Jason222 Posted April 25, 2008 Report Share Posted April 25, 2008 (edited) I would imagine that Cnc'ing would make a frame stiffer? As apposed to just using tubes, like at the seat and chain stays for example...likewise, CNC'd bits are probably more resistant to dents and full on hits? If you think of it that way...then it would be better/stronger if done properly? I've never seen anything Cnc'd crack...usually things go at a weld or at a tube... Edited April 25, 2008 by Jason222 Quote Link to comment Share on other sites More sharing options...
Ash-Kennard Posted April 25, 2008 Report Share Posted April 25, 2008 I would imagine that Cnc'ing would make a frame stiffer? As apposed to just using tubes, like at the seat and chain stays for example...likewise, CNC'd bits are probably more resistant to dents and full on hits? If you think of it that way...then it would be better/stronger if done properly? I've never seen anything Cnc'd crack...usually things go at a weld or at a tube...nah thats not true, ive seen cracks on them beforei remember explaining to someone because they thought cnc was a material Quote Link to comment Share on other sites More sharing options...
Bionic Balls Posted April 25, 2008 Report Share Posted April 25, 2008 Im betting that the 7075 echo cranks are machined from plain billet, if they were forged and then machined they would be far superior smile.gifA bit more research - middleburns are forged from 7075 and then heat treated to T6 before machining, probably explains why you dont get as many failing as deng cranks; the forging makes it a much stronger component, also explains some of the price difference too.i'm not so sure...7075 is precipitation hardened, not strain hardened, so the important thing is the heat treatment following the initial forging. As long as the forging billet has been strained enough to remove defects (voids/break up inclusions) i can't see how that would affect the final product significantly. I also thought that 7075 was best worked after annealing? not saying you're wrong (!), but where did you find the info on middleburn production? do they actually forge to a "crank" shape, or do they simply mean they use a stock 7075-T6 billet..? you could read that either way...anyways, i think most people have decided that CNCing is good adam Quote Link to comment Share on other sites More sharing options...
forteh Posted April 25, 2008 Author Report Share Posted April 25, 2008 You know more than me on the metalugic side, we only really touched on the subject at uni and it was so long ago Ive forgotten most of it Forging forces the material into a specific shape, with good design this can form a better material grain flow in order to relieve any stress during use.Bit of info on forging and material grain flowHowever naturally you cant make any shape with a forging (unless you forge it multiple times but I suspect annealing would have to take place between operations thus making it far more expensive) so forging your billet to the approximate size and shape before machining gives a far better grain flow If you imagine a round rolled bar has all the grain flow in one direction, if you wanted to form a rivet out of that bar you could simply machine the shank out of the bar (much material waste) but the only material area holding the head onto the shank would be the same diameter of the shank. If you were to forge the head on (by twatting it with a large hammer basically) the material is plastically deformed and squashed into the head shape, the means that the grain flows longitudinally along the shank and out in a radial pattern at the point where the head and shank meet. This grain flow is continued all the way through the material and forms a far stronger piece.I could well be wrong about working 7075 and tempering, it was a bit of a summation by my part The material on the middleburns I got from tarty, you can tell that they are forged to shape from inspection (got 2 pairs here to look at) - for the cost of them I dont think you could machine them to look how they do, the shape just seems too organic. Obviously I could well be wrong but Id happily bet a tenner that theyre forged to size and shape Quote Link to comment Share on other sites More sharing options...
Bionic Balls Posted April 25, 2008 Report Share Posted April 25, 2008 awesome....well...i reckon some of the forum may have learnt something today still not entirely sure about the grain flow thing...you are absolutely right, but i think the temper would homogenise the material in the final microstructure..only one thing to do..slice your cranks and borrow an SEM adam Quote Link to comment Share on other sites More sharing options...
craigjames Posted April 25, 2008 Report Share Posted April 25, 2008 burns are near net forged and then the cnc'ing is literally just a finishing process. much in the same way as raceface cranks. Quote Link to comment Share on other sites More sharing options...
The Duck Posted April 25, 2008 Report Share Posted April 25, 2008 CNC stands for...Hahaha. There was me thinking 'Oh shit, he really knows his stuff' then read your second post and thought 'Oh, maybe not because he can hardly string a sentence together'.Then took the liberty of whacking the first sentence and a half of your post into google, and came across this.Well done, you can copy and paste. Now say something useful... Whats that? You can't? Quote Link to comment Share on other sites More sharing options...
craigjames Posted April 25, 2008 Report Share Posted April 25, 2008 Hahaha. There was me thinking 'Oh shit, he really knows his stuff' then read your second post and thought 'Oh, maybe not because he can hardly string a sentence together'.Then took the liberty of whacking the first sentence and a half of your post into google, and came across this.Well done, you can copy and paste. Now say something useful... Whats that? You can't?hahahaha i was thinking exactly the same, oh dear. Quote Link to comment Share on other sites More sharing options...
Ash-Kennard Posted April 25, 2008 Report Share Posted April 25, 2008 LOL max Quote Link to comment Share on other sites More sharing options...
Andeee Posted April 25, 2008 Report Share Posted April 25, 2008 Makes the sponsored riders have a fit. LOL Plus its all fancy wancy for the fashion riders. Quote Link to comment Share on other sites More sharing options...
Shaun H Posted April 27, 2008 Report Share Posted April 27, 2008 As outlined above, CNCing allows you to remove material where it isn't needed to make parts lighter, without losing strength or stiffness. and i don't imagine that Deng is an engineer, and therefore doesn't look at FEA. I assume deng is a business man that gives the factory as little money as possible to do what his designers tell him is good! No doubt his employees use FEA all the time...everyone does...!You remove material where it isn't needed to make parts lighter through good design, if the same design is CNC machined it doesn't magically get lighter and stronger!I've heard from a reliableish source that Deng IS an engineer. It's not exactly surprising, seeing as he designs pretty much all the frames and parts...Hahaha. There was me thinking 'Oh shit, he really knows his stuff' then read your second post and thought 'Oh, maybe not because he can hardly string a sentence together'.Then took the liberty of whacking the first sentence and a half of your post into google, and came across this.Well done, you can copy and paste. Now say something useful... Whats that? You can't?Awwwww someone got there before me! Soon as I saw his post I whacked it in google 99% sure I'd see wiki at the top!CNCing is probably used by Deng out of convienience. He doesn't have to pay any mould costs or anything. All you pay for with CNC machining is set up costs and then you're charged for however long you take up a £200,000+ (they can actually get silly expensive...) machine's time.As mentioned earlier, CNCing is only good when good design is incorporated to begin with. But that's exactly the same as with any process... Except that if your design turns out to be shit and you cancel that 2nd batch you won't have wasted thousands on moulds...Is it me or is this just becoming a topic about materials! Had a feeling it was going that way as I read through!Choosing the right material (or best value at least) is VERY important. Quote Link to comment Share on other sites More sharing options...
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