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Bonnet printed...

by Ivan Sentch 8. February 2013 19:30

...still assembling though, this time I'm trying to assemble the border first then work in. With the boot I did one layer rows and attached them from the top and bottom in, I was surprised when there was a gap in the middle, I was expecting with the 0.5mm rail  the printer prints that I would have to sand it a bit to fit snug.

I put this down to the inaccuracies created when the print peals off the bed (due to inconsistent cooling rates) when it rises off the bed it also distorts out or in so if you don't compensate for this when you attach it all together you end up with things like this.

I've got some weights on it now so I'll take an in-progress picture later, for now here's a picture of my 250 GTO kit I built 10 years or so ago, it's also got the RB25DET in it that I'm planning to use in this (but I would like to transplant the v12 from a 750 I have been sporadically working on into it one day, hard to work on something that's already working though)

Tags:

Body | 3D Printing | Miscellaneous

3D Printing, what I've found so far

by Ivan Sentch 5. February 2013 08:55

I've got a Solidoodle 2 3D printer which has a build envelope of 150 x 150 x 150mm so the first thing I did is cut up the bonnet into to 150mm cubes (I should point out I didn't have the printer at this point so I couldn't test any of this), gave it some extruded sides for rigidity, first mistake. The printer can't print on thin air so I would have to build up the top extruded side at 45° or beter yet cut the squares at 45°. so I cut all the squares diagonally and then gave them 1.75mm depth, second mistake. 3DS Max 2011 (which is the design tool I'm using) gives depth along each segment's normal (imaginary line perpendicular to the average face direction) instead of uniformly in one direction (x, y or z axis). So start again, give the bonnet depth first, then cut, then make the extruded sides (and give them depth as well).

Once all this was done (just the bonnet so far) I had to rotate each segment for printing, export and convert into gcode, given the trouble I had creating the segment I only did one and waited for my printer to arrive. When it did it was pretty straight forward, plug the USB key in, use the software provided to turn the exported .stl file into gcode and print!

The first print worked fine except the printer didn't handle the 45° angle very well, it printed it but it had trouble and it wasn't true (was actually a bit saggy). I need all sides to be true or when I attach them all together it will be misshapen. So start again!! This time I gave it 5mm depth, cut it into 150mm squares and only extruded the sides by another 5mm (as being 5mm thick it's sturdy enough, the sides are only to enhance the accuracy when I stick them together, also it's much much much easier and faster doing it this way as well).

Another problem, converting it to gcode creates rails the print sits on (used to keep it stuck to the print bed as as it cools it wants to distort) and as I've used the full build envelope it looses the sides, also the bed is heated from the middle so the outsides are cooler and the edges curl up too much, but the last straw was the printer got to 109mm, threw errors and wouldn't go any higher. I'm sure there was just some adjustment required to fix this but with the rail and the warping I decided to start yet again, this time I did the boot as I had had enough of the bonnet by now.

Something I found out along the way was you can spray hairspray onto the bed to help keep the print stuck to the bed, also (which I have yet to try) use a pane of glass (sprayed with hairspray) on top of the bed (kept in place by paper binder clips).

The final solution that worked:

1) Give the object (boot) 5mm depth

2) Cut it into 105mm squares

3) Extrude the sides by 5mm

4) Export to .STL, convert to gcode (using the rail settings)

5) Heat the bed up to 95°

6) Spray the bed with hairspray

This works pretty well, occasionally the edges still peel of the bed but most of the bottom is still straight so there's enough to stick them together accurately.

Tags:

Body | 3D Printing | Design

Boot done

by Ivan Sentch 2. February 2013 09:28

The fiberglass body I will make by first making a plug, taking a mold from that plug and casting the body from that mold.

So the plug, I investigated a couple of options for this, the first, quickest and easiest was to get a big bit of foam CNC cut but the local CNC cutting shop said about $12,000 to $15,000 NZD, no thank you.

I then tried to find how other people have done this and found an interesting series of you tube videos "Bailey Blade" where the guy sliced up his drawing, printed it out onto MDF, cut and attached these together with foam in-between, then shaped it with elbow grease and time.

However I had a better idea (well we'll see anyway) of 3D printing the parts, this required the design to be given a depth and then sliced up into sections that will fit the print envelope. Then attach these together on a simple frame work (to keep it all true), so how much would that cost? (how much did that cost as this is what I ran with)

$499 USD printer from solidoodle, $35 NZD per 1Kg spool of plastic and calculating the m2 I would get from the average filament density (1.04 g/cm3) for that 1Kg (0.26m2) I will need 64Kg's to print out the 16m2 body at 2mm depth. this comes in at $2250 NZD which is cheap enough.

However once I got printing it turns out I needed 5mm depth as 2mm distorts too easily, but fortunately because it only prints 20% of the inside (it uses a honeycomb mesh to keep the strength) it still ends up being 0.26m2 per 1Kg spool so back on track.

It takes ages to slice these things up and prepare them for printing but it's sitting down on the couch stuff so I don't mind

I started printing 25 Dec 2012 and at this stage have printed out and assembled the boot:

Tags:

Body

First blog

by Ivan Sentch 1. February 2013 11:51

This will be a scratch built replica of a 1961 series II Aston Martin DB4, fiberglass body, space frame chassis using a donor car's bits (engine, drive train, suspension, etc).

The fiberglass body I will make by first making a plug, taking a mold from that plug and casting the body from that mold.

The donor car will be (at this stage at least, I may change my mind closer to the time of needing it) a Nissan Skyline GTS25T which is pretty cheap (about $4000 NZD if you're looking hard enough), fast (250Hp at 7psi and intercooled standard, no internal changes required to run 12psi), it's wheel track will fit the body (which is important as it's not easy to certify suspension modifications in New Zealand), and I'm already using this engine in my 250 GTO replica I built a while ago so I've got spare parts when I change that to a BMW V12 (much much later)

Once I've got the above I'll build the space frame chassis (can't design this until I can measure the suspension), I'll be tacking this together myself and then handing it off to a professional welder to complete.

Then attach the body, paint, interior, etc.

Tags:

Body | Chassis | Design | Donor Bits | Interior | Miscellaneous