Today on this very happy Friday, we are going to continue building our virtual stapler with the Anvil Spring. Over the past couple of weeks we built the Anvil and Anvil Rivet, now we will make a configured spring without a design table. The spring we make today will have three configurations: Default, As Assembled and Compressed each represent the three states of the spring, with the Default configuration representing the Free State. So let’s get started with all the fun.

Creating a Variable Pitch Helix

The Anvil Spring has 6 coils with closed ends and two active coils. To achieve this type of spring will need to create a Variable Pitch helix, instead of the most common Constant Pitch. To make the helix, first a sketch of a circle must be created on the top plane with the diameter set to .235″. Make sure that the center of the circle is Coincident with the sketch Origin. Exit the sketch.

From the Insert menu select Curve -> Helix/Spiral…

In the Helix/Spiral PropertyManager, select Variable Pitch in the Parameters section.

In the Region Parameters, fill out the table as shown below. Since the spring has 6 coils there are 6 records in the table. Coils 1, 2, 5 & 6 are the closed ends of the spring, since the wire diameter will be .020″ we want the pitch to be slighter bigger then the wire. In the column labeled ‘P‘, which represents Pitch, enter .021″ for coils 1,2,5 & 6. For the Free State of the spring the two active coils will have a pitch of .080″, enter that value in the ‘P‘ column for coils 3 & 4.

Set the Start Angle to 0.00deg, it doesn’t really affect anything on this model but I do find it makes things easier. Make sure the helix direction is set to Clockwise.

Click the green check mark and your helix should look like below:

Create Spring Wire Profile

With the helix created, it is time to create the sketch of the wire that will be used for the Sweep. Select Plane from the Reference Geometry fly-out on the Features toolbar or select Insert-> Reference Geometry -> Plane. In the Selections section of the Plane PropertyManager, select Normal to Curve and Set origin to curve.

Select the helix near the end of the curve that you intend to place the Plane. In this case, I selected towards the bottom of the helix since it is nearest to the origin. No reason… just thought it would be easier this way.

On the newly created Plane, create a sketch as shown below. For some odd reason, I can never get the center of a circle to be Coincident to the origin of sketch so instead I fully define the sketch with a dimension. The center of the circle is also set to be Horizontal to the model Origin. When the sketch is fully defined, exit the sketch.

Create the Sweep

In the Features tool bar select Swept Boss/Base or from the pull-down menu select Insert -> Boss/Base -> Sweep.

In the Sweep PropertyManager, you will be presented with two fields, Profile and Path. First select the Profile field (blue).

Then select the sketch of the wire profile.

Next for the Path (pink)…

…select the helix.

Click the green check mark and your spring is created. Now we could just stop there and we would have a perfectly good spring, but where is the fun in that. I want more…

Configure Spring Without Design Table

Most of the time when I create springs that will be configured for different compression states, I use a Design Table. Design tables are great, and I will be covering them later, but I thought it was a bit of overkill for this part. Instead, we will be using the Configure Dimension command to set up the spring for the different states. Since the only thing that will be changing among the three states is the pitch, we need to configure the dimension for the pitch. To show the dimensions that control the pitch, select the Helix/Spiral in the Sweep created earlier.

In the graphics area, all of the dimensions that make up the helix will be shown in blue. It is kinda of a mess but you should be able to pick out the Pitch dimensions. In this view you can move dimensions around, in order to see dimensions that hidden behind others.

Find the P.080 dimension for Rev3, this is the Pitch dimension for the third coil.

Right-click the dimension and select Configure dimension in the menu.

If you are a fan of the site, you surely have seen the Modify Configurations window. In the Modify Configurations window, create two additional configurations named As Assembled and Compressed. Enter the value .040in for the As Assembled configuration and .021in for the Compressed configuration.

Rinse, Lather & Repeat for the P.080 dimension for Rev2 as well. Since these are the only active coils for the spring these are the only values that will change between each configuration.

Spring Configurations Created

If all went well, in the ConfigurationManager you will see the newly created configurations for the spring. Double-click each configuration to ensure that there are no issues. When created a spring in this fashion, and you encounter a Rebuild error when you switch to the compressed configuration; ensure that the pitch is slightly larger then the wire diameter.

Spring in As Assembled Configuration

Spring in Compressed Configuration

All’s Well That Ends Well….

Believe it or not, springs are one of my favorite things to model. There are so many types and configurations of springs. I hope you can take some of the techniques discussed today and create yourself some impressive springs. As always, you can download the model I created to see exactly what  I did: Anvil Spring, Stapler (185). Have a great Weekend!

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