welcome back to switch & lever! today we're going to make a coin using a cncmill. if you're only interested in cool milling shots i suggest to skip forward to the timeindicated on the screen. otherwise, let's get started! coins have been around for virtually forever, from small to large, from round
3d printing for mold making, to square to whateverthehellshape this is. in metal, wood, plastic and maybe most importantly chocolate!gods, kings, queens, fictional characters and celebrities all havetheir own coins. there are even coins which aren't actual coins nowadays! so, whydon't you have your own? let's change
that, shall we? while there are many concievable ways to makea coin, in this video we're going to look at making a coin in 3d, together with a realistichead, and milling the result on a cnc mill from a piece of brass stock. now, there are two ways of making a realisticlooking three dimensional head on a coin, without modeling it from scratch, but unfortunatelyboth are somewhat time intensive. first one is perhaps the easiest one, butit does require you to aquire an actual 3d model of your head. there is software, evenfree software, from autodesk called 123d catch, which can take a series of photos and stitchtogether a decent 3d model. for an entire
head you need to sit perfectly still whilesomeone photographs your head from every concievable angle. for an entire head you could need between50 and 100 photos to get a decent 3d model from it. however, if you're only doing theprofile you could get away with less, as you could limit yourself to only doing one sideof your head. there are plenty of good videos and tutorials on how to use 123d catch toscan things, i suggest you check them out. anyhow, once you have the 3d model basicallyall you need to do is bisect it down the middle and squish it down so it's thin enough tofit on a coin. model the rest of the coin features around it and this will be the geometrywhich will guide the cnc mill. the second method is good if you don't haveaccess to a 3d model to begin with, or means
of making one, but you do have access to aphoto of the person you want to put on your coin. to use it on the coin you're going toconvert the photo into what is called a depth map, in which parts of the photo which areclosest to the camera are colored white, and things furthest away colored black with everythingin between being a gradient of gray. unfortunately, there is no easy way to simply convert a phototo this, so it would require some hand painting in a photo editing software to get the imageto how it should look. in your 3d software you need to find a functionto displace geometry using the depth map you just made. this is done differently in differentprograms, but look for displace or in some cases it may also be called heighfield. youmay need to go back and forth between the
photo editing and your 3d software a few timesto get the desired result, each time fine tuning the photo a bit. once done model therest of the coin around it and you're ready to go onto the next stage. but first a slight detour, while this videois about milling a coin, there is nothing stopping you from taking your 3d model andusing a service such as shapeways to 3d print your coin, even in metal. be aware thoughthat the cost difference between doing it yourself and having it 3d printed is prohibitive.so, if you have access to a cnc mill then that's the way to go. for this video we'regoing to be using a roland mdx-40a mill, which is really not made for milling metal, andrequires some special attention to do so.
because this mill is used mainly for millingsofter materials using double sided sticky tape on a mdf base is usually sufficient forwork holding, even for high speed machining. don't, like me, be fooled into thinking that'senough to hold when milling metal however. even if the tape holds the piece isn't securedproperly, it will vibrate and the result will be undesireable. because of this an entirelynew bed was made for the mill out of a sheet of aluminium plate, into this four holes weredrilled and tapped to securely hold down the workpiece. since we're going to be milling both sidesof the coin we need to make sure we can reliably mill the backside aligned with the front.therefore the workpiece was drilled with four
holes matching the holes in the new bed forthe mill and the centerpoint of them was marked so the mill could be zeroed on that point. as this machine is not meant for milling metal,even a soft metal like brass is tough on it, so the milling had to be slow, taking onlyfractions of a millimeter at a time. here we're using an engraving cutter with a 90degree included angle as it provided both sturdyness and could create some finer detailthan a ball ended endmill could do. as this wasn't a production run and i wasn't goingto make a lot of coins the speed wasn't much of a bother. it took between 2-3 hours perside of the coin, starting with a roughing pass to get most material out and then a finishingpass for the last fraction of material to
be milled away. once the first side is done we're going toflip the coin to make the backside. if you marked the centerpoint and centered the millwell for the front the backside should be milled in the right position without havingto reset the zero point. while doing it by eye isn't the most exact method with careyou can still get it within a fraction of a millimeter, close enough for no one to noticeif the alignment is off or not. make sure you've designated the screw heads as no-gozones for the mill as well, so you don't accidentally crash into them. i chose not to mill out the circumferenceof the coin, mainly because the milling machine
was underpowered. i did though mill up toa ledge which could serve as a guide when taking the coin to a belt sander to hog awaymost of the remaining material. the plastic was put there to protect the bottom of thecoin from scratching. setting up an angle plate and another pieceof plastic and wedging a file inbetween allowed me to hand file a right angle shoulder allaround the coin in a much more controlled fashion than the belt sander would allow.while time consuming it gave a very nice result. when you're done you'll have a very nice lookingcoin, but in my opinion still a bit boring. it's just bare metal, and it doesn't havelife to it. fortunately, that's easy to change, without having to handle it for a long timeto build up natural patina. since we made
this from brass there are many different waysto create patination, such as using liver of sulphur. unfortunately, not having accessto that meant finding another more direct method of creating a similar look. enter theblowtorch! heating up brass removes the shine, oxidizes the surface and makes it dull andunattractive. no worries, we're going to fix that with some matte black spray paint! justgive the coin a quick coat and then quickly wipe off as much paint as you can before itdries. this leaves paint in the recesses and makes it look dirty, but still doesn't quitebring the coin to the look we want. that's what we're fixing in the next step however.once the paint is entirely dry we can use a metal polishing compound, like this autosol,to polish up the high spots of the coin. the
reason we burnt it in the beginning is becausewe want to create a layered patina on the final coin. some areas will be dark becauseof the paint, some will be lighter but a bit dull because of the burnt oxidation and thehigh spots will be nice and polished. dirt and grime doesn't happen uniformely in thereal world, so try to emulate that for a more realistic result. when you're done it's possiblethat the paint looks a bit grayish because of the polishing process. to make it darkeryou can treat the coin with a bit of linseed oil. it will absorb into the paint, darkeningit and then harden over time. time to knock this up a level! a custom coinis all well and nice, but if you do have access to a cnc mill making a nice box for it isa fairly trivial matter. i ended up taking
a piece of oak, cut it in two and milled outa book matched box with recesses for three coins. while milling out the circumferenceof the actual box notches were milled for hinges and small recesses in the corners tohold neodymium magnets to keep the box closed. the coin recesses also were made slightlydeeper in the front allowing the coins to be easily removed by pushing the front ofthe coin down so the back pops up. if you have a camera in a dusty or grimy environmentand you still want to get up close and personal with what you're working on covering the camerawith saran wrap will work great. just make sure you stretch the plastic across the lensso there are no folds or bumps distorting the footage.
once the box is done and assembled give ita quick oiling or varnishing and you're done!
look at that fine ass box! thanks for watching this episode from switch& lever! while you're waiting for more material be sure to check out one of the older videos,and please do subscribe if you haven't already! until next time!
