1. I'm starting to think ahead to projects that I may build in the future on my DIY MDF cnc machine. I will at some stage want to make something that is double sided - the software side I can work out on my own easily enough, but I'm having a little trouble working out the hardware side of things.

    How can you ensure the best possible alignment for double sided machining?
    Are there any alignment approaches or stock mounting methods that can help?

    I can see a lot of room for error in this, so any info would be very helpful.

    Thanks

    Tom

  2. Quote Originally Posted by CraftyGeek View Post
    I'm starting to think ahead to projects that I may build in the future on my DIY MDF cnc machine. I will at some stage want to make something that is double sided - the software side I can work out on my own easily enough, but I'm having a little trouble working out the hardware side of things.

    How can you ensure the best possible alignment for double sided machining?
    Are there any alignment approaches or stock mounting methods that can help?

    I can see a lot of room for error in this, so any info would be very helpful.

    Thanks

    Tom
    The usual approch to this is some form of 2-part jig, one part of which clamps to the table and the other to the work. The two parts of the jig are joined by dowels or pegs and the workpiece part can be flipped over.

    Assuming the centre line of the jig is zero'd correctly, so flipping the work over retains the centreline accurately then machining will be coincident on both sides.
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

Name:	jig.gif 
Views:	374 
Size:	3.4 KB 
ID:	1221  

  3. Thats a great start - thanks....simple too.

    I just need to work out how to set the zero reliably & accurately now....any pointers on this?

  4. Quote Originally Posted by CraftyGeek View Post
    Thats a great start - thanks....simple too.

    I just need to work out how to set the zero reliably & accurately now....any pointers on this?
    Again, consider fixing the jig to specific fixing points on the maching table/bed. If your bed is MDF, then one option is to drill through and use tee-nuts inserted from underneath. These will then act as a fixed location for the jig base.

    In all cases you need some way of bringing your cutter back to a known, fixed, starting point... or some way to calibrate it to a known point. This is where homing switches are useful but how useful depends on the accuracy you are looking for.

    On a milling machine you rarely rely on the table location but zero off to the workpiece using a rotating edge finder tool in the spindle.

    In this case you'd zero off to the jig... jog to the jig edge util the tool gives a zero indication, then set this as a known value in Mach3 or whatever the software you use. Repeat on the other axis.

  5. I've just done a bit of searching into edge finders - that looks like the way forward, I'd not heard of these before.

    I can't seem to find a 6mm or 1/4" one though - they seem to be 10mm or larger...more googling required I think.

  6. #6
    Crafty Geek, edge finders are also known as wobblers or wigglers these come in smaller diameters.

  7. Quote Originally Posted by CraftyGeek View Post
    I've just done a bit of searching into edge finders - that looks like the way forward, I'd not heard of these before.

    I can't seem to find a 6mm or 1/4" one though - they seem to be 10mm or larger...more googling required I think.
    Chronos have a 4mm ones, a standard one EF4, and a Z-type EFZ4

  8. #8
    Only other thing to realise is that depending on what axis you flip the piece on, then one of the cutting axis will be a mirror image!

    Peter

Similar Threads

  1. Video of CNC machining a double sided part.
    By Shinobiwan in forum Woodworking Project Showcase
    Replies: 26
    Last Post: 17-03-2013, 11:23 AM
  2. Double gantry idea, What do you guys think?
    By craigrobbo in forum Gantry/Router Machines & Building
    Replies: 14
    Last Post: 25-12-2012, 10:01 PM
  3. Single or double??
    By Wobblybootie in forum General Discussion
    Replies: 7
    Last Post: 06-01-2011, 08:08 PM
  4. 4th Axis CAM Software Multi Sided Machining
    By alan2525 in forum Computer Software
    Replies: 0
    Last Post: 18-02-2010, 12:44 AM
  5. One sided drive?
    By Jeremy in forum Gantry/Router Machines & Building
    Replies: 5
    Last Post: 02-12-2008, 10:04 PM

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •