A vid I found on youtube to demonstrate to all the non-believers why you would want to build a CNC machine.
Moderators: sorry I didn't know where to post this
http://www.youtube.com/watch?v=RnIvhlKT7SY
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A vid I found on youtube to demonstrate to all the non-believers why you would want to build a CNC machine.
Moderators: sorry I didn't know where to post this
http://www.youtube.com/watch?v=RnIvhlKT7SY
Trying not to be a bore, i did like the misters sticking out the bottom of the head.
Saw one at a customers once, in the UK, making a wind tunnel model of a prop blade for a certain large four engined transport plane. About 8 feet long out of ali (looked like) and when it had finished, it looked like someone had spent a year polishing it! Truly amazing.
I think we all know what is possible, especially with 4 and 5 axis machines
but I still say WOW and am impressed
let me know if you've seen a vid which demonstrates CNCs capabilities as the bigger the library to show the other half the great the chance of convincing
PS. I've got 2x 1m and 2x 85cm THKs rails with 8 blocks, a 1m and 85cm THK screw, and a 50cm screw + rails n bearings, 3x Gecko 203s she doens't know about.
I just need to commit to a design and ask for your kind feedback.
building in 3weeks - finished in 6 weeks or much less HOPEFULLY
PPS anyone good at welding 90* corners with box steel within the M25 and need some pocket money?
PPPS Why are RSJs not used where long box section flexes/twists and 15-20mm plate is too expensive?
theres one on Youtube showing machining an 8 cyl V8 block out of the solid.. thats pretty impressve too...
http://www.youtube.com/watch?v=QsmiIeAkE-o
also a W16...
http://www.youtube.com/watch?v=GU32Q6QXtWQ
Nice ne Irving,I never get tired of watching these vids.
Don't care what anyone says the Japanese are at the forfront of Technology.
Irving: WOW!
What name is given to the tool used to get the final finish that removes most machining marks; making it look like its been hand polished for years?
for example finish on the vid I posted at the top
A finishing end mill cutter,if you noticed that cutter was a fine point.
Its a bit like a SMs aw the more teeth on the blade the finer the cutand vice versa.
Hi Williamturner1,Quote:
Originally Posted by williamturner1
RSJs are actually no better in bending than a similar sized box section, are are also very much worse in torsion. Plate, even thick plate, can also be poor because you need material away from the neutral axis for stiffness i.e. wide hollow sections.
See the 'gantry stiffness' spreadsheet in post#2:
http://www.mycncuk.com/forums/showth...ign-principles-.-.-.
If you have a box section which is bending or twisting too much you either to add additional supports, or need to increase the section size. Sorry, RSJs are not a panacea.
As for your new machine, sounds like you a have a nice list of bits - but naughty you for hiding them :whistling: ! Start up a new post with some sketches, scanned drawings, whatever you have, and we'll make some comments. It's worth adding what you want the machine to do.
Wicked Thread you linked to and epic spreadsheet!!Quote:
Originally Posted by routercnc
I'm considering 90 x 150mm RSJ over 120 x 80mm 4mm Box; partly as I have 4 meters of RSJ and no box but mainly as my brain tells me 90x150 RSJ wouldn't flex like Box Section would ... but the spreadsheet says otherwise
RSJ Data for the spreadsheet, 2nd entry in the table = 90x150mm : http://www.steel-beam.co.uk/universal-steel-beams.php
I've got 9 sketches on the back paper out the office recycling bin ... I just need a bit more time to filter the embarrassing mistakes before I post a few up and ask you to say which will be the most bendy and the least!Quote:
Originally Posted by routercnc
Thank you for the quick feedback. I can't wait for more and to start building!!
Me to, I didn't see a RSJ option in the sheet, did you use the I beam one? :whistling:Quote:
I'm considering 90 x 150mm RSJ over 120 x 80mm 4mm Box; partly as I have 4 meters of RSJ and no box but mainly as my brain tells me 90x150 RSJ wouldn't flex like Box Section would ... but the spreadsheet says otherwise
RSJ's have deeper flanges :naughty: than the webbs and therefore the majority of the mass is at the extremities of the section. Changing the values will change the Ixx value and therefore the deflection. If you stand back and think about it the rsj is slightly deeper and nearly a third (box 10kg, rsj 16kg) heavier in weight so it will deflect less. But the weight is more likley to be a problem for CNC :eek:
For a purely vertical load then an RSJ is the most efficient beam type there is, It just for a gantry most of the load is on the side and its poor torsion qualities let it down.
Without knowing the size or intended use of your machine it is pure speculation as the best options and problems you face.:whistling:
Best start that thred and let us know........
Well put Ross. I knew someone would want to have different flange and web thicknesses ! , but when putting the spreadsheet together I couldn't be bothered with the extra calcs. Maybe I'll add it.
Anyway, since most of the work in bending and torsion is done on the outer surfaces, then you could cheat and enter the flange thickness value as the thickness everywhere. This would probably give close to the correct answer, with a slight overestimation.
Since you have so much RSJ lying around and for economic reasons want to use it (fair enough !), assuming a conventional moving gantry router, RSJ could be made to work on:
1. Gantry sides: if one flange is mounted to the main beam and the other faces directly away from it
2. Baseframe long sides carrying the bearings: if used with the flanges facing up and down, with plenty of braces across to the RSJ on the other side to resist the torsion (you mentioned using profile rails and carraige which will resist a moment if the RSJ can be restrained)
Don't use it on the the gantry beam, or if you do consider plating over one open section to create a closed section on one face. Having said that if your gantry is short, or your requirements are modest, the deflection due to twisting may still be acceptable. Depends on your intended application.
Perhaps Ross knows more, but how true and straight are RSJs? Especially if it was intended for buildings. Aluminium profile is extruded through a die, and is pretty accurate. Ideal for a CNC machine. Maybe another option would be to sell the RSJs and put the money towards some Ali . . . ?
Bring on that new post so others can get back to the videos . . .
You guys are great!
Thank you so much for the feedback.Will get the designs up asap for feedback.
THANK YOU!