CNC SIGN PROJECTS - MAKING TEST PIECES -

CNC SIGN PROJECTS – MAKING TEST PIECES

Written By: Bill Griggs - Sep• 29•12

MAKING TEST PIECES

Part 8

In this eigth part of the CNC Sign Projects tutorial series we will be making test pieces for the sign. Since I only had one piece of oak I’d only get one shot at cutting the sign correctly So rather than risk ruining the oak, I put a piece of MDF board on the router table and ran the G code that I had created. I have been using MDF for the test material because it is cheap and easy to come by. I would try a technique and if it didn’t work I would just cut the next technique over the previous one. Usually I could get two or three tries before I had to change the wood.

FIRST ATTEMPT

I have also been experimenting with different color stains and paint to get the look I wanted. Here are some picture of the attempts. When I got a technique I was happy with, I will made the sign in the expensive OAK board. One thing I found is that the Best Bit for doing this kind of work is the Laser Point Bit from CMT. Here is a link to the Bit I used. I got it on Amazon (Disclosure).

The first cut I made was the PhotoVCarve file at .003 of an inch in depth. It took about 45 minutes to run the program from start to finish on my CNC Router. After I was done you can clearly see a silhouette of a cow head. I lightly buffed the surface of the material with a Scotch-Brite pad. The pad removed all the little, fuzzy bits and pieces of wood without removing the carving details. I used the vacuum to remove any dust from the surface of the MDF and then a Tack rag to clean the rest.

I use Minwax stain with a soft cloth to wipe onto the surface of the MDF. Then I used a clean rag to sweep off the excess stain. The stain spread into the wood around the cowhead, which was not what I wanted. So I decided to let the project dry overnight and try a different approach later..

PhotoVCarved at .003″ depth. Lightly wiped with a Scotch-Brite Pad.

Rockler 3-Pc Signmaking Bit Set, 1/4”” Shanks – $69.99
Retail Price: $79.99
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from: Rockler Woodworking and Hardware

When the stain dried the next morning, I lightly sanded the piece with a random orbit Sander. I hoped that a light sanding would bring the picture into clear view but it did not. I had made two mistakes with this test piece. The first mistake was not cutting deeply enough into the wood, the second mistake was to not seal the wood before applying the stain. I increased the depth of cut by .003″ and ran the program program again. This time the results were better. It looked clearer but it still wasn’t perfect. Since I was getting frustrated, I decided to try something different.

Minwax Provincial 211 stain was used on the first attempt.

SOMETHING DIFFERENT – SECOND ATTEMPT

Since I was starting to run out of time I decided to try making a V carve pattern instead of the photo V-Carve. I have had good success with V-Carve patterns before so I figured it would look fine. Since I was being cheap with my scrap wood, I I decided to cut the V-Carve pattern over my previous attempt. Some times being cheap pays off.

To create a v carving I had to go back into Aspire. I used the fit Vectors to bitmap function to create vectors from the photograph. I did this in several stages and kept the previous vectors each time. To keep the previous vectors, uncheck the replace existing vectors box. By using the Fit vectors to bitmap function this way, it gave me a pattern which was much more detailed. Then I took the vectors that were created and used them to create a v carving with a maximum depth of one quarter of an inch. I loaded the file onto a thumb drive, took it out to the machine and ran the program.

I hand cut the paint mask to stop Over spray.

After I ran the program I realize that the two images were not indexed together properly. The V Carving was slightly larger than the previous photo vcarve. Since it was just a test case I didn’t bother fixing it.

V-Carve test piece looked promising. but indexing was off.

PAINT MASK

I covered the bare carving with paint mask film. This protected the surface from over-spray. I used a Squeegee to burnish the surface of the paint mask to make sure it stuck down. I wanted to try as many different techniques as I could because I wanted to know which ones were the most efficient. So I just went ahead and sprayed the stencil ink into the carving. As you can see even with the mistakes this looked pretty good.
If you are having trouble locating paint masking film you can click this link to find some. GET CNC paint mask

LESSONS LEARNED

I learned many lessons while making these test pieces. First off I learned that the depth of cut is very important when is comes to making a Photo V-Carving. Too little depth and there is not enough separation between lines to make the effect work.. I also learned that paint mask film needs to be rubbed down or else it will peel away while cutting. Use a squeegee as a mandatory step. I also learned that it is necessary to seal the wood after carving but before color is added. The sealer prevents the color from bleeding into the surrounding wood.

NEXT TIME

In the next part of this CNC Sign Projects tutorial, I will show one more test piece I tried. It has a lot of potential and is fairly quick to do. It does take a light touch and a good bit of artistry but the results were good and it was fun to do.