How to Make a Three Axis CNC Machine (Cheaply and Easily)

The idea behind this Instructable was to fulfill my desire for a desktop sized CNC machine. While it would have been nice to purchase an off the shelf unit the issue of price as well as size proved prohibitive. With this in mind I endeavored to design and build a three axis CNC machine with the following factors in mind:

-Use Simple tools (needs only a drill press, band saw, and hand tools)
-Low Cost (this kind of got away from me however with everything bought off the shelf the cost for all parts is under $600 (significant savings could be made by skillfully sourcing some pieces))
-Small footprint (30" x 25" footprint)
-Usable working envelope (10" X-axis, 14" Y-Axis, 4" Z-Axis)
-Relativly fast cut rate (60" per minute)
-Small part count (fewer than 30 unique parts)
-Easy to source parts (all parts available from 4 sources (Home Depot + 3 online sources)
-Ability to cut ply-wood (Succesful)

Lets get started...

UPDATE: - Coming soon the ability to order pre-cut MDF pieces from oomlout

A salute to those who have laboured through to this point (and to demonstrate that it is reproducable) Here are some pictures of other peoples machines.

Photo 1 - Chris and his friend put together this unit; laser cutting the parts out of half inch acrylic. Not only does it look super it must weigh a ton. But kudos, anyone who's worked with acrylic knows laser cutting it is great but it is a very very unfriendly material to drill and there is a lot of side drilling in this design. Good job guys, check out more details (and photos including some testing with circuit boards) on Chris's blog rainbowlazer.com. I particularly like his work with making 3-d objects out of 2d cuts (here) .

Photo 2 - Sam McCaskill has finished his desktop CNC machine and it's looking really really nice. Super impressively he also resisted the urge to cheat and cut all his pieces by hand. I'm really impressed.

Photo 3 - Angry Monk's - With MDF pieces cut on a laser cutter and drive converted from toothed belts to threaded rod

Photo 4 - Bret Golab's - Bret has completed his and gone through the extra step of getting it setup to work with Linux CNC (a task I attempted and was foiled by complexity). If you're interested in his settings you can send him a message (Instructable ID: bretlyssii ) ). Great job Bret!

(If you have built one and would like it featured here, please send me a PM and we can arrange for the sending of photos)

I'm afraid I don't have the space (or the expertise for that matter) to go into the fundamentals of CNC here but there is one websites in particular I found quite useful in my research.

CNCZone.com - A discussion forum which has a DIY machine section which is a wealth of knowledge ( direct link )

Machine Details:

Cutting Head: Dremel or Dremel Type Tool

Axis Details:

X Axis
travel: 14"
Drive: Toothed Timing Belt
Speed: 60" min
Acceleration: 1" per second²
Resolution: 1/2000"
Pulses Per inch: 2001

Y Axis
Travel: 10"
Drive: Toothed Timing Belt
Speed: 60" min
Acceleration: 1" per second²
Resolution: 1/2000"
Pulses Per inch: 2001

Z Axis (up down)
Travel: 4"
Drive: Threaded Rod
Acceleration: .2" per second²
Speed: 12" min
Resolution: 1/8000"
Pulses Per Inch: 8000

The goal was to try and keep the tools required within the realm of an average handyman's shop.

Power Tools:

-Band Saw or Scroll Saw
-Drill Press (drill bits 1/4", 5/16", 7/16", 5/8", 7/8", 8mm also Q (5/16" closest imperial drill bit)
-Printer (seemed like the right category)
-Dremel or Similar Tool (to attach to the finished machine)

Hand Tools:

-Rubber Mallet (to provide "persuasion" when neccesary)
-Hex Keys (5/64", 1/16")
-Screw Driver
-Glue Stick (UHU) or spray adhesive
-Adjustable Wrench (or 7/16" socket and ratchet)

The attached PDF (CNC-Part-Summary.pdf) provides detailed cost and sourcing information for each and every required part. Listed here is only a summary

Sheet Stock --- $20
-a 48" x 48" piece of 1/2" thick MDF (any 1/2" sheet stock can be used I have plans to make my next version out of UHMW but cost was prohibitive this time around)
-a 5"x5" piece of 3/4" thick MDF (this is used to make spacers so any piece of 3/4" stock found around the shop could be used)

Motors and Controllers ---- $255
-An entire instructable could be written on chosing a controller and motors. In short what is required is a controller capable of three axes of control (with pulsed step and direction inputs) and motors with about 100 oz/in holding torque. I sourced mine from http://hobbycnc.com they have worked well and the kit was quite easy to solder. ( direct link )

Hardware--- $275
-These parts can be acquired from three places. The conventional items can be acquired at Home Depot, the specialty drive products are easy to find at any industrial supplier, I used McMaster Carr (http://www.mcmaster.com) (I chose them because they have a nice online store), and finally because of the large number of bearings required I found the best price from an online seller (http://vxb.com) which sells 100 for $40 (leaves quite a few left over for other projects) ( direct link )

Software --- (free)
-What is required is a program to draw your designs (I use CorelDraw), and a programme capable of interpreting these files into pulses to be sent to your controller. I'm currently using a trial version of Mach3 ( http://www.machsupport.com )but have plans to convert to LinuxCNC (An open source machine controller which uses linux) ( http://www.linuxcnc.org )

Router Head--- (extra)
-I attached a dremel type cutting tool to my machine however if you are more interested in additive construction (like fab@home or RepRap) you may wish to look into their deposition tools.

