CAD Resource Center

When creating CAD jewelry, new and old designers alike, sometimes lose track of the need to make a jewelry piece not only comfortable to wear, but also not so delicate that it will break too easily. The ring shown below is a perfect example of both of these problems. While it is very interesting from a design point of view, it has so many sharp areas, it is simply not safe to wear. In addition, it has a problem with the undercut. The connection of the head and the shank is vulnerable so the construction of the ring is not adequate for successful production. The ring is simply too weak and sharp. How to correct it: If the bottoms of each element were rounded, the undercut could be eliminated completely. Also, the entire ring should be thickened by at lease 0.2 – 0.3mm. Making these changes would make the model acceptable to produce and wearable, as the design in general is quite pretty.

 

Introduction

Most of you are probably familiar with the Boolean operations of union, subtract, and intersection from your algebra classes. In computer-aided design we use the same Boolean operations and they follow the same principles as their algebraic terms suggest; they are used to add, subtract and intersect elements of 3D models. In most CAD systems, Boolean operations are a central functionality, so for 3D jewelry designers, it’s critical to have a firm grasp of these operations and how to use them. This guide presents a general discussion of Boolean operations in CAD software, and how, why, and when they are used.

Boolean operations in computer-aided design:

Working in 3D usually involves the use of solid objects and the Boolean commands work only on solids or regions. Sometimes you will need to combine multiple parts into one solid, or remove sections from a solid. The three Boolean operations that let you do this are listed and defined below:

  1. Union – joins two or more solids into one that is based on the total geometry of all the solids.
  2. Subtract – subtracts one or more solids from another solid to create a solid based on the remaining geometry.
  3. Intersect – Creates a single solid from one or more solids based on the intersected region or geometry.

In 3D design, the term ‘primitives’ is used to refer to the basic geometric forms that you will use the Boolean operations on and they are considered the building blocks of 3D design. The common 3D primitives are as follows:

  • Cone

cone

  • Cube

cube

  • Cylinder

cyclinder

  • Sphere

sphere

  • Torus

torus

  • Tube

tube

Some CAD software also has more complex primitives, called extended primitives, but the forms listed above are the basic forms.

By using Boolean operations on the different primitives, we can create shapes and designs of different complexities.

Why is it so important to have a properly Booleaned model?

In the solid modeling that is used to create jewelry it is absolutely critical that the model be watertight. There should be no leaks at all. Think of the model as a totally solid object. Each part of the model must be joined into one solid object. Very often we see models with each and every prong as a separate object when, in fact, they should be as one part with the base. The printing process does not like the model to be made out of separate parts and in most cases it will be rejected by the program preparing such a model.

booleaned

How do I know if the model is Booleaned or not?

It’s very simple to determine if a model has been booleaned. If you click on any given part of the model, the entire model should be highlighted.

not booleaned

Are there cases when a model should not be Booleaned?

There are times when we don’t want a model to be booleaned. For example, if a model is designed in two or more parts, each part should be left as a separate objects. In other words, these parts should not be Booleaned. However, each individual part should be booleaned.

not booleaned, 2 parts

How to use the Boolean Operations:

Once you understand the importance of making sure your models are Booleaned, making them Booleaned is relatively simple to do. Most CAD software has easy to use Boolean commands.

Typically, you need to highlight the primitives that need to be Booleaned and then just choose the Boolean command that you want to perform from the properties browser, toolbar, or shape menu, depending on the CAD program you are using. Keep in mind that when selecting the primitives to be Booleaned, you normally highlight or select the part that is to be modified first, and the part that will be the modifier second. Once you’ve selected both parts in the proper order, you can now perform the Boolean operation that you want to perform.

Conclusion

Making sure that objects are properly Booleaned is critical to successful jewelry design. When objects aren’t properly Booleaned, the 3D printers will reject the design at best and at worst print a faulty model. Boolean operations are a central functionality of CAD programs and a basic tenet of jewelry design. Fortunately, most CAD programs make it very simple to use the Boolean operations, so once you remember to Boolean your designs, the rest is easy!

The model shown below is another example of a model that has sharp edges; this time the sharp edges are on the cross-section. To correct this problem, the edges should be rounded a little. The model also has a problem with the length of the small prongs; they are too tall. This could be corrected by making the length of these prongs no more than 0.5mm tall. Finally, the model could be improved by doing a boolean union to the model and making it into one solid piece.

One of the problems we see quite often here at Jewelrythis is that the lines used to help build the railing in a design get left behind in the file. The problem is that these lines will just get in the way of the printing process if they are left behind, so they must be removed. Below is a short explanation of how to find and remove these unnecessary lines.

im1

 

im2

The easiest way to find all of these lines, which are essentially just ‘trash’ and which will only be in the way when the model is prepared for printing, is to just click on the design and move it to the side.

im6

By doing this, you will reveal any unnecessary lines that were used to make the railing and then left behind in the design.

im7

Remember to check each separate object in the design for unnecessary lines. Thus, if there is more than one object, move it to the side as well.

im8

Once you’ve checked and removed any lines that weren’t needed, make sure you put the design objects back into their proper place and that you center everything properly.

im9

We hope you found this tutorial on how to remove rail lines helpful. Although it’s simple enough to do, removal of the rail lines is just one of several important steps in proper 3D jewelry design.

