One of the frequent insults hurled at Autocad is that it is not an intelligent program.
Problems with Xrefs
I have tried to steer my drafting life clear of xrefs, for the reason that when I'm gone, some IT Preventer
of Information technology will rename the main network drive or someone else will rename directories. All this will cause blank drawings to appear! Having said that, maybe the idea of "relative paths" is a good approach. Of course, if you have the files all in the same directory, then this is not a problem.
Say you have an item, say a magnet box, and this is to be placed in a layout, then the only
way to keep any automatic updating is to use the Xref mechanism in Autocad. This means that the item being
xreffed in needs to be "pure", that is, it has to be just a 3d model and no more.
This then means that you cannot have things like section planes in that model, or any other extras like 2D sketches.
Organizing your Assembly to go into a Layout Drawing
Yes, you can organise your magnet box drawing to be a series of layout tabs for each of the parts.
There are problems with this approach though: You have to have all your parts with distinct layer
names so that you can use freezing and thawing on a per viewport basis, and while this is possible,
setting it all up seems time consuming.
I have devised a layering system that copes with multi-level layouts. It makes layers like:
LEVEL 1 - FLOOR
LEVEL 1 - INTERIOR WALLS
LEVEL 1- PIPING
LEVEL 1 - BEAMS
....and so on. This seems to work well, and is heavily reliant on lisp routines to make it go.
The advantage is that there is a structure to the layer naming.
To tie this all in with the layer names you have to create for the above system is also a pain.
This can be got around by calling layers names like MAGNET BOX LID LEVEL 1, and when the xref turns up in the layout, then the lisp line becomes (command "-layer" "t" "*LEVEL 1*" "") ie it uses the * as wild cards.
Any Other Options?
One that might deserve some consideration, is to have a "pure" model, in which every item is on layer 0, so that when it arrives in the xref, it picks up the layer it is to be, and appears in the correct colours for that layer. Simple.
To enable parts drawings, this pure model would have all the individual parts (each a separate drawing file)
xreffed into it.
The nice thing about this system is that you could have a separate assembly drawing of the magnet box, and
any sub-assemblies could be easily arranged. In the assembly drawing you can go ahead and do sections.
OK, so what is the downside? A great pile of autocad drawing files is what you would end up with, instead
of one drawing with heaps of layout tabs on it. Coping with printing out a drawing set is probably not as
bad as it seems, as you can use saved sheet sets to deal with this. Your drawing register then becomes
a large clerical pain to fill out, that is if you decide to go down that route. To avoid this bureaucracy,
an alternative to listing them in a separate register could be to maybe keep them in a directory,
labelled say "150905 Magnet Box". In the drawing register, all you need is one entry:"150905 - Magnet Box".
Only the "pure" model, with a file name of 150905.dwg would appear in the main directory.
Saturday, April 20, 2013
Saturday, March 30, 2013
Drawing an archimedes screw in Autocad
Recently, a man at my work wanted me to draw the junction of a double screw conveyor. It was a long screw conveyor, and had a hanger bearing in the middle that was causing some trouble. This was the junction.
In the "olden days" I used to use a 2D lisp routine to draw a screw conveyor. This was my first request since those days to actually draw a screw. Usually we just draw the outside casing and this is all you really need, unless you are a manufacturer of screw conveyors.
No worries, I thought, I'll just draw a helix, and sweep a rectangle along the helix. Yes, it is that simple. If you have release 13 that is! At work I am on release 12 and spent 2 hours trying to persuade Autocad to this. In the end I googled it. Humf! It appears no easy "how to do it" is there. The nearest I got was someone drawing an acme screw thread.
After about 2 hours I discovered you could do it, but you had to input in a value for twist of about 30 degrees.
On another subject, my website, bilrocad.com seems in for the chop. At one stage I had advertising on it and thought it might pay it's way. This was not to be. The people at BlueHost did give me an extra year for free though.
