View Full Version : AutoCad 2007

26-07-2012, 12:40 PM
Hey guys im trying to master AutoCAd a little more.

I have one major problem, when im saving the file the plasma does not like it what so ever! god know why!

Also is there a way to get the torch to start in the center of of a cut out?


Web Goblin
26-07-2012, 01:48 PM
What cnc control are you using? Have you assigned the lead-ins, lead-outs, inner and outer contours to different layers in autocad?
Normally if you wanted the cut to start in a specific position then thats where you would start your lead-in from.

26-07-2012, 02:01 PM
To be honest im not sure. the machine is a blue marlin from techserve so its the techserve software which has a DXF to Gcode plugin

26-07-2012, 02:03 PM
This is the file... maybe you can see whats wrong with it?

26-07-2012, 02:10 PM
its would be ideal if i could draw the part in corel (wizz my way round that) and export to another program to create the proper dxf.... is there anything that can do this?

Web Goblin
26-07-2012, 03:26 PM
I think it is because you have used polylines and splines to create the parts of the drawing. I havent met a conversion program yet thet will handle them correctly for profiling. If you draw all of your parts as lines, arcs, and circles you cant go wrong.
Try this test program to see if it works for you.
The drawing is made using my layer template which I use for all of my cad drawings. It consists of all the seperate layers I need to make a valid drawing for my post processor. If you want to keep this layer template simply erase the drawing and then save the empty drawing as a layer template. Then when you want to make another drawing simply start from loading the layer template and draw everything using it, then simply rename the file when you are saving it so that you dont overwrite the template file.


Robin Hewitt
26-07-2012, 11:51 PM
Your part is easy to draw with AutoCAD.

Here it is step by step.

First set your snap to something useful like 1mm. Type SNAP spacebar 1 spacebar
You are now working to a grid so everything is neat and tidy.

Useful Function keys are F8 which toggles Ortho and F9 which toggles SNAP

The spacebar repeats the last command. The ESCape key will unselect everything you have selected.

To select items pick them individually or drag a box around them. If you start dragging from left to right you get only items fully inside the box. If you start dragging right to left you select anything even partly inside the box. If you pick individual items but are only able to select one, type PICKADD spacebar ON spacebar

Draw the round ended slots horizontally. Put in a circle, select it, click Copy and copy it across to the other end. Watch the bottom of the screen, it will tell you how far you have gone. Draw a rectangle to get the two sides. Select all 3 components and click on Trim. Click the bits you don't want and they disappear.

Select all four components of the finished slot and click Copy. Stick copies wherever you want.

Add the circle. Click circle, the default is centre then radius. Click for the centre, type in the radius.

Add the 45 degree rectangle. Select everything so far. Click Rotate. When it asks for the basepoint type Center (American spelling) then click on the circle. Type -45 for the angle, AutoCAD defaults to counter clockwise so you put in negative angles if you want clockwise.

Draw the other rectangle.

Select both rectangles and use Trim to lose the bits you don't want.

Select both rectangles and type Explode so they become lines.

To radius the corners click Fillet
Tell it the corner radius is 8 by typing R spacebar 8 spacebar
Click any two lines and get the fillets.
Press the space bar to repeat the last command, no need to do the r 8 bit again.

27-07-2012, 12:46 AM
Wow thanks for taking the time to write that robin!! I will most certainly give that a try tomorrow.

27-07-2012, 08:54 AM
Thanks Robin i felt like a VAD genius for 15 mins there thats awesome! you dont know of any good tutorials to draw 2D do you, just basic shapes etc like this one so i can get the hang of it?

One thing i struggle to understand is how you draw a fresh part in A/C as i would have no refrence points. in Corel its a lot easier to drag and drop lol

Robin Hewitt
27-07-2012, 09:57 AM
You usually start with a drawing on the back of an envelope, it has dimensions. Construction lines are your friend to set a base point. A construction line goes on forever so you can zoom out and select the lot with two right to left selection boxes then press the Delete key to make them all go away.

Put in two construction lines, one vertical, one horizontal and you have a basepoint. If they draw at whacky angles press F8 to turn ortho on and constrain them.

COPY the construction lines to the measurements on the envelope and you have reference points where they intersect. I usually do my construction lines in deep blue so I can recognise them for what they are.

