DXF files

[purcell]

I am a potential shopbot owner, but I have a question that I would like answered. I have been working with a shopbot owner who is having trouble with reading dxf files. Can I and how can I take drawings from an architect in dxf format and get them to read on shopbot. Any suggestions greatly appreciated.

[gerald_d]

Ken, let's use a bit of common sense here.....

Say we have simple square drawn with a CAD program, each side 4 inches long, and now we have a dxf file of that.

We take that file over to the ShopBot, which is basically a router, and it has a 0.5" cylindrical bit in the collet/chuck.

How do you expect the ShopBot to respond to the four lines in the DXF file? Must it cut a 4x4 hole, or must it cut around the outside of the 4x4 part? How deep must it cut?

As you can see, it is not a straightforward issue of a ShopBot (or any other CNC machine) simply "reading" a dxf file. This is where CAM programs come in, and you still have to drive those those programs to some extent. The SB is supplied with a CAD/CAM type program as well as a very basic (crude?) dxf to SB converter, but this process is never fully automated.

[bill.young]

Hey Ken,

It's hard to tell much without more details...what software is the architect using to create the file, what is the other ShopBotter using to work with the dxf file, and what exactly is the problem they're having?

AutoCAD is famous for changing it's file formats with every release...one easy thing to try is to get the architect to save in an earlier version of dxf...maybe version 12 depending on what the other ShopBotter is using to create the part files

Bill

[beacon14]

I suggested that Ken post his question here as I did not have enough experience to give him a qualified answer. Let's rephrase the question: What problems have people encoutered with exporting .dxf files between applications, and how have they solved the problem?

Most of the time I can import a .dxf into DesignCad or PartWizard with no problem. Once several years ago a friend e-mailed me a drawing with 4 gear shapes to cut out. When he came to pick them up he asked where was the 5th shape? His drawing had 5 shapes but only 4 came through in the file. We never figured out why.

In this instance, I could open the drawing but had what looked like a jumble of lines and numbers, with pretty colors. Had the client send it in various .dxf and .dwg versions, but all read more or less the same. Well, it turns out the lines imported with a thickness of .75", and the dimension lines were in yellow. Once I changed everything to 0 thickness and black, I could read it just fine (Ken - problem solved!).

[gerald_d]

Disregard my first post, I was barking up the wrong tree.

Let's try and generate a list of instructions to an architect who is going to do a dxf for us....(please add more):

1. Draw everything you want to have cut on one layer. Put dimensions, text, title blocks, on another layer or even better (to save file space) don't send them at all.

2. Use one colour of lines for everything you want cut.

3. Make all lines zero thickness

4. Save in the lowest level dxf available to you.

5. Zip the dxf before e-mailing (much smaller and avoids some problems with Outlook handling dxf mails)

6. Give one reference dimension so that we can check the scale.

7. Get rid of double lines (identical lines placed over each other)

8. Make sure that lines join each other exactly. No overlaps or gaps.

9. Remove shading. (Have had cases where we only got the shading and not the outlines!)

10. Avoid ellipses and splines, stick to straight lines and circular arcs.

11. Keep the file name down to 8 characters (for the DOSsies)

12. If an arc has a radius of over 5 miles, use a straight line instead.

13. Indicate desired orientation to grain direction.

14. Etc..............

Some of the above are not really essential, but they do make life easier for some CAD programmers.

[larry_r]

Recently bought a used 03 model PRT96 and was looking to make Bill Young’s Workstation. He recommends using .750 material, Best I can come up with is .700.

1.Has anyone built it with .700 material with good results?
2.I tried to convert the workstation sbp file into a dxf format using the SB converter so to adjust for the thinner material. It did not work so well. Any suggestions?

[beacon14]

what about using one of those "Plywood" bits which are just under .75" for hardwood plywood? If it's still too big send it out to be sharpened once or twice.

[rhfurniture]

Ken: Easiest path is:
Save as R12 DXF (1 part 1 file)
Import into partwizard (comes with shopbot)
Generate paths (apply cutter compensation) and fiddle.
I usually check it in a text editor at this point.
Cut....!$!

No sweat.

R.

[hespj]

I sometimes find saving as R14 works where R12 doesn't, so don't slavishly use R12.

PartWizard seems to read splines okay so I use these where I want. Converting splines to polylines can introduce gaps at line ends which causes problems.

I usually use black lines on a white background in CAD, but this can cause confusion as other programs draw these same lines as white on a white background, so I try and remember to recolour all lines grey before exporting.

I must say, if we can only import a drawing if we do this, this, this and the other, and then keep all our toes crossed it's a pretty poor show. Surely software has advanced beyond this?

[beacon14]

Here's another one I just ran into. I imported one of the versions of Ken's drawing and was confronted with what looked like a screen full of dots. I noticed that one of the dots looked more like a smudge. By zooming way in on the smudge I discovered that the smudge was the actual drawing, all the dots were just trash. I had to delete the extraneous stuff in order to see what I was working on.

