Parts should preferably be modeled with rule-based bodies and kept as simple as possible (cylinder = extrusion of a circle instead of rotation of a rectangular). For special cases (e.g., sweeps) it may be necessary to rotate a non-rectangular shaped sketch. This is geometrically allowed for high detail level (LOG) but generates more computational operations for the CAD file creation and results in a higher possible error rate when creating the geometry in CAD. In particular, see Section 3.5.3, “Regular Bodies for VDI Models” and Section 3.5.2.3, “LOG (formerly called "LOD")”.

The global alignment of the objects (direction of the X/Y/Z axes) must be set to match the orientation of the target systems.

	Note
	It is also highly recommended to avoid many rotations within parts (and assemblies) as these rotations create more operations in the CAD interfaces.

These are:

The alignment of MEP objects is explicitly defined in the VDI 3805 guideline: (for more details, see Section 3.5.2.6, “Sample objects”)

Axis orientation

For pipe fittings / pipe accessories, the prescribed modeling guidelines of VDI 3805 in the associated sheets are also binding.

Every domain (in VDI 3805 grouped in sheets) of MEP parts has its own orientation. Pumps, valves and others have different positions of the absolute zero point.

	Important
	The positioning of the absolute zero point (0/0/0), or the alignment of the X-axis on the pipe axis is prescribed in VDI 3805. The function Test part in PARTdesigner must be done successfully and without errors at every change of geometry / change of a sketch. (Mode "Architecture")

This is the basic requirement for a "Test-Meta" (geometry / variant check on project / directory level) to reach QA level >4. See Section 5.8.2.1.12, “ Test project / Test directory ”.

Simply structured, layer referenced and parameterized parametric sketches, and the immediate checking of the generated geometry with the PARTdesigner geometry checker (function Test part) in the correct setting, is the elementary basis for an easily readable data structure that can be maintained with little time expenditure.