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Building Tips and technical articles. => Paint and finishing => Topic started by: Howard Rush on May 28, 2012, 02:08:41 AM
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Sign shops to which I have taken CAD files to get paint masks made use a file format called .EPS (I think). Neither TurboCad nor my other CAD program has this format, so I take the file in .DXF, .DWG, and a few other formats, the folks at the sign shop fiddle with them and come up with a file their cutter can use. The last time I did this, the conversion didn't come out quite right. It converted my polylines to lines that almost, but not quite, matched the lines I gave them. Worse yet, copies of the same line came out different, so edges on masks I made to cover colors I'd tooted didn't match the edges of the color they were supposed to cover, with errors of up to .040" or so. What's a good way to do the file conversion myself, or should I stick to hexagons?
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EPS is encapsulated post script. It is a printer format that was used by apple when the first laser priters came out.
It contains vector drawing commands plus some bit map commands. Most file converter programs will try to scan convert a bitmap and get it wrong a little.
Your best bet is find a printer driver that will work for your cad system that will print to an EPS file rather than a physical printer.
I have used Corel draw, but adobe illustrator will open edit and save .eps files
http://en.wikipedia.org/wiki/Encapsulated_PostScript
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Howard has experienced the same thing I noticed here at home. I have an inexpensive cutter/plotter but I'm pretty sure the software operates about the same on the big stuff. I make a file with Corel, save as a .DXF and open with my plotter software. It's OK, but not perfect. An easier way for me it to copy and past from Corel and make sure that I "combine" all images in the plotter. Accuracy is the same and no lost detail. The most accurate way is to use the software that came with the plotter but the version I have is very limited. Of course, high end stuff is available through their outlet but out of my budget and I can live with .020 to .040 error. It repeats, so the file is aways the same from time to time. Howard is an engineer and I'm a machinist. Sometimes it is hard to live in and imperfect world.
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I took a picture. This is an attempt at Grandersonian swoopy lines. The basic mask had several lines separating different colors. My plan was to peel off a section of mask between two swoopy lines, discard that piece of mask, which the peeling would have distorted, toot some paint, then put an identical new piece of vinyl over that paint when it dried. That's what I did here. The piece of vinyl below the orange area covers a green area. Here's what it looks like after one coat of orange. The green peeks through where the masks didn't match. I can cover it with orange, but it will leave a Himalayan ridge.
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Here is the drawing I took to the sign shop. I had them cover the upper mask with tape. The lower mask, made with copies of the curves on the upper mask, was left untaped so I could use pieces of it to mask areas after they got painted. I could have avoided the mismatch problem by just having them make two copies of the upper file.
The lettering was another problem. I converted the letters to polylines in TurboCad, and they came out jagged in the conversion to whatever the sign shop used. I peeled them (and some paint) off and used extra letters from the last dog.
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Your best bet is find a printer driver that will work for your cad system that will print to an EPS file rather than a physical printer.
Thanks. Is there a way to check that .EPS file to see if it came out right?
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I guess I need to learn to write more clearly.
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Howard,, I got what you were saying,, I thought it was pretty clear,, anyway,
I am curious,, where are the checks,, blocks, and other square shapes,, How on earth will we ever recognize your airplane if its not orange with square shaped trim elements,,
is this some devious plot to align yourself with the infamous JCT stunt orginization, oh, wait,, yeah never mind
as to files and working with.
what I do here, I draw my mask files in CAD,, then I draw a bounding box around them of a known size,, say 24 x 12,, I select all the elements in the box,, and "control C" ( keyboard copy command), then I open my cutting software and use "control V" (Keyboard paste command)into the blank "page" in my cutting software.
I can then select the bounding box, and in my tools on the cutting software I can tell it to make that box, ( and all elements contained) scaled to the exact size, in this case 24x12. This has worked really well for me.
