Drop (no?) table foam eating MPCNC

After building a Lowrider to mill surfboards, it turned out too big is not very convenient…
So here comes the MPCNC without table!
The frame is kind of a torsion box built to let the Z-axis access the whole work area, having a thicker frame make it more rigid and eliminates the feet completely with still just enough room to get the drag chains under the steppers.
The footprint is minimized and only extended just a mm past the steppers to be able to store it sideway
all the electronics and wires fit inside the frame.

The idea is to machine an area, slide the foam block, machine the next… flip it at some point and keep going.

The deck was a great success! but, rookie mistake… i didn’t square the machine properly for 2 of the bottom sections… nothing some glue and spare polystyrene can’t fix!

The small areas not machined act as tabs and very easy to sand down.

Next step: high density PVC foam:

I’m always amazed at what comes out of those machines!

Next evolution will be to change the feet for some more advanced with wheels and the ability to turn the table upside down to use it as an extra table… small workshop problem :slight_smile:


Good solution for a specific problem.

Good work!

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Very creative!!

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Great !
To avoid squareness problems, it is possible to add a well squared ruler on the X axis under your frame so that you can trust it by pressing it against the stock and only have translations to do.

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The bloc of polystyrene was square, I marked the frame to align the center line after each move, the problem was the tube along the Y axis , now I’m checking the distance between trucks and corner support after moving the core by hand, For what I’m doing, +/- 1mm over 400 mm of Y and 600 mm of X is more than good enough.


Very awesome
So much fun building surf boards I did a wake surf for my daughter last year.
What a great idea thanks for sharing.



I made a full movie about the machine construction (definitely not a guide)
and the first board it made :slight_smile:


Very cool!

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Very Cool Indeed!

Awesome construction and result.
I am planning similar build, and I have 2 questions :

  • your mesh needs to be the length of the Z axis you will be working on right ? Otherwise your motor will touch the foam ?
  • would it be possible to change the mill by a hot cutter needle ?

I designed the machine with a Z axis longer than the longest bit I was planning on using (10cm) and so that the bottom of the table matches the bottom of the bit when it’s almost at the highest with a couple cm to spare for the movements.
Then when I was generating the GCode in fusion, I just set the blank to 10cm thick so that it doesn’t try to go deeper.

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  • would it be possible to change the mill by a hot cutter needle ?

I’ve wondered if a cutter like the following would work, but I expect it to be really slow:

It would be pretty simple to test, but I would not get your hopes up about it working.

The CNC hot wire foam cutters capable of larger works usually use nichrome wire stretched between dual Z axes like this one.

@dkj4linux made one a while back in case you guys are interested.

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@robertnu I was thinking indeed of this, instead of traditional wire cutter.

@Mat I think I will completely copy your MPCNC with the spindle and table to have 10cm Z working axis.

Couple more questions @Mat :slight_smile:

  • are you using height z layer per layer or only one pass ?
  • how much time machining the 8 faces ?
  • how much waste of polystyrene has been generated ? With or without a vacuum ?
  • only one pass… except for the last section below the nose as it was a lot of foam to remove there and I was overloading the spindle making it shut down.
    I found that when it’s starting to have issue or too much chatter, slowing down the federate helps, but stays faster than doing 2 passes.
  • around 10 to 15 minutes per section, except below the nose: 20 minutes.
  • the volume of the bloc containing the board - volume of the board = waste. everything that within te outline is is small beads going everywhere, and the rest is a big chunk. I didn’t install vacuum on the machine, but I was using my vacuum by hand to clean from time to time.
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