The Whole Cnc Thing...

[forteh]

What is the fascination within the bicycle industry (particularly in trials) with the notion that because something has been made using a cnc machine that it is automatically stronger and a better product?

Forging a component makes it far stronger, I just dont get this who cnc thing

Certainly the use of a cnc machining makes mass produced repeatabilty cheap and practical and has its uses particularly with deep pocketing and the like but it doesnt means its actually any good.

Sorry personal rant over, discuss....

[Z o o !!]

CNC stands for computer numerical control, and refers specifically to a computer "controller" that reads instructions and drives a machine tool, a powered mechanical device typically used to fabricate components by the selective removal of material. CNC does numerically directed interpolation of a cutting tool in the work envelope of a machine. The operating parameters of the CNC can be altered via a software load program.

CNC Router considered to be lighter version of CNC milling Machine and/or CNC lathe or combination of both .The structure more often seen in Gantry style.

In other way, CNC Router is a development on normal hand operated Router with computerized controlled movement of cutting tool with speed, feed and other machining parameters.

The general application areas of CNC Router are furniture industry, architects / builders for interiors and prototyping, signage industries ,etc..

The materials commonly machined using CNC Router are all type of Natural and artificial wood, plastics, rubber, aluminium sheets, lime stone, marble, synthetic materials etc....and harder material like steel ,granite, brass etc.....for engraving only.

Edited April 25, 2008 by OnzaTrials23

[forteh]

blah...

I know what cnc means, I have a degree in mechanical engineering

I meant why is the industry fasinated with the process and why do they claim it makes things stronger?

[Z o o !!]

I know what cnc means, I have a degree in mechanical engineering

why dont you go ask your proffesor or w.e.

[forteh]

why dont you go ask your proffesor or w.e.

I graduated 7 years ago, besides which why should they have an opinion on why the bicycle industry has a cnc fetish

[Muel]

I know what cnc means, I have a degree in mechanical engineering

I meant why is the industry fasinated with the process and why do they claim it makes things stronger?

They don't... Anyone who knows anything about engineering wouldn't say that, I've only ever heard it said that CNC is strongest in NMC, and rarely at that.

[N.Wood]

why dont you go ask your proffesor or w.e.

A : If he already has a degree, he won't be at uni anymore and therefore won't have a 'proffesor'

B : His 'proffesor' is extremely unlikely to be Deng or into trials, and therefore won't be able to answer his question.

[Luke Rainbird]

He's not asking about the ins and outs of CNC work, he's questioning why it's so popular in trials

A lot of it is down to the way Deng released a tonne of CNCd components, that have been deemed 'fashionable' as they were differrent and new, and a little pimp as they all came in a dozen colours. A lot of people who don't know more about the processes available take it as read that CNC = good = best way to make things.

I'll put my hands up and say that for some bits, CNC can be pretty nice, but there's a time and place, and shouldn't follow fashion over function

[Tango]

I think they do it for looks mainly. Take the python seat tube area every one copy'd it for looks a simple tube would have done but it needs to look good

[basher]

why dont you go ask your proffesor or w.e.

are you a f**king retard or something.

I supose it because alot of people have a half vague idea of what cncing is and it sounds cool so there attracted to it. And when cncing was introduced into trials it was usually to create a eye pleaseing thing such as cool bits on frames and because it was new they where thought to it was obviously better. People care so much more about how there bikes look and not ride these days and thats why they are loving the cncing so much and i guess because they think it looks cool and stuff it must be stronger

[forteh]

Its not just limited to trials or even NMC, go have a look through CRC and see how often the phrases cnc and strong come up in the same sentence

Its like the 05 echo cnc rims, how do you think any drilled/punched rims are made, blimey it was a cnc machine

Yes it can look pretty (although imho most of the machining on dengs frames is pretty rough) and can create a light, stronger component if its designed correctly to minimise stress raisers.

[Bionic Balls]

Yes it can look pretty (although imho most of the machining on dengs frames is pretty rough) and can create a light, stronger component if its designed correctly to minimise stress raisers.

answered it yourself really...! often it's used simply for looks...especially on some brake boosters (interesting brake booster article...proving that there's some seriously unnecessary processing!. In some cases, it might be cheaper than setting up a forging too...and it leaves a half decent finish so i guess you can save a bit there? i have no idea about the batch sizes of trials frames...? how many echo controls are there?!!

adam (studying metallurgy!)

[Al_Fel]

Its not just limited to trials or even NMC, go have a look through CRC and see how often the phrases cnc and strong come up in the same sentence

Its like the 05 echo cnc rims, how do you think any drilled/punched rims are made, blimey it was a cnc machine

Yes it can look pretty (although imho most of the machining on dengs frames is pretty rough) and can create a light, stronger component if its designed correctly to minimise stress raisers.

Question answered?

[TOBY-E]

Products manufactured using cnc machines have a near perfect surface finish, you can produce the product in far more detail. With forging it leeves a slightly bumpy finish (which you can see in xtp headtubes) this means they then having to go through the grinding process. Persuming forging is the same as sand casting and die casting etc you have to make the mould to near perfection, just to get the suface finish resonably good. which will most likely not be good enough to sell to customers staight out of the mould.

Sorry for spelling im on mothers computer and i cba dowloading spellchecker.

[spaceman]

Hmmm... Does Deng even perform FEA on his CNC'ed products?

Some CNC'ed stuffs are good, like maggy backings, etc.

[dave33]

just because its a cnc machine does not mean it will machine it to a perfect size or surface finish, the RA from cnc milling is going to be alot rougher than a cnc grinder! depeding on the feeds and speeds used.

iv be thinking the same question fro a while, and i would say that its so popular because its more a fashion and people think it looks good, also there isnt really a better/faster/cheaper manufacture process now with 6 axis machine centres that are used now, basicaly one part can be totally machined in one setup, and the machine can continue doing the same part non stop, with the help of bar feed systems.

the fact that once setup the machine can keep turnin out parts 24 hours aday 365 days a year is why echo parts are made like that.

i also do think that CNC is far to over used as a buzz word

and i suspect that only the frams and forks go through and aneiling and normalizing precessing after machining

Hmmm... Does Deng even perform FEA on his CNC'ed products?

Some CNC'ed stuffs are good, like maggy backings, etc.

would they still be good if they were milled manually ?

[Bionic Balls]

alright..well...in most cases in the trials industry, parts either come painted, anodised or polished. Whichever process you use to manufacture, the surface will still require treatment before it's finished, so I don't think theres much difference in that respect. As outlined above, CNCing allows you to remove material where it isn't needed to make parts lighter, without losing strength or stiffness. CNCing is done on forged billets...which are already more expensive than castings...the only thing i can think of that is cast is maguras..and that's only because it's the cheapest way.

Forging is stronger than casting. Forging in more expensive than casting. CNCing is done on forgings...so more expensive than forgings...

thats mostly how i see it!

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...!

and will people stop putting "persuming"...wtf?! that's not even close..

adam

[spaceman]

Manual mill is the same, just that the tolerances would differ by a lot. CNC is more accurate. Some people even manual mill brake pads.

I also agree that after CNC'ing, the products should go through heat treatment - as mentioned, annealing and normalising. Though plenty of coolent is being used in the cutting, the structure of the workpiece might be changed due to the heat from the cutter. (there might be a possibility)

[Bionic Balls]

i'm sure that if the parts needed annealing, they would do so...it's quite easy to model the cutting process..

how many cnc'd deng parts have you seen break (excluding the forks/frames as dave said..)? probably cranks..but that's fatigue usually...

[forteh]

Manual mill is the same, just that the tolerances would differ by a lot. CNC is more accurate.

I know a man that can manually machine down to tenth of a thou (thats 0.00254 mm in modern money)

Cant do it with the speed of a cnc machine though

CNCing is done on forged billets...which are already more expensive than castings...the only thing i can think of that is cast is maguras..and that's only because it's the cheapest way.

