Small Fixed Gantry Router Spec and Build

**shaunrod** · 26-02-2016

Hi All,

Long time lurker, first time poster.

I have need for a desktop type CNC router. My original thoughts of a chinese 3040 or similar have been dispelled quite early on from reading this forum. As i can't find an alternative within my budget it leaves no option but to build one.

. I would much appreciate any input from experienced CNC'ers to help me on my journey and sense check some of my decisions (il need it) before i buy anything.

So starting from what i want out of the machine.

1. Machine mostly hard and soft plastics for small prototypes. flat Carbon sheet. (Small amounts of alloy but not a priority)
2. Relatively good accuracy (0.2mm)
3. Run continually for a few hours for small batch production
4. Tool to learn more about home/DIY CNC without costing a fortune.

My budget for the build is around £700-1000. Building it is a learning experience for hopefully building a much larger and more capable machine in the future.

SPEC.
After doing some reading i have decided a fixed gantry machine ticks a lot of the boxes for what i require (stiffness/small work area). Cutting speed range - up 150IPM (2500mm/mim for us metric devotees) should cover most applications.

Machine foorprint: (footprint around 500mm x 600mm)
Cutting evelope: (around 300mm x 400mm x 70-100mm)
Ballscrew: 1605
Rail: Supported Rail on x,Y,Z (for cost reasons)
Spindle: water cooled 1.5kw or 2.2kw (possibly overkill but cant find an alternative that could be useful int he future)
Steppers/Controllers/BOB:Not my strong point but from using a few references and motor calc spreadsheet from the link below It looks like my selection "should" work. Although im not totally convinced as i can't find the torque/step graph to find the torque at top cutting speed.
http://www.ebay.co.uk/itm/2819021550...%3AMEBIDX%3AIT
Control: Mach3 with some form of Cam software (suggestions?) still doing research.motorcalcs
http://www.mycncuk.com/threads/1524-...otor-do-I-need

Construction.
Currently undecided on construction. I have access to chopsaw/arc welder and small workshop. I am not confident i can make a welded assembly accurately enough so i am thinking a hybrid alloy plate/extrusion and laser cut steel mostly bolted together to allow room for adjust ability (see images). This is possibly not rigid enough. concerned with gantry stiffness (from twisting caused by Z load). Second do this would be the flex in the gantry from side loads.

Also some feedback on the z axis would be appreciated (should this be reversed to give more height for parts).

Thanks in advance, Shaun!