Because of its extremely high hardness, cemented carbide can not be machined by conventional machining technologies like turning, milling or drilling. Cemented carbide has to be machined by grinding with diamond tools or by electrical discharge machining (EDM). CTD has an extensive and state of the art machine parc with machines and technologies specifically adapted to machining of cemented carbide.
Our technologies for cemented carbide.
CTD has high precision CNC cylindrical grinding machines that we use to grind cemented carbide up to 1500 mm length and 450 mm diameter.
CNC grinding machines for grinding of internal diameters with radiuses and profiles for special carbide from and cutting tools.
CTD has several rotary surface grinding machines. The grinding wheel is mounted on a vertical spindle and rotates parallel with the magnetic table. In this way a perfectly flat surface is obtained that is parallel with the back of the part. We can grind parts with diameters up 1500 mm.
We also have several horizontal spindle surface grinders.
Since cemented carbide can not be machined by milling or drilling, electrical discharge machining is the perfect technology to machine carbides. In the EDM process an electrical spark is created between an electrode and a work piece submerged in a dielectricum. This very carefully controlled electric spark produces an intense heat, melting a precisely localized area on the surface of the workpiece. The dielectricum act as coolant and flushes away the eroded metal particles.
A lot of experience however is required in order to avoid cracks in the work piece caused by internal stresses in the carbide. Special carbide grades have to be used in order to prevent corrosion during EDM. CTD can advise you in order to make the correct design and material choice.
Honing is an abrasive bore sizing and finishing process to improve cylindricity and surface finish of internal diameters after grinding. For cemented carbide, diamond tools have to be used with extra rigid mandrels. Typical applications are carbide liners for catalyst injection pumps.
Most of the dies for metal packaging are hand polished after grinding in order to reduce surface roughness. Cylindrical parts like punches, hyper compressor plungers and pump plungers are polished with a special diamond lapping machine to obtain roughnesses lower than 0.005µm Ra.
Since CTD manufactures many high precision parts, flatness is often a crucial parameter. With our lapping machines we obtain flatnesses of 2 light bands or less. Typical applications are found in cupper tooling, can ends, packing cups, ink scraper rings,…
Several tools and dies are hybrid with the wear resistant part or the cutting area made of cemented carbide with a steel body. CTD has CNC turning and milling machines to make the steel part of the tooling. These machines are also used to make hardened steel.
In hybrid tools the steel body has to be joined with the carbide insert. CTD has built up a lot of know-how in joining these two materials. We use following joining techniques:
HP-HVOF (High Pressure-High Velocity Oxygen Fuel) coatings are frequently used in applications that require very high wear resistance and where solid carbide can not be used because of the dimensions or cost.
The hardness of the carbide particles in the HP-HVOF coatings generate a wear resistance that is higher than hardchrome plating, electroless nickel plating, nitriding or ceramic plasma coatings. These HP-HVOF coatings can be applied on almost any steel, aluminium and nickel alloy parts.
During the HP-HVOF coating process, carbide particles are projected onto the surface at hypersonic velocity. Upon impact on the surface, the kinetic energy is transformed into heat. This creates coatings with exceptionally high bond strength and a density of almost 100%. The part temperature remains below 100°C during coating, avoiding structural changes.
Typical applications where HP-HVOF carbide coatings are used:
Nano-HVOF technology made it possible to apply HVOF-coatings on inside diameters starting from 80mm.
Typical applications of ID HVOF coatings are: