LBC service provider should arrange, or nest, the part to optimize efficiency and reduce mate- rial waste. Designers at manufacturing companies often are tempted to “pre- nest” their sheet, thinking that it will quicken the production process. How- ever, this practice often can complicate and impede the cutting process.
4Turn text into shapes.
If the vector design includes active
text boxes, the cutting machine won’t be
able to properly process the cut. To
include text with the cut, convert active
text boxes into shapes or outlines, a sim-
ple process using the referenced design
software.
Not sure if text boxes are active? Hover the cursor over the text, and convert any editable text into a shape.
5Don’t compensate for laser kerf
or beam width.
Beam diameter for most lasers ranges from 0.005 to 0.008 in., depending on workpiece material thickness. As the laser beam makes its cuts, material burns away and creates sac- rificial space called kerf.
It’s important, when sending a part nest to a laser cutting vendor, to not adjust the design to compensate for kerf. Rather, let the vendor use its own, internal software to place the beam along the design in order to deliver the specified part dimensions. Design the parts exactly to the size you desire, and allow the LBC shop to handle the rest by offsetting the beam accordingly.
6Space parts based on material thickness. Laser cutting machines can’t pass over the same place twice without creating accuracy issues. Therefore, take care to avoid overlapping or intersecting lines when designing 2D shapes. Separate each object placed on the nest for cutting according to the material thickness, to ensure a reli- abile cutting process. More complex and overlapping designs can be combined during assembly.
Today’s lasers and sensors allow nesting wth distance between cut edges of as little as one-fourth of the material thickness. At SendCutSend, we typically space parts at least 1X the material thickness apart.
7Connect all shapes
to the primary design.
Parts separated from the main nest, called orphan parts, will be lost if not bridged. The only exception to this rule is when the nest includes holes, which the laser can complete separately from the primary cut. The rest of the design should be bridged so that the laser can cut it in its entirety without losing parts.
8Carefully select the material type based on the application.
Choice of material will determine the detail, durability, weight and appearance of the laser cut metal parts. After identi- fying the most critical material features, narrow down the list of available mate- rials, and select one. Common materials cut with lasers include aluminum and titanium alloys, carbon and stainless steels, and copper alloys including brass.
9Keep maximum machine capacity in mind.
In addition to selecting the right material for the job, also carefully consider the capacity of the LBC machines available, and the available sheet metal sizes. For example, the most cost-effective designs will cut on sheets 48 by 120 in., which come straight from the mill. Laser cutting thickness capacity typically ranges from approximately 0.010 to 1 in. (and even thicker for the highest power lasers).
10Ensure interior geometry is at least 1x material thickness.
Holes or interior geometry smaller than the base-material thickness can be challenging to accurately and repeatedly laser cut, because the cutting process starts with a pierce that requires a certain diameter allowance.
11Create nest designs at full scale.
To ensure an accurate cut, design the vector file at a 1:1 scale with the physical part being manufactured. For example, to cut a 40 by 40-in. part, create the design file at 40 by 40
in. before sending it to a laser cutting vendor.
32 MetalForming/April 2020
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Separate each object placed on the nest for cutting according to the material thickness, to ensure a reliabile cutting process.
12
Complete all shapes and objects.
An LBC machine won’t be able to effectively cut an incom- plete shape. Cutting open or unfinished objects that are not self-contained will be distorted or look significantly different from the original design concept. So, ensure that all of the parts in the nest are self-contained and complete.