Hello Folks!
Here is the making of the master for our ARD
Jean supplied me with is design films for three etched sheets full of parts to build the master structure (decks and frames).
My task was to etch the parts, build a master, make a silicon mold and cast copies for both of us.
This time our master is made of a .2mm thick photo etched structure (decks and frames) of which the voids are to be filled with small blocks cut from construction board. This has been my favorite method since 2004.
The whole hull is then covered with etched walls (outer hull and the dock inside).
For the first time I wanted to have a hull as accurate and straight as possible, so I decided to have the filling blocks machined with a computer aided milling machine (i have one in my classroom)
Starting with Jean�s drawing files, I extracted the correct shape for each block, including thickness.
The file is converted into another format suitable for the machine and opened into it�s dedicated software. Here the grid zone shows the construction board small plank in which the parts will be machined.
Now surfaced area (in red outlines) are placed to fix the various thicknesses to be machined.
The CAD step is over. Now I�ll define the type of tools (cutter) to be used, and the tools cutting trajectories
This is an example for surfacing. I select a 3.17mm dia cutter in the �virtual� magazine and the soft automatically select the proper motion and cutting speeds according to the material.
Now I select the cutting depth. Here, this is a surfacing process: the cutter will move along a �squared spiral� from the center of the given area.
The software now compute trajectory, cutting speed and cutting depth
Done! The screen displays the tool�s projected trajectory (in green)
Same again with the other surfaced areas, then each part outlines
When done I start a simulation check to make sure my project is OK.
The software now computes the overall timing which is about 10 minutes.
Simulation complete: everything is OK.
Now it�s time to proceed with the real thing.
The construction board small plank is secured with double face tape on the machine board.
Starting to cut. First the tip of the tool slides to contact a sensor which tells the exact position (down to .001mm). This is called the origin point.
End of the surfacing step. The machine stops to allow a change of tool (I�ll do the part outlines with a 2mm dia. cutter)
Outlining each part
And DONE after 10mn.
A dry fit on the PE structure to check for accuracy
Here is a small movie to show that machining a more lively way:
http://s6.photobucket.com/albums/y205/b ... verted.mp4
Assembling the master.
Here�s a dry fitted bow
With its filling
I go backward from the bow. Each filling block is put in place, then secured with super fluid super glue.
The hull is complete. Now come traditional sanding, putty, sanding, putty again, another sanding and polishing.
A reminder about this method: as construction board is softer than the metal frames I go with a �blind� wet sanding until I hear the typical �rattle� noise which tells me I�m home.
I get a dimensionally extremely accurate hull shape quickly and without any check or measurement� just watch for the noise.
Now it�s the turn of the outer PE cover.
After etching the hull and dock sides I�ll have to do some preliminary work.
�Mad� Jean designed a very realistic �canning� effect on the hull (the hull plates bent inward by high sea): he did a relief full standard 3ft framing on the back side of the hull plating.
My job is to get embossed shape from the front side, exactly the same way the water would do.
For my etching alloy, I use nickel-copper (the so called �stainless�) which is stiffer and more elastic than brass. This is a good point for very tiny parts, but not suitable for embossing.
This alloy must be annealed, that is: warmed red hot and allowed to cool very slowly to get a mild alloy.
Warming is done with a mini gas torch.
Doing the canning. I used a traditional guilder burnishing tool for that very easy and amusing task.
Fitting the dock sides
Finishing
Bitts are overlong as these are master parts which will mold a positioning hole in the silicon.
Cast hull bitts will be treated as brass inserts.
A Mr Surfacer spray to check for defect and fill the small voids between parts and it�s done.
Doing the mold in silicon (I call this pink silicon� silicon carne)
Note the construction board stick, which has three functions:
- Save some silicon (I used 200grs)
- Makes the whole mold straight and more rigid... and a straight hull
- Prevent the silicon mold shrinkage (about 2%) which would make an undersized casting
The master and first casting
Now it�s Jean�s turn to add the two sheets of PE details he designed and I etched for him.
_Bruno
It's always a pleasure seeing what you can do with PE!