I love designing in Siemens NX, but keeping these files on my hard drive doesn't help anyone. I decided to put them out here for anyone who needs to practice material. Whether you're a student or just love CAD like I do, feel free to use these blueprints to sharpen your skills.
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CAD Modelling Challenge #5 — Engineering Drawing Breakdown
NX Modelling Challenge #5 | NXDATUM 04DTM23
This week's challenge is a heavy-duty industrial pivot housing. This component features a "pear-shaped" base and a multi-level cylindrical assembly. This part is a fantastic test of your ability to handle tangency between circular arcs, manage offset datum planes, and correctly interpret complex internal hole features across multiple heights.
The Base Plate — Pear-Shaped Profile
The base plate of this model is defined by two primary circles: a large R57 arc on the right and a smaller Ø54 circle on the left. The distance between these two centers is exactly 100mm.
These two circular profiles are connected by tangent lines to create the smooth, aerodynamic outer shape. The entire base has a uniform thickness of 25mm. On the smaller circular end, there is a Ø23 through-hole centered perfectly with the outer profile.
The Main Pivot Housing (Center Assembly)
The central feature is a rectangular-top cylinder that sits 40mm away from the center of the large R57 base arc. The overall height of this main assembly is 85mm from the bottom of the base plate. Notice the internal details: it contains a large central through-hole (visible in the dash-hidden lines of the front and side views).
Supporting this main cylinder are two small vertical lugs on either side. These lugs are 12mm wide and are spaced 54mm apart. Each lug features an R10 rounded top and a Ø12 hole centered at a height of 38mm from the top of the base plate (or 63mm from the bottom face).
Vertical Clearances and Offsets
A critical detail in this drawing is the 5mm clearance gap between the bottom of the main pivot cylinder and the top of the base plate. This means the cylinder is actually "suspended" and only connected via the side lugs or a central shaft.
Reading this gap correctly is essential for the final assembly mass calculation. On the left side, the Ø54 boss rises to a total height of 38mm from the bottom face (meaning it stands 13mm above the base plate).
Modelling Strategy in Siemens NX
Base Profile: Start by sketching the base profile on the XY plane: create the R57 and Ø54 circles 100mm apart, use the Line tool with Tangent constraints to connect them, and Trim the excess. Extrude this to 25mm.
Left Boss: Next, create the Ø54 boss on the left and extrude it to its 38mm total height.
Main Housing: For the main housing, it is best to create a Datum Plane offset from the base. Sketch the main cylinder and the side lugs.
Holes & Details: Use the Hole command for the Ø23 and Ø12 holes. Pay special attention to the 5mm gap—most students will accidentally unite the cylinder directly to the base, which would be incorrect based on the front view dimensions.
What This Challenge Tests
This challenge evaluates your precision with geometric constraints (specifically tangency), your ability to recognize suspended or "floating" features with clearance gaps, and your proficiency in managing multiple vertical height references (25, 38, 63, and 85mm).
Complete the model in Siemens NX, run mass properties, and submit your answer on the NXDATUM validation tool.
Created by NXDATUM | Siemens NX CAD Modelling Series | All dimensions in mm | Scale 1:1
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