As you might have noticed in the Sketchup file, my Lego block is not as hollow as a normal Lego blok.

This is for two reasons, it is much stronger this way and you don't have to mill as deep with very small tools.

Usually the deeper you reach with the smaller tool the bigger the chance it snaps. A more sturdy block will allow for easier clamping without accidentally deforming the workpiece.

As of yet I have not decided what I will make my block out of, but I am leaning in the direction of Aluminium to make an extraordinary shiny block.



Work procedure:

First step is to face a precise block to the absolute external dimensions of our Lego block

This block will be 15.928mm x 31.956mm x 11.700 (15.93mm x 31.96 x 11.70 as of yet I can not reliably measure real microns so ten micron steps will have to do)



Second step:

Mill the stubs



Third step:

Mill the bottom cavities



Fourth step:

deburr and polish



Milling:

The first file you need for this is a facing operation. A shallow wide cut to make your block the right dimensions.

I will use a 40mm face mill for this operation which can cut the entire block in a single pass. This is because I prefer to mount the longest side of the work piece to the Y axis bit mill in de X direction. (You find the file in the next step on instructables labled. 1step...)



In all the files you touche of on the surface of your block as Z=0. The left bottom corner of the model is x,y=0,0

The file allows you to cut away 1mm in 3 steps, one -0.9mm cut and two -0.05mm cuts this will give you a superbly accurate surface.



You can use this file on all sides of your block. If your block is some what small and for example only needs a 0.5mm deep cut, you can touch of on the surface of the block, move 0.5mm up and set that as Z=0. Use your Z=0 to give your block the right dimensions using a single milling program touching off 0 a set value above your acutal surface.

For example mil the side, between milling operations you measure your block is 0.085mm to large. 1-0.085= 0.915mm, Touch off on the surface of your workpiece, move up in the Z direction 0.915mm and set as Z=0.

I cut with 7500 rpm, 600mm/min 6 teeth 40mm indexable face mill, under cooling fluid. This is a light cut with a feed of 0.013mm.



Cutting the stubs, for this you can use the file labeled as 2Step.

Insert a 2mm flat end mill, again the top of your block is Z=0. I like to do an angular contour with a constant feed.

Your 2mm flatend mill will do 4 passes, 1 primary cut, 1 secondary cut with 0.8mm spacing and two finishing cuts with 0.05mm spacing. In a helical motion with a constant 1mm deep feed. After the stubs it will remove the rest material from between the stubs.



I cut with 7500 rpm 400mm/min 4 teeth 2mm coated carbide flat end mill. This is a medium cut for the tool with a feed of 0.013mm 1mm deep. I mainly wrote the programs this way so I am flexible in my material choice later.



Immediately after putting on the stubs my brain recognizes it as Lego.



Last is the bottom cavities. Step 3

I love consistancy, flip the block bottom side up in the clamp. And touch of the top (which is the bottom facing up) as Z=0, bottom left corner of the block is x,y=0,0

Same mill bit, same settings





All mill files have a TXT extension, this is because of problems I have with uploading. For some reason I get an HTTP error when uploading .NC files. But since they are basically txt files I re-extended them as txt. You can change this back to the NC extension after downloading.