However, I will tell you that frisket will stretch slightly as you place it if you are not dead carefull,, In fact I try to design around that fact when I lay out a scheme to avoid that sort of thing. I do not like two trim colors butting together as a rule. However, you can use the mask you have, then with 1/4" tape, clean up the butted edge to avoid the small variences that are basically inevitable when working on a 3D surface..
Hopefully I have communicated what I am trying to,, short version,, use the mask to get as close,, and establish the NEW edge for color,, use the tape to clean up the existing edge,, yes it is laborious,, but it works well with a bit of patience
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What Mark said about stretchy. If it'll conform to a wing with ribs without weird folds and whatnot, then it's stretchy -- given two identical pieces you'll still have a bear of a time getting it all right.
Multi-color trim may work best if you do it the way Randy Powel did on the latest one of his that I saw: plan your trim scheme and masking so that you paint a layer of light-color trim, then peel off a layer of masking, then paint a layer of dark, high-cover trim that won't show the light trim, then rinse & repeat for each color.
As far as software:
Inkscape will read in EPS files. It purports to import DXF files but I just tried it and it doesn't work very well. You could probably Google on "EPS file viewer" and find some joy -- or see if Evince is available for your machine; it's what Ubuntu Linux uses and it works quite well.
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Thanks, folks. Hexagons are coming.
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now Howard,, you can do what you want, it just takes a bit of cleanup masking,,
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Thanks. Is there a way to check that .EPS file to see if it came out right?
http://en.wikibooks.org/wiki/PostScript_FAQ
I don't know, way back when PS printers were new we used to enter simple commands into a ghoast script to calibrate the image. Like diaganol line or a square
You can't tell if the cutters import program CAD's output or the cutter is in error.
I would try a few simple shapes that did not come from acad program.
But I think you have better things to do.
maybe the copy paste is the best way to reduce errors?
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I got the mismatch fixed. Viva acrylic lacquer. Thanks, folks.
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Howard,
As long as I am at my current job (which could be changing soon) I have the capability to use the DXF files that you created. My vinyl plotter program will easily convert DXF files to vector files and it is extremely accurate. I draw all my paint schemes in CAD and then import them to my vinyl program. Just so you know.
Derek
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Thanks a lot, Derek. I do want to fix some of the shapes that came out funny. I'll send you the file.
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Howard, perhaps you could output them to a PDF file. Most systems have a way of doing that. PDF is not much more than PostScript on steroids and is the de facto standard for interchangeable file formats.
EPS (Encapsulated PosttScript) is mostly a way of writing PostScript code embedded in a series of PostScript comments that fully describe the contents of the image being "encapsulated". An EPS file can then be imported into another PostScript image and, for all intents and purposes, treated as a single element with regards to positioning, sizing , rotation, etc.
Yes, probably more than you wanted to know. (I've been writing PostScript code for 25+/- years.)
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I have the same issue with my laser cutter. The company runs the laser with Corel Draw. I started drawing with Corel 3 but since switching to AutoCAD in 2001, I've forgotten most of the neat stuff I could do in Corel.
Howard, my AutoCAD program comes with an EPS print driver so I still do all my drawing in AutoCAD and convert to EPS by 'printing' the CAD drawing with the EPS driver. You set the scale in the CAD program and it comes out right every time.
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I called the sign shop. They use a program called SignLab, the latest version of which accepts .pdfs, but not the version they have, according to the lady who did the file conversion. It imports .dxf files, which it perverts. For all I know it perverts .eps files, too. Mr. Haverly has kindly offered to cut me some masks tomorrow with his .dxf-friendly setup.
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Did you ever get this worked out?
For future reference download Inkscape for free from www.inkscape.org This program will convert a picture to a vector. You can then edit the nodes on the vector to get the correct layout. The button you want is under the "Path" menu and the actual command is "trace bitmap" which in the current version is Shift+Alt+B.
There is a great tutorial in Inkscape it is under the "Help" menu in the "tutorials" submenu. Click on "Inkscape: tracing".
