It is hard to believe that it was almost ten years ago I witnessed a CNC router in action for the very first time. I was fascinated and simply had to have one! Although I had been in the creative end of the three dimensional sign business for most of my life I didn't really know what I would do with one of these machines - but I just knew it could do fantastic stuff.

Along with the CNC router I discovered the wonderful material called Precision Board and the glues, primers and other companion products they offer. Since then we have gone through many tons of the material using it in most signs and projects we tackle. This journal will chronicle our many adventures both past, present and future. I'll talk from the perspective of someone who pushes these products to the creative limit on a daily basis. I'll be adding to the stories two or three times each week. -dan

Sunday, June 12, 2011

Using bitmaps to their best advantage

One of the most often asked questions I get concerning my TEXTURE MAGIC bitmap file collection is whether the files are big enough to cover a 4' x 8' sheet of material. The answer is yes. The next routing project for the Fox & Hounds Pub demonstrates this nicely. The piece we are creating today measures six feet long. It is the mantle for the fireplace in the pub restaurant.

 As a bit of a lark I drew the mantle concept with the phrase 'who let the dogs out?' carved into it. It was a tongue in cheek reference to the hounds that chase the fox. The owners absolutely loved it and it was there to stay. On this project we are striving for a heightened realism, with a slight twist towards fantasy. The woodgrains needed to be realistic.

I started by creating the vectors I needed to create the reliefs. The mantle has an arched bottom. The lettering has a somewhat old english feel to it to tell our story well. I added a 0.2" outline to the lettering. This would be painted dark to allow the lettering to pop off the woodgrain background.

As with all the files I build in EnRoute there are many paths to the same result. On this file I started with the letter outline and then modified these reliefs with the bevelled lettering. These would be floated into position after we created our background and then merged (highest) to form one relief.

I created a flat relief of the mantle, then imported the sandblasted woodgrain bitmap from my TEXTURE MAGIC collection. By default it opens to fit the plate defined. The bitmaps in the collection are 11" x 8.5" at 300 dpi. This is much too fine a resolution to create a router file. I generally design in EnRoute at 50 DPI - the limiting factor being the size of the bit we are going to use. The final pass on this file is going to be a 1/8" ball nose bit - plenty small for the detail I require.

So it is necessary to enlarge the bitmap big enough to allow the bit to route the detail. The sandblasted bitmap file from the TEXTURE MAGIC collection is actually six boards glue up, meaning there are six different woodgrains to choose from in this one bitmap file. I stretched the bitmap file out large enough vertically to fit my mantle into the woodgrain I chose for this project. Then I stretched it out horizontally as well to cover my  relief.

Then I used the apply relief command to apply the bitmap to the relief. The basic principle is that black does nothing. White raises the relief to the amount you specify. (I entered a value of 0.2" ) Grays do something in between, depending on their color value.

This was tool pathed with a rough pass using a 3/8" ball nose bit set at a 50% overlap.

The final pass was programmed using a 1/8" ball nose bit with a 80% overlap. I have found this generates superb detail in the 30 lb Precision Board which we use for the bulk of our projects.  The photo below shows that pass in progress on the left side of the relief.

As this file comes off the router I will be heating it to form the curved mantle I desire, then glue it up to a plywood box cut to shape. Stay tuned...