[mikejohn]

John says "I must say, if we can only import a drawing if we do this, this, this and the other, and then keep all our toes crossed it's a pretty poor show."
I think the problem is AutoCad wants you to use Autocad, Corel - corel, Artcam-Artcam and so on.AutoCads .dxf files always work well in AutoCad, but often cause problems elsewhere.
I have found exporting Corel in .eps often gives me good results.
Sometimes I have gone through as many as 4 programs to arrive at a good cutting file.
I agree it's a pain, but I can't see software houses wanting to help us out in the near future, if ever.
............Mike

[rhfurniture]

Actualy I think that a bit of line conversion and organisation can just be a routine preparation for toolpathing - I even have a block of my router table showing hold-down points etc that is great for laying out a job.
What is bad (my opinion) and sometimes downright dangerous is that different programs have different conventions, keyboard shortcuts etc. For instance plunging Z can be +ve (depth of cut) in one environment and -ve (shopbot) in another. Rotational zero can be along the X axis or along the Y with clockwise rotational movement described as -ve or +ve. I know you get used to it but it is confusing, mind consuming, and I have made many mistakes as a result when tired or using a program after a long break.
I am (very) slowly building a set of lsp tools that will make it easy to do simple jobs entirely within autocad - exporting sbp files directly. It will be 2d and 3d (just simple cut paths - no vcarving or mill wizard stuff). If anyone has done this before or wants to help, would be happy to share.
I've looked at tahlcam but it only writes iso gcode - actually I'm using it as a model - kind of tahlcam meets dotsoft.

R.

[wayne_walker]

I have drawn a part in AUTOCAD and saved it as a DXF-R14 and R12. When I go to bring it into Part Wizard to a create a toolpath it says "run time error '13' - type mismatch". The line thickness is set at zero. I have removed the dimentions which did not help.
I have looked in the search section, but did not see anything that will help me out. Anyone have this happen??

Thanks

Wayne

[Brady Watson]

Wayne,
No clue on that one...You can e-mail it to me if you like & I can see if I can get it into PW. If so, I'll send you back a PW .ART file.

-Brady

[artisan]

Wayne, I'm not very familiar with Partwizard as I don't use it....but I know from experience and reading the forum that there are issues when fonts are involved....are there any fonts such as labels or dimensions in your drawing? If so, delete them and try again....D

[wayne_walker]

Brady,
I will send you the file to look at and see if you can see something I am missing. I am still very new to AUTOCAD, so it could be the way I have drawn it!

Darrell,
I went in and removed all of the dimensions and that did not seem to help.

Thanks for you input.

Wayne

[mikejohn]

Wayne
If you wish I am willing to look at the AutoCad side of the problem.

...............Mike

[bcammack]

That part about converting really, really large radii to straight lines is sage advice. I can speak from experience that a G3 command with a 4.6 mile radius will make a $100,000 OMAG stop in its tracks and cry for momma. It's not just a ShopBot thing.

[mikejohn]

OK
Wayne sent me his .dxf file. I looked at it in AutCad, did nothing to it, re-saved it as version R14, put it in Part Wizard, created a 'cut along vector' file and it worked fine (even in inches
)
So that doesn't help Wayne at all.
I did notice minor problems with the file. in two places there is a gap.
I have exchanged emails with Wayne, and will post here a very simple lesson on how to re-create his file.
Then Wayne can try it, see if it works.

..........Mike

[mikejohn]

Gentlemen
What follows is basic, for someone new to AutoCad as Wayne is. Maybe it will help other newbies.
There is more than one way to create the same drawing in AutoCad, in any Cad, this is my way.

4564
This is the drawing Wayne sent to me.
There are gaps where the two red circles are, the arc with the green circle is exactly 1" radius, the others are different. The two yellow lines are straight (ortho the rest are not) All dimensions are very close to, but not exactly, on the inch or half inch. I assume that the drawing is supposed to be 'square', symmetrical, and all lengths accurate to the half inch.

4565
Not a great picture!!

(Top left)
[Ortho 'on', Snap 'on]
draw a short upright line (white)
offset it 9 inches.
Connect the lines (red)

Top right
Erase the first two white lines.
Offset the red line 6" (green)
Connect the ends of the red and green lines (yellow)
Offset these yellow and green lines outside by .5"

Bottom left
Offset the top and right line by 1" inwards.
Construct a circle with centre where these two lines cross, 1" radius. (red(

Bottom right
trim of inner 3/4 of circle, ends of the green and yellow lines, remove inner green and yellow lines.



4566

Top left
Offset red line 1", then move it right.
Extend outer yellow line to meet red line.

Top right
Mirror top right arc, selecting 'mid' point of upper green line, second point above (Ortho 'on').
Mirror both arcs, selecting 'mid' point of right, extended, yellow line, 2nd point left (Ortho 'on').

Bottom left
Remove the red line that you moved right earlier.
Extend outer left line to meet bottom right arc.
Trim lines from top left arc.
Construct construction line between bottom arcs. offset this .5" inside

Bottom right

Draw arc from left side of construction line, to 'mid' point of offset construction line, to right end of construction line.
Remove construction lines.

Not shown on drawing is to extend the first line you drew (red) left and right to join outer yellow lines.

I apologise again for poor reproductions of the graphics, and if this is very simple for many.
I save as R14, it works for me.

...........Mike

[gerald_d]

Havn't used ORTHO for years. Use Polar Tracking instead (45 deg increments).

[mikejohn]

Gerald
You did use it as a learner though

[wayne_walker]

Mike,

Thanks for the responce to my CAD problem. I thought I had a problem with the drawing but could not find it. I will go thru your process to draw the pattern and see how it goes.

Thanks,

Wayne