Tracing flat patterns with the sb probe

[ohurley@home.com]

We are new shopbotters and want to use our plywood boat patterns to make cutting files.We have the sb probe but the files sb provided are for 3d,I simply need a program to trace the out lines of flat patterns.Any and all ideas are wecome.

[bobbuttons]

you should look into digitizers. they have a pen or a mouse that can trace flat shapes. i am looking into them now so i am learning too. summagraphics and calcomp are 2 co's that make them they usually are 12" sq. working area. there is other info about them on this message board go to "keyword search" and type digitizer for the other posts.

[shuttle]

John,

I have a way... it may work for you.
If the plans are on paper, just scan them, load them into Corel and clean 'em up, then export as a DXF file and load that into Vector, even the scaling info from Corel works.
Another not-so-clean way, would be to take pictures of the pieces on a contrasting background, and again use Corel.
Fine tuning can be done in Vector.

I was told that the digitizing process is slow, if at all possible on flat pieces.

[billp]

John, I also have a technique which has worked for me in similar situations; I take an object which is too large to scan ( as your boat patterns will probably be), and lay them out on a background that they will easily be seen against. I then take a digital picture of them.The next step is to measure the "real" length/width of your object, and then use those figures as a guide while you use whatever programs you have to convert your digital pix into a format which your Cad/drawing program will read..You could actually use "regular"pix as well and just scan them into your computer. If your measurements are accurate you should be able to "scale"your drawings on the computer to give you accurate readings. This is sort of a "poor man's digital lofting" technique..

[billp]

Duh....Having just had my first cup of coffee I have re-read the previous responses in this thread and realized that Rob already mentioned a technique similar to what I've just suggested... All I can add to the method is that when I do it I take a .jpg image, go into Paint Shop Pro and convert it to a .wmf which is readable in Turbocad ( and most Cad programs I believe). If the image is not as clear as I'd like ( OR if I want to redraw/edit the image) I choose a different color and use a 'spline'curve to trace the image. Then I seperate the colors and use the redrawn image to save it as a .dxf file, and proceed in the regular fashion from there.. Monday morning, need more coffee.....

[bill.young]

John,

Being a boatbuilder myself, with patterns hanging all over my shop, edge finding is something that I've been interested in for a while now. It's not only handy for people that already have patterns, but lots of times it's easier to draw something on a piece of plywood and cut it out on a bandsaw than it is to draw it on the computer.

Techniques for edge finding is one of the up-coming "Bill's Corner" topics, but I'll give you a quick preview of what I've done so far. I've written a ShopBot file that finds a starting point on the edge of an object, and then makes a small arc to find another point. Every time it finds a new contact point it write the coordinates to a part file. The file just keeps making these arcs and saving the coordinates of the contact points until it's gone all the way around. The smaller the arcs, the higher the resolution. Sounds simple, doesn't it!

I demoed it at the Educators Camp ShopBot last weekend, and at this point it works pretty consistently with resolutions that are 1/2" or greater. When the arcs get much smaller than that, though, it sometimes gets lost. My guess is that it's a problem with my angle calculations; it uses trig to calculate the starting angles and it's been a LONG time since I had trig at school!

I've been covering the edges of my patterns with the "real metal" duct tape, connecting the tape to the input switch with a wire, and using a piece of metal rod in the router the size of my bit as a probe. That way the file that's created is already offset for the bit size. You could also use the ShopBot probe and have some new ends made for it for your different bit sizes. One of the neatest possibilities might be to use a bar code wand and be able to follow a line on a piece of paper. Just about anything that can trigger an input switch could be made to work.

I'll keep you updated on my progress and post the routine when it's ready

Bill Young

[swims@mindspring.com]

Bill, personally, I wouldn't trust a digital camera's lens distortion for that type of work, but, since you do it for a living, I'll file that process into my memory for future reference.

My approach to large scale 2-dimensional digitizing is much more low tech. What I have done in the past is trace patterns, in this instance guitar forms, on graph paper. I use the paper as a cartesian grid system and merely record the locations of where the traced lines cross readable x-y locations. I then use this text list to plot the points in Vector and use splines and lines to connect the dots.