Anyway, here is my method for release 13:
1. Draw a shaft - usually these are from 80NB pipe, ie about 89mm outside diameter, say 3000mm high.
2. Draw helix. In my example, I used a base and top radius of 123.75mm, 10 turns and a height of 3000mm.
3. Draw a rectangle. I drew one 158.5mm x 10mm so that my outside diameter would end up around 406mm.
4. Issue the sweep command, pick the rectangle and then pick the helix: Job done!
In the "olden days" I used to use a 2D lisp routine to draw a screw conveyor. This was my first request since those days to actually draw a screw. Usually we just draw the outside casing and this is all you really need, unless you are a manufacturer of screw conveyors.
No worries, I thought, I'll just draw a helix, and sweep a rectangle along the helix. Yes, it is that simple. If you have release 13 that is! At work I am on release 12 and spent 2 hours trying to persuade Autocad to this. In the end I googled it. Humf! It appears no easy "how to do it" is there. The nearest I got was someone drawing an acme screw thread.
After about 2 hours I discovered you could do it, but you had to input in a value for twist of about 30 degrees.
On another subject, my website, bilrocad.com seems in for the chop. At one stage I had advertising on it and thought it might pay it's way. This was not to be. The people at BlueHost did give me an extra year for free though.
Anyway, here is my method for release 13:
1. Draw a shaft - usually these are from 80NB pipe, ie about 89mm outside diameter, say 3000mm high.
2. Draw helix. In my example, I used a base and top radius of 123.75mm, 10 turns and a height of 3000mm.
3. Draw a rectangle. I drew one 158.5mm x 10mm so that my outside diameter would end up around 406mm.
4. Issue the sweep command, pick the rectangle and then pick the helix: Job done!
Thursday, January 3, 2013
Sheetmetal-Pretty Basic
Vanilla Autocad does not have a trick for doing simple folded sheet metal developments.
(Hey, we're only up to Release 18 or so, maybe in release 44....)
When I say simple, I mean a piece of sheet metal with one fold or two folds, both at 90 degrees.
Maybe I am the only draftee on the planet that sometimes does this, but it is always a painfully slow process when I do.
To do this manually, I draw an end on view as above, using polylines. I then would offset
the inner polyline to create a neutral axis, by half the metal thickness. In other words, the "K" factor I was using was 0.5. Which for steel should have been 0.4. I only realised this by looking up "sheetmetal developments" on the web, here is a good link, even if it is 1998! (In the link he does something similar, but to my mind, not as useful as my one.)
http://www.oocities.org/wpsmoke/acadsheetmetal/paper.html
The length of the neutral axis polyline is the length of the development. To get the position of the fold lines, I used to use midpoint snap to put a line on the corner and used it to trim the pline:
Then it was just a matter of clicking on that pine and checking out it's length on the properties palette, to give me the position of the fold line.
All this horsing around: surely I have better things to do? The upshot is an afternoon spent doing the following Lisp routines, which have not been fully tested by hordes of draftees, (apart from me!). So if you like to try them, make sure you cross check the first few by doing the manual stuff above.
To make sure you can check what you keyed in, a piece of text is generated at the end, and put on Defpoints layer (ie it does not print, but you can see it on the screen).
It uses the layer names "MED" for medium thickness lines, "hid" for hidden lines -ie the fold line , and "dim"
for the dimension lines. If these layers are not there, it should still work.
(Feed back??? Anyone out there????Hullooooo??)
A typical output in Autocad looks like this:
Here are the two routines: (cut and paste from here into Notepad.)
