Introduction: Hogwarts Crest - CNC Milling
What you will need:
- Programs: Vector program (Such as adobe illustrator or Correl draw, I will be using Vcarve). CNC Mill tool path design program (I am using Vcarve Pro 8.5). CNC Mill control Program (I will be using shopbot).
- Materials: A piece of wood, your CNC mill size will determine the dimensions you can allow. I am using up some leftover scrap plywood from another project. It is .75" thick and has about a 20x25" field of usable material.
- Optional: Acrylic paint, hanging hardware.
In this project I will demo uses of a vcarve, profile and pocket cuts on the Vcarve Pro 8.5 program with my ShopBot. We will also have lots of fun finishing and painting our Hogwarts crest!
Step 1: Bitmap to Vector Lines
Download any black and white bitmap image of the Hogwarts Crest, I selected a relatively simple one that would be easy to trace in Vcarve. You can also do this in any other vector program including illustrator and Corel draw.
After importing the image click on the icon of the chicken to trace the drawing. Using the sliding bars on the left-hand side you can control the vector quality.
Also remember to click the preview button, this will make it easier to control the results.
Step 2: Scale
Now you can remove the bitmap image and will have the vector outlines remaining. I am choosing to leave out the banners for this project and will focus on the crest. Click the "Set Size" button under the transform objects headline on the left menu bar. I am making the width 18", click the "Link XY" box to make sure the dimensions are stretched in one direction and remain proportional.
I will come back to resizing and placing your drawing to match the material placement later in this instructable.
Step 3: Plan a VCarve Toolpath
Pin the "Toolpaths" bar on the right so you have it accessible. Select vectors to create a V-Carve cut. I am using a 90degree 1/2 inch diameter VCarve bit and a 1/4" down-spiral to clear out the material. Refer to the images for my pass depth and feed rate settings. You may know settings that better match your bits, material and machine. Be sure to click the clearing tool option box so the vbit doesn't have to do too much unnecessary work. After you have determined your bit selections, feeds & speeds then hit the calculate button on the bottom of the toolpath bar.
Everyone's settings will vary depending on their machine, material and tools but here are mine:
Settings: V-Carve / Engraving Toolpath
- Cutting Depths
- Start Depth: 0.0
- Flat Depth: 0.25 (This is very important! That way the vcarve detail is on the borders of the recessed area rather than cutting all the way through.
- V Bit 90 degrees .5" diameter
- Pass Depth: 0.1"
- Feed Rate: 2.5"
- Pass Depth: 0.1"
- Feed Rate: 2.2"
- I like to use the offset option for the toolpath because it tends to yield a better pattern on the material. Although Raster can be a faster option.
Step 4: Profile Toolpath & Tabs!
One more toolpath to plan, the exterior of the crest. I went ahead and edited the vector lines on the border of the crest to eliminate the delicateness of the border.
- Cutting Depths
- Start depth- 0.0 inches. I am setting the Z axis zero to the top of the material.
- Cut Depth- 0.75 inches (The depth of your material)
- "Outside / Right" option
- Tabs- Be sure to add tabs to your profile cut, this will hold the crest in place while the machine is cutting out the silhouette. My tabs are going to be .5 x .5 inches. Also click the "Create 3D tabs" option, this will make de-tabbing it easier later.
- Ramps: I like to add ramps to my tool paths so the bits last longer, this eases it into the material rather than plunging it straight down. I also recommend the "Smooth" option for this.
Step 5: Preview Before You Cut!
Preview before you cut! Using the preview feature can help you catch lots of silly errors, believe me- it has saved me many times. Click "Reset Preview" and "Preview All Toolpaths" to see a 3d rendering of your project.
Step 6: Save a ShopBot File
Saving your shopbot tool paths. I like to save each path as a separate file, I also do it right before I run the machine to make sure that the file is the correct one and all the settings are right. Click the floppy disk save icon, select the tool path you are going to run first and then save to an easily accessible location.
I always save to the desktop and delete all my shopbot files at the end of the day. This way I never accidentally run an incorrect file.
