Invar parts and prototypes: Custom CNC Machining
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Invar: custom CNC machining

AC Manufacturing is a complete cnc machine shop capable of machining parts to customer specification (conventional and 5 axis machining). We can machine to print and accept the most common file formats including: .dwg .dxf .iges .step .sat as well as .pdf files. If you don't see your file format here let us know. Please send us files to: We can accept both small and large run jobs of custom machined parts.

We specialize in manufacturing cnc precision machined parts using 5 axis machines. With over two generations of knowledge and experience, our team is able to produce parts that require innovative tooling and fixturing in a timely manner with competitive price. With a full range of modern equipment, we deliver one-stop shopping for precision machined components, from small quantities to large volume.

We provide Turning and Milling, 3 axis , 3+2 axis & continuous 5 axis machining).

We accept both small and large run jobs, Minimum quantity for order is 1.
Short lead times are often available 2-3 days.
Standard lead time is 2 weeks.

invar cnc machining Invar alloy (UNS K93600), a 36% nickel-iron alloy known for its unique low expansion properties. The name Invar comes from the word invariable, referring to its relative lack of expansion or contraction with temperature changes. Invar alloy has a rate of thermal expansion approximately one tenth that of carbon steel at temperatures up to 400 oF (204 oC). Invar, a low expansion alloy, possesses the lowest thermal expansion rate among all metals and alloys from room temperature to 230 degrees Celsius.

Invar alloy proves to be an asset being ductile, having welding ability and machining properties like stainless steel. It does not expand nor contract over a wide range of temperatures. This metal alloy is unaffected by stress corrosion and cracking.This characteristic makes the alloy a candidate for a growing number of applications where dimensional changes due to temperature variation must be minimized and also in conjunction with high expansion alloys in applications where motion is desired when the temperature changes. Invar Alloy has been the metal of choice for low expansion applications for years. “Super-Invar” (31% NI-5% Co-Balance Iron) has found some favor because it has a near zero coefficient of thermal expansion over a limited temperature range. The useful range of Super Invar is limited to between -32° to + 275°C. because the material begins to transform from Austenite to Martinsite at temperature below-32°F

Invar is used where high dimensional stability is required, such as precision instruments, clocks, seismic creep gauges, television shadow-mask frames, valves in engines, and antimagnetic watches. In land surveying, when first-order (high-precision) elevation leveling is to be performed, the level staff used is made of Invar, instead of wood, fiberglass, or other metals. Invar struts were used in some pistons to limit their thermal expansion inside their cylinders. Machining Invar alloy is available in two variations. One is the conventional Invar alloy, used generally for its optimum low expansion properties. The second is a variation of the basic alloy known as Free-Cut Invar "36"® alloy (UNS K93050 and ASTM F1684). This alloy has shown improved machinability for applications where high productivity is important. It is also a 36% nickel-iron alloy, but with a small addition of selenium (Fig. 1) to enhance machinability. cnc machine shop

Machining Invar:
AC Manufacturing has the experience, knowledge, and CNC equipment required to machine a wide array of materials, including Invar. Our custom design and manufacturing services means you receive a unique solution to your complex component problems. Nickel alloys usually harden quite rapidly, and the high pressures that machining creates causes hardening and slows down progress, also causing warping in some of the material.

Invar alloy is not hardenable by heat treatment. Invar can be made harder through cold working only. Being tough and ductile, Invar is somewhat difficult to machine. High speed steel or sintered carbide should be used and the cutting edges kept sharp. The machinability characteristics of Invar are quite similar to austenitic stainless steels. In the annealed condition, invar will be more difficult to machine because it is soft and gummy. The tools tend to plow the alloy instead of cutting into it, and do not easily form chips. Surface scale oxide tightly adheres to and penetrates the surface to a greater extent than stainless steels. Machining is considerably improved by descaling the material. If there were standard machinability ratings applied for invar alloy, Alloy AISI-B-1112 being measured as 100%, the percentage suggested for invar would be Invar FM 60%.

Both Invar 36 alloys are soft like Type 304 and Type 316 austenitic stainless steels; the free-cut variation, in particular, machines similar to those two stainless grades. They all have the same high work-hardening rate, which requires care in machining. The standard Invar alloy produces stringy, gummy chips which "birdnest" around the tools and interfere with coolant flow. Chips have to be broken up using chip breakers. Chip breakers are also used with the free-cut alloy, but they do not have to be as deep as for the basic alloy because the free-cut chips are more brittle. Invar parts Large, sharp and rigidly supported tooling is recommended for both grades.

A positive feed rate should be maintained for all machining operations to avoid glazed, work hardened surfaces. In some cases, increasing the feed and reducing the speed may be necessary. Dwelling, interrupted cuts or a succession of thin cuts should be avoided. In general, the free-cut Invar alloy has produced a good surface finish as well as higher productivity. During all cutting operations, with both materials, care must be taken to ensure good lubrication and cooling. The two grades are very ductile, thus readily cold headed and formed. Stamping from cold-rolled strip is easily accomplished. Parts may be deep drawn from properly annealed strip.

Fabrication does add stresses which, unrelieved, can change the thermal expansion behavior. When that happens, parts placed in service as-fabricated may not meet design requirements. Thus, annealing and stress relieving thermal treatments may be needed to promote structural uniformity and dimensional stability. We use 5 axis machines such as Haas UMC 750 and Haas VF-5SS as well as conventional milling equipment (Matsuura RA-1G, MC 500V PC 2S and MC-510 VG)

AC manufacturing machine shop It is worth to remember The effect of heat treatment upon the expansion of the alloy is dependent upon the method of cooling. Rapid cooling (quenching) decreases the rate of expansion while the reverse is true when slow cooling is employed. Cold working is even more effective than quenching in lowering the expansivity. Subsequent annealing will remove the lowering of the coefficients induced by cold work in proportion to the temperatures employed, the alloy assuming the values corresponding to the annealed condition when a temperature of about 1100 oF is reached. Invar which has been subjected to cold working or machining may require a stress-relieving heat treatment for stabilization if the material is to be used for high precision work. This material is never used above its thermal inflection


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