When I lent my services to a collegue who was working on a film about 12 years ago, I was introduced to the world of cnc. I remember watching this huge machining centre milling out a slab of mdf and turning it into a fantastic set of gears. I knew that it would have taken me hours to achieve the same thing with traditional power tools. I decided then that I would invest in a cnc router for my own business Oxenham Design. At that time I could turn on a computer, but even to check email seemed like a crazy set of operations. I persevered and learned every piece of relevant software I could get my hands on. I am now fortunate enough to be using Vectric's ASPIRE software, and Techno cnc routers, which has helped us to create some amazing projects, both in part, or in full. I thought that this blog would be a great place to share "behind the scenes" adventures with the software, materials and equipment we use, as well as the projects we build.

Wednesday, 17 April 2013

Round in the square

Adding a round hole in the center of a square plate seems simple enough, but when coupled with the smoothing aspect of subdivision surface modelling, it can get a little confusing and frustrating to say the least.
But we're going to use the fact that the software averages out the vertexes, and rounds everything out to our advantage!
Here's a low resolution cube that was squashed a bit into a plate. The size isn't important for this task.
I've deleted the back face as we won't be using this at all.
I've added an edge loop down the center of the cube in both directions. This defines the center of the plate, and gives us some vertex edges we will use for our round hole.
And based off of yesterdays post, I've also added the edge loops really close the the edges of the plate. This will keep the corners of the plate sharp. And because I deleted the back face in the beginning, the edges that border that opening will stay sharp as there is no face for the software to average against!
Using the 'free tessellate' tool, I drew 4 more edges onto the face of the cube in a diamond pattern. If you use the shift key while in the 'free tessellate' tool, it will snap to the center of the edge your connecting to.

At this point it's wise to move the whole plate we made to location 0,0,0. This will aid in setting up the rest of the job at hand.
If we select the 4 points on the diamond, and look at the properties tab, we can see the overall size of the diamond shape. We'll be using this number for the next step.
Ive added a cylinder primitive with the default sections set to 8. If we smooth this cylinder, it will go round, so were going to use this as a template for our hole.
With our cylinder selected, we can change the size of it to match the numbers of our diamond shape I drew on the plate. Then we can move it to location 0,0,0. This will place it dead center of the plate.
Looking dead on, we can see the overall size of the cylinder is the exact same size of the diamond on the plate. We just need to add a few more vertex edges to our plate to get the hole shape we need.
I simply split the diamond edges out to the corner points. If you take the time to count, you'll see that every polygon still has 4 edges, this will smooth predictably for us. But we have a couple of steps left to our round hole.
Using the center yellow scale cube on the manipulator lets me move the 4 selected point outward at the same consistent rate.
We're done with the cylinder now, so I just deleted it. But now we have the lines we need for the hole.
We have 2 choices at this point. We can delete the selected polygons leaving the hole open, or we can extrude them back to create a pocket hole with a bottom to it. We're going to extrude them back.
Holding the ctrl key enters the 'extrude' mode. And then I simply extruded the octagon inwards. This is our low resolution pocket hole.
If I smooth this now, we get this shape. It's almost right, but not yet. You can see that the hole isn't very defined, and out of round, due to the low resolution.
I've added 2 new edge loops right close to the top and bottom of the hole. This increases the resolution at these 2 spots, which will keep the edges sharp.
You can clearly see that the hole is much more defined with the added edgeloops.
If I add one more edgeloop on the other side, so we end up with a loop on both sides of the hole opening, the hole will be very sharp and defined
Once we smooth it, it's held it's edge perfectly!

So in fact, using a SDS modeller like Hexagon, Blender, silo, 3ds max, etc, we can actually model anything from organic characters, to hard surface models like cars and appliances, with an exceptional amount of visual accuracy.

One of the renders we did a while ago featured this process for recessed set screw holes in a beer dispensing tap:
 This was all done in the computer, modeled in Hexagon and rendered in another software package.
There is no limit to the details that can be created by breaking big jobs into smaller pieces. I even modeled the threads that hold the tap handles. It was modeled at full size, so if the handle need to be fabricated, I can send the file to the manufacturer.

I think for tomorrow I'll pick an everyday item, and run another simple tutorial on how to model it.

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