Friday, February 4, 2011

Building a CNC Router: Part 1

A Woodworking Project

My background is Physics and Engineering. For years I have wanted to build a CNC mill, originally to drill printed circuit boards, but now my interests have shifted to woodworking. I have spent hours examining the many designs for CNC Routers on the Web and finally started my own design which I believe will be relatively simple to construct and align.

In this blog I will post my design as it progresses. The design will include both the construction of the router machine and the electronics. At the beginning of the construction section, a complete bill of materials, BOM, will be provided and will include sources for the parts.

Design Features:
  • MDF construction
  • Gantry Design
  • Steel bearing shafts with linear bearings
  • Lead screw: ½-10 single or double start Acme threaded rod
  • Nut: Antibacklash
  • Dremel or trimmer router


The purpose of this project is to design a CNC router for woodworking that can be constructed with woodworking tools and easily obtainable mechanical parts. The design will take account of the accuracy of woodworking and make assembly and adjustment simple. Further, the design will use wood furniture assembly hardware.

Several of the MDF pieces are duplicates and the shape and alignment of holes critical. Methods to do this will be shown and will require special jigs. The base front and back, as well as, the gantry sides and the Z-axis top and bottom plates are mirror images. To assure that the holes in these mirror parts are perfectly align, they will be drilled simultaneously after being pinned with 1/8" dowels. This method assures that, though distances between holes have an accuracy of 1/32", the mirror alignment is exact.

For construction you will need the following tools.

Essential Tools:
  • Drill press with a table and fence
  • Router
  • Forstner and router bits
  • Home made jigs
Additional Tools
  • Table saw with plywood blade, 80 teeth
  • Cut off sled for use with table saw
  • Cut off (miter) saw
  • Router Table
Substitutes for additional tools, but will make construction slower
  • Hand power saw with plywood blade and jigs

    Since the construct material is MDF and this project is basically a woodworking project, precision of construction is no better than 1/32 (.03”) of an inch. A further complication is the hydroscopic nature of MDF which is not as bad absorbing water as particle board but is no better than pine. This can be alleviated by sealing the finished MDF. As a result of this accuracy of construction, aligning the bearings and maintaining that alignment is a problem unless flexibility is built into the design.

    Construction projects for a drill press table with fence, cut-off sled and router table are also included in this blog. If you have the funds, the drill press and router tables can be purchased, but construction is not difficult and saves money. In addition, these projects are good training for building the CNC router.

    Note: As to the electronics, prototype pcb's for both the Toshiba TB6560 and the L298/L297 and a PIC based tester are completed and being tested. 

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