(These routines are free)
;Program written by Bill Le Couteur
;Auckland NZ
;Rev 0 date 3 JAN 2013
;THIS PROGRAM DOES ONLY SIMPLE SHEETMETAL BEND OF A 90 DEG BEND - U SHAPED TROUGH-BOTH UPSTANDS EQUAL
(defun c:DEVU()
(setvar "osmode" 0)
(setq KFactor 0.4)
(setq MetalThickness (getreal "\n Enter Metal Thickness"))
(setq InnerBendRadius MetalThickness)
(setq Length1 (getreal "\n Enter Upstand - Outside Dim"))
(setq Length2 (getreal "\n Enter Middle Section - Outside Dim"))
(setq MiddleSection Length2);;;keep this for later use in text
(setq MiddleSections (rtos MiddleSection))
(setq Length2 (/ Length2 2))
(setq TheWidth (getreal "\n Enter the width"))
(setq NeutralInnerOffset (* KFactor MetalThickness))
(setq NeutralOuterOffset (- MetalThickness NeutralInnerOffset))
(setq NeutralBendArcRad (+ NeutralInnerOffset InnerBendRadius))
(setq Length1Neutral (- (- Length1 NeutralBendArcRad) NeutralOuterOffset))
(setq Length2Neutral (- (- Length2 NeutralBendArcRad) NeutralOuterOffset))
(setq ArcLength (/ (* pi 2 NeutralBendArcRad) 4))
(setq DevLength (+ Length1Neutral Length2Neutral Length2Neutral ArcLength ArcLength Length1Neutral))
(setq HalfArcLength (/ ArcLength 2))
(setq DistanceToFold (+ Length1Neutral HalfArcLength))
(setq FarDistanceToFold (- DevLength DistanceToFold))
(setq TheOrigin (getpoint "\n Pick a point for the development"))
(command "UCS" "n" TheOrigin )
(if (tblsearch "layer" "MED") (command "layer" "s" "MED" ""))
(command "_rectangle" "0,0" (list DevLength TheWidth))
(if (tblsearch "layer" "dim") (command "layer" "s" "dim" ""))
(command "_dimlinear" "0,0" (list DevLength 0) "0,-50" )
(command "_dimlinear" "0,0" (list 0 TheWidth) "-50,0" )
(command "_dimlinear" "0,0" (list DistanceToFold 0) "0,-25" )
(command "_dimlinear" (list FarDistanceToFold 0) (list DevLength 0) "0,-25" )
(command "-text" (list DistanceToFold 20) "" "90" "BEND UP 90%%D")
(command "-text" (list FarDistanceToFold 20) "" "90" "BEND UP 90%%D")
(if (tblsearch "layer" "hid") (command "layer" "s" "hid" ""))
(command "_line" (list DistanceToFold 0) (list DistanceToFold TheWidth) "")
(command "_line" (list FarDistanceToFold 0) (list FarDistanceToFold TheWidth) "")
;;;;;;;;;;;;;;;NOW DOING THE TEXT TO ENABLE CHECKING THE INPUT DATA;;;;;;;;;;;;;;;;;;;;;
(command "layer" "s" "Defpoints" "")
(command "UCS" "W" )
(setq apt (getpoint "\nInsertion Point for Text: "))
(setq TheText "Data for this development input as follows: ")
(setq MetalThicknesss (rtos MetalThickness))
(setq Length1s (rtos Length1))
(setq Length2s (rtos Length2))
(setq TheWidths (rtos Thewidth))
(setq booText (strcat TheText "\nThickness: " MetalThicknesss "\nUpstand : " Length1s "\nMiddle Section : " MiddleSections "\nWidth : " TheWidths "\nK Factor Used is 0.4"))
(command "UCS" "n" apt )
(command "-mtext" "0,0" "200,-100" booText "")
(command "UCS" "W" )
(command "layer" "s" "0" "")
(princ)
)
Here is the other Routine:
;Program written by Bill Le Couteur
;Auckland NZ
;Rev 0 date 3 JAN 2013
;THIS PROGRAM DOES ONLY SIMPLE SHEETMETAL BEND OF A 90 DEG BEND ANGLE
(defun c:DEVL()
(setvar "osmode" 0)
(setq KFactor 0.4)
(setq MetalThickness (getreal "\n Enter Metal Thickness"))
(setq InnerBendRadius MetalThickness)
(setq Length1 (getreal "\n Enter Outer Length 1"))
(setq Length2 (getreal "\n Enter Outer Length 2"))
(setq TheWidth (getreal "\n Enter the width"))
(setq NeutralInnerOffset (* KFactor MetalThickness))
(setq NeutralOuterOffset (- MetalThickness NeutralInnerOffset))
