Lowcost capable CNC - Make vs Buy?

[Andrewg]

Indeed Jazzcnc,
So given I don't have a business case, but want to explore what the capability would bring to my workshop....the choice comes down for me at least to buy a Workbee or build my own for a budget of £1.5 to 2k. This forum shows that this second route is viable and is the route I am keen to take.

So what have I learnt a 'correct approach' looks like?

I should say I want a machine to cut hardwood in my furniture making workshop. 600x600 work area because I don't have the space and have plenty of processes for which this is big enough. Also helps with accuracy keeping small I believe. Want to cut joinery so 0.1mm repeatability. It will be a workshop machine that won't run all the time but when used needs to be reliable and quick (5m/min cutting?). A build I can complete in two weeks full time ideally..(planning, dreaming excluded)

Frame
Stiffness directly effects performance so important. Unlike manufacturers, DIYer does not worry about shipping, so a steel frame, welded ideally. Epoxy leveling process allows imprecision to be addressed. However I would like to go Ali extrusion and shimming if possible alternative to avoid epoxy and steel working plus flexibility to extend/change frame in future.

Mechanics
Linear rails, ballscrews and correct support bearings sourced from good chinese supplier as set. Leadscrews seem possible compromise that many designs accept, attractive as their lower profile nuts allow leadscrews to more easily fit between bearing rails and keep design simole. Guess wear and lower efficiency not a killer for home machine that operates fewer hours or am I wrong?

Dual drive Y axis seems to be preferred for simplicity now electronics can cope with squaring Gantry especially if drivers have stall detection.This especially of value to me as I want to be able to machines end of pieces held vertically through table.

Principle design challenge are the plates required to mount the components and join it all together. Aluminium can be machined with wood tools. Aluminium tooling plate is already flat, so either they can be cut and drilled myself or waterjet cut by contractor. Adjustability is principle to adopt rather than precision.

Gantry
Make it L shaped and use stiff large box section or extrusions. Extrusions make fitting everything much easier. Rails on front or top&front. One thing that eludes me is how best to join two extrusions to make L, what fitting works that way?

Electrics
Nema23 steppers are big enough for small/medium machine (exact force and inductance to be determined), matched with proper drivers (digital, stalll detection?) and serious power supply (toroidal). Homing limit switches, inductive for accuracy and reliability. Get shielding and earthing of wiring right. Think through positioning and routing of everything.

Electronics
Mach3 and printer ports are old hat. Ethernet and UNCNC or Acorn seem to get thumbs up, though there are also dedicated controllers and open source solutions based on grbl are getting better.

Build challenges
Machine accuracy is determined by build accuracy, so need a dial indicator and know how to use it!

A good design should make build process one of bolting together and aligning ideally, plus lots of wiring.

What have I overlooked?