MDC Vacuum

Engineered Process Solutions


Custom Engineering

Chamber Geometry

MDC is equipped to build custom vacuum chambers of virtually any complexity. Vacuum vessels can be built to your exact specifications from a rough hand-sketch, detailed engineering drawings or anything in-between. MDC’s engineering department uses the latest SolidWorks 3D CAD software and can accept drawings in DWG, DXF, IGES, STP or SolidWorks file formats. For a nominal fee MDC can supply a complete engineering documentation package on those projects for which the drawings were not provided by the customer.
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Unless specified otherwise the main body of custom chambers less than or equal to 10 inches in diameter will be fabricated from standard tubing. Nonstandard sizes under 10 inches and all sizes over 10 inches in diameter shall be fabricated from rolled stainless steel sheet metal. The chart below provides nominal wall thicknesses for most MDC chambers .

Typical MDC custom chamber

The accurate positioning of ports on MDC vacuum chamber is made possible with the use of sophisticated laser aligned fixtures. Five basic geometric parameters are required to define a chamber’s port positions. These spherical coordinate system parameters include a port’s focal point, focal plane, focal length, polar angle and azimuthal angle, figures 3 through 6.


For the purpose of this discussion all vacuum chambers shall have a base port located on a horizontal XY base plane which is perpendicular to the chamber’s vertical Z axis, figure 3 on facing page. Whenever bolt style flanges are used, bolt patterns shall straddle vertical centerline. In the case of Del-Seal™ CF metal seal flanges fitted with leak test grooves, the grooves shall be oriented vertically, figure  1.

Furthermore, all port flange seal faces shall be considered perpendicular with their mating tube axes, figure 2.

The focal point of a port, also referred to as a ports target point, is usually a position anywhere inside a vacuum chamber where an application task is to be performed. Its location is typically defined by the vertex or convergence point of one or more ports and other chamber features. Focal points can be thought of as sphere centers from which radial ports project. Even though focal points are inside a vacuum chamber they are not necessarily at the chamber’s center. Chambers can contain multiple focal points as required by an application. All focal points are located on focal planes which are parallel to the chamber’s main base plane. A port’s focal length is defined as an axial and perpendicular distance measured from a port’s focal point to the center of its mounting flange seal face. Minimum focal lengths require the use of tapped flanges. Clearance hole flanges require a minimum 1-1/2 inch tube extension in order to fit fastening hardware.

Polar angle is a port’s angular displacement about a horizontal axis. This horizontal axis of rotation intersects the port’s focal point and lays on the focal plane which is in turn perpendicular to the chamber’s main Z axis. Polar angles are measured in a north to south direction on a 180° scale between the focal point’s vertical axis and the port’s center line, figures 4, 5 and 6 on facing page. The north position is 0° and the south position is 180°. A port is said to have a 90° polar angle when the port centerline lays on the focal plane, figure 4.

Azimuthal angles discussed herein shall be measured in a counterclockwise direction with a 0° starting point and a full 360° scale. Azimuthal angle is a port’s angular displacement about a vertical axis. This vertical axis intersects the port’s focal point and is always parallel to the chamber’s main Z axis. The azimuthal angle is projected onto the port’s horizontal focal plane and measured in a counterclockwise direction beginning at the 0° or three o’clock position and ending at the port center line or center line projection. If a port has a polar angle equal to 90°, figure 4, the port’s center line will lay on the focal plane. If the polar angle is less than or greater than 90°, figures 5 and 6, the port’s centerline will be above or below the focal plane and must be projected onto it for a final azimuthal angle measurement.


Custom engineered chambers are designed and manufactured using state of the art metal machining equipment as well as conventional machining and welding tools. Unless specified otherwise the typical dimensional tolerances applied to all chamber fabrications shall be as follows...

Chamber fabrication tolerances have been optimized for cost-effectiveness and reproducibility. Chambers 24 inches in length or shorter will carry a ± 0.03 inch linear tolerance. Chambers longer than 24 inches but shorter than 72 inches will carry a ± 0.06 inch linear tolerance. All chambers will carry a minimum ± 1.0° angular tolerance. Deviations from these specifications must be discussed with the MDC technical sales engineers for feasibility and cost before they can be implemented. 

 Related Topics
 Vacuum components made to order
 Modifications to standard parts

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