CNC Router

We've decided to build a CNC Router.  We are building it to eventually build solid bodies as well as to do inlay and other work but also to learn about CNC machines especially for Dominic's future.  After considering a number of options we have settled on a variation of the JGRO CNC Router.  It appears to be a very good base to start with and has a ton of support on the CNCZone forum.  You can find the plans here in both PDF and DXF formats.

The JRGO is a gantry-type design whose frame can be built from MDF.  You can certainly use other materials but we've chosen to use MDF.  To sort out the most efficient use of a sheet of MDF I found a utility called Cut List that is extremely handy.  It takes a parts list with dimensions and solves for the most efficient use of a given set of input materials.  In our case we chose to use two 4x4x0.75" and two 4x4x0.50" sheets of MDF. (For some odd reason two 0.75" thick 4x4 sheets were a few dollars less expensive than a single 4x8 sheet so that's why we went with 4x4.  Also, 4x4 sheets are a lot easier to handle.)

Following are the files that I used with Cut List if they are of use to anyone else (NOTE: the Cut List input and solutions are based upon two 4x4 sheets of source material for each thickness required):

  Complete MDF parts list (XLS format)
  Cut List formatted input file for 0.75" MDF parts (TXT)
  Cut List solution for 0.75" MDF parts (PDF)
  Cut List formatted input file for 0.50" MDF parts (TXT)
  Cut List solution for 0.50" MDF parts (PDF)

 

References:          
  Following are some very useful reference sites:     Following are some useful threads on CNCZone.com  
           
  John Groeschel's site     A great all around FAQ thread Link
  BuildYourOwnCNC     Another very good FAQ thread (electronics and stepper motor focused) Link
  Build a home made CNC machine     Turning ACME screw ends without a lathe Link
  Peak Efficiency     A good JGRO upgrade thread Link
  CNCJay.com     A very good JGRO build thread Link
        Another good JGRO build thread Link
        And yet another good JGRO build thread Link
        A nice discussion of machine alignment Link
           

 

MDF sheets arrive home fresh from Menards.
MDF sheet about to meet table saw.
Dominic cutting the MDF.  It took us about 1.5 hours to process all of the wood.  The Cut List program made this part of the job a breeze.

We chose to cut the wood outside because MDF dust is really fine and gets everywhere.  It was a beautiful late fall day so outside work was great.
All of the wood cut and ready to be assembled in our shop.
Dominic beginning to assemble the Bed Support.
Dominic assembling the Base Support Structure.

I would highly recommend building the outer frame first and using corner clamps before proceeding to build the inner lattice.  You really want these support structures to be square.

Also, go very easy on fasteners.  MDF is prone to split if fasteners are driven into its edges.  We made sparing use of small brads (18 gauge.)

The completed Bed Support and Base Support Structure.
This was the work of UPS on the first shipment of lead screws from McMaster-Carr. There is a six foot piece of 1/2"-10 single start lead screw in the tube.  Ideally you want it to be straight for optimal machine performance.  UPS left the package at my front door in this condition.

Upon contacting McMaster-Carr they immediately shipped a new one with no questions asked and I had it the next day.  McMaster-Carr has superb customer service.

The completed set of adjustment blocks.  The large ones are drilled through with a 1.5" hole and then four 1/14-20 threaded holes for the adjustment bolts.  The small ones are drilled through with a 1" hole and the same 1/4-20 threaded holes.  All have 10-24 through holes for mounting.

All of the threaded holes are done by drilling with the proper tap drill, tapping the hole, soaking the tapped hole with CA glue which is allowed to dry overnight, and then re-tapping before use.  This results in significantly harder threads.

Use thin CA glue as you want it to easily run into the threaded hole and be absorbed into the MDF.
The completed set of linear guide assemblies.

Dominic threading mounting holes on the gantry.
The nearly completed gantry.

This is the bed of the machine after routing to inlet the universal T-Track that we have chosen to use for a hold-down system.  The T-Track is Rockler #26420.  We used a 1" Forstner bit to drill a pocket at the end of the channel to allow for easy entry of T-bolts.
For our machine we bought the 3 Axis Electronics Kit from Fine Line Automation.  This includes a Gecko G540 drive, three NEMA 23 - 380 oz-in stepper motors, 48V - 7.3A switching power supply, and cables.

We will be using Mach 3 CNC software that will be running on a Dell Optiplex G520.

 

 

For the mechanical components of the machine we chose 1/2-10 single start ACME lead screws (precision grade with black-oxide finish) from McMaster-Carr.  The anti-backlash leadnuts (part number AC12101-LN with a 1-3/16" machined square flange) and couplings (part number AC12101-AC with 0.250" bore) were ordered from DumpsterCNC.
The bearings for the machine were ordered from BuildYourOwnCNC, the 30 pack which includes all of the bearings for the linear guide assemblies in addition to those for the lead screws.  The lead screw bearings are pictured.

The bearings for the linear guide assemblies are type 608Z.  The bearings for the lead screws do not have any identifying markings.

The completed X-axis carriage.
The completed Z-axis carriage.

Starting assembly.  X-axis lead screw completed.  Y-axis in progress.
First stage of assembly completed.  Once we've completed the testing we will attach the cutting bed and the router mount.

Here's a video of the first movement of the axes.
The completed machine with a Bosch Colt palm router installed.  We will be using the machine to cut the router clamps for a full-size router as well as a Dremel tool so that we can cover a wide range of applications.

The machine in the process of cutting one of the router clamps for the Dremel tool.
A video of the machine cutting one of the router clamp pieces sized for a Dremel tool.  I modified the DXF drawing for the router clamps using DraftSight from Dassault Systèmes.  The tool paths and G-code were generated by CamBam.  The machine is run by Mach 3.  
   

       

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