Chapter 14 | Weldment Drawings 767 Chapter Project Project 14-1: For Figures P14-1through P14-10 , redesign the given parts as weldments. Use either 5-mm or .20-in. fillet welds. 14chapterfourteen Figure P14-1 MILLIMETERS Figure P14-2 MILLIMETERS Figure P14-3 MILLIMETERS Figure P14-4 INCHES
768 Chapter 14 | Weldment Drawings Figure P14-7 MILLIMETERS Figure P14-8 MILLIMETERS Figure P14-5 MILLIMETERS Figure P14-6 MILLIMETERS
Chapter 14 | Weldment Drawings 769 Figure P14-9 MILLIMETERS Figure P14-10 MILLIMETERS
771 • Learn how to use the Disc Cam tool located on the Power Transmission panel under the Design tab • Learn how to create and use displacement diagrams • Learn how to insert cams into assembly drawings Cams CHAPTER OBJECTIVES Introduction This chapter explains how to draw and design cams. Cams are eccentric objects that convert rotary motion into linear motion. Cams are fitted onto rotating shafts and lift and lower followers as they rotate. Cams can be designed and drawn using the Disc Cam tool. Displacement diagrams are defined and cams are generated from the displacement diagrams. The shape of the cam’s profile causes the follower to rise and fall as the cam rotates. Changes in the cam’s displacement cause the follower to accelerate. Excessive acceleration can generate excessive forces. Figure 15-1shows a cam drawn using Inventor. The cam bore includes a keyway. 15 chapterfifteen cam: An eccentric object that converts rotary motion into linear motion.
772 Chapter 15 | Cams displacement diagram: A linear diagram used to define the motion of a cam. Keyway Figure 15-1 Displacement Diagrams Displacement diagrams are used to define the motion of a cam using a linear diagram. The distances are then transferred to a base circle to create the required cam shape. Inventor will automatically create a cam from given displacement information. Figure 15-2shows a displacement diagram and a cam shape generated from the information on the diagram. The displacement diagram shown is drawn using only straight lines, which is called uniform motion. This diagram results in points of discontinuity that can result in erratic follower motion. Several different shapes can be used to smooth out these areas and create smoother follower motion. Base circle Follower - moves up and down Cam - rotates The displacement of the cam Figure 15-2
Drawing a Cam Using Inventor A cam is drawn using the Disc Cam tool by first defining the physical characteristics of the cam then defining the cam’s displacement diagram. A drawing of the cam will then automatically be generated. EXERCISE 15-1 Drawing a Cam ! Start a new drawing, click the Metric tab, and use the Standard (mm).iam format. @ Click the Design tab and click the Disc Cam tool located on the Power Transmission panel. The Disc Cam Component Generator dialog box will appear. See Figure 15-3 . The first cam position segment, the one between 0° and 90°, will have a broken line around it. The broken line indicates that the segment is currently active. Chapter 15 Chapter 15 | Cams 773 Enter the value. Enter the value. Enter the value. This value is the Motion End Position value. Click here. Figure 15-3 # Enter a Basic Radius of 15.00, a Cam Width of 10.00, a Roller Radius of 5.00, and a Roller Width of 5.00. These values are unique to this example.
774 Chapter 15 | Cams $ Enter a Lift at End value of 10.00. This value is noted as h max . % Click the Add After box. A third segment will appear to the right of the leftmost segment. ^ Click the rightmost of the three segments and drag the rightmost vertical line of the segment to the 360° line. This movement can also be accomplished by clicking the Motion End Position box, entering a value of 360, and clicking the Calculate box. & Set the end position of the leftmost segment for 90 and the end position of the middle segment for 270 by clicking the individual segment, entering the appropriate value in the Motion End Position box, and clicking the Calculate box. See Figure 15-4 . Click here to add a new segment. New segment Figure 15-4 * Enter a Motion Function of Cycloidal (extended sinusoidal) for the first and third segments. ( Click the Calculate button to implement the new Motion Functions . The middle segment of the cam, segment 2, is a dwell motion. Dwell portions of a cam have a constant radius so the follower will not move up or down during the dwell. Dwell segments are created, in this example, by having the Lift at End value of the first segment set at 10 and the Lift at
Chapter 15 Chapter 15 | Cams 775 End value for the second segment also set for 10. The Lift at End value for the third segment is 0.000. Figure 15-5shows the Calculation portion of the Disc Cam Component Generator dialog box. Note that the h max value is 10.000 mm and the h min value is 0.000 mm. Click this tab. Figure 15-5 ) Click OK. The File Naming dialog box will appear. _ Click OK. Figure 15-6shows the resulting cam. Resulting cam Figure 15-6 EXERCISE 15-2 Adding a Hole to a Cam ! Locate the cursor on the cam, right-click the mouse, and click the Open option. See Figure 15-7 .
