Sweet dreams CNC - more than one step beyond...

[sweetdream]

Having exhausted the 80's music metaphors, (ok, you might spot a few more) I thought I'd get around to posting some details and images of my CNC build "Sweet Dreams" now its finished, (does it ever finish??). Probably easier to start at the end and work backwards to the beginning...

[edit]Change of plan... I have a large box of papers, drawings, research and notes, (there were over 900 revisions to the main CAD!) as I come across the info or the images I'll post them. You may see some conflicting reference to past, present and future tense, but eventually it will all be in past tense! Apologies.. this might get a little random! lol [edit]

I'll start with the design specification, but here's a couple of teaser pics until I get the customary video uploaded.

In front of the Rose window at the ally Pally.
If you were at the London Model Engineering Exhibition at Alexander Palace back in January then you've already seen and heard it working! :-) Great to talk to so many knowledgable people and thanks for all the kind words.

You may notice two Echains feeding the same location on the Z axis? One has data, the other power. This principal is applied to the whole machine, data down one side, power the other. (Echain is cheaper than finding interference!)



Table, height adjustable and can be swapped out completely for 4th axis. 40mm box steel, weighs about 70kg without sand.


some boring soldering... more to come on that... :)

The electrics section.

Blue chosen as it matches my eyes! lol. The electrical "box" is er, unusual! The rear of the machine, has a base board across its entire size with hinges at the bottom (to the right in the above image), the view above is in the open position. Laid out horizontally with all the components easily accessible. In the closed position, airflow moves from the bottom of the box and out through the top. (right to left in the pic). aided by 12VDC 3 inch fans positioned by the transformers.

The base board is 22mm Buffalo board with 3mm alloy sheet bonded and screwed to it. This alloy sheet acts as the ground plane for all circuits and helps simplify the prevention of the dreaded earth loop. The hinges are positioned such that in the closed position, the base board, with all the components bolted to it is slightly over centre so gravity holds it closed. The alloy base board ground plane is electrically connected to the main frame.

From top left heading downwards;
(just out of picture) mains in, massive mains filter, 4xMCB, mains distribution rail in 150mm conduit.
(in picture)

Transformer cooling fan low voltage distribution
2 x 5VDC transformers
12VDC transformer
24VAC transformer for relay cluster and high voltage distribution
toroid transformer, rectifier and smoothing caps.
inverter
Moving right in the image
central conduit (75mm)
right of centre conduit
Power to machine front (round conduit)
secondary distribution board
data feed front of machine (round conduit)
data feed to Z Axis (round conduit)
Relay cluster including hot swap spares, (to Omcrom micro switches, Estop and height gauge)
power to Z axis (round conduit)
BOB

8A drivers far right.

All cables are numbered for easy FF. Thankfully, apart from a microswitch wired to a spare relay, no issues with cabling.

That brought a smile (mainly of relief!)



Warning; >Digression alert<
The evening came when it was all wired... circuits tested and retested, but no power yet applied. A quick phone call to a sparks friend saw the next morning arrive with a body who knew nothing of the build and the wiring. His job was to act as a blind test and verify all was as the wiring diagram said it should be. A couple of hours later and all the circuits are given a clean bill of health. It's time to turn the power on... or we could check it again... lol. It gets plugged in (all switches off) as the first switch is turned on (12v feed to pump, fans, misting system, work lights) fire extinguisher in hand, there is a deathly silence while we search for glowing wires, the faint whiff of the aroma of the magic smoke escaping... after what seemed like hours, we turned it off and went to the pub to calm down, walking like an egyptian perhaps?
:-)

The cable runs use Igus echain but some, eg linking the rear base board to the 5 screens at the front are run through the frame. Prior to assembly, the frame members were machined to accept lengths of 22mm copper pipe. These are electrically bonded to the frame and act as conduits for the cables and keep the sand off the wiring.