You can then edit the vector and save it as an .eps file. Most sign shops should then be able to cut the vinyl or send it my way :-)
I have started playing with cutting graphics for paint masks for use on my models. Here's an example of a graphic I did on my BVM Jets F-86 Sabre (unfortunately there was a tiny bit of bleed out on the left side of the graphic-it was a panel line that the vinyl came up a little while spraying).
-Scott
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Did you ever get this worked out?For future reference download Inkscape for free from www.inkscape.org This program will convert a picture to a vector. You can then edit the nodes on the vector to get the correct layout. The button you want is under the "Path" menu and the actual command is "trace bitmap" which in the current version is Shift+Alt+B.There is a great tutorial in Inkscape it is under the "Help" menu in the "tutorials" submenu. Click on "Inkscape: tracing".
You can then edit the vector and save it as an .eps file. Most sign shops should then be able to cut the vinyl or send it my way :-)I have started playing with cutting graphics for paint masks for use on my models. Here's an example of a graphic I did on my BVM Jets F-86 Sabre (unfortunately there was a tiny bit of bleed out on the left side of the graphic-it was a panel line that the vinyl came up a little while spraying).-Scott
Scott,
Nice job!
There is a "mask" that can be applied with a brush or spray, Dave Brown offers one for hobbiests. Works well on textured surfaces. Down side is after it's applied the cutting is by hand.
With vinyl masks, a trick is to seal the edge, this can be done with a simple coat of clear.
Charles
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Yup can use a sealer. On this one I just didn't press the vinyl down in the panel line well enough. Oh well. A tiny bit of paint will fix it.
Do you have a method to quickly convert a .jpeg or other graphics file to .eps?
-Scott
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Yup can use a sealer. On this one I just didn't press the vinyl down in the panel line well enough. Oh well. A tiny bit of paint will fix it. Do you have a method to quickly convert a .jpeg or other graphics file to .eps?-Scott
Scott, I'm on a Mac. There's all kinds of programs that take JPEG images and convert them to vector lines for the benefit of vinyl cutting or laser cutting. Other equipment also.
Thing is, generally, there's always a "clean up" with the lines. Sometimes this can be time consuming. As far as saving a file as an EPS. I don't have to. I save them as DXF files when I send them to my laser cutter. I've used a few cutters and all of them had no issues with opening the file as a DXF.
"The New American" was laser cut from my CAD drawings saved as a DXF file. Which BTW is my first attempt at designing a model in CAD. Generally, when I scratch build, I just draw lines on paper.
When you do graphics every day to make your living, you view it a bit differently, it's actually all the same but different.
This link will take you to some photos of my work. Everything is different, but the same process is used.
http://www.rcuniverse.com/community/profile.cfm?section=gallery&memid=11343
Charles
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Did you ever get this worked out?
For future reference download Inkscape for free from www.inkscape.org This program will convert a picture to a vector. You can then edit the nodes on the vector to get the correct layout. The button you want is under the "Path" menu and the actual command is "trace bitmap" which in the current version is Shift+Alt+B.
There is a great tutorial in Inkscape it is under the "Help" menu in the "tutorials" submenu. Click on "Inkscape: tracing".
You can then edit the vector and save it as an .eps file. Most sign shops should then be able to cut the vinyl or send it my way :-)
I have started playing with cutting graphics for paint masks for use on my models. Here's an example of a graphic I did on my BVM Jets F-86 Sabre (unfortunately there was a tiny bit of bleed out on the left side of the graphic-it was a panel line that the vinyl came up a little while spraying).
-Scott
Thanks, Scott. The sign shop totally hosed my mask. I think they freehanded the curves when they couldn't do the conversion. Copies of the same curve didn't even match. I somehow didn't notice this until I removed the bandages and saw the finished product. Derek then made a good file for me, and Mike Haverly cut good masks with his machine. I had to repaint the colors, covering blue with yellow and green with orange in places. The airplane ultimately came out OK.
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I do like the fade out on the tips.