This is my solution to the large MPCNC gantry flex problem. With a rack-style gantry, you could build the machine as long as you want in the Y direction! ..within reason of course.
The C-RollerCenters, C-RollerMounts, and C-RollerCaps in my pictures are old revisions. The files here are the most recent. So don't worry if your parts look a little different -they're even better.
... So, you want/wanted to build a huge MPCNC machine? Me too!
I wanted to build an MPCNC that could mill standard 4'x8' sheets of wood.
Once I built my machine, however, I realized there were a few rigidity issues that needed to be addressed in order to make this machine more effective at this size. Most of these issues were due to the Y-Axis rail flexing heavily under tool pressure when pushing in the X direction (which utilizes the longer Y rail for movement) especially near the center of the machine cut area. In 9' it's not unreasonable to have huge amounts of flex. So, with this Rack-Style Gantry the rail will only be 12" or so (depending on your preference), thus curing the problem. :)
(Another issue was sag on the support rails. See my thing:1800589)
...Print list. Quantity & Thing to Print (all parts oriented correctly. Do not reorient.)
- 2x C-RollerCorner_GR_CONV
- 2x C-RollerCornerM_GR_CONV
- 4x Spacer_Corner_GR_CONV
- 4x C-RollerCap_GR_CONV
- 2x C-RollerCenter_GR_CONV
- 2x C-RollerMount_GR_CONV
- 2x SpacerCornerC (stock spacer)
- 20x additional 608 bearings
- 24x 6-32 x 1-1/4" screws
- 24x 6-32 Nylock nuts
- 2x conduit for new Gantry X-Support rails ( Cut the same length as your machines X-Support rails)
- 1x conduit 12" for new Gantry Y-Rail
- 2x conduit 14" for C-RollerCorner support (length is new gantry Y-Rail + 2")
- New timing belt OR a smidge more timing belt to add on to your current belt (unless you really love zip ties?)
Pictures are worth many words. Look at them. I will briefly describe some main points, but you shouldn't have any issues assembling. Leave a comment if you run into issues.
If you built your machine the same way Vicious1 describes, then your Y-Support Rails should be higher than your X-Support Rails (They sit on top of them via stock MPCNC part SpacerCornerC). If your machine is this way, remove both the X and Y gantry rails and rotate your gantry 90* clockwise OR counterclockwise (we want the gantry Y-Rail to be above the X-Rail. see photos).
You can now recycle some of the old gantry Y-Rail. Mine was 9' long, so I cut 5' to make one of the two new Gantry X-Support rails, then cut 2x 14" pieces for C-RollerCorner Support and 1x 12" for new Gantry Y-Rail. Now you only need conduit for your second Gantry X-Support rail.
- Remove your stock C-Roller's from the X-Support rails and install on the two new Gantry X-Support Rails.
- Replace the stock C-Rollers on the Y-Support rails with RollerCenter.
- Install RollerCorner and RollerCornerM on either side of the new RollerCenters -flat edge out. (see photos)
C-Rollers can be removed and installed by removing the nut on the single-bearing side and 'walking' the bearing off.
- Lay the 2x new Gantry X-Support Rails into the RollerCorner's. use SpacerCornerC_GR_CONV for the RollerCorners. Use the Stock SpacerCornerC for the RollerCenters.
- Lay the 14" C-RollerCorner Support conduit across the RollerCorners and RollerCenter on either side.
- Install RollerMount_GR_CONV onto the RollerCenter pieces and install RollerCap onto each RollerCorner. Only lightly snug the screws.
-Install the stock C-Rollers removed from the X-Axis Support rail onto the new Gantry X-Support Rails (if not already done from Step Two).
- Install new 12" Gantry Y-Rail and Install & tighten stock RollerMounts.
- Slide the gantry on the X-Axis all the way to one side and tighten those RollerCaps and RollerMount_GR_CONV
- Slide to the other side and repeat. This will ensure all is square and spaced evenly for gantry.
I thought of this design while in the shower back in December.. I've been busy, but I finally managed to finish it up! So, I hope this helps anyone who built or is building a large MPCNC!
Post any questions or comments and I'll respond to them as fast as possible..
Also, thank you Vicious1 for your excellent MPCNC project!
I couldn't find any STEP files or Inventor/Solidworks files for the original MPCNC STL files.. so I hope you don't mind my hacky reverse-engineering. :/