The images below show a beautiful ring design, but it has a few problem areas that need to be corrected. One problem concerns the issue of comfort, an often overlooked issue, and another with how the prongs hold the stones. Also addressed is how to design the ring so that it is easier to clean and polish. These issues are explained and addressed below:

First, for reasons of comfort, the back of the ring needs to be smooth. Otherwise, the ring will be uncomfortable to wear as well as difficult to polish.

Screen Shot 2016-01-21 at 8.51.43 AM

Second, for better stone fit, the prongs in this design need to be adjusted so that they fit the stones better. Third, the area between the prongs should be u-shaped rather than v-shaped.

Screen Shot 2016-01-21 at 9.13.23 AM

Screen Shot 2016-01-21 at 9.12.52 AM

And finally, the ring should be separated into three pieces so the can be easily cleaned and polished. Other than these problems, this is a very beautiful ring design.

The 3D design of an engagement ring that you see below is truly lovely. Unfortunately, it has several design flaws. The design was submitted by HelloHello Designs and they have kindly agreed to let us use it as a teaching point. The main problems with this design are prong length, that the cathedral and the shank are joined, the thickness of the ring base, and comfort for the wearer. These problems are examined below.

60174

1. The prongs in this design for the large center stone are too short and should be made longer.

head prongs

2. The cathedral part of the ring should be created separately from the rest of the shank so that they are two separate pieces.

cathedral head

3. The ring base is only .82 mm, which makes it too thin. It is about the same thickness as the prongs (.75 mm) for the accent stones. The base should be made thicker.

ring base

4. And for purely practical purposes, although this ring looks truly amazing, if you were to actually wear it, you would find that your finger would feel pinched because there is a 1/2 mm gap in the top of the shank. This gap needs to be closed so that the ring can be worn comfortably.

Gap at top shank

 

The design you see below is for a fashion ring with a cathedral setting and a large central stone. It is shown here to demonstrate some design errors that could cause problems when the model is printed and cast. The model we are using for this purpose is courtesy of Alex Vavilov.

jtd_20150213_141659_1829_60972_1_16609

There are two issues with this design. The first is that the bottom row of prongs used to hold the side stones in place are chopped.

60972-chopped prongs

The second problem is that the edges of the shank are too sharp. Both of these design flaws that can create problems that will make it difficult to print and cast the model. For a closer look at these problems, feel free to Click to download this model .

jtd_20150213_141601_1829_60972_3_26274-400x400

In this tutorial, we look at a model that has problems with execution. While the ring design is very pretty, there are several issues that must be addressed before the ring can be cast and printed. They are reviewed below:

First of all the center head must not be one with the ring. This is a rule in 90% of all the models. Second, the height of the prongs above the center stone is not adequate. This is especially true for profiled prongs. The jeweler will damage these prongs during the setting and the damage will most likely be beyond repair. That is why the length of the prongs should be at least 1.5 – 2 mm. above the girdle. This will let the tool marks from the setting remain on the area that will be cut off after the prongs are bent, and the remainder of the prongs will be left intact. In this model, the length is only 1 mm. The last problem regards the continuity of the loop; it is breaking on the bottom part. When preparing a model – the modeler must always keep in mind the difficulty of polishing. In most cases it is actually easier and better to polish and then assemble ( solder) separate parts than it is to get inside difficult areas with the polishing brushes.

The table below was created for our viewers who would like to learn about and see the different types of shanks used in jewelry design. For each type of shank, we provide a corresponding image, a description, and a link to models on Jewelrythis with that shank.

Bypass
Rather than forming a straight line where the beginning of the band meets the end, the two sides of the band 'bypass' each other so that the end of the ring doesn't meet the beginning.


Criss Cross

Euro Style
With the Euro band, instead of the traditional rounded bottom, the shank is flat at the bottom.



Half Bezel

Knife Edge
Band has two slanted sides that meet at a point at the top.


Reversed Tapered

Split
On this ring, the shank splits from the head of the ring into two separate strands, which creates the look of two separate bands.

Split Pinched



Traditional



Below is a short list of important mistakes to avoid making when designing a clasp:

  1. Not finishing the clasp (no hole for the wire)
  2. Making the clasp too narrow for a hole- need to make it wide enough
  3. Not giving the clasp a rounded end.

Sometimes a model will be designed with a setting that actually makes it impossible to set the center stone. Another design problem often seen is that there isn’t enough support for the stone. These two issues are discussed briefly below:

Center Stones – impossible to set the center stone
top view2

Side Stone Prongs: long prongs – the bottom should be raised to support the stone from the bottom.
side prongs

Another View: bottom should be 0.72 mm higher than the original bottom.
side view