[danhamm@abccom.bc.ca]

Just to add my 2cents worth,
A few years back at a mine auction I bought a
mapping table, its top is hinged and made of lexan
and has a 1in.grid over the whole table the table size is 5x8 ft. you can put a drawing or whatever
in it and take a pic, all the co-ordinates are there for taking into corel or turbo cad or whatever you would use . I have used it but rarely
most of the stuff I have to deal with is to small
like a whole page of Japanese text. that has to be enlarged to 3in.

[rgengrave@aol.com]

John do you have the plans or do you have the boat parts?

It will take you 2 minutes to make a part file you need in any cad program.

Every file will have only 2 type of lines, STRAIGHT & CURVED, all you need is a framing square.

1.In a cad program draw a rectangle and then make it to the size of your part in X and Y.

2. Use the framing square to get your pitch and angle, now just add this to the rectangle with a new rectangle or circle and size it.

3. Now after you have it laid out on the screen you will want to group it, then all you do is trace your file with a line or spline tool, then just select the groped item and delete it, you know have a ready to cut file.

Ron V

[threadfx]

Taking from where Bill's barcode wand idea led me...

I seem to remember a little toy car that you could take a crayon, marker, etc. and draw a path on the table and the car would follow it. Must be very simple technology for it to work under those conditions.

For the which comes first the part of the file...

I used to work on the computers at a local boat manufacturer (Celebrity Boats). They weren't very technologically enabled, but they did have a huge CNC router capable of cutting several sheets of marine plywood in a single pass.

When they installed the router, they didn't change the way they built boats. They always built the prototype boat, then took it apart to see how they did it. To get the parts setup for the CNC router, they had a 4'X 8' digitizing tablet. They would spread out a piece or paper over the whole area, then trace the actual parts onto the paper and then go back and digitize the parts from that.

I would assume that large digitizing tablets like that were very, very expensive new, but they might be rather cheap now.

Just some ideas...

Aaron

[wdyasq@yahoo.com]

Once the probe program writes a file, how do it get converted back to a DXF file.

I have looked at my software and don't see a conversion tool.

???? can any one help??

[Wdyasq@yahoo.com]

I need to thank the support staff at shopbot.

Gordon sent me a 'trial' copy of a SBP to DXF converter. I'll have to try it to see if it will do what I need.

Ron

[densull@core.com]

That digitizer at Celebrity Boats (now Bombardier) is one of ours. They retired it for a time while subbing out some of their work, but now plan to have it rebuilt since they again need it. They just called this past week.

We're still building big digitizers, and, yes, they are expensive. They are not mass-produced, but built one or two at a time to fill customer orders. You can see the new 2001 model on our web site at http://skalarcnc.netfirms.com

The digitizers are $10,500.00 for the 4' x 8' model, and $11,900.00 for the 5' x 12'. The 5' x 12' powered table is $4900.00. You can build a table for the 4' x 8' models from plans and files that we furnish.

Don't be discouraged about the prices, however. We offer digitizing services to get your large patterns into DXF files. We charge $40.00 an hour (cheap) and we can usually do several patterns in an hour's time.

You can send us paper tracings of your patterns, and we'll return your files by email. See our web site for more info, or call skalar systems at 937 435 8151.

[threadfx]

Dennis,

Small world...

The last time I saw the digitizer had to be 8+ years ago.

Aaron

[drayrj@buffalostate.com]

I am attempting to scan particular lines on a drawing to determine their exact (x,y) locations.
I have extended the lines to the edges of the drawing so that moving the shopbot in a straight line parallel to the edge will cause the scanner to pass over the extended lines perpendicularly.
The bar code scanner is "normally on", connected to input #1 and seems to be working properly. Input indicator light #1 is highlighted untill the scanner crosses a line at which point input indicator light #1 is no longer highlighted.
With the shopbot positioned so that "MX,60" will cause the scanner to travel over the extended x lines, I tried the following program:
ON INPUT(1,0)Pause 5
MX,60
I had hoped the shopbot would move toward X=60, which it did, pause while I recorded the value, which I did, and resume traveling to the next line etc. It stopped on the first line and did not resume traveling. I then tried:
ON INPUT(1,0)Pause 5
ON INPUT(1,1)MX,60
I got the same result. What do I need? An IF
THEN GOTO ? I would appreciate some help in solving this situation as I was dumb enough to extend the lines on a bunch of drawings thinking this would be sure fire.
Thanks in advance, Red Cap

