Double side machining bricks

I try to machine a “brick” from both sides.
What I did:

  • Create the brick in fusion 360 as 3d and put it to the right size
  • Export top and bottom as DXF import it it in Corel Draw
  • Align top and bottom, make 2 bricks side by side
  • Define the size of the piece of wood I want to use and where to drill the holes for the clamping screws
  • I export top and bottom as SVG
  • in CC 5 I import one file and place one screw (see magenta cross) at the position where I have the first screw position in the wastboard. Next screws will come every 50mm on both axes. Now the bottom looks like this:

    *Same for the top

  • I checked all positions in CC for both sides, they are exact at the same position

  • So top and bottom shall fit !
  • Here the result from machining the bottom:
  • next step I flipped the stock around the X axis:
  • and the top looks like this:
  • looks not so bad but:

    there is a difference in the thickness of the walls 4,5mm and 2mm
  • My idea: Maybe the position of the clamping screws is not 100% right (I drilled the holes by hand in the wasteboard)
  • So I draw a line in x direction over the complete stock, mark one position at the top of the stock, screwed it to the wastboard and put the machine to the cross (sorry I did not took a picture of this step, so here a fake picture which shows my idea.)
  • with a V-bit I checked the position and found the biggest gap in x direction (which doesn’t matter) and only less than 1/2mm in y direction.
  • So the zero position fits very good to the screw positions in the wasteboard.
  • I compensate the small deviation by zeroing the machine again and did the same test.
  • Now the V-Bit das direct over the cross on the stock. With good glasses and looking from all sides I am pretty sure that the deviation is below 0,5mm
  • Now I got 4mm and 2,6mm so round about the 1/2mm I had adjusted but still 1,5mm difference.
  • The wall shall be 3,6mm
  • If I measure the overall size of one brick ist is 95,3mm (shall be 95,4mm) and 46,98mm (shall be 47,4mm)

So a very long text for a question :slight_smile:
Does anyone have an idea concerning the 1,4mm difference in wall thickness.
Do I forget something.

While I write this long text there is one idea for the next brick, I will flip the stock next time over the Y axis and see what happens than.

Thank you

1 Like

I would use alignment pins to ensure a perfect flip. Make 2 shallow holes in the waste board that will align with two shallow holes in first side that you mill. When you flip add dowel to align then screw/clamp down.

Every attempt I have made with 2 sided milling have failed until I adopted the alignment pin strategy.


@i3oilermaker I am wondering, but you are 100% right. Thank you.

What I did:

  • Add two holes for 8mm wood dowels to my stock:
  • Save the GCode for this two holes only and the Gcode for the complete side.
  • Next I tried to drill the two holes in the waste board. What I learned: You need a long router bit to drill a 25mm hole in the waste board. (mechanical limit of the machine was reached)
  • Next I machine the top side (inc. the two extra holes marked in red)
  • Put the dowels inside and flipped my stock.
  • The dowels came into the drilled holes (red).
  • The screws cam in the “old” holes (blue)
    *Here the picture after machining both sides which shows the setup:
  • I was wondering if the two wood dowels can help in such a case, where 3 screws are used to fix the stock.
  • Here the result:

    The difference between the 4 sides is round about 0,2mm.

I would never expect that good result.

Thank you.


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