Curved background

This section is for useful tips and tricks for Aspire
Post Reply
Posts: 2
Joined: Thu Apr 30, 2020 12:47 pm
Model of CNC Machine: TigerTec

Curved background

Post by FredrikB »

I working with signs and i have a question.
We produce acrylic logos/letters that i design in illustrator. Then i open them in vectric aspire and deside how the machine should mill the vector lines.
Now i have got a request to make some letters (boat name) that should be mounted on the backside of a boat. The surface of the boat is not flat, it is a little curved. The client wants the letters to be mounted flat to the surface whit no gap between the surface and the backside of the letter.
The client told me that they could 3d Scan the surface or maby get the curved area as a digital file from the boat builder.
So my question is: is it possible to 3d mill the backside of the letters so they will be flush to the surface without any gap?
If it is possible: how can i do it?
And what file format should the curved surface be in?

Best regards Fredrik

User avatar
Vectric Wizard
Posts: 2445
Joined: Tue Sep 22, 2009 9:52 pm
Model of CNC Machine: Anderson Selexx 510
Location: Henryville, PA

Re: Curved background

Post by dealguy11 »

If you can get a scan and accurate measurements, then you should be able to mill the backs of the letters to match. They should give you the scan in some format Aspire can import, like .stl.

Once you import the scan, you should check the dimensions of the scan to make sure they match the dimensions of the boat. If they don't, and you have to adjust, then resizing the imported component should adjust z height as well, which is what you need to maintain the curve.

You can then use a carving toolpath, probably with a large ballnose bit or cove bit (because you don't really care about fine detail) to make the curve on the back of the material. Unfortunately you are going to waste some material because you will need to space out your letters on the curve to make sure each letter has the right curve to fit exactly where it lands on the boat.

If you don't care whether the fronts of the letters are also curved, then you can just mirror the name and cut them out from the back backwards. If you do need the fronts curved, then things are a little trickier. You'll need to do a double sided cut. Once you flip the material to do the front, the back side of the letters will no longer be supported on the table because it will curve upward. You will probably need to carve a backer board with the same curve as the letter backs to support the letters while you carve the front.

I've just outlined a high-level approach. There would be more details to be addressed, of course. Best of luck on this project!
Steve Godding
Not all who wander (or wonder) are lost

User avatar
Vectric Wizard
Posts: 4518
Joined: Thu Jan 18, 2007 6:04 pm
Model of CNC Machine: 8020 Build 48X36X10 RP 2010 Screenset
Location: Leland NC

Re: Curved background

Post by TReischl »

Another example of "I have a cnc machine, so it should do everything" or as it is more commonly known "When you have a hammer everything looks like a nail"

What I would use the cnc machine for is to make a bending form for the letters. It can be made out of pine. Then cook the letters a bit and form them on the forms.

Just a note, the stern of most boats have very consistent curves.

I would use this method because A) it is a heck of lot faster than fiddling around milling the backs of letters B) I can try it out on a sample piece to see how it works all across the stern of the boat.

When I was first starting out in the early 70's we got a job to build a "hamster smoking machine" (cancer research stuff). It needed lots of plexiglass parts with large radii. And they had to be accurate because there were a lot of moving parts. That was the first time I saw an oven a person could walk into. Being low man on the totem pole, I got the job of going in the oven, getting the piece and then pressing it onto the form. We used a two part form with a bit of allowance for spring back. Two parts so we could clamp the piece, let it sit for another half hour in the oven to reduce spring back.
"If you see a good fight, get in it." Dr. Vernon Johns

Post Reply