Copenhagen Ship Curves, Plexi-Ply expensive - How to make them ?

I had been posted copenhagen ship curves -56 of them - in dwg, dxf and rhino files. I have asked to plexi or plywood laser cutting vendors and they want too much. I saw at one post , someone cut them with 0.35mm PET film with CO2 laser. Is it lot cheaper method and does PET film available everywhere ? Or what to do ?

Umut
Istanbul

 

Do you want to own a set or do you need to generate curves?

 

I have the curves dxf , I want to own the set, what would be the cheapest way , is making the set from pet film make it workable with pen or pencil ?

 

I have a partial set of thin aluminium,they were given to me by an old timer when he retired.I wonder if you have any local company that could cut some with a laser.They don't ned to be transparent and a metal cutting laser moves pretty quickly.

 

PET film is not stiff enough. Are you planning on drafting by hand? Unless what you are doing is really complicated, there is no need to have a complete set. If you want to own them just to have them, it will be costly. Otherwise, these are adequate: Curves https://alvindrafting.com/collections/curves?srsltid=AfmBOoroewTEs5qU-jDXQ2rt0o1idR9tQ9yRlMzyg6HCfDJ6E_8c2hla

 

I am the person who made the set from .35mm(.014") PET film. They are stiff enough as templates, though perhaps not as nice for regular use as something from Alvin, et al.. I worked for a firm that has the lasers and I have used the film for other template purposes so my cost was zero, since I was able to manipulate the CAD and run the laser outside my other salaried duties. The worst part about having a set is storing them...pics are quick from this morning.


Here are the original threads:
Copenhagen Ship Curves - anyone know the math behind them? https://www.boatdesign.net/threads/copenhagen-ship-curves-anyone-know-the-math-behind-them.69073/#post-960446 (mentioning the laser)
Copenhagen Ship curves was rhino, now dxf and dwg https://www.boatdesign.net/threads/copenhagen-ship-curves-was-rhino-now-dxf-and-dwg.59619/ (CAD data)

 

Hello Friend , Thank you for your help. I think there are too many different power laser PET film cutters in istanbul , I know cad machines are having hard time with curves and co2 burn the film and what about the quality of the finish at the edges. Would vendor do something to cutting code to cut the curves correctly or it isnt necessary ? And what could be the thinnest PET material would work for drafting if there is no 0.35mm PET film ? And do you have a advice for laser power and cutting speed either for 0.35mm or thinner ? And dwg , DXF ,rhino , which one is better for smoother cut ?

 

I saw your post just now , I am having hard time to read from screen. Yes I have a friend who can cut from thin aluminum but the cutting quality is raw. If I sandpaper the edges , does it solve the problem ? I fear sanding distort the curve ? What resolution sandpaper should I use ? And what would be advised laser power and cutting speed ? What can be done to lower the raw cut edge ?

 

The laser I used was from Universal, an older model that is not current on their website. They discuss cutting PET as a plastic material on the website.
PET Film - Laser Cutting, Engraving & Marking | ULS https://www.ulsinc.com/materials/pet-film
I want to say it was 50 or 100w CO2 (IR instead of UV) and ran at 26% power and 6% speed. The vendor should test this on one or two curves before committing. I also added a hole for hanging and a number to identify, which is only burnt into the surface and colored with marker.
Edge quality is good, they needed to be cleaned with isopropyl alcohol after cutting to remove the soot.
The CAD/CAM was not hard, I just used the data provided, added the hole and number, and nested it to fit the laser and material.
The laser is hooked to AutoCAD software and it treats the the laser output just like printing but with a custom driver for power settings by color, page size, and other lased-specific settings.

 

I can't help with cutting parameters for lasers as I don't know much about them,I do know that the edge quality can be quite good to the point where light sanding shouldn't be a big task.I can't really comment on distortions introduced by sanding as it depends on the skill of the person doing the work being at a high enough level to retain a fair edge.A reasonably capable person should have no great problem.

 

For a DIY job: a CO2 laser cutting 2-3mm acrylic makes fine parts, even with a cheaper glass-tube laser at 30 watts. Resolution of your CAD files, quality of the cutter drive hardware , and cutter firmware are all factors. If you get 'faceting' when the cutter translates CAD splines, that's about poor output translation from your CAD program, or poor conversion software in your cutter (CAM) software. It's up to the operator to sort that out. You really shouldn't need to sand edges, other than to break the corners. After knocking off any burrs from the laser, I use a machinist's deburrer and a plastic-specific bit to get a user-friendly edge:

The above tool might give you enough of a break to allow use of ink along with a mechanical pencil. If you need a bigger chamfer, use a 45-degree micro chamfer router bit with pilot bearing:


For manual drafting with pencil on vellum, I've always preferred transparent acrylic curves that let you see adjacent lines, or continuations of the line that would be buried if the template were made of wood or sheet metal.

 

The good old chordal deviation parameter! Like all other parameters,a bit of sense is needed.I once had the misfortune of dealing with a CNC programming comparative novice who set all his to a really low and unrealistic level in the belief that he would get a better job.The reality of almost 0.2mm backlash on the y axis ballscrew hadn't intruded into his mind.

 

OK, now we are deviating from the topic - but I'll bite: said CNC novice at a minimum should figure out how to use backlash compensation. Better yet, fix the hardware problem and stay away from software backlash compensation!