Discussion
The cape said:
Anyone know a good CNC company who could do a Buck from a CAD design for a car??
Cheers.
I was making a CNC machine to do just that; got most of the way through, but it was too far away for me to complete (in a mate's workshop, and he didn't really need it).Cheers.
I sold it about a month ago, but I'm not sure if the new owner would be doing bucks for a whole car though (small parts and plasma cutting is what he wants to do with it).
I would imagine it'll be pretty expensive - from memory, I was looking at about £6000 for me to get one made (about £1500 on the foam for the mold, and the rest on getting the bucks made) - but if it ended up nearer £10000, then I wouldn't be surprised.
The foam itself was £1500 - I wrote my own software to take the 1:1 scale STL file, and split it into 1200x600x150 blocks along with the necessary g-code. My car required at most 72 blocks - some blocks were partial blocks, several of which would've fitted onto one block. An estimate was nearer the 64-66 block mark.
However, that was just simple extruded polystyrene (i.e. the stuff used for insulation). It would've been better to have used some modeling grade foam (which we got some samples of, but didn't get as far as testing), as this stuff you could even tap. That would've doubled the price.
The CNC machine cost me about £4000 to put together (and I could make another one if anyone wants one
). For car building, we'd go for an accuracy of 1mm - which is enough so you don't notice it, and it doesn't spend weeks cutting the blocks. However, the machine had a basic accuracy of 0.0625mm in the XY planes, and 0.0125mm in the Z plane. It had a maximum movement speed of 18m/min (which isn't quite professional standards [30-90m/min], but close to it), and it could cut the foam at that speed (the modelling foam may have required a slower cutting speed).
However, that was just simple extruded polystyrene (i.e. the stuff used for insulation). It would've been better to have used some modeling grade foam (which we got some samples of, but didn't get as far as testing), as this stuff you could even tap. That would've doubled the price.
The CNC machine cost me about £4000 to put together (and I could make another one if anyone wants one
). For car building, we'd go for an accuracy of 1mm - which is enough so you don't notice it, and it doesn't spend weeks cutting the blocks. However, the machine had a basic accuracy of 0.0625mm in the XY planes, and 0.0125mm in the Z plane. It had a maximum movement speed of 18m/min (which isn't quite professional standards [30-90m/min], but close to it), and it could cut the foam at that speed (the modelling foam may have required a slower cutting speed).I believe that there are a few companies out there that do it.
One that might be worth contacting is
http://www.cordek.com/
They do ground heave products but I know that they have a the ability to do other things, they did an American Footballer.
Contact them they might be interested.
One that might be worth contacting is
http://www.cordek.com/
They do ground heave products but I know that they have a the ability to do other things, they did an American Footballer.
Contact them they might be interested.
The sensible "halfway house" is to use something like a cnc waterjet cutting machine to cut out plywood "ribs" from the CAD (section the model, add in transverse ribs (like bulkheads in a ship) at fixed intervals, then generate a simple .dxf of the profile of these, get them water jet cut 1:1 scale in cheap plywood). Assemble them on a "keel" at the correct spacing, fill between them with foam, and handcarve back to the ribs.
With a bit of practise you'd probably get 75% of the accuracy of a fully CNC buck, but with about 10% of the cost!
With a bit of practise you'd probably get 75% of the accuracy of a fully CNC buck, but with about 10% of the cost!
ChrisJ. said:
That's interesting.
What instrument would you take readings with on that gantry?
Forgive my ignorance.
As already mentioned, creating sections and building a buck is a tried and tested method. My initial method of capturing surface sections (all profiles) involved building the gantry, and with the help of a simple laser distance measuring device gave quite accurate co-ordinate measurements. Taken at small increments gives a very clear point cloud with which to work with. This method allows scans to be taken and also for re-engineered work to be checked as you go. ( the "Splinter" wooden car for eg)
I now use a portable hand held 3D laser scanner that collects 500,000 points of data a second and doesn't need the gantry. It does attach to the gantry though and the thought of a fully automated/motorised system does appeal.
A rough trial profile mesh is attached and the way the laser measuring device (not scanner) is attached is shown.
What instrument would you take readings with on that gantry?
Forgive my ignorance.
As already mentioned, creating sections and building a buck is a tried and tested method. My initial method of capturing surface sections (all profiles) involved building the gantry, and with the help of a simple laser distance measuring device gave quite accurate co-ordinate measurements. Taken at small increments gives a very clear point cloud with which to work with. This method allows scans to be taken and also for re-engineered work to be checked as you go. ( the "Splinter" wooden car for eg)
I now use a portable hand held 3D laser scanner that collects 500,000 points of data a second and doesn't need the gantry. It does attach to the gantry though and the thought of a fully automated/motorised system does appeal.
A rough trial profile mesh is attached and the way the laser measuring device (not scanner) is attached is shown.
Thanks for that. It's interesting.
So the handheld scanner can scan a lot from one position?
How much do these type of scanners cost?
I guess an automated one would be snazzy, but you'd only need that if you were doing a lot of this type of work?
The gantry reminds me of some photos I'd seen of how sections were drawn from existing panels back in the old days.
That was with a pencil attached to a guide, and a large sheet of paper!
So the handheld scanner can scan a lot from one position?
How much do these type of scanners cost?
I guess an automated one would be snazzy, but you'd only need that if you were doing a lot of this type of work?
The gantry reminds me of some photos I'd seen of how sections were drawn from existing panels back in the old days.
That was with a pencil attached to a guide, and a large sheet of paper!
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