Step 1: Laser cut your outer bowl
Firstly you will need to Laser cut your outer bowl using 3mm acrylic. I used black for the top and bottom section and orange light gathering plastic for the sides.
Step 2: Slot together your laser cuts
After you have cut all your pieces you will need to peel off any of the outer protective plastic.
Slot each of your edge pieces into the top section (the large circle) of your bowl first. It is easiest to do this with the top section laying flat on the desk.
Then add on the base ring and push down gently until all of the slots are in position and flush with the bottom of your bowl.
Depending on which size bowl you are making the base slots are slightly different. The lager bowl has double the slots to hold the bowl in place. You have now finished the outer section and are ready to make your inside bowl.
Step 3: Make your press form
Firstly laser cut six to eight disks the same size as the top section of your outer bowl and remove the protective outer plastic. Make sure the surfaces are clean and bond them together using super glue.
When you have glued on the last layer place it in a vice for 15 mins to set. You will be left with a press form looking like this:
Step 4: Cut and anneal copper sheet
Cut a piece of square copper sheet on a guillotine. This should be around 1mm thick and overlap your press form at the edges by around 10-20mm.
Anneal your copper using a large torch to a cherry red color.
Quench in water and then place in the pickle for five to ten minutes to clean.
Step 5: Press form your bowl
Place your laser cut press form on to the base of the press form machine. Then lay your annealed copper sheet on top making sure the copper overlaps equally around the press form.
On top of this you should place a thick sheet of rubber followed by a steel block.
Pump the hydraulic press up to about 5 bar of pressure and then release. Remove each of the items you have placed on the press one at a time. You may need to re-anneal and repeat this if you require a deeper bowl.
Step 6: Cut out your bowl
Thread your piercing saw tightly and begin to cut neatly around the edge of the bowl. There will be a line on the underneath left behind from the press form. Follow this neatly and try not to cut inside the line.
Step 6: File and sand
File the edge of your copper bowl with a large flat file until all of the saw marks are gone and the edges sit flush with your laser cut outer section when you place it on top.
Sand the edges of the bowl using 400, 800 and then 1200 emery paper. To finish the edge to a high polish rub a burnisher over it.
Then sand the surfaces of the bowl in a circular motion until any of the large scratches are removed. Start with a rough emery paper such as 2500 or 400 and work your way up the grades until you are happy with the finish.
If you want a really good finish on your metal, rub over finally using wire wool until you have en equal surface all over. Light should be bouncing off all angles and there should be no vizable linear scratches. If you are going to patina your copper it is a good ides to wear gloves at this point to keep grease off the surface of the metal.
Step 7: Oxidize your copper bowl
Make up your oxidizing solution in a tub large enough to contain your copper bowl. I tested both liquid liver of sulfur and platinol, but found that the liver of sulfur gave a much better surface finish.
Liver of Sulfur Platinol
To make up your liver of sulfur use enough warm water to cover your copper bowl. Add a drop of liquid liver of sulfur. Place your copper bowl in the solution for a few seconds, then remove and rinse under running water. Repeat this until you are happy with the color of your finish. Adding the liver of sulfur gradually and washing will leave a smoother and better bonded finish.
Finally dry your copper bowl with a towel and place on top of your laser cut outer section.
There are two different sized bowls available in this series, 180mm and 89mm width. Files are available to download below:
Laser cut bowl file
Press form file
Laser cut bowl file
Press form file
Why make a Laser cut bowl?
Laser cutting can be used as a very quick and accurate means of production when cutting multiple flat parts. It is much quicker that more traditional means of cutting with a saw and leaves a much neater edge. It leaves out the need to file and sand and polish the edges for hours on end. The laser leaves a very smooth and shiny finished edge.
These traits lead them selves well to producing accurate press forms. Without the laser cutter a more traditional means of making a press form would be to hand pierce a thick sheet of acrylic and then file all the saw marks out at a 90 degree angle. It is much quicker to laser cut multiple sheets of acrylic and glue together and the finish of the edges can be much neater depending on your filing ans sanding skills.
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