Friday, September 30, 2011

The Trend Towards Composite Materials

By: Gary Meyers, Product Manager-Milling

Today more manufacturers are opting for stronger, lighter composite materials—broadly known as reinforced plastics—instead of steel to reduce the weight of the parts they produce, especially within the aerospace, automotive and medical industries.

After all, lighter parts bring more fuel economy to aircrafts and vehicles, as well as effectively produce delicate prosthetic devices for patients. And while composite materials are more expensive than steel, prices are sure to drop with increased usage.

When it comes to composite materials with carbon fiber reinforced polymers, polymer matrix composites are the most commonly used. The material uses a polymer-based resin as the matrix and a variety of fibers, including glass, carbon and aramid, for reinforcement. Stacked or “sandwich” materials used for structural parts or panels typically combine aluminum or titanium with carbon fiber. Filler material can take on a layered or honeycombed shape and be ferrous or non-ferrous.

It’s important to remember, however, the consistency of composite material can vary depending on the application. But rest assured the material is strong and CVD coated diamond cutters and PCD inserts are the best choice to machine these materials because of their high-wear resistance.

Seco brings years of experience to composite machining, with dedicated tooling for the rapidly growing use of this material. Specific products include the Jabro JC800 line of solid carbide endmills, which features the JC840, JC850, JC860, JC870, JC871 and JC880.

JC840: A double helix cutter that eliminates delamination in stacked materials, as well as provides improved workpiece quality and process reliability that helps reduce scrap and costly rework.

JC850: A 4-flute ball nose cutter with a low helix design for 3D applications.

JC860: A honeycomb router ideal for side milling and slotting in honeycomb material. It incorporates a left-hand helix, creating downward axial cutting forces for the prevention of part lifting and delamination. Additionally, the JC860 has chip splitters that break the material into smaller pieces, reducing the risk of material clogging the flutes. 

JC870 and JC871: Available in coated and uncoated varieties, these multi-flute routers operate in a variety of materials and applications. The JC870 is an end-cutting tool that routes out pockets and recesses using circular interpolation, while the JC871 uses a multi-tooth end, making it ideal for side milling operations when machining close to the machine bed or fixture. Both feature a crosscut design that reduces the cutting forces on a workpiece.

JC880: A 4-flute endmill that provides excellent metal removal rate. It features center-cutting front teeth, making it very flexible in pocketing operations. With its low helix angle, the cutter also generates low cutting forces that reduce the risk of lifting the workpiece during the machining process.

If you’re unfamiliar with machining composite materials, there are some things you should know. While composite materials can run on the same machines as metal, the tooling is different. Once a cutting edge hits a composite workpiece, material removal comes across as shattering or splintering as opposed to the chip formation that occurs in metal machining. However, like in metal cutting, energy becomes heat in composite machining. Without chips carrying the heat away, the buildup can melt and damage the matrix. Therefore, tooling for composite materials features high positive rake angles to help eliminate heat and provide sufficient clearance angles to prevent the edge from rubbing the material during the cut. Because coolant may not be permissible in certain applications, the tool and tool path are the only variables that can reduce heat buildup.

The type of toolholder you use also plays an important role in composite machining. You should make sure particles are unable to penetrate the toolholder and collet chuck. Such fragments can cause damage by jamming screw threads and significantly increasing wear. Furthermore, workpiece geometry is an important consideration because complicated designs can cause clearance issues between the toolholder and the part. Finally, your toolholder should be a precise solution capable of running high speeds with low runout. Shrinkfit toolholders are the best option because they have a sealed interface between the tool and holder, provide high accessibility to the workpiece and run fast with low runout. In fact, Seco’s EPB shrinkfit technology provides a less than 3 micron runout, even at 3 x D.

Hopefully, this information is helpful to those of you thinking about following the composite materials trend. If you would like more information on this topic, feel free to send me an email or get in touch with your local Seco sales representative. We have a lot of experience in this area and are here to help you achieve a more lucrative business.

About the Author
At Seco, Gary works closely with product development, marketing and field sales to effectively launch new milling products into the market as well as ensure their long-term success. Outside of work, he enjoys outdoor activities, which includes running 5k and 10k races in the summer and downhill skiing in the winter.

No comments:

Post a Comment