Best Practices for Machining HYTAC® Plug-Assist Materials

Machining syntactic foam is not like machining other materials such as wood, aluminum or plastic. That’s why we have created guides to help toolmakers and thermoformers select the right tools and the right geometry for machining and cutting HYTAC® syntactic foams from CMT.

Properly machined, HYTAC® materials generally require minimal extra polish or surface preparation.  Following our guidelines will improve surface quality of the finished plug and aid consistency of plug performance.

Tools must be sharp to obtain a satisfactory surface finish when machining HYTAC® products. High helix geometry with a special point for upward chip flow, smooth sidewall and improved bottom finish is recommended. Dull cutters or incorrect geometries will result in poor surface conditions. High speed steel cutters are quickly dulled and are not suitable for use with syntactic foams. Solid carbide cutters are preferred due to the sharp edge and long life that may be obtained. Diamond coated tools may last longer, but are not required and have not been found to provide additional benefit in machining.

Once the tool is selected, dialing in an optimal feed rate on any CNC milling machine is done using the formula “Feed Rate = Chip Load x Spindle RPM x # of flutes.”  Chip load is the measure of thickness removed by each cutting edge (flute) in a single rotation.  The intended chip load for milling tools should be available from your tool supplier.  Optimal speeds, feeds and depth of cut when turning are listed on our turning guide.

If you have a new  job or just some questions about plug machining or polishing, contact us today

CMT Materials, Inc. To Expand in Europe with New Facility in Netherlands


CMT Materials, Inc. To Expand in Europe with New Facility in Netherlands

May 14, 2013 – Attleboro, MA

CMT Materials, Inc. will open a new location in The Netherlands this year. The new facility will include full inventory, sales and customer service personnel, and cut-to-size services.  “By setting up a physical presence that is centrally located in Europe, we will be better able to serve our European customer base,” says Terrence Woldorf, General Manager. “We recognize that our customers need quick turnaround times for many new thermoforming projects. This new location will allow users to get our HYTAC® products within 2-3 days.”

The new facility will provide same-day shipping within Europe, reducing lead times and shipping costs. The full inventory of HYTAC® syntactic foam products will be available in all sizes of rods and sheets. The company expects to begin shipping orders directly from the new facility on September 1. Details will be sent directly to customers over the summer.

About CMT Materials

CMT Materials is the acknowledged leader in the design and development of syntactic foams for use as plug-assist materials. The innovative HYTAC® family of products has been designed specifically for the thermoforming industry.  Plug assist technology allows plastics processors to reduce starting gauge, reduce cycle times and improve material distribution. CMT Materials will be promoting its new line of XTL thermoplastic syntactic foam at several major tradeshows this year including Chinaplas in May, SPE Thermoforming Conference in September and K in October. For more information, visit

Best Practice: Polishing HYTAC® Materials

HYTAC® materials may be polished to a smooth surface finish condition. A properly polished plug will reduce scratching and aid in plug life/reduce sheet stick to the plug.

Syntactic foams are a variety of combinations of epoxy, plastic and hollow glass microspheres.  The same properties that make these foams the top choice for plug assist can create challenges in polishing.  The goal of sanding is to smooth microscopic peaks to eliminate potential scratching, prepare the plug for use and to modify surface area for different frictional performance.

Thermoset Epoxy Syntactic foams (HYTAC-W, WF, WFT, FLX, FLXT and C1R) may be wet or dry sanded using random motion. When following CMT machining/turning guidelines, most users find 220 grit sandpaper provides the appropriate roughness as a starting point. Finer and finer grits may be used for finish rubs until desired the desired surface finish is achieved.

Thermoplastic Syntactic foams (B1X and XTL) may also be polished, but a good starting surface is critical. A surface that has been damaged in the machining process cannot be fixed by sanding. After following CMT machining/turning guidelines, most users find 400 or 600 grit sandpaper provides the appropriate starting point, though many move up to 1200 and 1500 for an ultra-smooth finish. HYTAC® B1X should always be dry sanded. Download our polishing guide for details.

CMT continues to work with our partners in industry and academia to develop new techniques for polishing HYTAC®. If you have a tip to share, please let us know!