These guidelines are provided only as a starting point in the process of designing Al/SiC components manufactured by TTC's technologies. It is highly recommended that before design decisions are made that you contact TTC to answer any questions that may you may have if your designs fall outside these specifications.

*Contact TTC for size and thickness limits for PRIMEX CAST™ applications

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Tolerances for Machined Components

Grinding
	Standard	Premium
Thickness	±0.05 mm ±0.002"	±0.025 mm ±0.001"
Surface Finish	< 1.1 µm Ra < 45 µin Ra	< 0.5 µm Ra < 20 µin Ra

(Ra = roughness average)

Note: Most finishing operations (e.g. plating, anodizing, chemical film, etc.) will roughen a ground surface so that the surface finishes indicated above will change to 63µin. Ra and 32µin. Ra for standard and premium, respectively (note: this does not apply to lapped finishes). In addition, many plating operations add sufficient material to make the above thickness tolerances more difficult to meet (see plating specifiction section).

(RFS = Regardless of Feature Size)
(T.P. = True Position tolerance)

Notes: Holes formed by wire EDM are usually more expensive than those formed by EDM hole drilling. This is due to the need to form a pilot hole via EDM hole drilling to allow wire threading for the wire EDM operation. Redesigning holes near the edges of a part, as slots or notches at the edge of the part, usually saves cost because notches can be cut as part of the wire EDM profiling operation.

Ram EDM

Surface Finish <125µin Ra, or

Notes: Ram EDM'ed features typically add significant cost and lead time.
Ram EDM tolerances are design dependant, please contact ITM for specific design requirements.

Countersinking

Dia. Tolerance: +/- 0.130 mm or ± 0.005"

Min. Distance from Edge of Countersink to another Edge: 0.381 mm or 0.015"

Flatness

Flatness of components machined from TTC's SiC/Al composites are dependent upon several factors, most importantly lateral dimensions and thickness. Please contact TTC's customer service specialist to discuss the flatness specifications for your application.

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General:

These design guidelines are specific to parts made from net or near-net shape. These parts typically have a 3° draft on all edges and holes, and 6° on slots and grooves. The drawing should clearly specify the direction of the draft on all edges and holes. It is best to work in conjunction with the tool design effort when determining how draft should be applied to any given design. These guidelines are generated based upon actual process experience. They will be updated periodically to reflect increases in our process knowledge base.

Datum Features:

When choosing datum features, it is important to consider the possible impact on the tolerance of other features. In particular, holes are the preferred feature for secondary and tertiary datums, due to the fact that the location of the center of the hole is not affected by a taper, as well as the ease of locating the hole center with a coordinate measuring machine (CMM). Using edges as datum features creates more difficulty for two reasons. First, small variations in the condition of the edge can change the orientation of the datum enough to alter the apparent position of other features and significantly affect their probability of being in tolerance. Second, locating a tapered edge with a CMM can be very difficult, depending upon how the edge is defined. Using an edge that has a gate remnant should be avoided if at all possible. The best choice for secondary and tertiary datum features would be two holes (preferably not close to each other). The next best choice would be a hole for the secondary datum and an edge for the tertiary datum. In most circumstances, adequate control of edges relative to holes.

 

Final Component Size and Feature Limits and Tolerances
	Maximum	Minimum	Tolerance
Lateral Dimensions	240 mm x 150 mm	25 mm x 25 mm	+/- 0.2 mm
Thickness	5 mm	1.5 mm	Std. ±0.1 mm Prem. ±0.05 mm
Hole Diameter	N/A	4 mm	±0.10 mm

Flatness:

A lapped plate will typically meet a flatness tolerance of 0.0008 mm/mm. This tolerance applies to parts with a maximum linear dimension of around 160 mm or less at a thickness of 3.0 mm. Thicker parts are typically flatter than thinner parts of the same profile. Parts which deviate significantly from this envelope would need to be reviewed for flatness on an individual basis.

Feature Location Tolerances
	Referenced to hole	Referenced to edge
Hole Position	< 120 mm distance ±0.12 mm or 0.25 mm T.P. (RFS)  > 120 mm distance ±0.1% of the distance	±0.20 mm or 0.38 mm T.P. (RFS)
Edge Location	±0.20 mm or 0.38 mm Profile	±0.20 mm or 0.38 mm Profile

(RFS) = Regardless of Feature Size

Minimum Edge Distance:

A minimum distance of 3 mm is required from the edge of a hole to the edge of the part in order to successfully manufacture the part. Increasing the edge distance from 3 mm to 4 mm further improves the producibility of the part. Since the part profile is molded to net shape, increasing the edge distance by the addition of local extensions along the profile is an acceptable approach to achieve the minimum distance.

