I was recently out at Cycle Underground with John and he ran me through the process of having the Candy Cranks chainrings manufactured.
Firstly my design is drawn up in Autocad.
The design is then programmed in Mastercam. This program tells the CNC machine what needs to be cut and which cutter to use.
The CNC God.
Raw piece of aluminum, waiting to go into the CNC machine.
The plate is clamped down on the jig ready for the first cut.
The first chamfer is cut on the back. Coolant is constantly sprayed onto the aluminium to keep everything cool.
Outside chamfer complete, 5 bolt holes are cut.
It’s now bolted onto the jig through the bolt holes so the middle section can be cut out.
Next the teeth are cut.
Continued… hit the READ MORE button below.
Teeth complete and middle section removed.
Off to the recyclers.
Next the patterned holes are cut.
The cutters, the rougher (on top), cuts the initial pattern out, then the finisher (below) smoothes out the edges.
The stars are finished.
Close up of the cutouts.
The Candy Cranks logo, BCD and tooth size is cut.
Voila! One raw chainring.
This is where the boyfriend comes in handy… it nows needs to be sanded, first with 240 wet and dry paper, then with 360 wet and dry paper for a finer finish.
Back from the anodizers, the stars are painted to the desired colour.
On the bike and ready to go!
24 responses so far ↓
1 Rie - Nagoya // May 13, 2010 at 4:46 pm
Ohhhhhhhhhhh AMAZING!!! Woww! It’s great to see how it is made. Very impressed…
2 nimz // May 13, 2010 at 4:47 pm
THIS IS SO COOL!!!!!!!
3 CyclingWMD // May 14, 2010 at 5:30 am
Rad post! I SO need to get one of these with like, marijuana leave cutouts, hehehe..
4 Jjay Ali // May 14, 2010 at 2:10 pm
thanks for this post. now i know how it was done. i am loving it very much.. those white stars.
5 Meg - Sydney // May 14, 2010 at 3:36 pm
Thanks guys, glad you liked it!!
@CylingWMD not the first time I’ve heard that, they might be a good seller
6 Bob Darlington // May 15, 2010 at 6:41 am
Why 5083 alloy? Probably not the best idea for bike parts and chain rings. 7075-T6 for the win in this area. Please let us know how it holds up in use.
7 Dan // May 15, 2010 at 12:25 pm
Not so much a “how to” as a “watch how it’s made” post. I was hoping for instructions or some gcode action.
8 Revolverkiller // May 15, 2010 at 2:55 pm
is that a pink chain? a belt what is that??? i like it
9 Randwick Rider // May 16, 2010 at 5:40 am
Brilliant! I love seeing how things are made!
10 thundering+eejit // May 16, 2010 at 8:51 am
How+did+you+manage+to+get+such+clear+pictures+thru+the+polycarbonite+window+of+the+CNC+machine+?+
Maybe+you+didn\’t.+
Maybe+you+had+the+door+open+.
But+the+door+is+interlocked+…..
So+did+you+defeat+the+interlocks+?+
But+isn\’t+that+illegal+?
11 John // May 16, 2010 at 9:05 am
I have to agree with Bob on this one. 7075 is structurally similar to steel, but I’d still be concerned about the wear over time.
12 John // May 16, 2010 at 9:07 am
“feed-hold”, thunder. Or maybe it was magic.
13 Meg - Sydney // May 16, 2010 at 10:02 am
@Revolverkiller, yep it’s a pink chain, the rest of Em’s bike is amazing as well, everything is colour co-ordinated. http://www.candycranks.com/archives/3285
@Bob and Dan, 5083 is the Australian Standard Marine quality alloy (ie, they build ships out of it because it’s light, strong and has a high corrosion resistance in sea water). 7075 isn’t as accessible in Aus and it’s very expensive.
John from CU has fabricated 1000′s of chainrings over many years for every type of rider/bike out there from messengers through to Olympic athletes and he just recently finished a bunch for Cadel Evans. 5083 has proven itself to be long lasting through active use
@thundering eejit, John needs to open the door to change the position of the bolts, remove excess metal, swap the cutters etc, it’s not a non-stop continuous process from beginning to end.
@Randwick rider, glad you liked, it’s pretty cool seeing the whole process!
14 Andy // May 16, 2010 at 11:26 am
Very pretty sprocket.
But windows with sharp edges create stress concentrations – really curious to see how it holds up to use.
15 Meg - Sydney // May 16, 2010 at 5:03 pm
Hey Andy, there are no sharp edges on the chainrings, the narrowest point on the stars is 2mm wide.
16 john bosevski // May 16, 2010 at 6:51 pm
hey meg,
gorgeous photo essay….absolutely awesome.
your photos came out a treat and the info you put together is spot on……..looks great mate.
just one thing…..you really need to make it clear that you do know your stuff……all the girls are full of praise and all the boys are busy showing you how much they dont know.
our secret is out…..they know we defeated the interlocks….lookout here come the cnc police.
so funny
17 Madeline // May 17, 2010 at 5:55 am
So cool! I like that you hand paint in the stars like that. I want to get one of these rings on my own bike. Support small business!
18 Kevin - Oregon // May 18, 2010 at 2:26 am
I’m curious about the process of design in AutoCAD, any chance for a quick tutorial on that?
19 Revolverkiller // May 20, 2010 at 11:56 am
yes i’d love some tips on how the chamfer was determined then programmed into mastercam
20 anon // Sep 8, 2010 at 10:19 am
@thundering+eejit
Not on a Haas mill. Setting 51, iirc. Or just unscrew the two hex screws on the side and slide the door up, neither will interfere with the operation of the machine, and this being aluminum, i’m not too worried about tool breakage during the time it would take to snap a few photos. you could even just hit the feed hold.
21 Fred // May 9, 2011 at 2:41 am
I would like to know more about the pitch, width, and landing size for the gear teeth. (if you have that info)
Great article! I’m drooling over the milling machine right now.
22 Carlos // Oct 30, 2012 at 1:26 am
Now+go+out+and+buy+yourself+a+nice+Haas+VF-2+CNC+mill,+and+get+to+work.+They+run+upwards+of+$100K,+US.
23 David Zagorodny // Nov 1, 2012 at 2:18 am
Why not laser or water-jet cut patterns?
24 Andrew // Nov 9, 2012 at 5:26 pm
7075 is overkill for a sprocket, there isn’t enough tensile load to justify the expense and the lower grades, even 6061, tend to work harden better, making the part more wear resistant. @Carlos that seems pretty steep for a Haas. For this sort of part one of their mini-mills would work fine and they run under 30k last I checked. @Revolver any mastercam tutorial will teach you enough to program the chamfer. It is a contour around a circle with a depth of half the difference between stock thickness and tooth width. @John B what you said, lol. @Fred machinery’s handbook ver. 27 pg 2441. More info on transmission chains than you ever wanted to know
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