outer ridges on a coin

[aroff]

Looking at making a personal USMC coin for my son

anyone have a clue as to making the outer ridges (reeding) of the coin
I have a 3 axis machine

ty
andy

[LittleGreyMan]

Something like this?

Simply use a 3D vector for the ridges and cut it with a 2D profile toolpath with a small end mill. In this case, I use the 3D rope clipart and used the create boundary vector function to generate the appropriate vector.

Got a nice result engraving in paperstone. The outer cut was made with a Ø6mm end mill. The medal Ø is about 50mm.

[aroff]

awsome idea
ty so much
works great

[TReischl]

If you are talking about putting the ridges on the rim of the coin (like on a quarter, half dollar, etc) there is no way I know of to do it on a 3 axis machine. This requires a rotary axis (which can be used on a 3 axis machine which has either the X or Y axis locked).

[LittleGreyMan]

Simply use a 3D vector for the ridges

Sorry, I meant a 2D vector of course.

[LittleGreyMan]

Here is the final result. Unfortunately, I have no photo which shows the ridges.

[aroff]

how did you get the flat part so clean and shiny with no cut lines
have heard the only way is a de-burring tool using a special machine

[LittleGreyMan]

The tool is called Photoshop.

Just kidding, there is no photo editing.

If you look carefully, you will see shallow cut lines.

Here was the process:
-roughing toolpath: Ø6 mm endmill with 0.2 mm allowance
-finishing raster toolpath 1: Ø6 mm ball mill along X (0°), 10% stepover
-finishing raster toolpath 2: Ø3 mm ball mill along Y (90°), 10% stepover
-finishing offset toolpath 3: 30° engraving bit, 40% stepover (only 0.2mm with a 0.5mm flat Ø)

Using so many toolpaths was probably over cautious but I had never cut this material before. No manual finishing, just a spay paint.

If want a good result, you'll have to run several finishing toolpaths. For larger parts, using rest machining is generally a good option. Just think out of the box (the screen when you use a CAM): think of the physical process and what will physically happen when you run the toolpaths.

And believe Vectric's simulation tool, it is very reliable and useful. But you will sometime reach limits of a screen rendering. In this case, cut lines were much more visible on screen than on the actual part.

Hope this helps.

[martin54]

how did you get the flat part so clean and shiny with no cut lines
have heard the only way is a de-burring tool using a special machine

There are different ways to machine & leave no or very faint cut lines, you could use a pocket toolpath with an endmill for the flat parts, just use vector boundaries to define the pocket cut.

The size & stepover of a ball nose bit will also make a difference if machining as part of a 3D model, smaller the step over the less chance of having machining lines

[aroff]

i have 1/64 and 1/32 bn and em
will have to try it
have ordered copper, aluminum and brass
cant buy it locally

[TReischl]

Aroff, you might check the local scrapyard if you cannot find it locally.

There are no stores here that sell copper, etc, but wow, the scrapyard has literally tons of it separated out. Sheet, bar, fittings, you name it.

[aroff]

never gave it thought
ty