Very nice. I like it more in alu.
What will be overall size and cutting area.

 

Nice plates What thickness is it on the aluminum you use and what kind of aluminum alloy is it?

 

I finally got my 1/4" 6061 aluminum parts made.. I took the files to a friend with a water jet table, modified the files to eliminate the "OX" logo because the machine only does "thru" cuts. Then threw the cut parts into a tumbler to smooth out the edges...

 

This is the finished parts. Still a ways to go before the OX comes alive!

 

No i havent tested the eccentrics. I will be ordering most of my parts this friday. Is there something other than just a hole there? Yea, the last part of the video shows the parts in a tumbler of stones.. The stones can be changed out depending on how coarse or smooth of a finish you want.lol looks like a big shaky tub...

 

I couldn't find an economic source for fibreglass sheet in Australia let alone knowing where I could get it NC cut. So, I too opted to make a set of Aluminium Waterjet cut Gantry parts. I also drew up some corner brackets and had them cut them cut with the plates. For me this worked out an economical method to get these parts, especially since I got the corners as well. The operations manager at the Waterjet company even gave me a discount when I told him what I was building and he was actually quite keen to potentially add one of these machines to his workshop after he sees mine.

 

It's probably vegetable oil <snicker>

 

Hey guys, I'm looking into getting some plates cut from steel or aluminum at a local shop around here, laser/waterjet. Whichever I get the best price on. I was getting the files ready, to send off for a quote. Robert, I was going to use your files, but when I push them over to a dxf format for autocad the scale gets wacked out. For some reason, when I try to scale it back to correct proportions, based on the sketch up measurements, autocad seems to refuse to get it exactly the same.

Any Idea why Sketchup isn't exporting it accurately?
On a side note, in the waterjet thread he posted a dxf, which is in mm, spot on with the model...

 

Hi SlyClockWerkz, the DXF I posted is identical to the one posted in the files tab of the Ox build thread. The only change I made was to erase the OX logo and add the corner brackets. I drew the corner brackets manually.

Also, it may work fine but I would steer away from Steel due to weight. Based on material densities and assuming same thickness, the Al plates would be about 1.5 heavier than G10 (Garolite?) plates, steel plates would be nearly 4.5 times heavier than G10 and 3 times heavier than Aluminium. The Gantry plates in Aluminium weight ~1.6-1.7kg. My feeling is you would want to keep the Gantry light as possible to reduce stress on the motors and belt.

Cheers
Anthony

 

What if the steel plate was 1/8" and or had webbing cutout (think trusses) in the un used areas? The design isn't dependent on the plate thickness if I recall, except you may have alittle extra screw sticking out.

Just trying to think of all the possibilities.

 

I haven't done the sums but a thin steel plate may deflect more under cutting load than a thicker G10/Aluminium section.

I'll pull out the old textbooks tonight and do some comparative deflection calcs.

 

Would be much appreciated. If you are feeling energetic, maybe list the gist of how you go about calculations? Thanks!

Edit, the eccentric nuts may not work though unless shaved down

 

I ended up using ASB's dxf, and used a few of your little touches. Where the only changes you made the openbuilds logo? Did you change any critical dimensions, such as the v wheel spacing/diameter?

Thanks!

 

I found an online calculator here, http://www.engineeringtoolbox.com/cantilever-beams-d_1848.html.

Ran some numbers to get some generic deflection results for different materials and thickness. It is not an accurate representation of what would actually occur on the OX Gantry.

For this comparison I've assumed a catilevered plate 180(width) x 200(high) and 3 & 6mm (thickness)

Variables;
Load (F) - Assumed 100N (10kg)
Length of Beam (a) - 200
(b) = zero, assumes load is at end
Moment of Intertia (I) @3mm thickness I=405mm^4; @6mm thickness I=3240mm^4
Mod of elasticity (E) (N/mm^2); G10 = 18600, Aluminium = 72000, Steel = 200000

Summary;

Deflection @3mm thickness
G10 = 35.4mm
Aluminium = 9.1mm
Steel = 3.3mm

Deflection @6mm thickness
G10 = 4.4mm
Aluminium = 1.1mm
Steel = 0.4mm

So, based on this, I suppose a 3mm steel plate wouldn't be any worse than the fibreglass one at 6mm, Although it would still be a bit heavier.

You could probably use the eccentrics from inventables, they have a short shoulder.

 

So basically, 3mm steel has slightly more deflection than a 6mm aluminum plate, and would perform slightly better than 6mm g10(garolite). A definite option/route to go down depending on cost to make.
For the eccentrics, I could always just use a spacer to mimic a 6mm width.
Either way, I'll see what the laser/water jet guys have to tell me.

Thanks guys!