The Perfect Hole

This process is based on more than 45 years of technical experience in the field of high precision machining (finishing) of small bores and diameters. It covers the following elements of this process: 1) diameter, 2) bore sizing, 3) cylindricity and 4) surface finish. These are superfinishing processes on bores of 0.002" thru 0.200" with lengths of up to 12", and the O.D. grinding of diameters of 0.020" thru 0.315" with lengths of up to 35". Tolerances of ± one micron are achievable on a variety of materials.

This process requires that a pre-existing hole be provided initially as this process does not "drill" holes but rather completes them to exacting tolerances and finishes required.

Facts and explanations concerning Wire-DSM process are:

Tolerances – Achievable tolerances depend on two key factors: the material being machined plus productivity and quality trade-offs. The following can be expected:

• diameter ± 1 micron (0.000040")
• roundness ± .5 microns (0.000020")
• cylindricity ± .5 microns (0.000020")
• surface finish RA 0.025

Note that these tolerances are based on a broad range of materials. Not all materials allow tolerances this close because of their hardness and make-up.

Stock Removal – Wire-DSM is a highly accurate efficient process. It can easily remove stock amounts of 5 microns (0.0002") up to 150 microns (0.006"). This range is attainable over the entire length of the stock to be machined.

Materials & Shapes – Various materials may be machined using this process. These may include soft materials to materials with very hard and brittle characteristics. These would include tungsten carbide, ceramic, ruby, and PCD (polycrystalline diamond). Continuing development in fixturing also allows the clamping of tubular parts with an O.D. of up to 20 mm (.080") and overall length of some 300mm (12"). Various other non-std. parts can be qualified by special request.

Process Basics – Parts can be machined in either single or batch quantities depending on part width.

The bore sizing includes the use of a high precision wire as a tool for hole sizing. These wires can have a length of 10 to 20 meters (40" – 80"). The process is unique in that the part is rotated around the wire versus the conventional method of rotating a tool within the part. The machines used in this process are able to maintain process stability and control throughout the production of the parts.

Application examples

The following examples are medical applications that have been completed using the Wire-DSM process.

Stents –- these devices are used to expand restricted coronary vessels. Once implanted these devices expand and give support to existing vessels.

Stainless Steel Mini-Tubes – small

tubes made from stainless have various uses in the medical field including gene/bio-chemistry applications, lab instrument components, manufacturing process for implants.

Dental implants – titanium is widely used in surgical applications. Characteristics of this material make it suitable for body implants in the field of dentistry and reconstruction of body parts. This particular part requires a mirror surface finish and is used to position and hold the prosthesis as well as protect the nerves of the teeth. The relatively long length comes from the fact they are semi-finished products.

Limitations – Wire-DSM offers machining solutions with very few limitations. The thin wall thicknesses were not a critical factor as all parts were cast in the arbor before placement in the machine for sizing. This prevents the tubing walls from expanding while machining is taking place which in turn gives the bore sizing operation the opportunity to produce micron size tolerances on the I.D. These same tolerances are also allowed when using the O.D. grinder to produce cylindrical parts which must be concentric to the bore.

The examples covered here are but a few of the applications that were performed using Schlafli machines for boring and O.D. finish sizing technique (Wire-DSM).

Operations were performed using Schlafli Fine Hone and Acuwire-L machines.

O.D. operations were completed using the Schlafli Precigrind 2000 machine.