Tassie 5-axis

[timothys87]

Hi All,
My name's Tim, a designer based in Hobart. First time post and build so please be kind . That same old story of that I thought I should share and contribute after lurking for many years.

So the machine is a 5 axis moving table fixed gantry machine designed for timber and non-ferrous; with a capacity of 2440 x 1220 x 600mm (complete 5 axis machining area in terms of offset) max speed of 25mpm. It's a tad bit overbuilt! - I got lost in a CAD and FEA land.

All linear axis (X, Y, Y slave, Z) use 32/32mm TBI rolled ball screw, with the ball nut housed inside DIY rotating nuts made from lasercut steel. There's a pulley ratio of 1.46 using AT10 belting, to a leadshine "easy servo" Nema 42 12nm. Hiwin 20mm linear rails are used, mounted on a bed of epoxy steel (using the piano wire encasement technique for mounting)- so far looks to be a clean 0.1mm accuracy (very happy about!).

The two axis head uses two SHG-2UH-32-80 harmonic drive secondhandys off ebay. The head is constructed from laser cut steel (slot/tang welded). Once again nema 42 closed loop steppers are used with AT5 belting and pulleys. The spindle is a 4kw Chinese air cooled model from ebay.

On the electrics side I went with a KFLOP board.

So basically all the physical work is done. I'm just waiting on the electrics to be finalised and installed, and once the machine is running I can build the vacuum table and vacuum source. I've probably left a bucket load of details out, so if you have any questions I'm happy to help...

[snowyskiesau]

Nice first post!
What are you planing to cut on it?

[timothys87]

Plans are for mostly board products and solid timber(furniture maker), but also opened up for contract cnc machining.

[Lucky Phil]

Hi Tim, great looking machine, will be watching your post. Also good to know of another CNC'er in Hobart. If you feel the need to share more info about your motors & controllers I'll be listening as I am going to use Leadshine closed loop on my machine.

[timothys87]

Hi Phil,
I'm using the leadshine es-mh342120 and es-dh2306. I've hooked them up and gave them a whirl using the protuner software. The control board I am using is the KFLOP by dynomotion. There appears to be a pulse width/timing issue for the step/dir signals between the drivers and control board that I wasn't aware of when I selected them; but it seems that there are a couple of delay line solutions using something like a LTC 6994-2. I have some help for an electrical engineering friend so we should be able to muddle our way through! Hopefully I can be more helpful when things are clearer.

[timothys87]

This one goes out there for all those who like to rotate their nuts, instead of wasting so much motor power to spinning the screw.

As the ballscrews I bought from alibaba didn't come with seals, I had to devise my own using brush seals (door seal) and some nitrile backing. Inside the assembly are two very big AC bearings (shimmed), and from the rear you can see the preloader. I haven't been able to measure any backlash using a dial- but when the machine is running properly I can get a more accurate reading with real machine stop/start/acceleration. The photos are the 2x rotating nuts for the moving table.

[timothys87]

Here are some more photos of the rotating nuts for the moving table. A dust cover is fitted on the chassis with a small nitrile seal in place, so the pulleys and belting cant get clogged with wood dust. The two "mirrored" chassis fit directly on the central moving table span.

[timothys87]

The gantry rotating nut has a different bracket/mount structure, but the core is identical. It mounts to the Z carriage, and travels withing the two 250x150 gantry span lengths.

[timothys87]

The z- rotating nut is quite different in structure as it fits largely within the 150x150 z column. The motor + motor pulley reside inside. I had to cut away a portion of the z column to allow this, but it was the only solution to integrate it all together.

[rusel]

great looking build
How did you find the steel tube for flatness for the rails when fitting?...how did you get the epoxy that level.
Yes rotating nut make more engineering sense with the screws always in tension.
Would like to see the drawing of how the big AC bearings are mounted....
Russell

[drmnz]

Hi - Great looking build. What sort of software do you intend using for drawing as well as CAM? Cheers, David

[snowyskiesau]

I'd love to see a video of this machine in action or better still, in person.

[epineh]

Nice build so far !

What sort of timing issues are you having ?

I helped a mate who built a couple dozen custom commercial machines, and he used the kflop/kanalog with Lenze servo drives, from memory the pulse speeds were up to 400KHz so it was fairly going for it. I can ask him a few questions if you give me specifics. I don't see why you need to delay the pulse train, possibly modify it to suit faster speeds as you will run out of headroom.

Cheers.

Russell.