How do I digitise some templates

[Moondog]

Hope someone can point me in the right direction.

A boatbuilder friend of mine has a design that he has all the template shapes cut in plywood (cut by hand) and we want to Digitise these to a CAD program. There are no scale drawings as he is an old fashioned boatbuilder that did it all by schetches and trial fitting.

Is there a way of transferring the shapes/templates to CAD or similar so I can produce the required cutting files.

cheers

[whiteriver]

Check out the yahoo group for Mach2. Art is working on making a mach2 wizard CMM. So you can just use a cheap $200 Deskcnc touch probe and mach2 to digitize it. Asumming your machine is useing mach2. It also has a teach function for plottong points that way.

Donny


www.whiterivermfg.com

[buscht]

A few of ways that I know of.

1. Find a local kitchen countertop company that has a large flat bed digitizer. See if they will let you borrow it to digitize your templates. Often they go to the job side and make templates to match the customers walls and counters. Then they come back to the shop and digitize these templates into CAD.

2. Use your own CNC Router. Put a pointed dowel in the spindle. Move this around over the template (Manually) and start recording the locations. Some software has a way to record these spots for you, but I am not sure about this. You can always write them down and reenter into your CAD.

3. Trace the templates onto grided paper. Measure the X Y points and enter into your CAD manually.

[Moondog]

thanks guys....

thought about using my machine to plot the points...problem is that there are many templates to copy... enough templates to fill 27 sheets of plywood....

If you used the machine to plot the points.. straight lines are easy.. but with curves how many points would you need to take....

[buscht]

It takes 3 points to define an arc.
I think the automatic routines like Donny mentioned just make alot of close points and these are connected with small lines. They are so small that you can't distinguish them from proper curves.

Another thought, I remember reading on the shopbot website about some auto routine they wrote using an edgefinder to digitize templates. You might want to look over there and ask on their forum.

[fyffe555]

How big are the parts? This is a common problem with boat building, there's a few threads in CNCZone about getting gcode from hull drawings.

If you can't digitize it because they're too big, or you don't have a digitizer, then you could just reverse the lofting process manually. Do a google on lofting or boat table of offsets. Grid the part with 1" ( or other appropriate scale) spaced grid squares and take a set of offsets ( x,y from a known center or station line) from it. Enter the offsets into your cad and then fair the curves. If the part is a station mold and symmetrical then you can copy the one side to the other.

Andrew

[jcc3inc]

Moondog,

I have made a CNC controller which is somewhat similar to the TurboCNC unit in that it runs in DOS. One program I made is a digitizing application. It is an "interactive" digitizer in that the operator first surveys the shape to be digitized, determines where a straight line starts and ends, where an arc or circle starts and ends, and marks these points.

He jogs the machine to a start position, (0, 0) and enters a keypress. Next the machine is jogged to the shape's start point where he enters a starting RS-274D command. He moves the machine to the next point (let's say it starts with a line), enters a keypress and the program generates "G1 XnnYmm". Assume the next portion is an arc; he jogs to a midpoint of the arc, enters a keypress, and proceeds to the end of the arc where another keypress records the arc data as "G2 Vnn Ymm Ipp Jqq" (where mm, nn, pp, qq are numbers). Thus digitizing generates the G Codes for the shape of interest. The operator can enter a specific M or G code after any gode generated.

I have digitized shapes with good success. While the program is not polished, it should be quite practical for what you want. What controller do you use for your machine? I would be interested in generating a digitized program if you had a sample. Let me know what you think!

Regards,
Jack C.

[buscht]

I found the link to the shopbot article.
I thought that it was kind of neat and he specifically talks about boat building templates.
http://www.shopbottools.com/bcedgefinder.htm

[Moondog]

Thanks for the interest and ideas.....

There are approx about 80 parts, some small, some large...it would takes me weeks to plot the shape jogging the machine. The curves require a lot of points to accurately re-create the shape.

Is there something like an pointer or edge finder?.. somethiing that you can just lay down and trace the shape by following the edges?....

The new Palm Pilots have something very similar but on a smaller scale... you write on a pad and the shapes/letters are loaed into the computer... it uses an X Y recognition software.

cheers

[buscht]

Yes, there is. It costs about $8400 US. That's why I suggested you ask around at cabinet shops to see if they will let you digitize on their machine.

http://skalarcnc.netfirms.com/

[Moondog]

buscht.. yes I started asking around yesterday.. no luck yet but I will keep trying.

jcc3inc.. I am using Rutex and Mach2.

I appreciate your input guys and I will continue to search for a solution.

thanks

[jphagen]

What you can do is photograph them, directly from the top. Save the jpeg or bmp to
the computer, open in coral trace, save as a dxf.
Then import to your cad program. Rescale to a measured dimension taken off the part.
The rest of the drawing should be very close to an accurate dimension after this.
It helps to try take as high a contrast photo.