Friday, 10 August 2012

CNC drill machine challenge rules

A few people have been asked about the CNC drill machine challenge and it seems that not everyone has access to the BuildBrighton Google Groups page. So here's the preliminary post, outlining the basic rules for the challenge:


After making what felt like millions of boards for the midi workshop, we've decided to make a cheap, little drilling machine for making homebrew boards.
As the discussion went along, we decided to see if we could make the smallest, cheapest machine we could. Almost immediately we couldn't agree about a single thing for our machine, so we've decided to make one each and compare them.

Matt gets loads of stuff cheap off ebay by buying in bulk. 
Chris gets stuff cheap by extracting it from old hardware using hammers.
Matt uses Eagle and could create NC Drill files directly from it to drive the machine
Chris uses ExpressPCB and a convoluted print-to-pdf-then-convert-to- svg method of generating drilling data

Matt wants to make a machine that can drill large, panellised pcbs - double eurocard size (200x160). 
Chris wants as small a machine as possible to fit on a shelf when not in use, and rarely makes boards bigger than a 50 pence piece.
Chris doesn't get the whole open hardware movement and still prefers PIC microcontrollers over AVR. 
Matt thinks an Arduino-based machine would be much more open to hacking if other people used our plans to make their own boards.
Matt can get cheap linear bearings and has experience of making a gantry-based cnc device
Chris thinks he can cobble something together out of ball-bearings and sellotape
The list goes on and on....

So, we've come up with our own hacker challenge. Hopefully this could be the first of many - little projects that we can work on in small groups or individually, then present back to the group.
It would be really cool if other people joined in (or maybe even joined forces) to come up with alternative ideas for this first challenge.

We'd love to see some alternative ideas to make a drilling machine - we've come up with some parameters (it's not really a contest, so it's not fair to call them rules) but here's what we've eventually agreed to work towards. Because it's a machine that we're hoping others will want to try and make (assuming either design eventually works) our first rule is about cost and availability of parts.
It's easy to hit ebay and Rapid and Farnell and blow a small fortune, but that puts it out of reach for a lot of people. Similarly, it's possible to smash open some old hardware and salvage some cool stuff but no-one else might be able to get hold of the same equipment, and would need to find alternatives. So the rules are


  • If buying all new components, not more than £50 on the entire build (just think about it, a cnc based device for under £50!)
  • If using salvaged hardware (stepper motors from old printers, for example) not more than £20 total build cost
  • As we're building a small machine, the footprint of the device, when put away, should not exceed A4 size (210x297mm)
  • But it'd be useless if it could only drill tiny pcbs, so it has to be able to drill up to half eurocard sized boards (100x80mm)
  • Any bought components should be accessible to everyone and you should reasonably expect to be able to purchase the same components from the same, or alternative suppliers 12 months from now (so you can't win a job lot of motors from some bloke off ebay and put cost of materials down as 50p)
  • Overseas suppliers can be used to keep costs down, as their price per unit is often much less than UK suppliers.
  • The device is to be platform independent - it can use any microcontroller and any software can be used to control the machine, including homemade software/drivers. 
  • It has only to work on any one platform, not all
  • For accuracy, the drilling machine should be able to drill a 1mm hole in a max-sized 2mm pad and leave a complete copper ring intact around the hole
  • For building materials, assume a price for acrylic sheets as £1 per mm thickness, per A4 sheet
  • Cheaper alternatives (such as mdf or laser ply) can be used instead of acrylic for the chassis if required
  • Trivial components and the cost of pcb etching, running a laser cutter etc and consumables will not be used to calculate total build cost
  • The price for delivery of all components bought online will be included in the final cost

More rules may be added as the build goes on, but only to clarify any points that may arise, not to act as a restrictive force to deter alternative ideas.

So there we have it. Another stupid challenge that probably won't get finished (or much beyond the planning stages) But there's nothing like seeing someone making more progress on a project than you, to act as a catalyst and get things moving along. So who else fancies joining in?

The prize? We'll use the "best" design for a "proper version" of the machine for use in the hackspace for all members making their own pcbs. Better than money or other tangible goods, you get to win kudos!