Step 7: Clamp Material & Match Material Location to File
Now it's time to get to the physical world! You need to secure the material to the plenum or waste board bed. I am just going to screw down the material where I know the tool paths won't overlap. You can also use custom rabbit clamps to hold down the material if you don't want to drill through it.
As you can see, I have oddly shaped material that is scrap from a previous project. You can see where I drew a box on to the material so I know where to place it in the program. I created a box and placed it in my drawing where it is on the bed. There I placed and scaled my crest to fit into the box.
Step 8: Bits!
You can see the 3 Bits I am using.
Bottom: V-Carve 90 degree, .5" diameter
Middle: .25" Downspiral bit for Pocket clearing
Top: .375" Downspiral bit for Profile cut
Step 9: Zero Z Axis
Once you have inserted the bit it is time to zero the Z-Axis. Hook up the Z-Axis plate and copper alligator clamps to the router. In the ShopBot program type in the C2 command to zero the Z-Axis.
Now the program knows where the top of the material is.
Step 10: Things to Remember
Things to remember before running the file:
- Your zaxis is zeroed
- The tool is in the "Home" location
- The shopbot router is "engaged"
- Your vacuum shoe is secure
- Your vacuum is on (I always forget this one)
- WEAR SAFETY GEAR! I wear safety glasses and ear muffs all day long in the shop. It is loud and you want your hearing to last as long as possible. Also it is good to wear a respirator for particularly dusty projects.
Step 11: Running a ShopBot File
In ShopBot make sure the X & Y Axis are set to home before running the file.
Make sure you select the correct ShopBot file, you don't want to run the incorrect toolpaths. This is an easy mistake to make, always look at the time stamp to ensure it is the most recent save.
Don't touch the computer while the machine is running, ShopBot has a safety feature that will stop the machine if any buttons are pressed. Do utilize this if you see that something is going wrong.
Order: I am running the Pocket Clearing file first, then the V-Carve detail path and finally the profile cut.
Tip: For the Profile cut, be sure that it cuts all the way before you remove it from the bed, this way if you need to increase the depth and cut it again then it is guaranteed to line up.
Step 12: Untab
Time to untab your work! I just use a chisel and mallet to knock out the tabs though there are several ways to cut the piece away from the exterior scrap material.
Step 13: Flesh-trim and Roundover
Option 1: The cleanest way to cut off tabs is to use a flesh trim bit on a router table. Luckily I have access to one, you could also use a hand trim router. To clean up the edges I also used a 1/16th round over bit which softened up the edges when you hold the crest.
Option 2: No router table? No Problem. You can always sand them off on a belt sander or do it the old fashion way and use a rasp/ file.
Step 14: Step Back and Admire Your Work
We still have a little way to go with finishing but this is a great chance to step back and really take a moment to be proud of your project & to reflect on things you might do differently next time.
Things I might do differently:
- Select a better material such as Apple Plywood. I did use scrap ply so there are a lot of chunks and holes in the material. This doesn't concern me too much because I will be filling it in and painting it but nicer material is always better.
Step 15: Sanding
Sand down the edges and pockets with gradually increasing grits. I started at 120 and worked my way up to 200.
Step 16: Prime
Now onto Painting! The way you finish your crest is completely up to you, it might be nice to leave it natural if that is closer to your aesthetic preferences. However, if you decide to paint it then you will need to prime the crest first, I used a basic acrylic white gesso.
Apply two coats evenly across the surface, try not to allow it to build up in the corners or fill the pockets. We do want the natural shadows of from the depth of the cuts to stand out.
Step 17: 3-Zone Painting
This is a simple technique to give depth to your work using acrylic paints. It consists of 3 paint layers:
- Base color
- Start by filling in the backgrounds of each house with their respective colors. I have also decided to make the border a golden yellow.
- Add some water to a dark color paint, usually black. Apply liberally to crevices and details of the animals.
- Using a rag wipe away the color, it should leave a darker residue in the cracks giving the recessed areas more dimension.
- Using a "dry brush" or a paint brush that hasn't been dipped in water. Pick up a little bit of a lighter color and brush to the top surface without letting it leak into the cracks.
Step 18: Hang It Up!
Be proud, hang it up and start planning your next Harry Potter Themed Party!