DIY 3 Axis to 5 Axis Conversion - Gluing Multiple Pieces/Master Pattern

Discussion in 'Boatbuilding' started by ProtoFabLab, Apr 2, 2021.

  1. ProtoFabLab
    Joined: Nov 2020
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    ProtoFabLab New Member

    I just converted my CNC to 5 axis, so now it makes it much simpler to mill larger shapes. Anybody have any actual experience gluing multiple milled pieces of a pattern into one complete structure while maintaining a relatively tight tolerance? If so, any advice?

     
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  2. wet feet
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    wet feet Senior Member

    I have done that sort of thing but it was with the facility to vacuum bag a large job on a cast iron surface table and we pushed the pieces together very firmly before applying the vacuum.The glued had a tiny bit of lubricating ability and it was a good idea to use dowels or machined locating features.
    Now you have a 5 axis machine,how do you determine the tool length and how easy is it to enter the actual value in your post processor?I have thought about a 5 axis machine but the cost of reliable software on top of the mechanical challenge is rather daunting.It appears from the video that the work was done in 3 axis mode,presumably with differing G54 values for each part of the operation.
     
  3. rxcomposite
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    rxcomposite Senior Member

    I used to work in a PCB factory and we use CNC drill. We program the drill pattern using a non functional reference point/hole, minimum of two holes. With a hole placement accuracy of better than half a mil the drilled PCB can be stacked together using the holes and it will be perfectly aligned. These holes are also use as guides when die punching several pieces.

    You can try drilling the base for the reference holes, inserting a guide pin (round pin with flats for easy removal) then securing the pre drilled (foam?) blocks. Have another base ready drilled with the same locating multiple holes pattern. When you remove the machined part, just insert it into the assembly jig and everything will be aligned.
     
  4. ProtoFabLab
    Joined: Nov 2020
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    ProtoFabLab New Member

    Thanks so much for your replies.

    Ok, machining locating features will be the way to go. Interesting point about vacuuming.

    I use RhinoCAM and Mach4. There are many included post processors in all of the professional CAM softwares. I had reverse engineer the coding and build my own post processor once I converted to 5 axis.
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    The tool length is determined in the basic CAM programming process. In RhinoCAM, there is a machine definition file that defines the parameters of your machine.

    The video is 5 axis machining, operating in 3+2 format, and 5 axis simultaneous as you may be used to seeing. It still outputs values for all 5 axes in the code while using this mode. My machine runs in simultaneous mode as well.

    I think this is it. I had to read it 3x, but I have it. Thanks for shedding some light on this, it will help me get started :)
     
  5. rxcomposite
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    rxcomposite Senior Member

    With a limited size your cnc can handle you still can make a large base for gluing/assembly.

    Say your max capacity is 300 x 300 mm but you are going to make a 900 mm model. Drill 4 holes in a square pattern simultaneously on the base assembly and your assembly jig. You will be drilling your CNC base at max capacity but your assembly base will be a lot longer. Say more than 300 wide by more than 900 long,

    Drill only the 300 x 300 mm pattern on the upper portion of the base jig. Remove from CNC and place 2 locating pins on the upper portion of the CNC base. Mount the long assembly jig in the CNC base. This time, only the two LOWER holes will be secured/aligned with the pins.

    Reprogram the machine so that only the two lower holes will be drilled in the assembly jig. Remove and step again the mounting process. Repeat until you get the at least 2 rows of holes x 3 (or whatever length). Now you have a base with that you can fit your sub assembly. Just add locating pins.

    Make a sketch of what you are going to do.

    For the blocks, drill two holes in the same spacing but in the center of the 300 x 300 mm pattern. When you put the blocks on the assembly jig, it will align and fit perfectly.

    This is a project I am working on except that I will build a 3 axis CNC with a 360 x 1,000 mm capacity. I have the electronic parts, stepping motors, and the router but the big aluminum extrusions are so damn expensive.
     
  6. ProtoFabLab
    Joined: Nov 2020
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    ProtoFabLab New Member

    Do you have to use aluminum extrusions? Can you simply weld up some steel?
     
  7. rxcomposite
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    rxcomposite Senior Member

    Controller.jpg
    I don't have it yet but can get it on line. Square steel might work and is cheaper. Just need a good welder/fabricator. I don't have a steel fabricators table.

    Problem is I have already the bearings. I am looking at commercial aluminum profiles. The ones they use for making aluminum doors because it is available locally. As soon as they lift the quarantine, I may be able to move around.

    I am using this controller.
     
  8. baeckmo
    Joined: Jun 2009
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    baeckmo Hydrodynamics

    Interesting projects guys! But I imagine that the stiffness of the guiding and frames is important to ensure dimensional stability? If that is the case, then steer away from alu due to its modulus of elasticity and thermal expansion coefficient.
     

  9. rxcomposite
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    rxcomposite Senior Member

    These are the extrusions that is considered standard in the CNC machines. Bigger ones are available for machines that cost thousands of dollars. They are the ones with 4' x 8' working area.

    Maybe the rooms are climate controlled for those who claim up to half a mil in accuracy.
     

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