776 Chapter 15 | Cams @ Right-click the mouse and click the Edit option. See Figure 15-8 . Figure 15-7 Right-click the mouse and click the Open option. Figure 15-8 Right-click the mouse and click the Edit option # Click the house-shaped icon, the Home tool, above the ViewCube and create an Isometric View, then right-click again and click the New Sketch option. See Figure 15-9 . $ Create a Point, Center Point. See Figure 15-10 . % Right-click the mouse and click the Finish 2D Sketch option. ^ Click the Hole tool and enter the values shown. & Click OK.
Chapter 15 Chapter 15 | Cams 777 * Right-click the mouse and click the Finish Edit option. See Figure 15-11 . The cam will appear. See Figure 15-12 . Right-click the mouse and click the New Sketch tool. Isometric view Figure 15-9 Right-click the mouse and click the Finish 2D Sketch tool. Point, Center Point Figure 15-10 Figure 15-11 Figure 15-12
778 Chapter 15 | Cams Sample Problem SP15-1 Design and draw a cam that meets the following specifications: All linear dimensions are in millimeters. Base circle 5 Ø80 Dwell 5 45° Rise 5 mm using harmonic motion over 90° Dwell 45° Rise 5 mm using harmonic motion over 90° Drop 10 mm using parabolic with linear part motion in 90° Bore 5 Ø12 Cam width 5 10 Roller radius 5 8 Roller width 5 10 ! Create a drawing using the Standard(mm).iam format. @ Click the Design tab. # Select the Disc Cam tool. The Disc Cam Component Generator dialog box will appear. See Figure 15-13 . Dwell Segment 1 Figure 15-13
Chapter 15 Chapter 15 | Cams 779 Segment 2 Follower rises 5.000 mm. Dwell Segment 3 Figure 15-13 (Continued)
780 Chapter 15 | Cams $ Enter the cam values. % Click the Add After box. Height at the end of Segment 4 End at 0 Segment 5 Figure 15-13 (Continued)
Chapter 15 Chapter 15 | Cams 781 The cam will require five segments to define its motion. Segments can be added by using the Add Before or Add After option on the Disc Cam Component Generator. ^ Complete the displacement diagram using the given specifications. Isolate each of the five segments and enter the appropriate values. For example, the first segment is a dwell for 45°. Set the Motion End Position for 24.00 deg and Lift at the End for 00.00. & Click Calculate after each segment input has been completed , then click OK. Figure 15-14shows the finished cam. Figure 15-14 Finished cam Cam profile Cams and Followers Figure 15-15shows a cam that was previously created in SP15-1 . Figure 15-15 Start a New Assembly ! Create a new Standard (mm).iam drawing. @ Use the Place Component tool and add the cam created in SP-151 . # Right-click the cam and click the Create Component tool. See Figure 15-16 .
782 Chapter 15 | Cams Right-click the cam and click the Create Component tool. Figure 15-16 New Component Click here for a new template Select the template EXERCISE 15-3 Creating a Follower ! Click the Create tool and create a new component named FOLLOWER. The Create In-Place Component dialog box will appear. See Figure 15-16 .
