Cncproject

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Contents

Overview

In Mid 2009 we used this CNC Project to kickstart our hackerspace. It was an excellent group project which acted as a medium for getting our members to know each other on a more personal level. Through this project we learned valuable skills from each other including Software, Hardware, and Mechanical skills.

Unfortunately we did a terrible job at documenting the project. This is likely do to the fact that each person held a piece of the puzzle and there were multiple tasks taking place at the same time which all came together in the end. The initial build happened very fast and once we got into the detailed work part of the members moved onto new projects which only a few put the finishing touches on the CNC.

In September 2009 the CNC came to life when we attached a pen to it and started drawing cartoon characters. A few months later we were cutting metal.

After using the CNC a few times we realized that we make a few design errors. We used the Aluminum Angle and Roller Blade Bearings method for the slide rails. This requires that the roller blade bearings be mounted flush on the rails. Do to our design flaws we were not able to accomplish this for the Y Axis of our initial design. The CNC ran just fine with the bearing not totally flush. But they started eating into the rails and after about 30 runs the Y axis was so loose that it lost all of it's accuracy.

Flash forward to July 2010. The hackerspace is moving along well and we have some money in the bank to fund this project and get it working properly. We have left the X Axis alone since it works just fine with the Aluminum Rails. We have completely redesigned the Y and Z Axis to use Thomson Steel Alloy Linear Shafting and Support Rails from Grainger. These are 3/4" precision rods which you need to purchase to length. You'll have a tough time trying to cut these yourself. We also used Dayton Mounted Bronze Bearings which are self lubricated. We're not sure how the impregnate the oil in the bronze but it's a cool trick and solves all our problems.

You can see the second revision here

There is still a bit of touching up to do in order to get this thing to look normal again. The wood we used is expensive so we wanted to recycle as much as we could of the old design. It turns out that not much was salvaged. The sides look like Swiss Cheese which we are covering up. We'll give everything a coat of paint after that.

So as mentioned before. We were horrible at documenting our progress. All the details below are from memory. So if you plan on making your own CNC use this as a guide but not an instruction manual. You'll need to come up with your own measurements.

FAQ

Q: What can it cut?

A: Wood, Aluminum, Plastic, PCBs and any other soft materials. We tried steel and it broke the bit. Aluminum breaks bits often as well but it's doable. This is the kind of PCB that can be created with a CNC milling machine:

Suggested Reading/Viewing

CNC Project on SourceForge

3D Solidworks Design files are available on Sourceforge. Read the Sourcefoge and Tortoise SVN Tutorial on our website for details on accessing these files. If you are already familiar with subversion than you can checkout the files from: https://hhscnc.svn.sourceforge.net/svnroot/hhscnc. Note: You may need to request permission for Euler357 to access these files. You can do that on sourceforge or by sending us an e-mail with your username.

Design Specs

Original Specs

To keep the machine relatively inexpensive (total cost < $1000 but probably under $500 with donated materials) we are considering the following:

  • Similar to euler357's machine only slightly larger size and possible 4th axis (rotary).
  • MDF construction
  • "Skate bearing" linear rails as shown below
Skate bearing linear rails
  • DIY kit or custom built controller (twerpling) (http://www.hobbycnc.com/products/hobbycnc-pro-chopper-driver-board-kits)
  • 3/8-16 standard threaded rod for linear motion
  • DIY anti-backlash nuts (possibly from HDPE or Acetal)
  • EMC Software (http://www.linuxcnc.org/)
  • X-Axis Linear Rail Aluminum Angle 1/8 X 3/4 X 36"(3feet)
  • X-Axis Linear Bearing Built from 8" Alum Angle and 4 skate bearings.
  • 5/16 Bolts x 5/8L
  • 5/16 Jam Nuts
  • 3/8 Nuts and Washers
  • 1/4-20 Cross Dowel Nuts, Bolts(various lengths from 1" to 3", and Washers


New Specs

  • MDF Used for Base - Glued and Brad Nailed
  • Cheap Plywood for ends of base to raise off table
  • Expensive imported Baltic Birch for Gantry for robustness
  • Skate Bearing linear rails for X Axis only
  • Steel Alloy Rods and Bronze Oil Impregnated Bearings for Y and Z Axis
  • Rotozip (not a Dremel)

Tools

  • Brad Nailer
  • Clamps
  • Table Saw
  • Drill
  • Square
  • Level
  • Tape Measure
  • Socket Set
  • Wrenches
  • Screw Drivers
  • Plunge Router

Bill of Materials

  • 18mm Baltic Birch 5' x 5' Sheet
    • We purchased this locally from http://www.cayceco.com/. You should also be able to buy this from your local Woodcraft store. This is not available at Lowes or Home Depot. They do have Birch but it's the 6 layer birch and not the 13 layer birch. The 13 layer board is much stronger and guaranteed to be free of voids.
  • 3/4" Medium Density Fiber(MDF) board
    • This can be purchased at Home Depot or Lowes. We used MDF to build our base because we knew it was flat and it's fairly inexpensive. We spray painted the MDF to seal it from moister. Any moister would cause it to swell and not be flat.
  • 1/4 - 20 Cross Dowel Nuts
    • These nuts are expensive and probably added $40 or more to the cost of our machine. They look very nice and are incredibly strong. Regular nuts work perfectly fine but may require you to drill larger holes. We also found square nuts but have not tried them yet. They would allow a much smaller hole to be cut.

  • 3/8" x 3' Stainless Threaded Rod
    • The threaded rod is used to drive each axis. We mounted motor and coupled them to the rods using hose and hose clamps. These were a pain to get on so we recently changed the coupler to an actual off the shelf product which I will list below.
  • Grainger 4X175 Shaft Coupler Body
    • 3/8" Coupler
  • Grainger LoveJoy 4X236 Shaft Coupler Body
    • 1/4" Coupler

  • AC38101-LN ACME 3/8-10 (1 Start)
    • These are Anti Backlash nuts. When the CNC changes directions you would have a small amount of play in the threads if you used a standard nut. Anti Backlash nuts don't have any play and will allow you to make more precise cuts with the machine.

  • Roller Skate Bearings
    • These can be picked up at your local sporting stores or specialty roller skating stores.
  • Rotozip RZ20 Kit
    • We may actually be using an RZ15 but I could not find one online. The RZ20 would work just as well. We needed a powerful tool in order to cut wood and aluminum. A Dremel just was not cut out for the job.

Build Procedures

Construct Base

The base of the CNC Machine needs to be rigid to avoid problems with accuracy caused by the flexing of the cutting surface. In the above photo you can see that we used an excessive amount of cross bracing. We built the base using 3/4" MDF to reduce the cost of our CNC but you could use Birch or any other quality plywood. We used wood glue to construct our base and brad nails to hold the framing members in place while the glue dried.

The frame was then sandwhiched between two sheets of 3/4" MDF to complete the base.

Fabricate Linear Bearings

Fabricate Linear Rails

Attach Rails to Base

Fabricate Gantry

Attach Gantry to Base

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