V2 – bigShoulders
DIYLILCNCv2 (a.k.a. Big Shoulders) is a robotic cutting tool that you can build yourself*. All the required CAD files can be found here. The DIYLILCNC project is Taylor Hokanson and Chris Reilly. Feel free to get in touch with suggestions or questions once you RTFM and check out our builder’s forum. Cheers!
*Note: DIYLILCNCv2 is still totally in beta. We have a functioning prototype, but the design is ever-evolving (so the design may change after you buy parts). While you can do-it-yourself, there are some challenging steps that involve working with dangerous levels of electricity. If you are unsure about something, reach out to a local university or hackerspace for tips.
1 About
DIYLILCNCv2 is designed to be as user-hackable as possible. All specs are flexible, and may change depending on how you construct your specific build.
- Footprint: (H)18" x (W)32" x (D)26" | 456mm x 809mm x 654mm
- Working area: (X)12" x (Y)13" x (Z)4" | 310mm x 340mm x 110mm
- Table travel (cutting): depends on spindle, bit, and material to be cut
- Tool: 1/4" | 6.23mm collet whip-Dremel
- Can cut: wood, plastic, foam, light metals and more
In order to build your own functioning DIYLILCNCv2 you'll need the following:
- A week of evenings and a full weekend (depending on skill level)
- Basic shop skills/tools
- Basic electronics skills/tools
- Between $500-$1000 dollars for parts (prices vary by source, desired features)
- Plywood panel kit (plans are free, CNC fees vary widely)
DIYLILCNC is an open source initiative tasked with increasing the accessibility of CNC tooling/education for the broadest possible audience. As such, all of the intellectual property generated by the project is free to download, remix and redistribute, even for commercial gain (details). All we ask is that credit be maintained in all derivative works, and that these works carry the same license. If you're not sure what this means, feel free to get in touch.
PS: For this and many other open source projects, we like to rely on the "smell test" when in doubt. Not too long ago, an enterprising web denizen copied our entire DIYLILCNC v1 design document and submitted it to an online contest. In some ways, this was not explicitly in conflict with the letter of our Creative Commons license. After all, this individual did credit our authorship (even if they did move the details from the first to the last page of their submission). Naturally, we felt that this violated the spirit of our license and had the contest entry taken down.
2 Getting Started
We're doing our best to support our two main build communities: those working inside and those working outside the United States (bonus cautionary tale). We recommend that both groups use Metric parts wherever possible, though certain Metric items are more expensive and difficult to source in the US. We'll provide Imperial alternatives for these items (such as the aluminum angle rails), but make sure to note when Imperial substitutions require a different set of matching gantry panels.
Many of the tools listed below are recommended. Although you could probably assemble this kit entirely with hand tools (assuming you already had the panels CNC milled), a jigsaw and cordless drill would really help.
Tools:- Horizontal band saw (or hacksaw/miter box)
- Table saw (or band saw)
- Drill press (or cordless drill)
- Brad nailer / 1" brads (or wood screws)
- 2 Pony clamps
- 8mm bolt clearance bit, pilot bits
- Combo square
- Soldering iron
- 4' x 4' sheet of 1/2" plywood (for base)
- 4' x 8' sheet of 1/2" plywood (for gantry, if you CNC the panels yourself)
- Wood glue
- Goo gone (for label removal)
- Solder
A robot isn't much use without a brain. You'll need a PC with a parallel port to run the DIYLILCNC. Wish you could use USB? So do we, and we researched long and hard before choosing parallel. In a nutshell, parallel will allow you to use an old underpowered PC to keep things cheap. This communication protocol also allows for real-time signalling, which is particularly crucial in an open-loop control system. While you can find USB stepper-control boards out there, they tend to be underpowered for this application.
We've kept the PC out of the budget because this type of box can often be had for free. Alternately, you might choose to build your own on the cheap.
3 Base
Build a torsion box. Most of the parts in this kit are held together with hardware, but this item should be nailed/glued.
4 Y axis
There are two Y Rail Assemblies in the DIYLILCNCv2 design. Although each assembly is made up of an identical set of panel pieces, note that the left and right assemblies are actually mirror images of one another. The following instruction set describes a right-handed assembly (meaning you'll install it on the right-hand side when facing the front of the machine). Make sure that you orient the panels in mirror fashion when building the left-handed assembly.
Verify that the OD (outer-diameter) of your bushings match the OD of the hole at the center of each of the Shoulder Block Interior Panels. You want a pretty tight fit so that your bushings don't rattle around. However, if the hole is too tight, your bushings can go in at an angle and cause binding problems.