To get the slots evenly spaced around the circle I'd draw one centered on the circle, move it left, move it up. Then use the MIRROR command twice, CENTERed on the circle, to turn one in to four.

When locating stuff I tend to draw lots of unnecessary lines and circles then delete then after they have served their purpose. If you want a line to start from the middle of something, type LINE MID then hover the mouse over it, easy to start the line at half the SNAP grid dong that but you can figure it out.

Edit: Forgot to mention END gets you exactly on the end of something. PERP will take you to a perpendicular on the object you select. If you press the spacebar when it asks you for a startpoint it locates you to the end of the last item you drew.

Type in a command and the command box at the bottom of the screen tells you what AutoCAD wants and gives you options. The command box dates from when AutoCAD used two screens, one for the graphics, one for the text. It is so useful it never went away.

If you play with it you will soon get the idea.

Incidentally it doesn't care whether you use upper or lower case. The spacebar is the same as the Enter key unless you are inserting a block.

04-08-2012, 12:00 AM
I think it is because you have used polylines and splines to create the parts of the drawing. I havent met a conversion program yet thet will handle them correctly for profiling.

Splines = BAD
Polylines = Good

I use polylines exclusively and Vectric's software works 100% of the time with my drawings.

Say you have a rectangular shape, and you want to start in the middle of the edge.
Here's what I do.

First, draw the rectangle. This will be used as a base for the final part.
Using the polyline tool, use a Midpoint or Nearest snap at the point you want to start. Then, click on the endpoints in the order (direction) you want the tool to go (Use running OSNAPS with Endpoint turned on). After clicking the last endpoint, hit "Enter" to exit the command. Now, delete the original rectangle, which should be visible in the open section of the new , open, rectangle. Then, select the new one, right click and choose polyline edit, and choose close.
Save as .v12 dxf and you should be good to go.

I actually use a macro (http://home.comcast.net/%7Ecncwoodworker/AC2GC.html) that I wrote which exports g-code from within AutoCAD.

Robin Hewitt
04-08-2012, 10:02 AM
I actually use a macro (http://home.comcast.net/%7Ecncwoodworker/AC2GC.html) that I wrote which exports g-code from within AutoCAD.

Well done, most impressed. I baulked at working from within AutoCAD and took a different tack. I read a .dxf file and a .txt file that defines the missing parameters. I drive the mill directly, no G-code at all.

I looked at polylines, figured out how one magic number could define an arc but never wrote the interpreter. I just explode them before I export.

I found the trickiest bit was where the tool was too big to fit in all the little nooks and crannies, meaning I had to discard lots of entities. I did it, nearly, but should a pocket have a constriction below tool diameter I only get half of it. I found picking up on a sub-pocket surprisingly tricky, too easy to get phantoms. Remembering that a subsequent tool might have to do waste removal only on the uncut section was beyond me.

05-08-2012, 02:35 PM
Thanks. :smile:
For me, using polylines means I didn't have to figure out how to join lines and arcs. The downside is that it forces the user to know exactly what he wants to do, as you basically are drawing your toolpaths. It took me about a week to get that magic number (Bulge) into IJ g-code.

I try to avoid as much math as possible. So there's no pocketing, other than circles, which are easy. I rarely do any other pocketing, and if I need to, it only takes a minute or two to draw the pocket toolpaths. (A few offsets, and then trace with a polyline).

I have a test version that let's me assign machining order to entities, and have plans for multiple tools. But I'll probably need to learn VB.net first, as I've found that 64bit AutoCAD does not run VBA code as efficiently as 32bit AutoCAD does.

Robin Hewitt
05-08-2012, 03:31 PM
I probably wouldn't know VBA if it jumped up and bit me in the knee, sounds like AutoCAD will remain a closed door to me.

Perhaps that is why you had problems stitching lines and arcs in to closed loops, it's easy in C#.
I wanted everything defined in the drawing and one easy to edit text file so I could avoid a whole mess of buttons :beer:

05-08-2012, 04:15 PM
Perhaps that is why you had problems stitching lines and arcs

With polylines, there was no need to attempt it, so no problems. :smug:

Robin Hewitt
05-08-2012, 05:51 PM
Can't argue with that :very_drunk: