# CNC Macined Components VS. Forged Components???



## rocpyro (Feb 7, 2005)

So I figured this would be the best forum for a question like this, I have alot of high end components that are cnc machined and some that are forged. I never really gave it much thought until I realized that my older Race Face Deus stem is machined, whereas the newer models are forged. Why did they do this? They weigh about the same, they are probably going to be as strong, is it just that its easier to forge compononts and therefore they can cut costs for essentially the same product? I know Shimano does a ton of forging, and yet aftermarket companies like Thompson and Hope use machined parts. What are the differences, pros, cons, and production cost advantages of one over the other? BTW, from a visual standpoint, I like cnc machined parts WAY better than forged. I don't wanna hear which looks cooler, as everyone will porlly have their own prefrences, but I wanna hear some tech info. Thanks in advance!!!!!!


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## ScareyH22A (Sep 24, 2006)

Forged cranks feel mushy and flexy to me. :shrug:
Race Face XC (forged)
Race Face Atlas (machined)


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## SlimTwisted (Jun 14, 2006)

Forging uses intense heat and pressure to transform a solid slug of alloy material into the final shape while CNC Machining uses computer software and precise cutting tools to cut or shave a slug down.

Forged aluminium is about 300 percent stronger than cast aluminium, yet less material is needed to produce the same "cast alloy spar", which results in a lighter overall product.

Casting is a relatively inexpensive way to produce a high-quality, fairly strong alloy. There are two methods used. One, system is known as gravity casting... whereby the molten material is poured into a mold and allowed to cool. These molds are usually made by machining a piece of material on CNC machine equipments to produce a mold that only requires minor finishing (like drilling or possibly trimming of some excess metal) to be considered complete. The other slightly more effective system used is the low pressure or _negative pressure _casting. Here instead of pouring the molten material into the mold, the molten alloy is drawn up into the mold using a high-pressure vacuum. This eliminates much of the trapped air found in gravity casting process, producing a stronger alloy spar that is less porous than a gravity-cast one.

In conclusion- Probably cost shaving efforts. And you have to admit, as is the case with Ventana bikes, CNC parts look awful trick.


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## Spero (Apr 6, 2005)

I was under the impression that machined components were stronger and last longer, but...

http://www.forging.org/facts/wwhy3.htm
http://www.sealtightsolution.com/html/cold.htm
http://www.discusscooking.com/forums/f90/knives-forged-vs-machined-21028-2.html

...I guess I was wrong


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## rocpyro (Feb 7, 2005)

SlimTwisted said:


> In conclusion- Probably cost shaving efforts. And you have to admit, as is the case with Ventana bikes, CNC parts look awful trick.


So true!:thumbsup:

Now, I know how the different processes work, but what I want to know is the finished product differences between the two. The only viable comparison I have it the one already mentioned, the crank stiffness issues. The only exception would be the saints I have on a bike, wow are they stiff. But on the other hand, Ive also ridden diabolus, and theyre stiffer. I'm about to buy Race Face Deus cranks for my XC rig because of this same reason. Does the difference make any of you buy one product over another because of this? Is there a place where forged parts are preferable to use over machined?


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## Ultra Magnus (Jan 13, 2004)

There's a lot that goes into the decision of whether to forger or machine a part. Most forged parts require some kind of after machining anyway, but usually are closer to a net shape. The alloy used has more to do with strength than the process. A forged 6061 part will not be as strong as a machined 7075 part, but theoretically it will be stronger than a machined 6061 part. I've never found any documentation (I admit, I haven't looked that hard) that quantifies how much stronger a forging is over a machining of similar parts from the same alloys. 

In the times that I've used forged parts, the almost all required a fair amount of after machining, and strength wasn't the driving force for using a forging, I always design components using the billet published strenght numbers and add a little safety factor, so if the forgin is stronger, it's just more safety. It normally comes down to economics. Some shapes could only be machined by 3d milliing with a ball end mill, and that's very expensive, so getting a near net shape by forging wins out. With forgings though, you have to buy expensive dies that is a recurring cost as tools wear out, so that also has to be considered. Also, the machine tooling is usually more complex because the odd shape of a forging is harder ot hold on to rather than a rectangular bar or round stock for a billet part. You save money in material costs with fogings, since you are making less chips. For a billet part you could (and often do) start out with stock that weighs in at 10lbs, and you cut it down to a skeleton that's only 1/2lb. The machine shop will charge you for all 10lbs of material, even though they get to recycle the chips.

BM


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## rocpyro (Feb 7, 2005)

Spero said:


> I was under the impression that machined components were stronger and last longer, but...
> 
> http://www.forging.org/facts/wwhy3.htm
> http://www.sealtightsolution.com/html/cold.htm
> ...


Very informative articles!!! THe first one was especially good, because of all the comparesons. But even w/ this, the MAIN advantage still seems to be cost, right? I mean, they talk about better grain alignment and less scrap, etc, but has anyone seen a machined part fail(within reason)?


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## jeffscott (May 10, 2006)

Forging Accurate, high production speed, parts can be heat treated before final machining, higher first production cost, large scale production

CNC Accurate low production speed, limited heat treatment options, low forst production cost smaller scale production, Sharper edges and corners can casue stress risers.

Forging involves the plastic flow of the metal. This means the temper, and alloy and heat treating must be will planned and executed. (larger scale)

CNC is a very simple cutting process temperatures are ususlly low so a particular alloy and temper can be purchased and the properties held through the entire production process. (Simpler smaller scale)


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## rocpyro (Feb 7, 2005)

bmadau said:


> It normally comes down to economics. Some shapes could only be machined by 3d milliing with a ball end mill, and that's very expensive, so getting a near net shape by forging wins out. With forgings though, you have to buy expensive dies that is a recurring cost as tools wear out, so that also has to be considered.
> 
> BM


Wow, thanks man! So I guess this explains why for smaller companies it is more cost effective to machine parts, as their sales are smaller than a huge manufacturer. It also explains the case of my Race Face Deus stem, being unsure about the success of the product, they machined the first generation, saw that it was a popular item, and decided to invest in forging for the newer version. Interesting.


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## Shayne (Jan 14, 2004)

*Go Ask That Question On The Vintage Board*

Double Post
Sorry


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## Shayne (Jan 14, 2004)

*Go Ask That Question On The Vintage Board*

You'll get a bunch of pictures I'm sure.

The Heyday of CNC bike parts ended long ago.


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## rocpyro (Feb 7, 2005)

Shayne said:


> The Heyday of CNC bike parts ended long ago.


I know what your saying, and I don't totally agree w/ you. Technology is definately being pushed in machined parts, for reasons that have already been discussed, like product runs w/ smaller numbers.

look at the newer race face cranks like the deus, atlas, and diabolus, all hope brakes, People still love their thompson stems and seatposts, Avid ultimate vees, and plenty of hubs. I wouldnt say its heyday is over. Maybe the machined and anodized all sorts of colors fad is out tho.


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## K'Endo (Dec 23, 2003)

Machined parts are made from billets that are either forged or cold-rolled. Aluminum that hasn't had such treatment is too soft and bendy to be useful.

Machining allows more freedom in designing a part. However, care must be taken in the design to avoid introducing weak points in the component. There are advantages and disadvantages to either and it's a good designer that makes the advantages shine through.

http://www.sheldonbrown.com/dp-forging.html

Kn.


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## Jayem (Jul 16, 2005)

SlimTwisted said:


> Casting is a relatively inexpensive way to produce a high-quality, fairly strong alloy.


Not always, extremely exotic alloys and casting processes can produce extremely strong parts, such as the casted single crystal alloys that make up turbine blades on turbine engines.


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## Cheers! (Jun 26, 2006)

Casting can be just as strong. Semi Solid Solidifications, which is a method of growing crystalline internal structures can be just as strong as a continuous forged casting of a bilet. Many times parts such as jet turbine blades can not be produced via traditional machining of solid chunks of metal. These blades are usually hollow on the inside and require precise control of the grain structure in certain axis to produce a blade that will not fail when spun at max RPM of a turbine engine. 

FYI the most critical components used in aerospace are all made from machined forgings. Where the ingot was carefully monitored for temperature, rate of cool, alloy compositions with each step of the forging process (from melting of raw material, to mixing of various metals to make your allow, removal of impurities, density, pouring, rate of pouring, rate of cooling) are all documented. Hence the heavy price on anything that is aerospace. There is a paper trail of each process of the forging. 

I believe the question you are asking is: Is a casting part (usually Sand casting) stronger than a part machined from a billet? THe answer is No.

Also a lot of times you will see manufactures sand cast parts, then do final machining on them. An investment casting for parts that change every year is very very costly. Example of sand cast aluminum part that got final machining would be the 2005-2006 SRAM X9 rear derailers. The derailer body is weaker than the derailer hanger (usually made from machined 1/4" plate aluminum). This causes the derailer to break before the hanger. The casting of the X9 derailer parts is very very poor. The porosity of the aluminum is poorly controlled, and have many voids under inspection by a microscope. The break in the metal shows jagged grain structure indicating poor crystallization.


