Engraving Silver & Gold Pendants
We decided to produce our own designs for a range of sterling silver and 9ct gold pendants.
We knew from past experience that unless a large number are cast, it is not cost effective to go down the route of having rubber moulds made for each and every design. So how do you create pendants quickly and still keep the price affordable in small batches?
We investigated a number of techniques and processes and decided to lash out and acquire a CNC (computer numerical control) mill. This allows us to create a design on a computer and from that, produce as few or many copies as we like. Sounds like a plan, should be easy!
The information below is general in nature and does not describe all of the many steps involved, nor any of them in great detail. We have spent many hours fine tuning these processes and can't give away all our secrets!
There are essentially 4 steps from go to woe in the process of using a CNC milling machine to produce pendants.
Creating the design.
The first step is creating a design, which is usually roughed out on paper and redrawn until we are happy with the result. This is then transferred to the design computer for finishing into a vector image.
Processing the design (CAD)
This can be done by scanning the original (and then processing it) or by recreating it in a CAD/graphics software package. As our pendants are 2.5D rather than 3D, we chose to use CorelDraw as our design software.
So our designs can be reproduced in various sizes, it is important to have them as vectors rather than bitmap images. Vectors can be resized without any loss of quality, whereas bitmaps lose quality when they are enlarged.
A bitmap image file records the colour and brightness of each dot in an image.
The lines in the smaller image are sharp and distinct and are suitable for creating an engraving.
The image in the lower left was doubled in size creating the larger picture of the girl.
The lines in the larger image have become blurry and jagged and would not be suitable for use as an image for engraving.
This is what happens when a bitmap file is increased in size, because the new dots added to create the larger image have to be 'guessed' by software.
A vector image file however is a mathematical definition of the colours, lines, shapes, curves and points in an image.
This means it can be made any size without the loss in quality that occurs when enlarging a bitmap file.
Building the milling instructions (CAM)
After we have our image saved as a vector drawing it needs to be processed to produce the instructions for the CNC milling machine to follow. This is done in CAM (computer aided manufacture) software. Each component in the drawing must be selected and a cutting style applied to it.
Some lines need to be cut within the line, some outside the line and some on the line. There are also 'pockets' where the whole inside of a shape needs to be engraved. This is all done within the CAM software and can be time consuming.
Creating the pendant (CNC)
The results of selecting the cutting styles of the image are saved to a 'g-code' file which is loaded into the cutting software that controls the CNC milling machine. The cutting software moves the cutting tool in the milling machine on 3 axes (yes, that is the plural of axis), left/right, back/forward and up/down. This creates the lines and patterns on the silver or gold pendant by removing metal and leaving a depression.
These depressions may then be darkened (tarnished) with a liver of sulphur solution and final polishing is then performed.
Some videos are below which better show off the beautiful Circle Pattern Designs
This is our first engraved pendant in 925 sterling silver. (July 2014)
The dimensions are 24mm x 18mm x 0.9mm
The engraved section has been darkened with a liver of sulphur solution and polished to a mirror finish.
We will soon be offering a wide range of our own designs in addition to taking custom orders where you provide us with the design of your choice.
did the 60's go?
This is our first geometric pendant and has been coloured with liver of sulphur to darken the background.
Each piece is our geometric range is a limited edition engraving.
As the colouring is applied by hand, the results will be a little different on each one.
The maximum we will produce of any design is 10 and many will be 'one off' unique and exclusive designs.
Our geometric range will be available for sale soon.
Our second pendant was given a reduced time in the liver of sulphur and the result is a blue/green tinge to the background.
This is a great effect but it will darken to grey in time.