Part to G-code
The Mill turns a part into G-code for a hobby CNC router of the 3018 kind, running Grbl. You give it your part, say how it sits on the table, pick your bits from your own tool library, and it works out the cuts: facing, pockets level by level, and drilling. It machines with several end mills, largest first, and each smaller one cleans only what the bigger ones left: inside corners tighter than their radius, slots too narrow for them, holes no drill matches. The kernel runs in your browser, and nothing is uploaded.
This page machines the built-in plate. Open the Mill beside this page and follow along.
The part
Drop a STEP, IGES, Rhino (.3dm), OpenCascade (.brep) or ACIS (.sat) file on the view, or choose it with Open a file. A file with several solids asks which one to machine. For this page, press Example: plate: an 80 × 50 × 12 mm plate with a pocket whose corners are rounded only 1.5 mm, a 4 mm slot and four 3 mm holes. Your part and your settings are kept in this browser, so a reload brings you back where you were.
On the table
The Mill cuts from above, so the part must sit the right way up. Click a flat face of the part and it goes down on the table; with Clicked face up pressed, the face you click faces up instead. A curved face cannot sit on the table, and the Mill says so. The two turn buttons spin the part a quarter turn about the vertical; As loaded puts it back.
The stock is the part's box plus a margin, 2 mm on each side and on top and none below, or a block of the exact size you have. The zero, where your router's X0 Y0 Z0 is, is the stock top's front-left corner unless you choose its centre; the green marker shows it. The skin, 0.3 mm, is what the pockets leave on the walls and floors for a finishing pass. The Mill warns you when the stock is bigger than the machine's travel; it does not stop you, in case your machine is bigger.
Tools and material
The tool library comes filled with common 3018 bits: flat end mills of 6, 3.175, 2 and 1 mm, a 3.175 mm ball end mill and 3 and 5 mm drills. Tick the ones you will use; the 6 and 2 mm end mills are ticked to start. End mills run largest first, then the drills. Add, change or remove tools as you have them, and use Export library and Import library to keep it as a file.
The material fills the spindle speed, feed, plunge and depth of each pass from a chip-load table, capped by the machine: by default up to 10 000 rpm and 1000 mm/min, which you can change under Machine. These are starting values: listen to the cut and adjust. They are deliberately cautious, but every machine, bit and board is different. A value you type is yours: changing the material keeps it, and Reset gives the material's back.
Machine
Press Machine. The kernel recognises the part's levels, pockets and holes and plans the cuts; the job then plays in the view on a block of stock, with the controls under the button: play, a speed, a slider through the job, and the stock coloured by height, by tool, or by how far it is from the part. While the kernel works, Stop under the view ends it and starts the kernel afresh with your part.
Under Left uncut is what no tool could reach, each in the kernel's words with the heights it spans; click one to see its outline in the view. With both end mills ticked, as they start, the 2 mm one cuts the slot and cleans what the 6 mm one left wherever it fits, and only what even it cannot reach is listed. Untick the 2 mm end mill and machine again to see what the 6 mm one leaves on its own: the slot and the pocket's corners. The plate's four 3 mm holes stay in the list until you tick the 3 mm drill and machine again.
Take it home
Download all saves a zip with one program per tool, in the order to run them (plate-1-T1.nc, plate-2-T3.nc, ...), and setup.txt: the stock size, where the zero is, each tool with its speeds, and what is left uncut. Each program can be downloaded alone too. Load the first one in your sender, set the zero, and change the bit between programs.
What the Mill does not do
- One side, from above. Faces that cannot be seen from above (undercuts) are reported, not cut. There is no flipping the part for a second side, and no tabs to hold a part cut free.
- No 3D surfacing. Sloped and curved walls are left in steps at each level, and reported.
- Flat and ball end mills and drills. V-bits and bull-nose bits are not planned with.
- No machine control. The Mill writes G-code; sending it to the machine is your sender's job.