For this section you'll need:
- Vertical Brace Panels
- Shoulder Block Panels
- Y Rail Panels
- 8mm bolts, washers and nuts
- skate bearings
- rod bushings
Mount a Belt Tensioning Assembly in the appropriate spot on a Shoulder Block Interior Panel. The orientation of this panel is crucial: when you hold it in your hand, the Belt Tensioning Assembly should be left of center an slightly lower than the Bushing Mount.
You should also add a rod bushing to the center hole at this time, oriented so that the lip is on the same side as the Belt Tensioning Assembly. This part should be snug but not tight - if you have to push too hard, ream the hole a bit (but not too much!)
5 Z axis
For this section you'll need:
- Z Cart Panels
- Z Sled Panels
- 8mm bolts, washers and nuts
- Skate bearings
- 2 Stepper motors
- ACME rod/nut
- Aluminum angle
Attach the Z Cart Front.
Slide the Z Sled Rails through the arrow-shaped slots in the Z Cart Top. Push them until they are securely seated in the diamond-shaped indentation in the Z Cart Bottom. Add two Z Rail Spaces to the top and the bottom of the rail pair to fix in place.
Thread the ACME screw into the ACME nut in the Z Sled. Twist the screw until the nut is about halfway down the length of the screw.
Use a shaft coupler to connect the shaft of the Z Axis Motor to the top end of the ACME screw. You may have to loosen the bolts on the Z Sled to get it to snap onto the Z Rails.
6 X axis
For this section you'll need:
- X Rail Panels
- 5mm bolts, washers and nuts
- 8mm bolts, washers and nuts
- 1 Stepper motor
- 2 shaft couplers, 2 belt pulleys
- Drill rod, aluminum angle
- Timing belt
Bolt the remaining stepper motor to the X Rail Motor Mount with 5mm hardware.
Pass the rails/motor through the center of the Z Cart. Continue to push until the rails bridge both left and right Shoulder Blocks. Add four X Rail Spacers, and fix in place with 8 bolt/nut combos.
Insert a length of 1/4" rod in the Exterior Panel of the left-hand Shoulder Block and push until about 1" | 50mm is exposed at the Interior Panel. Now pass the rod through a belt pulley, then continue to push until the rod makes contact with the motor spindle. Fix the rod in place with a coupler, but let the pulley float for now.
Repeat these steps for the right-hand Shoulder Block.
Pass the timing belt through the Belt Slot in the front left Vertical Brace. Continue to pull the belt until you can pass it first around the belt tensioner, then around the pulley, and finally through the Belt Slot at back rear. Fix in place with a pair of Belt Clamp Panels. Cut the pulley to length, leaving yourself a little extra on either end for adjustment. The biming belt should be somewhat taught and equally tight on both sides. Experiment to find the right setting for your rig. Once the belt is taught, fix pulleys in place on drive rod.
Repeat these steps for both the right-hand Shoulder Block and the Z Cart.
7 Motor Controller
Please read the instructions that come with your HobbyCNC controller/motor kit very carefully. Here are a couple of gotchas that we found through trial and error:
- Watch your jumper settings, especially when setting Vref. These must match the software settings in EMC2.
- Install a bleed resistor on the big capacitor, and do not touch any part of the electrical system unless this cap is fully discharged.
- Install a power LED/1k resistor (not included) between 5V pad and ground on your board. This also shows you the status of the big cap.
- Use consistent motor wire coloring.
- Do not plug/unplug wires until the system has been powered down for a couple of minutes.
- Take the time to build a case. Good airflow for cooling is critical.
- The included power switch is meant for much smaller wires. Purchase a beefier one and throw the stock part out
- Solder all three drive chips to the board, then hold up the heat sink to mark all 6 drill holes at once. If you lay these out with a square beforehand you'll never get the alignment right.
8 EMC2
Download and install Linux/EMC2.
Open an .NC file with EMC2. Jog the tool to a safe middle range, zero each axis, then run the job up in neutral territory. Once you're confident the scaling is right, re-zero so that your tool actually meets your material.
From the OS desktop, run APPLICATIONS > CNC > Stepconf Wizard. See this link for a page-by-page walk-through of all EMC2 Stepconfig settings.
Most of the settings in Stepconfig are determined by the HobbyCNC controller board and the motors it ships with. One key setting, however, called "leadscrew pitch", is determined by the hardware that you happened to purchase with your build.
X/Y: The pulleys on the DIYLILCNC are mounted directly on the motor shaft, so the system will travel a linear distance equal to the outer diameter of the pulley for each turn of the motor. Thus, LEADSCREW PITCH = 1 / CIRCUMFERENCE.
Z: Figuring Z-axis ratios is a little more challenging. Start with the following equation:
- LEAD = PITCH x STARTS
- Lead: The axial distance the nut advances in one revolution of the screw
- Pitch: The axial distance between threads
- Starts: The number of independent threads on the screw shaft
...and then calculate LEADSCREW PITCH = 1 / LEAD.
