ROUTING: Routing Polyethylene
Polyethylene is a widely utilized plastic in the thermoforming
and sheet fabrication industry. These
manufacturing processes involve secondary routing
operations to produce the end product. Part of the
popularity of this material can be attributed to how easily
it is routed when proper cutting
tools and procedures are a part
of the manufacturing process.
Plastic is generally classified as
soft or hard for routing purposes.
Polyethylene falls on the soft
side of the equation and mostly
utilizes “O” flute geometry routing
These tools are available
in straight and spiral configurations
with single- and double-edge
how the chip
needs to be
has a neutral
move chips in
an upward or
flutes, while the
should rely on
When the part is held solidly, these tooling choices accommodate
the removal of chip without adversely moving the
part being routed. Most “O” flutes in the marketplace are
single-edge because they provide increased
capability without sacrificing edge finish.
Double-edge tools usually become a part of the routing
process when more refined edge finish is required or tool
balance is an issue.
Beside the type of tool selection, tool diameter is always
a critical issue. Plastic fabricators, particularly sign makers,
tend to use small tool diameters because of small radii and
material waste considerations. However, with a softer
material like polyethylene, larger tool diameters can play a
positive role. The larger the diameter, the more flute space
is available to remove gummy chips. Also, the larger diameter
provides more stability and increased benefits fits in the area of better edge finish. Larger diameters are beneficial,
but the end-user should be cautious in this area, as
well. Single-edge tools should never be applied in a CNC
machine in diameters over 3/8 of an inch. These tools in
larger sizes can create out-of-balance issues. When larger
than 3/8 is required, double-edge tools should be utilized.
These tool selection ideas are general in nature and provide
a good starting point for decision making in this area.
In order to enhance this process, the end user can visit
www.plasticrouting.com or any number of tooling or manufacturing
sites to get specific tool recommendations on
polyethylene and a variety of other plastic materials.
Polyethylene, like most soft plastics, will produce a curled
chip. The range of chipload to produce and maintain a
properly curled chip is somewhere between .004 and .009.
Chipload is actually the thickness of the chip, and is a function
of the feed rate and the spindle speed of the CNC routing
machine. The size of the chip has a direct correlation on
the edge finish and the ability to adequately remove soft
chips (See Figure 5). When chiploads get too far outside the
recommended range, the tool or knife marks are more
prevalent, thus adversely affecting edge finish (See Figure
6). Conversely, when chiploads become too small, the ability
to clear chips without melting becomes problematic.
Consequently, it is imperative to maintain a fairly narrow
range of chipload to maintain both of these parameters.
Polyethylene is a mainstay in the plastic fabrication
industry. It is one of the easiest plastics to cut, but only
when the proper tool selections and chipload requirements
For more information, click on the author biography at the top of the page.