[beacon14]

try this:

BEGIN:
ON INPUT(1,0) GOTO PAUSE
MX,60
PAUSE:
ON INPUT(1,0)
PAUSE 5
GOTO BEGIN

let me know how it works

[Drayrj@buffalostate.edu]

David J. Buchsbaum aka Beacon 14, I gave your idea a shot and if I typed it in correctly it diddn't work. When the scanner crossed a line it simply kept going. You did, however, get me headed in the right direction.
Here's what eventually worked:

BEGIN:
mx,60
ON INPUT(1,0) GOTO CONTINUE
CONTINUE:
PAUSE 5
ON INPUT(1,1) GOTO BEGIN
GOTO BEGIN


Thanks, Red Cap

[beacon14]

Not sure why my routine didn't work, but I'm glad I helped you get it figured out. I'm not very familiar with the bar code wand - when you pass a line and the 'bot stops, does the switch go back on immediately or does it stay off until the machine continues moving?

[bill.young]

Hi David,

A bar code wand just gives a momentary "blip" when there's a change in contrast, and then the input switch quickly changes back to it's original state. This can cause problems when a wand crosses over a line. It triggers when it goes from the white paper on to the line, and then triggers again when it leaves the line and goes back onto the paper.

Bill

You going to make it to Bill P.'s Camp?

[beacon14]

Thanks Bill for the clarification.
Yes, I'm happy to say that I will be there this year. I'm looking forward to it.

David

[dingwall]

What ever happened to Bill's edge finder routine? I tried to download it today and couldn't find it.

[bill.young]

Hey Sheldon,

They should still be included with the DOS software, but in the Windows software they've been combined with the 3d probing files into a Virtual Tool called the Copy Machine. The routines work the same way they did before but hopefully the new interface makes it easier to make changes and select options...you don't have to go through the process of figuring out which routine you need to use any more. And there's now a help icon to click for Frequently Asked Questions.

You run the Copy Machine by selecting it from the Tools menu or typing TC at the command line.

Bill

[dingwall]

Thanks Bill.

[donchapman]

2001-2005 subject update?
What methods do you boatbuilders,etc. use now to reverse engineer parts too large to scan? I've digitally photographed a disassembled uncopyrighted chair and am thinking about trying Bill Palumbo's method of converting the photos to dxf files and I'm not too concerned with a little bit of optical lens distortion since the copy of the chair doesn't have to be perfect. I have some past experience in raster to vector conversion of photos, graphics, and fonts using Adobe Streamline and mainly remember many hours of tedium, frustration, and ok but not great end results. Just thought I'd ask if anyone has any new improved tips or techniques before I dive in.

[ron brown]

Don,

I've had my best success with tracing over parts in RHINO. Then with tooling in mind, treating it as a new design. On scanned parts I willl try and determine what the original curves SHOULD be and build control points from there. A lot of the pieces I model have a picture with notes and measurements taken for quick reference.

But, with all things CNC... you only need to do it one time.

Ron

[rustnrot]

Hello everyone, I am running the edge finding routine using the conductive tape with rigid probe. It works perfectly. What I cannot get to work is the .dxf file that is created will not open in my cad programs, either BobCAD or Rhino3D. I experimented with this a few months back and finally got the .dxf files to open. Are there some "steps" that need to be added manually to the file so it can be opened? I'm thinking Bill Young gave me some text to add at the beginning of the file so it would open but I simply cannot recall right now.

[bill.young]

Hey Tom,

How about emailing the dxf file to me and I'll see what I can figure out...I don't have BobCAD but do have Rhino.

[rustnrot]

Bill comes to the rescue once again! The problem, folks, is I have been trying to scan only a portion of a pattern, i.e. not all the way around it. I just wanted one edge of it, that's all, I was going to add other edges to it using cad after I imported into cad.

Anyway, since I did not go all the way around the object I need to add the following to the .dxf file at the very end (by using a text editor).

SEQEND
0
ENDSEC
0
EOF