Celtic Cross

[edcoleman]

OK, I mentioned this project in another thread and it was suggested that I explain the whole process....here goes:

I had a customer call and ask for a celtic cross design based upon an old stone cross they had seen while traveling in Scotland. Here’s a picture of the side of the cross they wanted me to re-create:


18927.jpg

I searched clipart sources for anything that might be applicable, but didn’t find anything too useful. Then I contacted an artist specializing in original celtic designs. She gave me an estimate (which I thought was very fair) for creating the artwork for me, but more importantly suggested that I push my limits and try and do the design myself. I figured that she’d most certainly do a better job at the artwork, but that it might not be the most “CNC-able” so I figured I’d give it a go. Here is the result:


18928.jpg

Programs used: Corel Draw and Vcarve Pro.
Machined on the shopbot and artwork laser engraved with a 35W ULS laser.

Here’s how I got to the finished product:

1)via web searches I found a celtic cross outline that I liked the proportions of and then pasted the graphic of the stonework inside the outline

2)I printed out the overlayed graphic and then used tracing paper and a pencil to use the underlaying graphic as a guide to create the shape of the branches and leaves. I tried to simplify the branches (keeping in mind that I needed to machine this thing).

3)Once I got a graphic I liked I scanned in the paper tracing into the computer to use as a basis for the vector artwork. Using Corel Draw I placed the scanned image on one layer and created a vector tracing layer on top of it. Sort of the same thing I did with the tracing paper and pencil in real life but on the computer. Now, I could have skipped the pencil and paper step and done everything in Corel from the start, but it was much more natural for me to refine the design with a pencil rather than a mouse.

4)To complete the decorative graphics I used a feature of corel that applies shading to a region and give the illusion of a 3D bevel, then added clipart for the animals and knotwork.

5)Export the cross outline vectors to VCarve Pro and do toolpathing for the cutout of the cross.

6)With the cross cut out, convert all the decorative graphics to a grayscale bitmap with a black background and send that bitmap to the laser engraver. The laser did an area clear of the dark areas and just “shaded” the vines and animals. See below for what I'm talking about:


18929.jpg

7)The cross was cut with a tennon at the bottom which was fitted into the base to make a free standing finished piece.

8)Finish the completed project with tung oil.


The point of the original post in the other thread was that pushing your limits can result in surprising yourself and you can be that much more proud of the end result if you do it all yourself.

-Ed

[harryball]

Pretty. That's the creative stuff I'm talking about I wish I had more time to do. Great job Ed.

What kind of wood is that and how long did it take for the tung oil soak in to be dry to the touch?

"35W ULS laser"
:-( one day... I'd be happy with a small mini laser like the epilog mini-18. I've got $6k set aside for a laser engraver so far... still waiting.

Robert

[Brady Watson]

As usual Ed, your stuff looks great! Keep up the good work!

-B

[edcoleman]

Thanks for the feedback, Robert and Brady.

The wood is cherry and the finish is a tung oil product made by waterlox

www.waterlox.com

It's really a nice finish and easy to apply. Here's the "trick" a furniture maker gave to me:

Apply the waterlox liberally using a rag, brush, etc and allow it to soak in for about 20 mins.

with a clean rag wipe off the excess finish and allow to dry overnight

Next day...buff the finish with 0000 steel wool, blow off all fibers and reapply finish as before.

Repeat this for at least three coats.

For a satin finish buff out the final layer with 0000 steel wool. For a gloss finish buff out with 0000 steel wool lubricated with mineral oil.

The nice part about this finish is it is very "repairable" if at any point there is a a problem you can simply apply more of the oil to build up the finish. The only caveat is if you have used the mineral oil for a gloss finish you need to strip the oil or the new coats won't stick. I've never had to do this, but "Dawn" dishwashing detergent was recommended for this process if necessary.

-Ed

PS: Be very careful with the oil soaked rags used in this finish application. They are a potential fire hazard as they dry. I haven't had a problem myself but know of fires that have started due to careless handling at the above mentioned furniture maker's shop.