Chapter 15 Chapter 15 | Cams 783 @ Click the Browse Templates box. The Open Template dialog box will appear. # Click the Metric tab. The Open Template dialog box will change. $ Select the Standard (mm).ipt format; click OK. The Create In-Place Component dialog box will appear. % Click OK. ^ Move the cursor into the drawing area and click the left mouse button. See Figure 15-17 . Click New Sketch Figure 15-17 Select a sketch plane aligned with the front surface of the cam. & Right-click the mouse, click the New Sketch option, and select a sketch plane aligned with the front surface of the cam. * Use the Rectangle tool and sketch a rectangular follower (10 3 10 3 60) as shown. ( Click the right mouse button and select Finish 2D Sketch. ) Extrude the follower sketch 10 mm. _ Right-click the mouse and select Finish Edit. See Figure 15-18 . + Use the Constrain tools Tangent and Flush to constrain the follower to the cam. See Figure 15-19 . The Move and Rotate Component tool may have to be used to position the follower so it can be constrained.
784 Chapter 15 | Cams EXERCISE 15-4 Creating a Follower Guide ! Right-click the mouse, click the Create Component tool, and create a new component named GUIDE. Use the Standard (mm).ipt format. See Figure 15-20 . @ Click the top surface of the follower to create a new sketch plane. Rectangular sketch Right-click the mouse and select the Finish 2D Sketch option Extrude the sketch Right-click the mouse Click here Cam Follower Figure 15-18 The Tangent constraint applied Figure 15-19
Chapter 15 Chapter 15 | Cams 785 New component Select new template standard (mm).ipt Create a square 1 mm from the top surface of the follower Create a rectangle as shown Extrude the rectangle towards the cam Figure 15-20
786 Chapter 15 | Cams # Click the Project Geometry tool located on the Draw panel under the Sketch tab, and click the four lines of the top surface of the follower. Right-click the mouse and select the Done option. $ Sketch a rectangle around the projected top surface of the follower, then use the Dimension tool to define a 1-mm clearance between the guide and the follower. % Sketch a second rectangle around the first rectangle as shown, then right-click the mouse and select the Done option, then the Finish Sketch option. ^ Use the Extrude tool to add a 5-mm thickness to the guide. & Right-click the mouse and select the Finish Edit option. See Figure 15-21 . There are many different types of cam followers. Figure 15-22shows four different types. As a cam turns, the follower is pushed up and down. A spring is often used to force the follower to stay in contact with the cam surface. Knife Roller Sliding Pivot with roller Figure 15-22 Figure 15-21
Chapter 15 | Cams 787 Chapter Summary This chapter explained and illustrated how to draw and design cams, which are eccentric objects that convert rotary motion into linear motion. Displacement diagrams were defined and used to generate cams with the Disc Cam tool located under the Design tab. A follower was created, and the cam and follower assembly was animated. Chapter Test Questions Multiple Choice Circle the correct answer. 1. Which of the following is not a type of cam follower? a. Rectangular c. Sliding b. Knife d. Roller 2. The basic shape about which a cam is created is called the a. Roller radius c. Base circle b. Cylindrical face d. Eccentricity 3. The acceleration and forces in a cam follower are affected by a. The cam’s material b. The shape of the cam’s profile surface c. Poisson’s ratio 4. Why are keys used with cams? a. To control their pressure angles b. To transfer rotary motion for the driving shaft c. To change the effects of the basic radius 5. Which of the following is not a standard cam material available in Inventor? a. Steel SAE 1030 c. Aluminum Alloy Alclad 7075-T6 b. Malleable cast iron 33-8 d. #2 Pine True or False Circle the correct answer. 1. True or False: Cams are eccentric objects that convert rotary motion into linear motion. 2. True or False: When a cam has a constant radius it creates a dwell motion. 3. True or False: The base circle of a cam is its outside diameter. 4. True or False: The part that contacts the profile surface of a cam is called a follower. 5. True or False: Cams can be animated. 15chapterfifteen
