CNC Gantry Router -- Blackfoot

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Tools Formerly at the Asylum.
Blackfoot CNC Router

Side view.

General Info
MakeArtisan's Asylum
ModelBlackfoot
Serial1
Mfr. SpecsUnknown
Manual
Asylum Info
RubricN/A



This tool was replaced by a ShopBot.

In January 2011, a CNC gantry router went into service at Artisan's Asylum in Somerville, MA. This machine is capable of cutting a full-sized sheet of plywood, with table travel of 97" x 49". It has served as an educational tool, introducing dozens of hobbyists, woodworkers and digital fabrication enthusiasts in the Boston area to digital fabrication of large artwork and structural objects. Since completion at Artisan's Asylum, the CNC gantry has been used to create furniture, signs, prototyping and mechanical components, mold forms, artwork and production items.

Notes, plans and details on anything related to the Blackfoot CNC router at Artisan's Asylum are located on this page.

To schedule time, you need to make a reservation.

Contents

History of the Machine

The machine was built by Judah Sher from October to December, 2010. The design is based on the 4' x 8' Blackfoot CNC plans at Build Your CNC. Jeff Jackson purchased the machine from Sher on December 19, 2010 and is currently leasing it to Artisan's Asylum. Classes on the use of the Blackfoot are currently taught by Judah Sher.

Capabilities

As of August, 2011:

  • Can cut a full sheet (49" x 97") of MDF, MDO, plywood, or any other engineered wood sheets.
  • Over 7" of travel in Z.
  • Rapid moves of 300 inches per minutes in X and Y.
  • Installed with Porter Cable 7518 3.25 HP router motor.
  • Controlled by EMC2 (Enhanced Machine Controller 2) via Linux CNC 10.4, a slimmed-down Ubuntu distribution running a real-time kernel.


Startup Procedure

  1. Remove tarp from the table
  2. Power on both power strips located under the table. This should cause the computer to boot.
  3. Once the login screen has been reached on the computer, log into your account.
  4. Launch EMC2
  5. BEFORE DOING ANYTHING ELSE: on the keyboard:
    1. Hit F1.
    2. Hit F2.
    3. Click the "Home All" button on the screen.
  6. Using the keyboard, move the gantry over to where you are standing.
  7. Install a cutter in the router
  8. Affix your spoil board (if you are using your own) and work piece to the table.
  9. Open your gcode file (.ngc) in EMC2.
  10. Touch off the machine so that the origin point in your file lines up with the corresponding point on your work piece.
  11. Run your file.

Maintenance Log

August 3, 2011 (Jeff J.):

-- Z-axis backlash was measured and set to 0.006". It was measured by lowering a cutting tool in 0.001" increments until it clamped a piece of paper against a block of MDF on the table. The tool was raised until the paper was no longer clamped, and the amount raised was taken as the backlash. This was repeated quite a few times, and the backlash setting in the EMC *.ini file was set to 0.009" and the tests were repeated. The final backlash setting that produced the best and most repeatable behavior was 0.006".

-- Massive backlash (> 0.100") in the Y axis was traced to a loose set screw holding the chain sprocket to the Y-axis motor shaft. The sprocket could rotate about 45 degrees without turning the motor shaft. The sprocket was reset, and the set screw tightened with a small amount of thread locker included. This resulted in greatly improved cut accuracy.

-- Unusually loud movement sounds from the Z-axis stepper motor were traced to a loose connection in the controller box. The Gecko 540 came with DB-9 connectors for connecting to the motor leads. The Z-axis connector had loosened slightly, weakening one of the connections for the motor wires. The connector was firmly pushed back into place, but these connections need to be monitored regularly.

There has been significant maintenance done to this machine from January - July 2011. An overview of some of this work may appear here at a later date. (Jeff J.)

Technical Information and Resources

This is a good blog article about measuring and setting backlash. Software backlash compensation in EMC2 is described here.

CAD and CAM Software

This wiki page has some good, up-to-date information on CAD and CAM programs for people who prefer GPL software.

http://wiki.linuxcnc.org/cgi-bin/emcinfo.pl?InkscapeHowto

Some free or low-cost CAM options:

Latest version $150, trial version with 40 free sessions, or free-to-use older version

$150, free trial version that only exports g-code for a few provided example files

Google SketchUp is a 3D modeling program that seems to be popular with a lot of people, particularly people who are new to CAD. I (Jeff) have not had the pleasure to try it, but I plan to. There is a free version and a Pro version, which runs about $500. Unfortunately, only the Pro version exports drawings in a CAD/CAM friendly format like .dxf.

However, this web page at a site called Cerebral Meltdown has a free plugin for the free version of SketchUp that will export directly to CamBam (.cb) file format. The website also has a good description of what the plugin does and how to use it. I have not tried it, but it sounds quite useful!

Update: There is a SketchUp to DXF or STL export plugin for the free version of Google SketchUp available here. A quick test with a few basic shapes seems to work.

Solidworks: We have Solidworks in the classroom, and HSMWorks is installed, which allows the creation of .ngc files for the router. Tutorial is good, however, the output of the EMC .ngc files has to be edited (commented out) in two places.

  • There is a line very near the top of the .ngc file which has the line, "G28 G91 Z0." This

is a 'return to home position' move, and preliminary tests showed an issue with it (moving through the object, which is not good).

  • There are two lines near the bottom G28 G91 Z0., and G28 X0. Y0. which need to be commented out. These

tell the system to go to 0,0 of the CNC, which is unnecessary.

  • NEW [2012-Nov-06]

An updated .cps file has been created by HSMWorks. Examples and notes are also located on the ZOAC drive, in the blackfoot_cnc directory. This File:Emc2.cps is the updated driver. Essentially, this new file removes the required editing steps above, and allows rational tool changes.

Tooling Supplier Resources

See Sources For Cutting Bits


Q & A

What cutters does the Asylum currently own?

None. For a variety of reasons, operators must supply their own cutters.

Does the machine have a duty cycle? Can it cut all day without pause, or will that burn something out?

We are still figuring this out! In theory, the machine should be able to run for long periods without requiring a cool down. In practice, we have had a couple of the stepper motors driving the axes over heat and burn out, and we have fixed the problems that caused this. As we use the machine more and more, we will monitor motor temperatures. Additional testing and adjustments should allow the motors to run at stable temperatures, and the machine would only need to be stopped for changing cutters and workpieces. --Jeff


Stackup

  1. Stock/Workpiece
  2. Sacrificial
  3. Grid - 6" grid of 1/4-20 threaded holes -- MDO?
  4. Torsion Box

Storage of flat stock

  • reinforce plus 2 or 3 shelves?
  • rollers?
  • separate by thickness
  • scrap pile
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