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PostPosted: April 13, 2018, 3:01 pm 
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Joined: July 22, 2017, 6:45 pm
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I am thinking about building a few mid engine chassis for a group of friends and its a lot of notching. I would like some idea of cost to have tube laser cut. Of coarse every one who does this will not even give a hint of price to laser a 1.5" with .095 wall fish mouth on both ends. Any idea of cost? I would think 70 tubes, both ends, laser cut cost each tube should be easy to give a number even if it might be 200% to high. I have narrowed it down to between .50 cents and $200 per end. Can anyone do any better than that?


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PostPosted: April 14, 2018, 8:03 am 
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My experience has only been with thousands of chassis parts cut with lasers, Vs 3 or 4 units. In which case, the parts/process is relatively inexpensive. One of my friends had a custom alloy steering wheel section cut and it was $135, which was 85% CAD and set-up. He probably could get another 10 or 15 steering wheels for $20 more plus matl. Avg processing cost the Z06 alloy chassis panels was just over $2 each. But you are asking the wrong question! Can you pre-cut chassis tubes and build the frames that accurately without any or very little distortion that all the pre-cut tubes fit correctly with out a full frame jig. The answer: probably not. :( Save your money and get a tube notcher.
DaveW


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PostPosted: April 14, 2018, 8:23 pm 
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I've built a couple bikes/motorcycles with CNC notched and bent tubes from Cartesian tube, also goes by VR3 engineering. Not cheap but absolutely outstanding product. They're not laser cut but done with a tiny end mill in a CNC lathe. The fit is awesome. I would never notch my own tubes on a big project again, totally worth the money when you factor in your time and sanity.

So much fun to weld!!! In my experience it nearly jigs itself because the joints are so tight. Bolt down your hard points and snap it together.

First was a recumbent bike. This was 50 notches and 3 bends for about $600.

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Second was a small motorcycle frame. This was 90 notches and 6 bends for about $900.

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Closeup of quality:

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Alex


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PostPosted: April 14, 2018, 10:20 pm 
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Joined: October 19, 2010, 11:57 am
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Location: Waterloo, WI
I recall at least one person on these boards getting a "set" of tubes laser cut but I haven't been able to find who it was.

One thing we have done in the bike industry is use laser cutting to make slots and tabs for self fixturing ability. Where I work we used the laser to make slots to hold brackets and cable guides but I recall that Cannondale would make entire front triangles that slotted together.

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PostPosted: April 15, 2018, 9:00 am 
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This subject comes up every few years or so. The basic book frame can be cut and tacked together by a couple of guys in a long weekend. Unless one has a production line, I doubt that the price vs time savings of CNC cut tubes is really there.
IF you think that by spending another $1-3K for laser cut tubes is going to shorten the build time significantly, I highly doubt it. IF you think that laser cut tubes will allow for a more straight or accurate chassis after welding, well again, welding technique will have a bigger effect that the tubes themselves. But like the cars we build, each builder has their own spin on their build choices.

You might want to read this thread:

http://www.locostusa.com/forums/viewtopic.php?f=39&t=13104&hilit=laser+cut

It is an old thread. I don't know if prices have gone down or up since then.

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PostPosted: April 15, 2018, 11:14 am 
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rx7locost wrote:
You might want to read this thread:

http://www.locostusa.com/forums/viewtopic.php?f=39&t=13104&hilit=laser+cut

It is an old thread. I don't know if prices have gone down or up since then.


Yes! That's the one I was thinking about!

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PostPosted: April 24, 2018, 9:45 pm 
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Joined: February 4, 2018, 10:08 pm
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Location: Effingham IL
I have some experience with laser cut chassis.
The first one was the mid-engine v8 project from 30x1.5mm that I designed in 2013
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Lancia chassis.jpg
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Lancia laser cut joint.jpg
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And I can tell you that laser cut tubes are going to shorten build time a LOT. It was one-off build and still, I think that with round tubing no way you can build chassis faster with tube notcher. One thing to consider that if you are going for laser cutting probably you already have CAD model. :lol: That makes you slower at the design stage and much faster at the assembly stage. Personally, I just hate to cut off metal and redesign things on the go.
The second was Shortcut chassis in 2015.
And when you using a laser, not like notcher but actually design things with laser cutting in mind that were things become real kicker!
Tab and slots, self-jigging, bend-by-hands, closed angles and other design techniques become real time-savers.
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shorcut tube pack.jpg
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Sometimes you can avoid using jigs, tooling or design limitations. For example lobster back style 4-2-1 equal length exhaust collector made from one part(all 4 runners).
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Exhaust 1.jpg
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exhaust 2.jpg
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I do not have experience with laser cutting tubes in the US. In Russia cutting DOM tubes were around x3 to a price of the metal. I still have all DXF files for Shortcut chassis and if someone has contacts of a trusted laser cut shop we can get a quote for 10-20 chassis. :twisted:
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Chassis.JPG
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PostPosted: April 24, 2018, 9:53 pm 
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Those headers look awesome!

My one foray into laser cut tubes didn't end up with me ordering any, but definitely planning to use them in the future.

The Tab A into Slot B aspect as well as labeling each tube really would make assembly a snap. The cost at that time wasn't cost prohibitive if you were doing 4-5 at a time. So if anyone is going into production that way would be awesome.

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PostPosted: April 25, 2018, 9:53 am 
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Glad it worked out for you. For me, I found that heat distortion causes the tubes to move around to the point that any super-precision assumptions of where the other end of the tube should be kinda goes away. In other words, if a CAD tube is cut to 16.789", heat distortion will cause the opposite end to be somewhere between 16.7-16.9", and a lot worse on longer tubes. Yes, swapping sides during welding helps, but as a professional racecar fabricator once told me regarding weld distortion, "If your chassis points end up within 1/4 inch of where they're supposed to be, you're doing well."

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PostPosted: April 26, 2018, 7:26 am 
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Yupper on the 1/4"
Some mfgd side rails have to be PRE-BOWED in a fixture by more then 3/4" so after welding they are straight. But in a production process the rail is welded all at one time, Vs allowing any cooling to occur to reduce distortion. DaveW


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PostPosted: May 6, 2018, 6:23 pm 
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Interesting reply's. I did find a supplier in Los Angles that gave me a number of $4 each fish mouth Based on 100 or so tubes with 50 different tubes. Assuming there would be one tube on each side of the chassis that is the same as the other side. He wanted an idea of qty of each tube because the loading of the programing of 100 different tube files will be more per part than 100 of the same tube. So 100 tubes fish mouth both ends is approximately $800. I have a nice cold cut saw, tubing notcher along with the complete machine shop full of Haas CNC machines but I still like the idea of having the tubes lasered and save the time so I can relax and tig nice little pretty welds.


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