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## Kristof (Mar 12, 2007)

K'Endo said:


> Machined parts are made from billets that are either forged or cold-rolled. Aluminum that hasn't had such treatment is too soft and bendy to be useful.


Yes, cnc machining allows u more freedom to design a part. Specially with sophisticated CAD/CAM software. But it all depends on quality anyway.

Kris.
______________________

Cnc machining your way into XXI century


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## clarkgriswald (Dec 19, 2003)

*With forged and*

cast parts you have better control of the molecular stucture of the material. This control allows the manufacturer to align the molecular stucture for the most desired configuration/strength for the application. Forged and cast parts can be machined to their final shape.

Parts machined from a bilet, solid block or cyndrical, are constrained to the molecular stucture of the bilet.

Short version forging and casting allows manipulation of the molecular structure of the material. Parts machined from a bilet do not allow that manipulation.


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## lebikerboy (Jan 19, 2005)

The best bike components are cold (near net) forged then CNC'd. Take for example the original Kooka cranks vs. Race Face. The Kookas (machined) snapped, the Race Face (forged) didn't.


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## mikedesign (Jan 25, 2004)

cheers is right on the button here

its very dependant on so many variables as

i work in defence (makes me sound big and clever) but really there is a big big gap between the materials and manufacturing tech you see on your bike and the type of thing you find trundling round pointing 120mm shells at things

the nose oleo on the f16 for the netherlands airforce is made by growing a crystaline part 
and it is one of the strongest forms of aluminium there is no forging needed

in simple terms forging aligns the material grain and the simple casting methods just randomly throw in crystals
these processes can all be pushed to incredible levels by the methods which cheers pointed out but by the time you get to the point where a casting can compete like for like its aerospace money again or materials that dont like to be forged hot or cold

the aerospace folks use every trick to pare down weight to the bare minimum and strength to the upper reaches of its design specification

if someone told you after you had ridden your bike 20 times it was useless even though it looked ok you wouldnt buy into that 

yes i know completely different industries but if you wanted to make a bike part of anywhere near the same kind of quality you couldnt afford to buy the material

you think a piece of aluminium is created equal no sir think long and hard about the marketing hype


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## Pooh Bear (May 25, 2006)

Well, hub shells should be forged around the flanges at least. I had a GT CNC hub flange rip out while building the wheel from new parts. The spoke didn't even reach proper tension.


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## JackPower CNC (May 9, 2017)

CNC machined with Titanium ,Perfect


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## MozFat (Dec 16, 2016)

are we not talking three different processes here. Casting (poured in a mold, and maybe a bit of machining to dress it up, to set fit etc), forged (heated and hammered/ pressed into shape), and CNC machined (single block or billet cut into shape). 

Casting generally would be the cheapest, forging the most expensive to set up, but cheaper for high volumes, CNC better suited to lower volumes and easier to change or make adjutments.


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## Mr Pig (Jun 25, 2008)

Cheers! said:


> Example of sand cast aluminium part that got final machining would be the 2005-2006 SRAM X9 rear dérailleurs. The dérailleur body is weaker than the dérailleur hanger (usually made from machined 1/4" plate aluminium). This causes the dérailleur to break before the hanger.


Interesting. Last year I sorted a bike for a guy who's dérailleur had snagged up somehow. SRAM dérailleur was snapped, hanger was unbent.


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## root (Jan 24, 2006)

Ive got a personal examples. Chris King hub, flanges cracked and exploded. Same bike, rear hub DT Hugi hubs, built same time with same spokes, nipples, rims both 3 cross, ridden same conditions 20+ years and still going strong. 
1st gen XTR derailleur, i love those. First finally wore out, second was on stollen bike. Vs numerous XTs of same vintage snapped bodies. 
Alcoa MT rims on friends Landcruiser, car drove into front side of rear tire, he basically ended up driving over the front corner of the car. Wrecked the tire (and the o ther car) but forged rim perfectly fine and straight.
My Advan TE37 rims on car are darn light and beautiful. Havent really done much to test their strength though. 
Forging good.


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## Cleared2land (Aug 31, 2012)

*Resurrection of a ten year old thread huh*



JackPower CNC said:


> CNC machined with Titanium ,Perfect


And why is this perfect?


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