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Thread: CNC router for Plaster Moulds

  1. #1

    CNC router for Plaster Moulds

    Hi,

    I'm looking at purchasing a CNC machine to produce plaster molds which will then be used for ceramic slip casting.

    Here is an example of a mold:
    01-plaster-moulding-ceramic-mould-casting-investment-casting.jpg


    I'll be using a 3D CAD file to mill from.

    Has anyone here used a CNC router to mill plaster? Or has anyone here used a router to produce circular/concave objects.

    And any advice on an entry level Router which I could use.


    Thanks in advance.

  2. #2
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    Plaster is a pretty soft material, so I see no reason why you couldn't use just about any CNC machine designed for wood and soft metals. Out of curiosity, how deep do you plan to go? Looks like an interesting way to design custom awards...
    Hi-Tec Designs, LLC -- Owner (and self-proclaimed LED guru )

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  3. #3
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    It looks like you would need a 5 axis cnc to produce those.

  4. #4
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    CNC Routers are Master mould making machines. You don't have to have a 3D object to produce moulds to make them.
    .

  5. #5
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    The only concern I would have is getting the plaster dust into the drive mechanism and mucking it up.
    Please help support the Creek.

    When everything is coming your way, you're in the wrong lane.

    - Steven Wright

  6. #6
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    Quote Originally Posted by Jerome Stanek View Post
    It looks like you would need a 5 axis cnc to produce those.
    I may be missing what you're seeing, but I don't see a need for anything other than 3D for those. All of the cut lines for the mold show are along the max extents, so no undercuts (even the base is a separate piece, in case you missed that... it's a 3-piece mold).
    Hi-Tec Designs, LLC -- Owner (and self-proclaimed LED guru )

    Trotec 80W Speedy 300 laser w/everything
    CAMaster Stinger CNC (25" x 36" x 5")
    USCutter 24" LaserPoint Vinyl Cutter
    Jet JWBS-18QT-3 18", 3HP bandsaw
    Robust Beauty 25"x52" wood lathe w/everything
    Jet BD-920W 9"x20" metal lathe
    Delta 18-900L 18" drill press

    Flame Polisher (ooooh, FIRE!)
    Freeware: InkScape, Paint.NET, DoubleCAD XT
    Paidware: Wacom Intuos4 (Large), CorelDRAW X5

  7. #7
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    you could do it in 2.5D but would take some jigging to get it done. If you look there is milling on 90% angle

  8. #8
    Thanks for the response people.

    I would like a router which could create mould depths of 140mm (5 inchs)

    Would a router with a specific bit be able to do this? (Assuming I was creating a box and the router head has reached a corner)



    To Keith, it would make mould making more efficient and much more accurate.


    Thanks.

  9. #9
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    I don't know much about them, but isn't this a good excuse to buy a 3-D printer?

    Perry

  10. #10
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    Quote Originally Posted by Perry Holbrook View Post
    I don't know much about them, but isn't this a good excuse to buy a 3-D printer?

    Perry
    A 3D printer would be a slow-going process, and in the end he'd have a positive image... he'd have to take the extra step of making a negative mold. Best to just make a negative right from the start.
    Hi-Tec Designs, LLC -- Owner (and self-proclaimed LED guru )

    Trotec 80W Speedy 300 laser w/everything
    CAMaster Stinger CNC (25" x 36" x 5")
    USCutter 24" LaserPoint Vinyl Cutter
    Jet JWBS-18QT-3 18", 3HP bandsaw
    Robust Beauty 25"x52" wood lathe w/everything
    Jet BD-920W 9"x20" metal lathe
    Delta 18-900L 18" drill press

    Flame Polisher (ooooh, FIRE!)
    Freeware: InkScape, Paint.NET, DoubleCAD XT
    Paidware: Wacom Intuos4 (Large), CorelDRAW X5

  11. #11
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    Be aware that every mold cut with a CNC in industry is polished to remove the final lines from the cutter. Unless of course you want the lines for design purposes. What dimension is 5"? What plaster are you intending to use for the molds? Production molds are usually gypsum cement, or high strength gypsum cement. Using that stuff will probably eat bits quickly. Not sure I would want even plaster of paris coming through a fan cooled spindle or router. Better get something with water cooling.

  12. #12
    Excellent Idea. Custom candles also came to mind when I saw your award mold.

  13. #13
    We had a class last semester that used our CamMaster CR408ATC to do exactly this.

    http://digitalceramics2013.wordpress.com/

    https://www.dropbox.com/sc/q0g8mcowvvua4jq/HyMwd2b5wM

    By tracking down some others who had done this, we learned that machining the molds when they were a bit green (not fully cured) produced the best results. Since the green plaster was soft it was much less abrasive to the tooling and it produced chips rather than dust. If the plaster was DRY it produced loads of fine dust that dulls tools and can get into and reek havoc with linear bearings. We tried to mill 7-10 days after the blocks were cast, if they got past that, rehydrating the block by submersing in water for ~20 minutes then drying for 4-6 hours seemed to bring it back to a more machinable state.

    All of the forms in the webpage above were produced on a 3 axis machine. Mostly using 1" and 1/2" end mills and 1/4", 3/8" and 1/2" ball end mills. Post machine finishing will be required if you want to remove all machine marks, extremely small step-overs will create a pretty smooth finish but can take forever. In most of the students' work the tooling patterns were a design element which limited required post-processing. A spinning tool cannot make a square corner, so if you have them in a design, they have to be made some other way (chisel ir clay tools if the plaster is green). If you're going 5" deep, you're going to need some long tools and/or extended tool holders if on a machine with a tool changer.

    About any CNC router should be able to handle work of this nature as long as it has the necessary z clearance and travel. If you're using multiple tools, a tool changer will increase productivity and make life easier. An industrial spindle rather than a portable router is always a good thing.

    -kg
    Kevin Groenke
    Fabrication Manager
    UMN Design

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