This is a simple project especially useful for using up corners and off-cuts. Each section can be made individually then combined to form a decorative surround for a mirror, clock, round photo or etc.
The decorative designs are engraved then the piece cut out, i use a small V-bit to carve then a 4mm straight shank cutting bit to trim the edges and pocket the inlaid section for mounting the mirror but of course you could use anything appropriate. In this example i'll be using 19cm mirrors brought for next to nothing from a home furnishing store however scaling the designs is a simple matter.
There are three sized pieces in this, thirty degree section which requires 12 to make a full circle - these are perfect for making a clock, each section could have it's own number on. There's also a sixty degree section which will require six to make a full circle and a 90 degree section which requires four to make a full circle - these can be combined in anyway that adds up to three hundred and sixty degrees.
And of course if you have some nice wood wood then this is a great project even without the engraving stage, 4, 6 or 12 pieces of different woods all joined together with jigsaw tabs could look lovely on it's own.
oh and don't be put off by how bad the one in the image looks, it's just all my test bits from when i was working it out - i'll find some nice bits of wood and make a nice one then update the picture as soon as i'm able...
Step 1: Select or Draw Your Design to Be Engraved
Either download some of the depthmaps I've provided or download the appropriate template file, these are available as both SVG [titled cutting template] or XCF [for editing in GIMP and including example layers and masks]. To use these simply draw your own depthmap into the pink space provided. The green space will be removed during the routing process so that can be ignored in this step.
A depthmap works by assigning hight values to shades of grey, if you have the total depth as 4mm then fifty percent black will engrave down 2mm. It takes a bit of practice to make good depthmaps and it's probably worth looking for some guides online. The only thing you really need to worry about when designing your own depthmaps for use in this project is if you want them to join up neatly at the round tabs then it's best to leave a boarder around where they meet as the same colour -i've found it easier if this is either black or white, also the case for where edges meet.
The XCF files have a white mask with a cutout around the shape of the engraving section, make sure this is applied so that there is nothing to engrave outside the useful area.
When you've completed your image rotate it to match the cutting guide [svg file] you'll be using to cut out your piece and ensure it's cropped tight around your image so it looks like the example images. -I do mine rotated 90deg clockwise so they fit on the offcuts of wood i have, if you're going to rotate it another angle then make sure to rotate the cutting guide accordingly so everything lines up. It can be helpful to print one out at the desired orientation so you can measure the bounding box size needed in the engraving stage.
Step 2: Convert Depthmaps and Engrave
To convert the depthmap images into toolpaths I use a brilliant little program called dmap2gcode; it's free, multi-platform and easy to use. There are plenty of instructions, guides and example depthmaps available online for this program so if you're new to it check out the scorch works website.
Each of my depthmap files is named with a hight value in mm, this is needed by dmap2code to scale the image. The rest of the settings are upto you but i've included a suggestion z depth also, although of course feel free to experiment changing this if you do use any of my designs.
Step 3: Cut the Outline
For the final stage with the CNC machine you'll probably need to change to a cutting bit, i use a straight shanked 4mm bit.
Download the cutting guide template to match the size of the piece you engraved, the file for the smaller section is named 'cutting template 30 deg'. The template files have two closed sections, a smaller green section and a larger pink section - the large pink section is the outline. First route a pocket of the appropriate depth into the green section, the difference between the top and bottom of the pocket is the depth the mirror will be inset - don't forget if you're engraving down 4mm you'll need to lower the depth of the pocket an extra 4mm also. When using different thickness woods it might be desired to use different depth pockets so that the bottom of the pocket upon which the mirror is set are the same hight from the floor [or wall] but the engravings are raised to different heights.
I use the free online tool path generator makercam to make my tool paths, simply open the SVG in makercam [make sure to go into makercam options and change the import dpi to 90 as it's an inkscape file] and select the smaller section -i do this by highlighting the inner curve as it's the only one not on both paths. Set a pocket here, then select the top section and do an outside profile to cut the entire piece out.
The final step is to put the origin (or zero point) to somewhere that you can line it up on the engraved piece, i use the middle of the top circle or the top right hand corner of the engraving. Calculate and Export the gcode then line your router bit up to the point you set as your zero point when making the gcode.
When you're happy send the file and hopefully it'll neatly cut out the piece neatly, i've only had one bit misaligned so far -which was the piece i set up to take a photo explaining how to align it... so it goes....
Notice even though the test piece [with a number 8] is misaligned [obvious if you look at the left side of it] the pocket and edge cutting allows it to fit neatly into the piece.
Step 4: Glue It, Paint It, Stick Something in the Middle and Call It Done.
Finish it to your tastes however you would a normal woodworking project, wood glue works well.
I've included all the dimensions of all the inlay, outer circle and etc in case anyone wants to cnc a back board or plastic window for it when being used as a clock, picture frame or etc.
Mirror Diamater = 190mm
Total diamater = 250mm
inner diameter = 125mm
I haven't glued or mounted the one in the picture because it's just scrappy test bits cut into old plyboard and reclaimed planking, but when and as i get off cuts from nice bits of wood which carve well i'll assemble a collection of good pieces, varnish them and make it all lovely...
Step 5: Where I Put All the Files You Might Need
I've included a load of example depthmaps in all sizes including examples of text, waves and some design elements to give you an idea of the sizes that work well.
I would recommend if you're designing your own then cut one without engraving to get a good idea of the pieces you'll be making.
There are three freeCAD files one for each sized piece, this are useful if you want to modify sizes - the sketches are full constrained which enables you to simple change the radius of the circles and everything else remains relative to each other.
Finally sorry my art isn't very good, maybe it'll improve with practive but in the meantime if anyone with artistic talent wants send me some then i'd be much obliged and include them here or put a link to them...
Recap on tools used;
0.5mm 10deg cut cone V-bit - ordered from china, cheep but amazingly effective.
4mm straight shank 4 edge cutting bit - also cheep from china.
Design - FreeCAD open source CAD
depthmap design - GIMP open source pixel editor
engraving paths - Dmap2gcode open source gcode generator
vector clean up -Inkscape open source vector image editor
cutting path - www.makercam.com free access cloud gcode generator
entertainment - www.librivox.org huge collection of brilliant free audiobooks recorded by volunteers.
i've love to see if you use any of these files or are inspired by anything.