Q.: Why CNC?

B.: Well when we started with our production line, we did this at a small scale as we wanted to do it all ourselves without outside investors. I had been working too hard for 15 years on making a name with Witchcraft to give other people too much influence.

Soon the demand had grown bigger than we could handle so we started to look for methods to increase production. Most boards are made with molds but with our constant development of wave boards and our extensive range of boards with close steps in volume we did not feel of going into this direction. We wanted a more flexible system that would give a very good and constant quality. CNC seemed to be the best option for these reasons:

-A very helpful tool in the developing of shapes with a very high accuracy

-Very short lead times between finished prototype and going into production.

-Continuous and gradual development. Any developments, no matter how small, can be put through very easy and immediately whenever the designer thinks it is worthwhile without any further costs. No big jumps in design from year to year.

-No need to send the master model to the factory

-No need to make a mould from the master model

-No mould costs: freedom of making an extensiv range with as small a steps in volume as necessary without even having to look at a minimum amount of boards that would need to be sold just to make up for the mold costs.

The disadvantages of not working with moulds are productivity and production costs when a certain model would get a lot of demand but with our extensive range, that won´t happen too soon and with our distribution system without the need of importers because we produce within the EC, we can make up for those higher costs.

In the future with this system it would also be possible to mill moulds directly with this system, which would be more accurate then drawing a mould from a board that has already been used and may have deformed.

Q.: How did the 3 of you get together?

B.: I had been looking around which shaping programs were available on the market, which ain´t many. For windsurf boards there was Shape 3D and DAT Designer. I tried the trial version of both of them allready in the past and found them pretty hard to work with but at the time just out of curiosity as I did not have the need to buy a CNC machine. This time I put more effort into working with them and simply tried to design a Witchcraft. But I found them just too hard to work with and leaving a lot of room for mistakes unvisible on a computer screen, inspite of all the tools to check smoothness. It was still hard to make fluent lines. This is probably also due to the fact they can also (or in the 1st place) be used for designing surf boards which can be much more diverse and extreme in shapes. Then our dutch dealer (SAVAGE WINDSURFING in Scheveningen), told me that JWK had kept on developing his own shaping program. JW had developed this program as a hobby shaper to make hotwire templates to cut and rough shape the blank with. He had send me this program years ago to hear my opinion but at the time I had not put too much effort in it and it still had some flaws in operating it if you were not the designer. However it had one advantage over the other programs and that was that it worked with full fluent lines. So the dealer put me back into contact with JW. It turned out he had improved his program a lot so we started to talk about how we could make it useable for CNC production. JW also knew another student of the TU Delft who had started making CNC machines as a hobby and during his studies had allread built up a small company designing and making CNC machines.

Q.: Bouke, how do you design boards with Virtual Shaper?

B.: There are 3 modes: Design, construction and CNC.
In design mode you design the outer hull shape of the board. When you design a new shape, you start from a default shape. Then you go down the list of the menu:

-Rockerline: This is an extra feature especially developed for our parabolic Witchcraft rockerline. It´s defined by length, nose and tail rocker and scoop derivate. The last one serves to fine tune our parabolic rockerline. The standard rockerline design will give more freedom to design but will also give more possibilities of making it less fluent. It also has a rockerline evaluation tool.

-V-shape: You can design the V shape, degree, start, max and end and the ?flow?

-Concave: Same thing as above. With a combination of concave and V you can design a double concave.

When that is all defined you can start ?shaping? the tucked line, outline and deck shape by moving the control points for the B-spline lines. When you do this you can constantly check the 3D view, crosssections and important parameters such as width, volume, thickness, tail and nose width and thickness.



And finally the inserts:

-Finpositions and angles

-Footstrap positions, openings and angles

-Mastbox position



A very useful tool is the separate scaling of length, width and thickness.

In Construction mode you can define all spaces for the inserts, sandwich thicknesses of deck and bottom plus any tapering, heel cushions, block reinforcements of hard sandwich foam and the shell expansion plus cuts. In the 3D view you can check if everything is in place.



And in CNC mode you enter the cutting tools, which tool is used for what, overlaps of tool paths, revs, feed. Design the blank and position the board inside the blank. With the blank thickness, Virtual Shaper will also take into account the cutting length of the used tool and if necessary split the cutting depth up in more layers. And finally generate the G-codes to drive the CNC shaping machine.



Blank.

All files, design, construction and CNC can be copied on other projects, which saves a lot of work once the first ones have been made. Then you only need to adapt the changes.



Tool paths for bottom, deck and inserts. Notice how the deck is shaped in 2 layers and the grey tool paths for the inserts.

Q.: Jan Willem Krijger, can you explain in rough how your program works?

JW.: As many CAD programs today Virtual Shaper works with B-spline curves and B-spline surfaces. The nice feature of B-splines over other types of curve definitions is that only the end control points situated on the curve and the curve tends to follow the other control points. By definition a B-spline has a continuous curvature (is fluent). In other surfboard design programs your able to design individual cross sections but often it?s hard to make a smooth surface from the defined cross sections. In Virtual Shaper you define control lines over the length of the board which in turn define the control points for the cross sections. If the control lines are fluent, the surface is also fluent.

Q.: So then how did you continue?

B.: So when I decided JW´s program was the one for me, it was time for the 3 of us to get together and do some brainstorming. So in the summer of 2007 JW and Kevin came to Fuerte for 3 weeks so they could see the custom production and develop ideas from that to do as much by CNC as possible.

I think having the 3 of us together and all being open minded and creativ specialists in their own field, we did come up with a system that is far more comprehensiv than what´s on the market today.

Seeing the way we produce boards in our workshop, JW looked at all aspects of the shape and construction he could possibly incorporate and Kevin looked at everything that could possibly be made with a CNC machine.

This resulted in a system that can CNC all parts necessary to build a windsurfboards. It can calculate the heel cushions to be shaped at once together with the deck, it can calculate and cut all openings for reinforcements for the boxes and cut the parts out of PVC sandwichfoam to fit inside. It can calculate and cut or mark the bottom sandwich till the tucked under edge line and the complete fold out of the deck sandwich to go around the rails including cutting away excessiv material. And it can calculate and cut all openings for finboxes, mastbox and footstrap plugs.

Q.: JW how did you calculate these heel cushions and sandwich fold outs? Being not a simple square shape this seems pretty difficult?

JW: Because heel cushions always need to have a smooth shape we thought up a way to define the outline as an ellipse and the depth with another B-spline curve. This shape is then projected on the surface of the deck. This enables the designer to define heel cushions which progress smoothly into the surface of the deck.

From my background in marine technology I?m familiar with shell expansions. So I knew it must be possible to calculate the fold outs of the sandwich foam. I searched the internet for articles about shell expansion it turned out to be a vast scientific research topic because it?s not only applied in shipbuilding, it?s often used in the game programming to map texture to surfaces. It turns out it?s quite difficult to map a 3d surface to a 2d surface because you have to correct for some distortion. But eventually with the help of some articles I developed a nice algorithm. Now the designer is able to define the placement and the number of cuts he (or she) wants to make and the program calculates the fold out.



Deck sandwich fold out (shell expansion).

Q.: K, how did you make it possible for all these parts to be made on 1 machine?

K.: Yes that was a bit of a challenge. Normally you would need 2 CNC machines to do this, one to mill the actual boards and the other that could cut parts out of a sheet of PVC foam. The advantage we had was that I was designing the machine from the ground up we have no constraints. So by taking into account from the beginning of designing that we needed several functions in a single machine. We were able to design the machine such that the CNC controlled vacuum suckers retract under the table. This leaves a flush surface that can be used for normal machining operations. So in fact Witchcraft has 2 machines in one, a boardshaping maching + a 3D milling machine with vacuum table.

Q.: Were there any other practicle problems to be solved?

B.: Well yes, the first thing was that we wanted to save on polystirene waste so to first cut the rough blank with a hot wire instead of starting off with a square block and mill that down. This however created a problem for the positioning and fixing off the blank. The second problem was the turning of the blank once 1 side was done. The actual fixing is fairly easy with vacuum suckers and a vacuum pump. But how to position them?

I heard once that another shaper, who was working with CNC, always needed hours of measuring with rockerlines to position the blank and then again to do the other side. So I asked the others if this could not be done automatically. According to JW it would be easy to calculate the positions but for Kevin it created a problem to physically move them and to drive them with the control box.

K.: Yes this was a nice challenge. I have a lot of experience with 3 and 4 axis machines. But now we needed to control 6 extra vacuum suckers as well. So we needed control of 9 axis. There are very few CNC controllers on the market that can handle this and still be affordable. So we developed a clever solution that made use of our standard 4 axis software but with a newly developed hardware pcb and software to work with it for this project.

I wont give all the details but the principle is based on the fact that we never need simultaneous 9 axis control. First the vacuum suckers are raised into position and when the blank is loaded they stay stationary during the actual milling. The motion controller is the switched via the software to control the 3 axis milling.

Our controller does 4 axis simultaneous motion, so we had to reduce the 6 sucker motions to 4. But that was not a problem since surfboards are always symmetric around the lengthwise axis, so the dual suckers supporting the middle 2 positions could be controlled from a single signal. So our machine could be controlled from a 4 axis controller.

As for the whole process, after looking at it from all sides, we decided that the best way would be to work in the same follow up as had been proven over many years. So first cut the blank by a hotwire template calculated and cut by the system and position the blank in the machine. Then cut the outline, shape the bottom and cut out spaces for finbox reinforcements. Then take the blank away to apply the bottom sandwich material. This is necessary as with the deck shaping, the polystirene blank becomes so thin at some points, it would break or bend when shaping. Then replace the blank and shape the bottom part of the rails and mill the openings for the finboxes.



Fin boxes and rail shaping.



Rail shaping.

As Kevin had designed the machine with a vacuum table to cut all sandwich parts, we could use the table as a horizontal reference for the repositioning of the blank with 2 tools for the nose and the tail. Simple but effectiv and quick.

Then the blank needs to be turned so the activators for the vacuum suckers are moved to the new position, the blank is placed back in the machine and the deck is shaped and openings for reinforcements are cut. Any heel cushions are shaped straight away with the deck shaping and do not have to be done afterwards.



The first layer of the deck shaping.



And the 2nd.

During all shaping the extracting system sucks up 99% of the dust and collects it in a bag, ready for recycling.

The suckers are lowered into the vacuum table again and all necesary sandwich parts can be cut.

After the deck sandwich is applied, the blank is put back in the machine once again and the insertholes for the deck are cut out.

All the rest of the work has to be done by hand so far. For the future Kevin thinks it should be possible to make a painting and possibly also a laminating robot for windsurfboards.

We are very happy with the result, it is even better than we hoped for and also the adaptation to the system went better than expected even if we did have to solve a few problems. To regain some of the developments costs we are also planning to offer the system to other shapers. The cost price is actually still lower then other systems on the market, making it a good investment, even for smaller custom board builders. Even if in the end it is still only a tool to help designing and building boards and the actual performance of the boards still depend on the shaper and his ideas, this is the perfect tool to realise those ideas??