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.

Friday, 16 December 2011

Fixing those jagged edges......the easy way!!!

Yesterday I touched on smarter toolpathing to get rid of the jagged vertical edges that can crop up in Aspire. Especially if you didn't pick the right modeling resolution at the start of a project. I generally model at a very high resolution, but the jagged can still rear it's ugly head.
One of the things to keep in mind when doing this is, a ball nose cutter on a 3D finishing cut is calculated to the CENTER of the cutter. Roughing passes are calculated to the EDGE of the cutter.

On the text of the Shelby sign, I have modeled the text, I also modeled an offset lip from the text, and then the textured base where all of this resides. The text lip is there in case I want to add a color behind the text to make it pop.
Here is the result of the first 3D toolpath. You can definitely see the jagged portions of the text. There are also a lot of places my 1/4" cutter was unable to get into.
 Now Aspire will do everything it can not to compromise the model in anyway, jagged and everything. This is why I kept all the text portions as separate components.
I am using a 5.5 degree tapered ballnose for the text cleanup on this. It has a 1/4" shaft and tapers down to a 1/32" ball tip.I selected the vectors I used to generate the text portion, and offset them outwards by just over half the diameter of the previous cutter. As I used a 1/4" ballnose for that run, my offset was set to .130". This lets my small tapered cutter clean off the rad left by the 1/4" ballnose cutter, right back to the original text vector. Normally I would offset my original text vector by half the diameter of the tapered ballnose, but the results were so small it didn't matter much. Now before I toolpath this, I want to hide the text component as shown in the above image. This lets Aspire ignore the text portion on this particular cut, as we don't want it to try and protect the jagged edge text.
The next important part is to select an OFFSET 3d machining strategy between the two selected vector boundaries. This strategy will let the cutter follow the outline of the vector text, effectively milling away any jaggedness, while still respecting the geometry under it. I also repeated the process for the text lip. This process works wonders for vertical edge cleanup and can save a ton of hand finishing work later.
The difference can be quite dramatic depending on the modeling resolution you choose in the beginning. Using this kind of toolpathing can even let you get away with a larger 3d maching stepover, which can be very noticable when it comes to the vertical edge.
 I got the first coat of primer on this one today, and will get the second one on tomorrow.

I was also able to cut another sign today that will be an experiment between 3d textures and flat bed printing. That should be fun!
8)
JO

1 comment:

  1. Very nice. And that is why I will always go to you for any 3d machining. If you want the best, go to the best. And you my friend bar none are the best. Thank you as always for your blog posts, they have become an integral part of my day and even inspired me to create my own blog.

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