Gantry design question

[D.C.]

Interesting paper, but the structure they refer to in there, if I understood it correctly, is actually a support column not the moving gantry itself. While the paper starts off talking about the gantry all the study work is on the column design. So the jury is still out on whether a lightweight CF gantry beam is better. However, the information is useful as regards the gantry supports. The issue however, is for the small sizes we generally build, i.e. a gantry side 300 - 500mm high or so, does the complexity of forming such a structure give any benefit over a slab of 20mm ali?

You are right, I stumbled across that while trying to find papers on the use of honeycombs or CF, there seems to be remarkably little available to be honest I was more taking away the general principle of 'honeycombs good if used correctly' rather than the specific application they refer to.

were brittle and didn't stand friction wear very well.

IF CF gave any major performance along with even a small cost saving benefit the big boys would be all using it by now and I'm pretty sure there will be a few CF Gantry's, components or full machines stuffed in some corner of some company's R&D department.??

There's always got to be first that takes a gamble so with That said you go for it and we'll all watch learn.!!. . . I for one will be the first to congratulate you if it works and performs has expected. ( I'll do the Nah nah told you so has well. . . Lol)

Wish Good luck if you do.

CF is brittle and really sucks for friction that's true, but every material has it's limitations hence why we don't use rubber for roof suporting girders. That said, it is a bit worrying that nobody else is doing it, I don't know if it's because it is a really stupid idea or because I'm a genius and smarter than an entire industry full of inteligent professionals. ( I vote for it probably being a stupid idea!)

Hmmmmm.

I think maybe the best thing to do would be to design 2 gantrys, if I can get the cost difference down to £50-£100 I might take a punt just to see what happens. I was orignally intending to epoxy the surface fittings on but if I bolt through the structure instead if it all goes horribly wrong I should be able to fix it by adding a couple of thick reinforcing sheets. ( I'll engrave one with 'JAZZ WAS RIGHT!' if I do just to remind me what to do with my next good idea.)

[mekanik]

You are right, I stumbled across that while trying to find papers on the use of honeycombs or CF, there seems to be remarkably little available to be honest I was more taking away the general principle of 'honeycombs good if used correctly' rather than the specific application they refer to.



CF is brittle and really sucks for friction that's true, but every material has it's limitations hence why we don't use rubber for roof suporting girders. That said, it is a bit worrying that nobody else is doing it, I don't know if it's because it is a really stupid idea or because I'm a genius and smarter than an entire industry full of inteligent professionals. ( I vote for it probably being a stupid idea!)

Hmmmmm.

I think maybe the best thing to do would be to design 2 gantrys, if I can get the cost difference down to £50-£100 I might take a punt just to see what happens. I was orignally intending to epoxy the surface fittings on but if I bolt through the structure instead if it all goes horribly wrong I should be able to fix it by adding a couple of thick reinforcing sheets. ( I'll engrave one with 'JAZZ WAS RIGHT!' if I do just to remind me what to do with my next good idea.)

Hi DC
Welcome to the forum
I am really glad you raised this question, I have thought that a CF Gantry had to be more ridgid than all the ally extrusion, when i was @ the Model Engineering exhibition a couple of year ago there was a turbine driven photo graphic aerial platform (Heli Movie Camera thingy) and its space frame was made from 8mm thick CF composite plates.
I can see no logical reason why an exreemly ridgid gantry cannot be constructed using a mould and the vacuum infusion technique.
I made an item just using fibreglass and @ 12mm thick it was both ridgid and had substantial mass.
If i ever get round to building i would certainly give it a try.
Good Luck

[D.C.]

Hi DC
Welcome to the forum

Thanks for the welcome, I think the CF is a non-starter for me though, I realised when checking the easycomposites website that there must be bug or browser conflict as the prices were not changing when differing thicknesses and sheet sizes were selected. What I had priced up as being about double\triple the cost turns out to be ten times or more expensive.

Ooops...

The aluminium honeycomb from there is still a good price though so I may look at doing a laminate design but it would be with thin steel or aluminium not CF, it's a shame but I'll have to shelve it for a few years and see if the price of carbon fibre comes down.


I did find a similar thread to this one on cnczone and apparently there is one company that do use composites for CNC but it is for an ultra precision machine:
DMG | DECKEL MAHO | GILDEMEISTER - HSC 20 linear | Precision Center

There is also this company making ultra high end machine components from composites beams with steel linear rails attached (look at the piccy):
Composite Machine Building Components


They both use composites for extreme rigidity, as do photographers, astronomers, sailors etc etc so I think the idea is sound but the price needs to lose a zero off the end before it comes into the reach of the dirty plebs.