Step 1: Cutting Your Strips
The first step of the quest is to decide how you will achieve your chequered pieces.
The simplest way of doing this is to start by taking 2 Seperate colours of Corian and cut them into strips the same width. My Corian pieces are 13mm thick and I am wanting to achieve a 50mm diameter sphere, so each half would need to be 25mm.... Placing 2 pieces on top of each other would be 26mm, leaving a millimetre spare to play with!
Step 2: Lick N Stick
After the strips are cut, they need laminating together. Each side needs to be keyed up with 80 grit sandpaper so that the epoxy resin binds properly to each piece of Corian. Line up the strips, alternate the colours whilst adding resin to each side, then clamp together.
Step 3: Square, Chop, Lick Then Stick
Once they are dry, sand the excess resin away to get a flat surface on each side, or use a router with a skimming but to flycut a flat face.
Square up the slab and trim the excess away, leaving your stripey slab! Now, set you fence on the band saw to the same width as the thickness of material, in my case 13mm and trim the slab into slices.
Offset the strips to create the chequered effect and then glue again using epoxy.
Repeat the process until you have enough material to slab ontop of each other to create the correct thickness to cnc.
Step 4: CAD Time!
While it's glueing, take the time to design the model in a CAD package, in my case I use solidworks, and get your maths right!!
Step 5: Nearly Time for CNC
Now we have our pieces slabbed, it's time to square up, double check fit ment and size.... The slabs can then be taped down to the baseboard ready for the cut.
But first, the operations an tool libraries need to be set using your CAM package, I'll be using Alphacam.
Step 6: CNC Machining
When using the CNC router, we tend to use an MDF baseboard, which we manually offset from the bed when loading the cutting operations into the computer. The baseboard I there and an insurance policy so we don't crash the cutting head into the aluminium vacuum bed.
Once the vacuum bed is activated and the board is sucked down, we can begin machine! :)
When designing the ball on the computer, I had to make 4 cutting operations in total, 2 for each Half of the ball. The first operation is roughing the INSIDE profile of the ball. This is so we have the cavity of the material removed and a flat surface area so that we can flip the material over and machine the outside profile.
Now I know that your thinking "how do you line up the material so it's bang in the centre?" Well, before we stick the material down to the baseboard, we "score" the baseboard. This gives the outside profile of the part, showing where it's most outer edge is. From here, we use double sided tape to attach the material to the scored baseboard.
When machining Corian on the CNC, we slow the feed rate right down as it is a very hard material and the CNC is relentless. Run it too fast and the part could explode or the cutter being used will wear down quickly, heat up and damage itself. Too slow and you run the risk again of splitting the material at it's glued seems. Corian takes time to understand how it likes to be machined, so bare that in mind!
Step 7: Polishing and Finishing
Polishing the parts is reletively hard work and very boring! :( but on the upside, it's the finishing stage! :)
Because it's so small and curved, we don't want to use power sanding equipment on it as it will put flat spots in the surface, so all will be done by hand.
You will need a range of wet and dry papers. Start by using 320 grit and flat off any machining marks left by the CNC. Move onto 400, then 600, then 800 grit to finish. You could keep on going but from my experience polishing Corian, 800-1000 grit is a nice finisher to get a decent gloss.
Remember, between each sanding grit, dry the ball off so you can see any areas that may need attention.
Time to bring the shine! :) use a rag to apply your polishing compound and another rag to buff it off. Use a corse and fine compound on the surface. Finish with a regular car paint surface polish.... And.....
Step 8: Final Product
WA-LA! A machined chequered ball which is a secret hiding place for those small items like rings or necklaces!
Don't forget to Instagram me: jfworks so that you can see all the things I make!