I would guess that all of the deng products are machined from plain billets (which have been forged) but how many of his products are actually forged into shape in order to give the correct grain structure that gives forgings their strength?

Are the machined deng cranks (gu/zoo/czar/adamant/echo) machined from a crank shaped forging (presumably taken from the forged echo cranks?) or are they machined from plain square billet? Material specs quoted on tarty would seem to indicate that theyre not the same.

[Bionic Balls]

i'm pretty sure echo forged and cnc cranks are completely different...looks and material wise...

no idea which are stronger/stiffer but without the offer on tarty, there's a big price difference!

[SCOTTY___]

I know a man that can manually machine down to tenth of a thou (thats 0.00254 mm in modern money)

Cant do it with the speed of a cnc machine though

I would guess that all of the deng products are machined from plain billets (which have been forged) but how many of his products are actually forged into shape in order to give the correct grain structure that gives forgings their strength?

Are the machined deng cranks (gu/zoo/czar/adamant/echo) machined from a crank shaped forging (presumably taken from the forged echo cranks?) or are they machined from plain square billet? Material specs quoted on tarty would seem to indicate that theyre not the same.

tenth of a thou, thats pretty f**king accurate.. seeing as i have to work in imperial for those americans ;p

And you've basically answered your own question. They are forges Alu billets, that are then CNC'd to add "strength" in ways which "patterns"can be crafted to help alter stresses that Trials riding gives. Hence why there all tested for strength etc

My 10cenc anyways

[Greetings]

It's mainly a gimmick to boost sales. But it so happens that CNC'd parts are often made of a better grade of aluminum and so they last longer - not necessarily because they've been CNC'd.

Cranks are a good example. Echo Forged are made of 6061 grade aluminum. It's a poor grade at least from my experience, the tapers get damaged really quickly.

Then you have Echo CNC cranks which are made of a much better grade of aluminum, are also forged and CNC milled to give them that special look. Most if not all 7075 cranks are CNC milled. So in this case, they're bound to last longer - not because of their finish but because of the material used. Such experience leads people to believe CNC parts are actually stronger. In some cases they are since machining parts from a solid block of aluminum means there is less chance of small air pockets or micro cracks in the material.

[hI-OOPS-CAPS]

its probably best lookin at parts in particular. they cant really forge hubs, rims, frames so its only the simpler parts that can be forged really

i dunno if forging can be automated? or semiauto but products would be more expensive and heavier. probably wouldnt get the consistency of a cnc'd part.

[forteh]

It's mainly a gimmick to boost sales. But it so happens that CNC'd parts are often made of a better grade of aluminum and so they last longer - not necessarily because they've been CNC'd.

Cranks are a good example. Echo Forged are made of 6061 grade aluminum. It's a poor grade at least from my experience, the tapers get damaged really quickly.

Then you have Echo CNC cranks which are made of a much better grade of aluminum, are also forged and CNC milled to give them that special look. Most if not all 7075 cranks are CNC milled. So in this case, they're bound to last longer - not because of their finish but because of the material used. Such experience leads people to believe CNC parts are actually stronger. In some cases they are since machining parts from a solid block of aluminum means there is less chance of small air pockets or micro cracks in the material.

Dzien dobra Inur

Sorry I had to, polish lodger

Im not too familiar with the suitablilty for forging of 7075 as opposed 6061 but 7075 is a far higher grade of material and in its annealed state appears to be stronger than heat treated 6061. In T6 condition 7075 is almost 40% stronger in shear than 6061 T6

Some 6061 info

Some 7075 info

Im betting that the 7075 echo cranks are machined from plain billet, if they were forged and then machined they would be far superior

A 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.

edit: hubs are very easy to forge, rims are extruded and frames are fabrications, nearly everything else on a bike can be forged. Forging can be fully automated, aslong as you have material going into one side it will produce forgings falling out the other side

Edited April 25, 2008 by forteh