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TMD Staff | March 3, 2014

Medical implant punch broaching

As orthopedic medical implants continue to improve, the manufacturing processes required to make these parts are adapting. Answering these changes is an expanded product line to include tools used for machining orthopedic implants.

Using a bone screw as an example, once machining of the outside contour of the titanium screw and the threads are completed, via a turning operation, the hole for a screwdriver is still a challenge. While this was once the domain of rotary broaching tools, pecking and shaping-type operations are becoming more popular.

The latest advancement is to use a standard rotary broach without the rotary broaching tool holder. The broach is locked into position using a tool holder or collet, and pecked or punched into the part’s pilot hole in small increments. If the chip accumulation begins to interfere with broaching, the broach can be removed, the chips drilled out, and then the broach can be brought back into the hole to resume work.

The broach material of choice is M-42 high-speed steel. Cobalt and higher hot hardness give the tool advantages compared to broach materials such as M-2, PM M-4, and PM T-15. TiN coatings are also popular upgrades to improve tool life.

Finally, the hexagon form is still the most popular. The hexagon removes a smaller amount of material in the corners of the pilot hole than a square or hexalobular form. However, sometimes broaching is unsuccessful due to excessive pressure, depth of hole, the need to broach full form without an oversize pilot hole, or due to large hex sizes

In this case, the punch broach can form a rectangle one-third the hexagon form. After broaching the first rectangle, the part (or possibly the broach) can be rotated 60° and broached again. After repeating one more time, a hexagon has been created without the force required to punch full form.

Polygon Solutions offers standard inch and metric size rotary broaches that can be adapted for this type of punch broaching. Broaches are available in 8mm shank or 0.500" shank, and can be made with various broach materials and coatings. Rotary broaches can also be made without the standard back taper to further strengthen the tool for punch broaching.

Polygon Solutions Inc.
www.polygonsolutions.com

 

Hydrodynamic bar feeder centers and feeds

Lexair’s Mini Rhinobar bar feeder automatically centers and feeds small-diameter bar stock to maximize the productivity of Swiss-style CNC screw machines and small fixed- or sliding-head lathes.

The single-tube bar feeder uses the hydrodynamic principle to center 6ft (1.8m) or 12ft (3.6m) bars as small as 0.04" (1mm) diameter quickly and easily. The bar stock is supported in an oil bath in the feed tube, and as the bar’s rotational speed increases, hydrodynamic forces move it toward the center of the tube and stabilize it, delivering shorter cycle times and superior workpiece finishes. Feed tubes ranging from 0.125" to 1.625" (3.2mm to 41.0mm) diameter are available in 0.125" (3.2mm) increments to minimize the bar-to-feed tube clearance and achieve maximum throughput.

The outer barrel is a precision-extruded aluminum tube, held in place with a single clamp to further minimize barrel vibration and control Z-axis motion. A removable pendant allows the operator to control the bar feeder remotely, while a positive pusher retention system ensures high efficiency operation with minimal labor.

Lexair Inc.
www.lexairinc.com

 

Pressure/vacuum pump with mobility, efficiency

The 2250 WOB-L piston pump is quiet, offers low vibration for smoother running across all speed curves, and features magnesium components that help limit the pump’s weight to just 2.5 lb. The brushless DC motor offers low power consumption for long battery life as well as variable speed from 1,000rpm to 3,000rpm, so airflow can be varied according to application requirements. An optional closed-looped controller allows motor speed to be maintained at a pre-set, constant rpm regardless of load or voltage fluctuations.

The 2250ZC35/24 has an open flow of 0.6cfm (17L/min), maximum pressure of 17psi (1.17 bar) and reaches a maximum vacuum of 22.0" Hg (745 mbar). The standard head configuration has 1/2" hosed barbed fittings, but is also available with 1/8"-28 BSPT threaded ports.

Features & benefits

  • Unique head/cylinder design
  • Oil-less operation
  • Permanently lubricated bearings
  • Stainless steel valves
  • High performance piston seal
  • Die-cast aluminum & magnesium alloy components
  • Thin-wall, hard-coated aluminum cylinder
  • Wetted parts treated for corrosion resistance
  • Dynamically balanced
  • Brushless DC motor
  • RoHS/REACH compliant

Thomas, A Gardner Denver Product
www.gd-thomas.com

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