Ellipsoidal Head (2:1) 2D in AutoCAD:
First of all, consider the following Calculations to draw in AutoCAD to Draw an Ellipsoidal Head or dish in Software you should follow the six points as follows
- Internal Diameter
- Crown Radius
- Knuckle Radius
- Straight Face
- The height of the Head or Dish
First, you should how much Internal Diameter and Thickness of the Ellipsoidal Head or Dish required for the client. For Example, he wants 1650 mm ID x 10 mm THK head required.
Next open the AutoCAD Software select a New Template per your need to consider the Units Example or in Inches, Millimeters, Centimeters etc. I Considering Millimeters. Select the acad and Choose the Open template with Metric then the drawing units in Millimeters.
Draw a Vertical line 1650 mm in AutoCAD file by using line Command.
Crown Radius (CR) = Internal Diameter (ID) 0.90
= 1650 X 0.90
= 1485 mm
Draw a Radius of the Circle 1485 mm on the exact endpoint of the Vertical Line. By using Circle Command.
Step 4: Draw a Horizontal line 1650 mm on the outside and select the Center point of the Horizontal line and coincidence with the end point of the Vertical line. By using the Line and Move Commands.
Next, Draw two Vertical lines at the exact endpoints of the Horizontal Line and the two lines should Contact with the circle as shown in the figure below.
Next, you have to find the Knuckle radius to Draw the End curves of the Ellipsoidal Dish Head or Dish then the formula for Knuckle Radius is
Knuckle Radius (KR) = internal Diameter (ID) X 0.17
= 1650 X 0.17
= 280.5 mm
Finally, you have Knuckle Radius 280.5mm
Next, using the Fillet command at the two end positions give fillet radius 280.5 mm on both sides and next trim the unwanted lines and circles on the above by using the trim and Delete commands.
How to Give to Straight Face to complete the total Drawing the shortcut for the straight Face is (SF) to find the SF you should know what are the General Requirements for to make the pressure Vessel Head as per the ASME Section standards (American Society of Mechanical Engineers) before Design the any of the product should follow the sections and standards.
How to Give Straight face (SF) to Dish?
Internal Diameter of the Head or Dish is 1 meter above considering SF = 50 mm
500 mm to 1 meter Consider SF = 40 mm , below 500 mm Consider SF = 30 mm
I am making 1650mm Internal Diameter Dish then only I am considering straight face is 50 mm
Draw the two vertical lines 50mm by using line command on the endpoints of the fillets what you created before as shown in the figure.
Step 8 :
Next, how to give the thickness of the dish in drawings by using the offset command you can give according to this drawing the thickness of the dish is 10 mm thk what we discussed before, Actually the thickness of the dish is varies it is not exact 10 mm after the pressing process to make over the dish thickness is reduces but it should in 8-9 mm not exceeds more than 1 mm.
Next, How to find the Height of the Ellipsoidal Dish by using this formula you can find the height
The height of the head or Dish
= ID X 0.25 + S.F + THK
= 1650 X 0.25 + 50 + 10
You can also find the Height in AutoCAD by using the Linear tool after design or draft all Drawing completely as shown in the below figure.
Note : All Dimensions are in millimeters.
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