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6th February 2014, 05:37 PM #16SENIOR MEMBER
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Agreed, the Red book should help, had trouble getting a link so I hope this works
try this https://www.google.com.au/url?sa=t&r...,d.dGI&cad=rja
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6th February 2014 05:37 PM # ADSGoogle Adsense Advertisement
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6th February 2014, 09:06 PM #17SENIOR MEMBER
- Join Date
- Sep 2009
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- Newcastle
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- 549
Thanks for all the input and suggestions everyone. Sorry for slow reply.
A taut wire had not occurred to me. I'll look in to that as a method.
I'll do a bit more research on what epoxies are available.
That's exactly how I had thought to do it, but the difficulty I see is that tube or parallel flange or universal beam will all be uneven to a reasonable extent on multiple surfaces. This means when I move the beam along it may end up slightly tilted (e.g. not square in the vertical plane) even if it is square in the horizontal plane. It's possible obviously (otherwise large accurate machines would not exist) but could be very painful.
I've looked at deflection tables and calculators (plenty available on google, though it can be hard to find metric ones). The load will not just be vertical on the beam. There will also be horizontal and torsional loads from the router cutting which need designing for also. I'm aware of the effect that increasing the section has on stiffness / deflection. Doubling from 100x100 to 200x200 results in 10 times the moment of inertia. I'd been looking at a 200x200 beam for my gantry.
Example sites:
structural steel & oil field suppliers,channels, sections, angles, sheets, bars & gratings, beams, flange beams, columns,
Steelweb Steel Section Data - Structural
Lets compare a universal beam of about the same weight (therefore cost) (100 uc 15 Steel Data) to 100x100x5mm square section (100 x 100 x 5 Steel Data)
Universal Column
Weight:
Overall
Overall
Flange Thickness:
Web Thickness:
Root Radius:
Moment of Inertia - XX
Moment of Inertia - YY
14.8 kg/m
99.0 mm
97.0 mm
7.0 mm
5.0 mm
10.0 mm
3.18 million mm**4
1.14 million mm**4
Square Hollow SectionWeight:
Overall
Overall
Flange Thickness:
Moment of Inertia - XX
Moment of Inertia - YY
14.2 kg/m
100.0 mm
100.0 mm
5.0 mm
2.66 million mm**4
2.66 million mm**4
The SHS is much stiffer in the Y direction whilst being slightly less stiff in the X direction. That's without looking at torsion, where the I beam falls down particularly.
At the end of the day we are talking wood and plastic cutting forces, which are no where near steel cutting forces. Stiffness does have very real advantages in accuracy etc.
Yep, exactly, this is a hobby. Thus my asking if other members, most of whom are hobbyists also, if they had a suitable machine.
I have not approached businesses, nor will I do so, as I'm well aware this would be overly expensive as a single job.
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7th February 2014, 08:42 AM #18SENIOR MEMBER
- Join Date
- Jun 2011
- Location
- Australia east coast
- Age
- 71
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- 1,469
However you approach it, it's going to be very painful. That's the nature of what you're trying to achieve. Especially if you want more than one side straight, flat *and* at 90 deg to the other(s).
I can think of a few ways to fixture on a HM to do it but if you don't have access to one, there's probably no point. Short form, machine one face until you run out of travel then set up an angle plate or parallel bolted to the table edge so you can clamp onto the machined vertical face then keep traversing along. You're always clamping on the vertical machined surface after the first cut and can check for wind. Reduces your available travel some but that's a tradeoff. Other clamps and distortion prevention due to clamping I leave as an exercise for the operator....
I've made some pretty long angle plates like this on a HM using a big face cutter in the spindle but never had to reset so I can't say with 100% confidence that you won't get some variation from a single plane - but then I'd give no guarantees the steel won't banana on you as soon as you cut it anyway. It's the nature of RHS/SHS to do that....
Good luck with it.
PDW
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