Bridge Gantry Profile

**~andy** · 10-10-2013

Originally Posted by JAZZCNC

Don't waste your money is my answer.!! . . . . . What width Gantry do you want.?

1m total length, 600mm travel. This does allow for a very tidy set up, the stepper directly coupled in c channel and simple Z plate.

**JAZZCNC** · 11-10-2013

Originally Posted by ~andy

1m total length, 600mm travel. This does allow for a very tidy set up, the stepper directly coupled in c channel and simple Z plate.

I wouldn't use that stuff got to many . . . It's.!!

It's light duty thin wall stuff.
It's too narrow in middle with potential to twist.
It doesn't provide ideal or easy rail fastening because slots are in wrong places.
It will fill with and collect chips if plan is to face forwards, (say this because of your simple Z plate ref.?)
It won't allow for simple Z plate if rear facing has the top of channel restricts access to ballscrew so placing ballnut bracket further back than needed.
It's not going to provide anything extra the L shape does.
It's going to cost 3 times the price of L shape.
It's going to be weaker than L shape has it's thin walled and narrower.

Bottom line is It's inferior and 3 x the price.!!! . . So why bother.!

**~andy** · 11-10-2013

Not fussed about the cost of the profile, if it provides an easy build. I've seen this profile with rails on the front and the screw in the middle.

It would be for a wood router so collection of chips shouldn't be an issue as 90% of the waste will be sucked away.

Just wondered if it was up to the job from a technical perspective (ignoring better/cheaper designs). I don't have the knowledge to say if the figures on the drawing are are acceptable for the purpose or how they compare.

**JAZZCNC** · 11-10-2013

Originally Posted by ~andy

Just wondered if it was up to the job from a technical perspective (ignoring better/cheaper designs).

Well If you have too much money then go for it.! . . It will work that's for sure but it would be a dumb thing ignoring better cheaper design don't you think.?

Problem with this stuff thou other than cost is it's light duty thin wall stuff so could resonate or twist/flex in longer lengths. It won't allow much easier build because there's more Drilling and tapping involved because the slots don't allow easy ballscrew mounting. Drilling and tapping profile is a pain on thick walled stuff but this thin walled stuff is rubbish for tapping and holding threads.

Also don't think just because you have vacuum that the shelf won't collect enough chips and fine dust to be a pain.!! . . . It will collect very quickly esp on material like MDF that produces fine dust. . .You'll need a very good Vacuum and dust shoe to contain every thing.

Personally I don't see the point of using this stuff has it's not really making anything easier costing 3 x times the price and is inferior in strength.!

**John McNamara** · 11-10-2013

Hi

Steel is three times stiffer than aluminium and for machinery stiffness is more important than strength in most cases. Any sort of deflection will add to the "Error budget" for the machine. Remembering that (Among others) the sum of all errors for misalignment, frame deflection, bearing slop and temperature have to be added together to calculate the maximum error.

Google search compare Steel to Aluminium: https://www.google.com.au/?gws_rd=cr...ared+aluminium

Regards
John

**~andy** · 11-10-2013

Originally Posted by JAZZCNC

Well If you have too much money then go for it.! . . It will work that's for sure but it would be a dumb thing ignoring better cheaper design don't you think.

I'm not ignoring a different designs outright. Just looking at the options.

Originally Posted by JAZZCNC

Problem with this stuff thou other than cost is it's light duty thin wall stuff so could resonate or twist/flex in longer lengths.

I can't tell with extrusion, and I don't know enough to be comparing section modulus and moment of inertia figures over other designs. It's a very strong cable tray really after all.

Originally Posted by JAZZCNC

It won't allow much easier build because there's more Drilling and tapping involved because the slots don't allow easy ballscrew mounting. Drilling and tapping profile is a pain on thick walled stuff but this thin walled stuff is rubbish for tapping and holding threads.

I was thinking of drilling and tapping to a plate, and mounting off that to get the correct height.

**JAZZCNC** · 11-10-2013

Originally Posted by ~andy

I was thinking of drilling and tapping to a plate, and mounting off that to get the correct height.

I understand your thinking and desire to makes things that bit easier if your time or equipment challenged and i'm not trying to put youoff profile or push you into any particular design but the point I'm trying to push is if you must use this Profile for time and tool reasons then you won't save any work over the L design that uses Profile costing third the price. You will actually create more work and less strength/stiffness.

I use both steel and profile and like my comments before I know 100% the L design along with profile works perfectly for the application of cutting light to Medium hardness materials. Steel would be my first choice every time if heavier duty machine required or Budget was limited has it's simply the best way to achieve both. It's just time intensive compared to profile and needs more equipment/skills to work.

Like John says there's much more to successful machine than material strength and I can tell you for sure building a machine with the mindset of compromising machine strength or design in favour of easy building is recipe for a under performing machine.!