Single Point
Diamond Turning

Welch Mechanical Designs, LLC (WMD, LLC) provides optomechancial engineering services and original equipment manufacturing (OEM) to customers. WMD, LLC has Single Point Diamond Turning (SPDT) capabilities for its OEM. WMD, LLC also offers this contract SPDT manufacturing service for manufacturing challenging parts and surfaces in a timely or cost effective way.

Equipment

Our Ametek — Precitech Nanoform 700 diamond turning machine enables us to process large parts (up to 700mm diameter). Our SPDT machine also has Slow Tool Servo (STS) capability for cutting free form surfaces. In STS mode, the cutting tool's position is determined as a function of radius and spindle angle. Off-axis optics up to 700mm diameter can be processed. Typically off-axis optic diameters are limited to 1/2 of the swing diameter because of the need to cut at least two parts offset from the SPDT machine axis using a common fixture. Using STS, we can also create off-axis optics with an offset distance much larger than the swing radius of the machine — which is the traditional limit.

Materials

While large optics are our strength, we routinely cut small mirrors and lenses as small as 1mm diameter. Challenging crystalline materials like ZnSe, Ge and BaF2 are routinely processed. Surface figure values of 1/10-wave P-V on 50mm diameter parts with 30 Angstrom RMS micro roughness values are common.

Inspection Packages

An inspection package can be provided if requested by the customer. These packages can consist of written visual inspection reports, dimensional inspection, contact profilometry plots, individual surface and assembled system wavefront interferograms, and surface microroughness interferograms at various magnifications. Our surface inspection equipment is regularly calibrated using NIST traceable standards.

Our Unique SPDT Services

WMD, LLC is different from other small companies providing contract SPDT services. WMD, LLC maintains a highly-skilled engineering team that can assist customers with developing entire designs as well as optimize their existing designs' use of the SPDT process. Come to us with individual surfaces to be diamond turned, SPDT parts that require substrate machining, and complete optical systems like telescopes, beam expanders, and spectrometers.

Our engineering backgrounds help us understand the processes that affect not only the SPDT surface but the entire system. For example, our high-durability, reflective metallic coatings applied to SPDT surfaces. Metallic coatings applied to SPDT surfaces and subsequently exposed to harsh environments frequently fail earlier than similar coatings applied to traditional polished glass or ceramic optical surfaces. Through continuous efforts to improve our processes, we have applied protected silver coatings to SPDT surfaces that will survive the accelerated life testings described in Military Specification MIL-M-13508.

Our engineers and technicians understand the importance of metrology. While SPDT technology allows optical surfaces previously only dreamed of to be cut, the old saying, “...if you cannot inspect it, you cannot make it”, is still as true as always.

Many small SPDT suppliers have minimal inspection equipment. WMD, LLC has on-machine contact profilometry also known as Ultracomp for measurement of aspheric and any other surface cut. We have a Zygo GPI XP/D Fizeau interferometer along with various transmission spheres, transmission flats, two 60cm x 60cm flat reference mirrors for large part testing, and the ability to expend the interferometer aperture to 45cm for certain tests. Our Zygo NewView600 white light interferometer can measure surface features below 1nm in height and is used to provide quantitative surface roughness data. This piece of equipment eliminates the need to use common qualitative, and subjective, descriptions for surface roughness such as “color” or “orange peel”.