(setq NeutralBendArcRad (+ NeutralInnerOffset InnerBendRadius))
(setq Length1Neutral (- (- Length1 NeutralBendArcRad) NeutralOuterOffset))
(setq Length2Neutral (- (- Length2 NeutralBendArcRad) NeutralOuterOffset))
(setq ArcLength (/ (* pi 2 NeutralBendArcRad) 4))
(setq DevLength (+ Length1Neutral Length2Neutral ArcLength))
(setq HalfArcLength (/ ArcLength 2))
(setq DistanceToFold (+ Length1Neutral HalfArcLength))
(setq TheOrigin (getpoint "\n Pick a point for the development"))
(command "UCS" "n" TheOrigin )
(if (tblsearch "layer" "MED") (command "layer" "s" "MED" ""))
(command "_rectangle" "0,0" (list DevLength TheWidth))
(if (tblsearch "layer" "dim") (command "layer" "s" "dim" ""))
(command "_dimlinear" "0,0" (list DevLength 0) "0,-50" )
(command "_dimlinear" "0,0" (list 0 TheWidth) "-50,0" )
(command "_dimlinear" "0,0" (list DistanceToFold 0) "0,-25" )
(command "-text" (list DistanceToFold 20) "" "90" "BEND UP 90%%D")
(if (tblsearch "layer" "hid") (command "layer" "s" "hid" ""))
(command "_line" (list DistanceToFold 0) (list DistanceToFold TheWidth) "")
;;;;;;;;;;;;;;;NOW DOING THE TEXT TO ENABLE CHECKING THE INPUT DATA;;;;;;;;;;;;;;;;;;;;;
(command "layer" "s" "Defpoints" "")
(command "UCS" "W" )
(setq apt (getpoint "\nInsertion Point for Text: "))
(setq TheText "Data for this development input as follows: ")
(setq MetalThicknesss (rtos MetalThickness))
(setq Length1s (rtos Length1))
(setq Length2s (rtos Length2))
(setq TheWidths (rtos Thewidth))
(setq booText (strcat TheText "\nThickness: " MetalThicknesss "\nLength 1: " Length1s "\nLength 2: " Length2s "\nWidth : " TheWidths "\nK Factor Used is 0.4"))
(command "UCS" "n" apt )
(command "-mtext" "0,0" "200,-100" booText "")
(command "UCS" "W" )
(command "layer" "s" "0" "")
(princ)
)
Happy developing!
(Hey, we're only up to Release 18 or so, maybe in release 44....)
When I say simple, I mean a piece of sheet metal with one fold or two folds, both at 90 degrees.
Maybe I am the only draftee on the planet that sometimes does this, but it is always a painfully slow process when I do.
the inner polyline to create a neutral axis, by half the metal thickness. In other words, the "K" factor I was using was 0.5. Which for steel should have been 0.4. I only realised this by looking up "sheetmetal developments" on the web, here is a good link, even if it is 1998! (In the link he does something similar, but to my mind, not as useful as my one.)
http://www.oocities.org/wpsmoke/acadsheetmetal/paper.html
The length of the neutral axis polyline is the length of the development. To get the position of the fold lines, I used to use midpoint snap to put a line on the corner and used it to trim the pline:
All this horsing around: surely I have better things to do? The upshot is an afternoon spent doing the following Lisp routines, which have not been fully tested by hordes of draftees, (apart from me!). So if you like to try them, make sure you cross check the first few by doing the manual stuff above.
To make sure you can check what you keyed in, a piece of text is generated at the end, and put on Defpoints layer (ie it does not print, but you can see it on the screen).
It uses the layer names "MED" for medium thickness lines, "hid" for hidden lines -ie the fold line , and "dim"
for the dimension lines. If these layers are not there, it should still work.
(Feed back??? Anyone out there????Hullooooo??)
A typical output in Autocad looks like this:
Here are the two routines: (cut and paste from here into Notepad.)
