Frequently Asked Questions in the Routing of Plastics #1
Over the past year and a half, several questions about plastic routing have continued to come up. Some are material-specific, while others apply across multiple plastics. The following summarizes several of the most frequently asked questions related to CNC routing of plastics.
What Can Be Done to Improve the Finish on a Cut Part?
Vary feed rates and spindle speed, and use solid carbide tooling with geometry specific to the material being cut.
For soft plastics, use single-edge solid carbide straight or spiral plastic O-flute tools. For rigid plastics, use double-edge solid carbide straight or spiral tools with standard or O-flute plastic geometry.
What Causes Material to Reweld to the Part or Tool?
Heat is the primary cause of welding. Avoid dwelling in the cut by using better programming techniques, such as exit-ramp corners instead of stop-and-go corners and ramp-in entry rather than straight-entry boring.
Increasing feed rate and/or decreasing spindle speed can also help reduce heat buildup and limit rewelding.
How Can Burns or Clouding of Acrylic Be Avoided in Hand or Air Routing?
Use two tools: one to rough out the shape and another to perform the finishing pass. Both tools should be solid carbide.
The roughing tool can be a straight or spiral tool designed for acrylic routing. The first cut should leave approximately a 1/8-inch margin for the second pass. The finishing pass should then be made with a three-flute acrylic finishing tool.
What Is the Solution to Stacked Sheet Routing When the Sheets Weld Together?
In some applications, spiral tooling can accentuate the problem. A solid carbide straight O-flute is recommended, either single- or double-edge depending on feed rate and spindle speed.
When the material is fixtured properly, the individual sheets can act as natural chip breakers.
What Is the Solution to Small Parts Moving When Cut From Vacuum-Held Sheet Goods?
Cutting forces may overcome the vacuum hold-down. Reduce the cutter diameter to approximately the same thickness as the material being cut—for example, a 1/8-inch diameter tool for 1/8-inch material.
Straight or slow-helix downcut O-flute solid carbide tools can also help control the part.
What Can Improve Finish on Plastic Window and Door Parts?
If finish is a problem, try single- or double-edge solid carbide straight O-flute tools instead of the recommended high-speed steel spirals.
What Tool Can a Small Sign Shop Use for Many Different Plastics?
Solid carbide slow-helix or straight O-flute tools can cut a broad range of thermoplastic materials.
What Is the Best Tool for Cutting Fiberglass-Reinforced Parts?
Trimming fiberglass can be accomplished with standard solid carbide FGR, or fiberglass-router diamond-cut, tooling in both CNC and air-router applications.
Routing parts in a CNC environment is best performed with chipbreaker-type solid carbide tools. Routing fiberglass by hand is best performed with straight-flute carbide-tipped tools, which provide additional cutter-body strength.
What Is the Difference Between Routing Plastic and Wood?
Plastic materials vary in consistency and abrasiveness from soft thermoplastics to abrasive reinforced thermosets, just as wood varies from soft pine to abrasive teak or MDF.
One tool will not cut all plastic materials well, just as one tool will not cut all wood materials well. Plastics also have unique physical properties that require specific cutting geometry for optimum finish.
It is the exception rather than the rule for one tool to cut both plastic and wood or wood composites equally well.