Frequently Asked Questions
- What tolerances can Insaco hold?
- Does Insaco sell ceramic (or glass or sapphire) in bulk?
- Can sapphire be cast or molded to final shape?
- How does crystal orientation affect sapphire properties?
- How do I know which ceramic to specify?
- How can I get ceramic pieces for less cost?
- Does Insaco work on prototype quantities?
- What materials does Insaco machine?
- How can two ceramic parts be joined together?
- Can Insaco fabricate ceramic/sapphire spheres or balls?
- Can holes be tapped in ceramics?
- What considerations apply to designing piston/sleeve assemblies?
- Designing for machinability
What tolerances can Insaco hold?
The nature of diamond grinding on ultra hard materials translates into tight tolerances being routinely achieved. The actual limits to the attained precision depend on variables like the machine tool used, the general shape and size of the part, and the sequence of operations needed to complete the task. Although our shop standard for machining is +/-0.004″, we generally halve this on the first pass of operations. Secondary operations can further narrow this to +/-0.0001″. Our flat lapping operations can best be recorded in millionths of an inch. We have done bearing parts that have tolerance in the millionths of an inch. We welcome discussions about desired tolerances and often provide constructive advice regarding practical limitations and cost considerations.
Does Insaco sell ceramic (or glass or sapphire) in bulk?
No, we are a machining company. We don’t produce any materials, nor do we stock for resale. We do buy materials from which to fabricate parts finished to customer specification.
Can sapphire be cast or molded to final shape?
No. Sapphire cannot be molded like some other materials. Industrial sapphire is created by melting aluminum oxide (Al2O3) at 2040°C and then encouraging crystal growth with a seed and careful control of the environment. Growers have developed several unique methods for growth, with varying levels of resultant quality, size, and cost. The EFG or Stephanov methods allow the directed growth of shapes like ribbon, or even tubes, however there are many limitations to what can be done. The Czochralski, HEM, or Kiropolous methods allow the highest optical quality sapphire, but the result is a rod like “blob” of crystal called a boule, that must be machined into usable shapes and sizes.
How does crystal orientation affect sapphire properties?
Sapphire is an anisotropic, rhombohedral crystal. Anisotropic means that the material exhibits physical properties differently depending on the material orientation. Sapphire can be harder to machine along one axis than another. For most applications this is unimportant, however should be considered. Sapphire is “birefringent” which is a refractive feature that offsets wave transmission up to 0.8% at right angles to the optic axis. Birefringence is eliminated along the optic or C-axis. For certain applications, C-axis sapphire should therefore be specified to avoid birefringence concerns.
How do I know which ceramic to specify?
Insaco does not produce or sell ceramic materials themselves. For this reason, we can offer advice without bias. Alumina is the most common technical ceramic and hence most readily available and usually lowest cost. Properties of alumina are exceptional in many ways when compared to conventional materials like steel. If the use conditions exceed these properties, other technical ceramics such as Silicon Carbide or Zirconia may be better choices even though less available or more difficult to fabricate. Please see our materials webpage for more information on the materials we frequently machine.
How can I get ceramic pieces for less cost?
Most ceramics can be formed (cast, molded, pressed) in a soft state with features in place. This is not unlike forming a red brick as used in building a house but before it gets kiln fired. Once fired, the ceramic shrinks considerably which creates distortion and allows tolerances typically of only 2% (or .003” whichever larger). If these tolerances are acceptable for the end use, like a brick for your house, then the cost can be low. If tighter tolerance is required, then additional work like diamond grinding is required. So, careful consideration of tolerances for your application may avoid the need for and expense of post-fire grinding. Insaco’s many years of experience will allow us to work with the customer and help design the part so that it is the easiest and least expensive to fabricate.
Does Insaco work on prototype quantities?
Insaco welcomes small lot or even single piece orders as well as production series. Obviously the single piece prices will be higher because set-up and handling costs can’t be distributed over a larger base. Small quantities may also preclude use of larger, more automated machine tools. But big orders usually start with small orders, and small orders are always welcome.
What materials does Insaco machine?
Insaco’s first business in 1947 was fabricating sapphire parts (i.e. phonograph needles). This work was all accomplished through a diamond grinding process, which is extremely accurate, though painstaking, and the only practical method to machine complex shapes using this crystal material. Once we established our expertise working with extremely hard, yet fragile materials we began accepting work fabricating other extremely hard technical ceramic materials such as alumina, zirconia, silicon carbide, among others, as well as glass that included quartz and fused silica. Insaco does not machine metals or plastics simply because they are too soft to be machined effectively with our fine diamond wheels. Please visit our materials webpage for a list of materials we have worked on in the past with links to specific material properties.
How can two ceramic parts be joined together?
There are several methods to join ceramic parts, but the final application may pose limits. Simplest to consider is an epoxy glue. Although straightforward, epoxies cannot survive high temperatures and will outgas in vacuum environments. Press-fitting a steel thread form into a precision bore and then bolting two ceramic parts can be successful in some applications. Ceramics can also be vacuum metallized and then separately furnace brazed into permanent assemblies.
Can Insaco fabricate ceramic/sapphire spheres or balls?
No, but we have sub-contractors who have the highly specialized equipment and experience to do that.
Can holes be tapped in ceramics?
Tapping a thread into metal is performed with a single-point tool. Technical ceramics are processed by diamond grinding and this technology does not allow fabrication of an internal thread. So Insaco can only offer threaded holes in softer machinable ceramics like Macor.
What considerations apply to designing piston/sleeve assemblies?
Insaco has the capability to fabricate ceramic piston rods and mating sleeves to extremely tight tolerance. Tolerance on straightness is key as well as diameters of course since a curved rod will jam in a mating tube. We recommend setting a nominal diameter target and a very tight cylindricity/straightness and gap tolerance for the pair to assure consistent performance. Although we can achieve tighter, gap tolerance of one to two microns in series production has been shown useful for pumping liquids.
Designing for machinability
Each feature shown on a part drawing will require some level of fixturing, set-up, run time and inspection to achieve. Sometimes a designer will include a nice external radius on an edge without great thought. But this feature can drive costs where noting “edge-break for handling” for example is much simpler if a true radius is not key to the design. Or sometimes larger parts might best be designed as assemblies where the key wear area is ceramic but the supporting bulk of the part can be less expensively designed in steel. Insaco engineers are happy to review customer designs and identify cost driving features for discussion. If the design process is not yet final, cost reductions without harming part application may be possible.