Surface Finish:

Standard Lapping 2.3 µm, maximum   Premium Lapping 0.8 µm, maximum

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Design Guidelines for PRIMEX CAST™ AlSiC Components

From the component designer's viewpoint, designing parts to be made from PRIMEX CAST^™ based composites is nearly identical to that for conventional aluminum. PRIMEX CAST™ based components, cast from MCX-1605™ and MCX-1405™can be cast using any of the conventional aluminum casting methods (e.g., sand, investment shell, permanent mold, or high-pressure die). However, MCX-1195™ is limited to investment shell and high-pressure die casting techniques.

Designers can apply similar draft angles and can expect to achieve similar dimensional tolerances process for process, as if conventional aluminum casting alloys were being used. Some process differences do exist, (e.g., melt handling, melt flow, shrinkage, and gating issues) but these differences are most often the responsibility of the foundry engineers.

As with casting, the machining parameters used for PRIMEX CAST™ based composites are similar to those used for conventional aluminum. Speeds and feeds, at the low end of those used for conventional aluminum, are utilized. However, because SiC is very hard, and is itself used for cutting tools, the machining of these SiC reinforced composites requires the use of diamond or poly-crystalline-diamond cutting tools. These composite materials are also amenable to conventional lapping and EDM machining.

As with casting and machining, conventional aluminum coating and plating materials and methods are readily applied to components made from PRIMEX CAST™ based composites. This is true whether components have "as cast" or machined surfaces. Likewise, standard techniques for Hot Isostatic Pressing and quality inspection are routinely used.

TTC strongly recommends that customers involve us in the design process. While the customer undertakes the mechanical and thermal aspects of the design, TTC and its foundry engineers can provide valuable input on alloy and process selection, as well as on manufacturabliity issues. Involving TTC early in the design process will help to minimize design iterations, while maximizing the efficiency of the design process.

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Metallization & Surface Coating Specifications and Tolerances
Plating Type	Industrial or Military Standards	Standard Thickness	Thermal Exposure Blister Limit in Air
Nickel-Boron*	ASTM B607	3-8 µm 100-300 µin.	15 min.@450°C
Nickel-Phos.*	MIL-C-26074	5-13 µm*** 200-500 µin.***	1 hr.@450°C
Nickel-Phos.*/ Nickel Sulfamate**	Mil-C-26074/ QQN-290	3.8 µm Phos. Ni  3.8 µm Sulf. Ni. 150 µin. Phos. Ni 150 µin. Sulf. Ni.	30 min.@340°C
Nickel-Boron*/ Gold**	ASTM B607/ Mil-G-45204 & ASTM B488	3-8 µm Ni 1-3 µm Au 100-300 µin. Ni 50-100 µin. Au	15 min.@450°C
Nickel-Phos.*/ Gold**	Mil-C-26074/ Mil-G-45204 & ASTM B488	5-13 µm Ni***  3-8 µm Au 200-500 µin. Ni*** 100-300 µin. Au	X
Nickel-Phos.*/ Tin** (matte finish only)	Mil-C-26074/ Mil-T-10727	5-13 µm Ni 8-20 µm Sn 200-500 µin. Ni 300-800 µin. Sn	X
Nickel-Phos.*/Silver**	Mil-C-26074/ QQ-S-365	5-13 µm Ni  3-8 µm Au 200-500 µin. Ni 100-300 µin. Au	X
Anodize	Mil-A-8625 Type II, Class I	N/A	N/A
Iridite (Chem. Film)	Mil-C-5541 Type IA & Type III	N/A	N/A

(Note: Surface finish of plated or chemically finished components may see up to 380 µm or 15 µin. (Ra) increase in surface roughness.)
* Electroless Plating, ** Electrolytic Plating, *** All applications that must pass salt corrosion testing require a minimum of 650µin - 16.5µm high phosphorus nickel plating
X = blister limit for this type of plating exceeds the melting point of most common solders used for the specified applications.

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Electronic File Transfer

Preferred:
Autocad (.dwg file type), Drawing Exchange Format (.dxf file type)

Acceptable:
IEGS, MS Word (.doc or docx file format), MS Excel (.xls or xlsx file format), MS Power Point (.ppt or pptx. file format) Adobe Acrobat (.pdf file format)

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