Modeling and Assembling an Engine Valve System in SolidWorks: A Comprehensive Guide

Welcome back to the Multibody Dynamics using SolidWorks blog series! In this blog, we’ll walk through the complete process of modeling and assembling the components of an engine valve system in SolidWorks. This guide covers the creation of each part—cam, push rod, rocker arm, valve, and valve mount—followed by assembling them into a complete mechanism. After the modeling, we will proceed to the multibody dynamics simulation. This method offers a clear, detailed approach for students and engineers learning Multibody Dynamics (MBD) using SolidWorks. 

Step 1: Modeling the Cam 

The cam is the first part we will create. Start by opening a new part file and setting the unit system to millimeters (mm). Here’s how to model the cam: 

1. Sketching the Cam Profile: 

1. Use the Front Plane to start the sketch. 
2. Begin by creating a center-point circle using the circle tool. The outer circle will have a diameter of 25mm, and the inner circle will have a 10mm diameter. 
3. Once the two circles are placed, add tangent lines to connect them. 
4. Make sure the smaller circle is vertically aligned with the larger circle by using the make vertical constraint. 
5. Trim unnecessary parts of the circles and lines to create the cam profile. 

2. Extruding the Cam: 

1. Once the cam profile is complete, use the extrude boss base feature to extrude the cam by 10mm. 
2. Use the midplane option during the extrusion to ensure the cam is symmetrical, which will make the assembly easier. 
3. After the cam is modeled, save the part file with a suitable name. 

Step 2: Creating the Push Rod 

The push rod, also known as the cam follower, is the second part to model. Follow these steps: 

Sketching the Push Rod: 

1. Start a new part file and create a sketch on the Front Plane. 
2. Draw a vertical line that coincides with the Y-axis, and extend it out horizontally. 
3. Add a 3-point arc to form the upper part of the push rod. 

Revolving the Push Rod: 

1. Use the Revolve Boss/Base tool to revolve the sketch around the vertical line. 
2. This will form the cylindrical shape of the push rod. 
3. The dimensions include a vertical height of 110mm and a horizontal width of 2.5mm. 
4. Save the part. 

Step 3: Designing the Rocker Arm 

The rocker arm transfers motion from the push rod to the valve. Here’s how to design it: 

1. Sketching the Rocker Arm Profile: 

1. Open a new part file and use the Front Plane. 
2. Begin by drawing lines and arcs to form the basic shape of the rocker arm. 
3. Create two concentric circles at one end. The inner circle will have a diameter of 12.5mm, and the outer circle will be 30mm. 

2. Adding Tangency and Constraints: 

1. Apply tangent constraints between arcs and lines to ensure smooth transitions. 
2. Use Smart Dimensions to set the dimensions for each segment. For example, the top arc should have a radius of 71.5mm, and the second arc should be 47mm. 

3. Extruding the Rocker Arm: 

1. Use the Extrude Boss/Base tool and set the extrusion thickness to 20mm. 

Step 4: Modeling the Valve 

The valve is a critical component in the engine valve system. Follow these steps: 

1. Creating the Valve Sketch: 

1. Open a new part file and sketch the valve on the Front Plane. 
2. Draw vertical and horizontal lines to form the valve stem. The vertical height should be 80mm, and the horizontal section should be 10mm. 
3. Add 3-point arcs to form the valve head. 

2. Revolving the Valve: 

1. Use the Revolve Boss/Base tool to revolve the sketch around the central axis, creating a cylindrical valve. 
2. Ensure the arc radius of the valve head is set to 45mm. 
3. Save the part. 

Step 5: Creating the Valve Stem 

The valve stem acts as a guide for the valve. Follow these steps: 

1. Sketching the Valve Stem: 

1. Start a new part file and sketch the valve stem on the Front Plane. 
2. Draw horizontal and vertical lines to form the profile, with the main vertical section being 10mm in height and 0.5mm in thickness. 

2. Revolve the Valve Stem: 

1. Use the Revolve Boss/Base tool to create the 3D shape of the valve stem by revolving the sketch around its vertical axis. 
2. Save the part. 

Step 6: Assembling the Engine Valve System 

With all components ready, it’s time to assemble them in SolidWorks Assembly: 

1. Aligning the Parts: 

1. Start by opening a new assembly file and importing the parts: cam, push rod, rocker arm, valve, and valve stem. 
2. Use axis and plane constraints to align each part with the assembly. For example, align the rocker arm axis with the right plane of the assembly. 

2. Setting Mates and Constraints: 

1. Add necessary constraints to ensure the parts move correctly in relation to one another. For example, set the cam axis to coincide with the push rod axis, and add distance mates where necessary. 

Step 7: Preparing for Motion Analysis 

Now that the assembly is complete, you can proceed with setting up the multibody dynamics simulation in SolidWorks. 

Enabling Physical Dynamics: 

1. Use Physical Dynamics to test the interaction between the components. This helps in simulating how the camshaft pushes the rocker arm, which, in turn, actuates the valve. 

Conclusion 

By following these steps, we’ve modeled and assembled the essential components of an engine valve system using SolidWorks. This approach to learning Multibody Dynamics using SolidWorks not only familiarizes you with the software’s modeling tools but also sets the foundation for more complex simulations in mechanical systems. 

In the next blog, we’ll cover the motion analysis in greater detail, providing a complete look at how the engine valve system operates dynamically in SolidWorks Multibody Dynamics. 

This blog is part of our ongoing series on Multibody Dynamics. 

If you missed the previous posts, check them out here.   

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