Parent Category: Big Blue Saw Blog
Created: Friday, 26 February 2016 17:10
Written by Julie Simancek
With greater availability of digital technology, we have seen an increased demand for waterjet cutting jewelry components. This is the first part of a two part article on how to use Big Blue Saw’s waterjet and laser cutting services to get the best components and parts for that new jewelry line you are thinking of creating.
It all starts with a drawing
Firstly, we will need a drawing of your new part. Personally, I like start out in my sketchbook, and fiddle around with construction paper until I have a few shapes that really catch my fancy.
Now it’s time to get these digitized. I could scan in my sketchbook, and then try using a tracing program to trace these shapes, but that would give me shapes that are imprecise and a little wonky. Wonky doesn’t work for stone settings or creating parts that fit together well. So drawing it out in design software is the way to go.
There are a whole slew of free and paid CAD programs out there in which you can design your pieces. Some are easier to learn than others. The more the program is focused on engineering clients, the harder it will be to pick up and learn- however once you have something designed in say, Solidworks, all of the pain pays off. The settings I design in Solidworks can actually exist in real life and they keep their dimensional constraints. Which is a fancy way of saying that I can dictate exactly what size I want all of the elements in a part to be. No designing it and then realizing it won’t fit my stone in real life.
If you have and are familiar with Adobe Illustrator, you are already a step ahead of the game. Illustrator can be used to create vector images and DXF files. The difference between a vector image and your familiar jpeg, is that you can scale up or down a vector image without losing detail or having your curves devolve into choppy pixel soup. From Illustrator, you can save your drawing as a EPS file or get a DXF export plugin from PluginsWorld.com, and export a DXF file.
Don’t have Illustrator? There are also a lot of free CAD programs out there that you can download and use for your drawing. Click here for a list of our recommended CAD software.
Get it all down in black and white
Essentially, all the cutter needs to know is what is the part and what is waste. This is similar to when we were kids and cut snowflakes out of construction paper. You want your part to be easily defined as a black and white outline or silhouette. Like this:
Plan around the limitations of the cutting tool
In the drawing above, two of the rings have 1 hole and the third has two.
The waterjet can’t make holes that are perfectly round that are less than 0.1”, and in the 0.04” to 0.09” range, any holes that it does make are oblong and not perfectly round.
The laser cutter can cut holes that are smaller than that, but the plastic can get really melty and ooze into the hole it just cut.
So for the sake of making sure that every hole I cut will be accurate, I only have the machines cut the holes that are 0.1” and larger. All the smaller holes you see in my examples are drilled out with a drill bit in my Foredom rotary cutting tool.
Interior corners can also be tough to get accurate as well. If the angle of the hole in a part is smaller than the kerf of the waterjet or laser cutter, it will cut that corner a bit short.
So in this drawing, we have a interior corner that is sharper than what the waterjet can do. Instead of trying to cut that tiny bit and messing up the corner, it will round the hole off where the blue line is.
When I’m designing for these kinds of cuts, I usually use the Fillet tool to smooth down these interior corners, thicken up connections between areas, and create smooth transitions from one side to the other. Software like Solidworks will allow you to create exacting designs where tiny tips of stars touch other thin webwork designs exactly in the center with extreme precision, but that doesn’t mean that when your part is cut from the material that it will be as perfect as you designed it. Super thin areas of webwork design get blasted into oblivion in the waterjet, and the laser cutter will cut things so finely that even gentle handling after cutting makes it crumble. Be sure to keep all of the parts of your designs thick enough to withstand general wear and tear.
So how thin of a strip can you cut with the waterjet? Well, that depends a lot on how thick your metal is and how supported it is. Cutting a lace pattern out of sheet metal would be cool, but you’ll want to scale the design up till the individual lines in the pattern are 0.09” or larger. Otherwise the water stream is going to blast the material away and end up doing waterjet air guitar in the pattern you’ve designed. Waterjet air guitar doesn’t give us pretty pieces to work with.
You might be able to cut a few thinner lines if they are surrounded by solid parts. You could cut something like this and have it work out:
Those two thinner strips in the middle are connected on both ends and supported by the thicker edge on the pendant. What wouldn’t cut well would be something like this:
Trying to cut that could work out one of two ways. One, the strip down the middle is too thin and gets blasted into oblivion under the water stream. Two, because it is unsupported, it can start to vibrate like a tuning fork under the pressure of the water stream. That wiggle will make the cutting path wiggly- and I’ll end up with a mess instead of the pendant I wanted.
If that was my design, and I needed to cut a bunch of these for a line of jewelry, I would make my CAD drawing look like this:
Then after cutting on the waterjet, I’d cut the bottom of the strip off with my jeweler’s saw.
Checking your corners and hole sizes.
A quick easy way to check your part to make sure that it will cut well is to create a hole and corner tool. So for checking hole sizes, draw a circle that is 0.1” in diameter and change the outline to something easy to see like orange. Now use the selection tool to drag the orange circle over the holes in your piece. If they fit inside the circle, they may cut oblong or get messed up. Same goes for interior corners, draw a circle that is 0.04”, and drag it over all of the interior corners. If the corner is smaller than the circle, then the waterjet is going to stop short of going all the way in. Which means that you’ll need to decide if you want to get in there with a file or jeweler's saw post cutting.
What about shapes?
If you’ve ever looked at the costs involved in getting a custom stamping die, you know why most jewelers only own a circle cutter. Fact is, you can use the waterjet and laser cutter to blank out a ton of shapes in metal and plastic, but there are some limits to this. Metal shapes that are smaller than a dime run the risk of getting blasted away the same way tiny strips of metal do. They also will have to be tabbed to a sheet so that they don’t fall into the water tank on the waterjet. Here is a link showing what small waterjet cut features look like. The little “V”s at the top of the parts are the tabs. If your parts are tiny or have a bunch of rough edges, there may not be a good place to put or they may obstruct the perimeter of the part enough to make usability questionable.
That said, if you need 100 triangles, 40 kitty pendants, 20 new bangle bracelet bands, 60 ring bases, and 12 earring dangles; the waterjet can cut them all out of the same sheet of copper or brass in a single sitting. With no fees for custom machining separate stamping dies for each shape.
Can you cut precious metals and sheet I send you?
Usually we can. There are some brittle elements like gallium that shatter in the waterjet, so we can’t guarantee materials that we haven’t cut before. We’ve tried cutting glass, and it has always shattered, so we won’t take that in. There are some metals like gold and platinum group metals where the drops and lost sweeps negate the benefits of waterjet cutting, so plan your profit margins accordingly.
If you can cut it with your jeweler’s saw, it should work in the waterjet. Our laser cutter doesn’t have the muscle to cut metal.
We also can’t do same line cutting. We do have some kicking nesting software that will get you the most mileage out of your sheet though. If you are looking to have me cut your sheet, email me at firstname.lastname@example.org and we’ll talk about the particulars.
The ideal parts, cut just the way you want them.
So what works the best in the waterjet? Bigger components that would take a ton of time and skill to saw out with a jeweler’s saw. Chunky ring bases, statement necklace bibs, cuff bracelet blanks, bangle bracelets, shapes for pendants and earrings all work really well when they are designed with the waterjet’s abilities in mind. The accuracy of the machine means that cutting geometric shapes is a lot less of a hassle than when doing it by hand, and the edge clean up for a waterjet part is less than for a hand sawn piece. So get designing, and stay tuned for round two where I show off some examples and talk about finishing techniques!