This is a log documenting my first CNC router. Same story, long time lurker and I’d like to let some images do the talking because I lack the CAD skills. Any input would be gladly appreciated.
The machine is to cut Wood, Foam and aluminium in an envelope (X,Y,Z) of 1200mm, 850mm and 200mm respectively. I would be happy with 0.1mm repeatability, but would be prepared to settle for less.
The construction is mostly steel, but I plan on using some aluminium profile on the gantry for reasons of weight and simple straightness.
I found a scrap steel table that was rather straight and seemed a good bet…and that it was. After mapping the X axis rail mating surfaces with a dumpy level and set square I set about to grind it by angle grinder, but will likely cast these surfaces with an infusion epoxy. I really like the dumpy level and want to engrave a plate to allow more repeatable measurements (currently I employ eye-averaging and a spread sheet and statistics and whant to use a 1:10 sloped lines with 1mm graduations to give me 0.1mm steps and perhaps the ability to interpolate)
The X and Y axes will be spring loaded rack&pinion drive and V groove wheel guides. These are to be fashioned after the Mechmate, ground out of steel 70x70x6mm angle iron cut to 70x40x6mm with the 40mm end receiving a V-track profile. The whole process is surprisingly achievable after one has done it but I intend to run a conventional bearing running underneath tensioned by ex-center bushing and bearing to keep the assembly on the rails.
Once I have the initial machine constructed I could always use the bottom of a milled slot in the table as a relative reference to grind more accurate track out of angle iron as I go along (and the epoxy cast base will certainly help in this regard)
Initially the 15 tooth 1 Module R&P will be direct driven until I can build a belt reduction gear box for the axes. My calculations seem to result in a 3-4:1 reduction, but the belt reduction is certainly not cheap by the look of things and for first I will cut light wood.
The gantry uprights will be steel U-channel (100mm x 50mm) milled (and in the case of an over-eager machinist surface ground on one side) and attach to the aluminium gantry by means of T-slot fixtures and an angle plate.
The Gantry will be constructed from 45mm x 90mm aluminium profile (see http://www.cncdirect.co.za/htm/profile.html ), but with steel guides (as above) running on the top and bottom of it to give the structure additional strength and provide a suitable V track for the Z car. This profile is an exceedingly stout beam.
The Z axis is to employ 20mm unsupported shaft and a ground base plate and end-plates (reamed and slotted) to accept the linear shaft. Actuation will be by 10mm pitch ball screw.
The spindle is an Ebay water cooled 2.2 kW unit with VFD.
Lastly the motors will initially be fed by a Hobby CNC Pro 4 axis (slaved X Axis) board and Keling 276oz-in 8 wire motors. I have Geckodrive 203Vs , cncdirect.co.za BOB (excellent unit and support is fantastic) and 1200 oz-in motors for a stalled Mechmate project on hand that may do duty on this router, or get the Geckodrive 540 for this, but if the hobbyCNC can do the job, it might at least be worth a try (lest my 8x20 lathe not escape a gang zoning)
Thanks
Martin