788 Chapter 15 | Cams Figure P15-1A Figure P15-1B Chapter Projects Project 15-1: Millimeters Draw the Cam Support Assembly shown in Figure P15-1 . For this example the nominal dimensions for the bearings are as follows. More detailed dimensions can be found in the Content Center. DIN625—SKF 6203 (ID 3 OD 3 THK) 17 3 40 3 10 DIN625—SKF 634 4 3 13 3 4 GB 2273.2-87—7/70 8 3 18 3 5 The nominal dimensions for the rectangular key are 5 3 5 3 16. The values for the compression spring are as follows: Wire diameter 5 1.5 Inside diameter 5 9.0 Loose spring length 5 24 Preload spring length 5 23 Fully loaded 5 20 Working spring length 5 21 Right coil direction Active coils 5 10.125 15chapterfifteen
Chapter 15 | Cams 789 Figure P15-1C Cast Base P/N ENG-2008-A MATL = Steel Figure P15-1D
790 Chapter 15 | Cams Figure P15-1E Follower Subassembly Holder P/N AM-232 MATL = Steel Figure P15-1F Follower Post P/N AM-256 MATL = Steel Figure P15-1G
Chapter 15 | Cams 791 Project 15-2: Millimeters A. Draw the following cam: Base circle 5 R73.0 Face width 5 16.0 Rise 10.0 using harmonic motion in 90° Dwell for 180° Fall 10.0 using harmonic motion in 90° Bore 5 Ø16.0 Keyway 5 2.3 3 5 3 16 with a radius value of 2.3 Follower diameter 5 16 Follower width 5 4 Shaft P/N SHF-4004-16 MATL=Steel Shaft O 16 x 120 Keyway See detail Figure P15-1H Detail drawing Figure P15-1I
792 Chapter 15 | Cams B. Mount the cam into the Cam Support Assembly defi ned in Project 15-1. See Figure P15-2 . Figure P15-2 Project 15-3: Millimeters A. Draw the following cam: Base circle 5 Ø73.0 Face width 5 16.0 Rise 8.0 using double harmonic motion—Part 1 motion in 90° Dwell for 45° Rise 6.0 using double harmonic motion—Part 1 motion in 90° Dwell for 45° Fall 14.0 using double harmonic motion—Part 1 motion in 90° Bore 5 Ø16.0 Keyway 5 2.3 3 5 3 16 with a radius value of 2.3 Follower diameter 5 16 Follower width 5 4 B. Mount the cam into the Cam Support Assembly defi ned in Project 15-1.
Chapter 15 | Cams 793 Project 15-4: Millimeters A. Draw the following cam and add a Ø24.0 3 16.0 hub. Place a Ø16 hole through the hub and cam. Add an M4 hole though the hub located 10.0 from the top surface of the hub, and insert an M4 3 4.0 CSN 02 1181 Set Screw. Base circle 5 Ø73.0 Face width 5 16.0 Rise 6.0 using cycloidal motion in 45° Dwell for 45° Rise 6.0 using cycloidal motion in 90° Dwell for 45° Fall 12.0 using cycloidal motion in 90° Bore 5 Ø16.0 Keyway 5 2.3 3 5 3 16 with a radius value of 2.3 Follower diameter 5 16 Follower width 5 4 B. Design Mount the cam into the Cam Support Assembly defi ned in Project 15-1. Modify the shaft presented in Project 15-1 by removing the keyway. Assign the modifi ed shaft a new part number, SHT-466E. Project 15-5: Millimeters A. Draw the following cam: Base circle 5 Ø73.0 Face width 5 16.0 Rise 12.0 using harmonic motion in 90° Dwell for 180° Fall 12.0 using harmonic motion in 90° Follower diameter 5 16 Follower width 5 4 B. Design Make the following modifi cations, then mount the cam into the Cam Support Assembly defi ned in Project 15-1. Make the cam’s bore 20.0. Modify the shaft to have a Ø20.0. Select a new key based on the Ø20.0 shaft, and add the appropriate keyway to the shaft and cam. Select a new bearing to accept the Ø20.0 shaft. Modify the hole in the Cast Base to accept the outside diameter of the selected bearing. Consider using a counterbored hole to mount the bearing.