R E D C O™ U H M W
F A B R I C A T I O N & M A C H I N I N G R E C O M M E N D A T I O N S
Redco UHMW semi-finished material can be planed on conventional, high speed woodworking machines. Using sharp carbide-tipped blades, feed rates of up to 2mm/blade revolutions may be achieved.
High speed top milling machines are suitable for machining Redco UHMW semi-finished product. Special milling machines with horizontal, vertical, angle, and fly-cutting attachments make economic large-scale production of shaped articles possible. To ensure the most efficient removal of swarf, milling cutters with coarse pitch are recommended.
Redco UHMW semi-finished product can be drilled on drilling machines, and on lathes and milling machines. Twist drills are generally used but for larger diameters, pointed drills and circular cutters may also be used. With good swarf removal, local overheating can largely be avoided. If excessive heating should occur in high speed drilling, cooling may be achieved with compressed air, water, or cutting soluble oil.
Threads can be cut in Redco UHMW GUR semi-finished product with normal metal cutting tools, either on a lathe (recommended speed 20-30 rpm) or by hand. In principle, knuckle threads are preferred, but vee threads still possess adequate strength properties because of the high notched impact strength of the material.
Because of its high melt viscosity, friction and butt welding are the only practical methods for joining Redco UHMW by welding. In butt welding, the cleaned joint faces are held under slight contact pressure against the heated tool at 200-220°C until a layer of about 4mm deep has become plastic on both sides. The two parts are pressed closely together under an axial pressure of 10-20 bar (depending on the material thickness) until cold. If the material is greater in thickness than 30mm, axial pressures of 50 bar and above are required, and in such cases presses or special welding machines are frequently used.
The high solvent resistance of Redco UHMW restricts the range of suitable bonding agents. Two component contact adhesives provide only moderate joint strength values. An improvement in adhesion can be obtained by pretreating the surface. The usual methods are pretreatment with chromosulphuric acid, flaming with the oxidizing flame or an electrical method (spray discharge). Suitable equipment of various types is available.
Semi-finished material made from Redco UHMW may either be sawed by machine on band or circular saws used for wood, or by hand with sharp wood or metal saws with side-set teeth. Band saws are particularly suitable for large cross sections since they conduct the heat away and allow high cutting speeds.
The band saw blades may be 10-30mm wide and about 1-2mm thick with the circular pitch between 3 and 10mm. To prevent the saw blades from becoming jammed, the teeth must be set at approximately 0.5mm. When using circular saws, saw blades with a minimum setting 0.5mm are also preferred. Normal cutting speed for band saws is 1,000-2,000m/min and for circular saws, 3,000-4,000 m/min.
Machining is the principal method used to fabricate finished parts from Redco UHMW. When dimensional stability and distortion requirements of the finished product are most stringent (particularly under alternating thermal stress) annealing of the semi-finished product is recommended. Depending upon applications, annealing temperatures between 100 and 160°C can help relieve molded-in stresses. Semi-finished material made from Redco UHMW can be sawed, turned, planed, milled drilled, stamped and welded easily on woodworking or metalworking machines. The following general directions should be observed in these operations: To obtain surfaces of high quality, tools should always be sharp. For the most purposes, normal tool steel is satisfactory through many fabricators use special steels.
The optimum cutting speed is between 250 and 1,000 m/min. At lower cutting speeds cooling is not required, but at higher cutting speed range, water cooling or the use of soluble cutting oil is essential. In all cases, care must be taken to avoid heat build-up in the machining operation, so that the work piece does not smear the cutting edges. In milling and turning, the feed should not be too fast and the depth of the cut should be greater than 0.3mm.
Because semi-finished Redco UHMW products can be machined to a high quality finish on the lathe, economical mass production – utilizing high speed, light metal working machines – is feasible. Cutting speeds of up to 600 m/min may be used. Although care must be taken to remove all swarf, cooling is not usually necessary except for deep cuts, which require the use of compressed air or soluble cutting oil.