Details

-the metric components and especially the cross nuts aren't very popular and I had to visit several Home Depots in my area before I had enough.
-I couldn't find a way to link to parts directly on the MCMaster Carr site. To find them go to www.mcmaster.com and search for the part #

I had some experience Scroll Sawing pieces so I choose to use a glue on pattern method. What is required is to print out the PDF pattern files onto tiled pages, then glue on each pattern, and cutout each piece.

File Name and Material:

Summary: CNC-Cut-Summary.pdf
0.5" MDF (35 8.5"x11" tiled pages): CNC-0.5MDF-CutLayout-(Rev3).pdf
0.75" MDF: CNC-0.75MDF-CutLayout-(Rev2).pdf
0.75" Aluminum Tube: CNC-0.75Alum-CutLayout-(Rev3).pdf
0.5" MDF (1 48"x48" page): CNC-(One 48x48 Page) 05-MDF-CutPattern.pdf


(note: I've added a DXF version of the 0.5" MDF pattern to this step (DXF-05-MDF-SimpleDXF.dxf) I have removed the cross drilled holes and writing from this file to make it a manageable size, if anyone would like any of the drawings in a different format or including different information please just drop me a line and I'll do what I can)

(note: I've included the original CorelDraw format drawings in a zip file (CNC-CorelDrawFormat-CutPatterns(Rev2).zip) for anyone who wishes to do some editing)

(UPDATE: There is now a choice in patterns for the 0.5" MDF layer, you can download one file (CNC-0.5MDF-CutLayout-(Rev3).pdf ) with 35 8.5"x11" pages tiled, or you can download one file (CNC-(One 48x48 Page) 05-MDF-CutPattern.pdf) which has the entire layout on one 48"x48" page to print on a large format printer or tile yourself)

(Step by step)
1.Download the three layout pdf files
2.Open each in Adobe Reader
3.Goto the Print Dialog
4.(IMPORTANT) in the page scaling dialog select "none"
5.Check to make sure the file didn't accidentally get scaled to do this measure the printed ruler on page one of each pattern (make sure it matches up with a ruler you trust) (I didn't do this the first time and accidentally printed out a copy at 90% size more on this later)

Next step is to Glue the pattern to the MDF stock and Aluminum Tubing

1.Glue the tiled pages to your sheet stock (MDF) ensuring the edges match up
2.For the aluminum tube the pattern must be glued to two sides. If the Tube is laying flat on a table and you glue the side A patterns to the top side B can be glued on either of the side faces.

Tips:
-Use lots of glue
-Have something near by to help push down each piece
-Patience
(if anyone else has tips on doing this I would love to hear them)

Not too much to say for this step simply cut around each outline.

I must apologize at this stage I succumb to the desire to cheat. As mentioned earlier I accidentally printed out my initial pattern at 90% size. Unfortunatly I did not realize this until this stage. So left with a 90% scale set of pieces and having moved across country I was now within reach of a full size CNC router table. I gave in and cut my pieces using this machine. However it was unable to do the drilling of holes so back to the real steps (this is why all the pieces from here on out do not have paper patterns glued on them)

I have not counted but this project requires a lot of holes. The holes which are drilled into the edge of the material are particularly important so just take your time, you'll appreciate it later when you need to use the rubber mallet only sparingly.

The areas with holes drilled overlapping are an attempt to create grooves if you have a table router that would work much better for this.

If you've made it this far I must offer my congratulations and suggest it only gets better from here. Looking at the pile of pieces picturing how it manages to become a machine may be a tad abstract so I tried my best to create instructions as close to those produced by LEGO. (downloadable in the attached pdf CNC-Assembly-Instructions.pdf). But in the interest of amusing along the way here is a timelapse of me putting my machine together.

Almost there. All that is required is to wire up your motors and controller following their instructions, and to set up your control software using the included instructions and the machine specific details included here in step 2.

There you have it hopefully you are finished and ready to go into production. I hope I have not left out any crucial details but if you think of something you'd like to know which I have omitted please just ask. Finally to demonstrate that it all works a video of my machine cutting out a pattern in pink foam.