(These routines are free)
;Program written by Bill Le Couteur
;Auckland NZ
;Rev 0 date 3 JAN 2013
;THIS PROGRAM DOES ONLY SIMPLE SHEETMETAL BEND OF A 90 DEG BEND - U SHAPED TROUGH-BOTH UPSTANDS EQUAL
(defun c:DEVU()
(setvar "osmode" 0)
(setq KFactor 0.4)
(setq MetalThickness (getreal "\n Enter Metal Thickness"))
(setq InnerBendRadius MetalThickness)
(setq Length1 (getreal "\n Enter Upstand - Outside Dim"))
(setq Length2 (getreal "\n Enter Middle Section - Outside Dim"))
(setq MiddleSection Length2);;;keep this for later use in text
(setq MiddleSections (rtos MiddleSection))
(setq Length2 (/ Length2 2))
(setq TheWidth (getreal "\n Enter the width"))
(setq NeutralInnerOffset (* KFactor MetalThickness))
(setq NeutralOuterOffset (- MetalThickness NeutralInnerOffset))
(setq NeutralBendArcRad (+ NeutralInnerOffset InnerBendRadius))
(setq Length1Neutral (- (- Length1 NeutralBendArcRad) NeutralOuterOffset))
(setq Length2Neutral (- (- Length2 NeutralBendArcRad) NeutralOuterOffset))
(setq ArcLength (/ (* pi 2 NeutralBendArcRad) 4))
(setq DevLength (+ Length1Neutral Length2Neutral Length2Neutral ArcLength ArcLength Length1Neutral))
(setq HalfArcLength (/ ArcLength 2))
(setq DistanceToFold (+ Length1Neutral HalfArcLength))
(setq FarDistanceToFold (- DevLength DistanceToFold))
(setq TheOrigin (getpoint "\n Pick a point for the development"))
(command "UCS" "n" TheOrigin )
(if (tblsearch "layer" "MED") (command "layer" "s" "MED" ""))
(command "_rectangle" "0,0" (list DevLength TheWidth))
(if (tblsearch "layer" "dim") (command "layer" "s" "dim" ""))
(command "_dimlinear" "0,0" (list DevLength 0) "0,-50" )
(command "_dimlinear" "0,0" (list 0 TheWidth) "-50,0" )
(command "_dimlinear" "0,0" (list DistanceToFold 0) "0,-25" )
(command "_dimlinear" (list FarDistanceToFold 0) (list DevLength 0) "0,-25" )
(command "-text" (list DistanceToFold 20) "" "90" "BEND UP 90%%D")
(command "-text" (list FarDistanceToFold 20) "" "90" "BEND UP 90%%D")
(if (tblsearch "layer" "hid") (command "layer" "s" "hid" ""))
(command "_line" (list DistanceToFold 0) (list DistanceToFold TheWidth) "")
(command "_line" (list FarDistanceToFold 0) (list FarDistanceToFold TheWidth) "")
;;;;;;;;;;;;;;;NOW DOING THE TEXT TO ENABLE CHECKING THE INPUT DATA;;;;;;;;;;;;;;;;;;;;;
(command "layer" "s" "Defpoints" "")
(command "UCS" "W" )
(setq apt (getpoint "\nInsertion Point for Text: "))
(setq TheText "Data for this development input as follows: ")
(setq MetalThicknesss (rtos MetalThickness))
(setq Length1s (rtos Length1))
(setq Length2s (rtos Length2))
(setq TheWidths (rtos Thewidth))
(setq booText (strcat TheText "\nThickness: " MetalThicknesss "\nUpstand : " Length1s "\nMiddle Section : " MiddleSections "\nWidth : " TheWidths "\nK Factor Used is 0.4"))
(command "UCS" "n" apt )
(command "-mtext" "0,0" "200,-100" booText "")
(command "UCS" "W" )
(command "layer" "s" "0" "")
(princ)
)
Here is the other Routine:
;Program written by Bill Le Couteur
;Auckland NZ
;Rev 0 date 3 JAN 2013
;THIS PROGRAM DOES ONLY SIMPLE SHEETMETAL BEND OF A 90 DEG BEND ANGLE
(defun c:DEVL()
(setvar "osmode" 0)
(setq KFactor 0.4)
(setq MetalThickness (getreal "\n Enter Metal Thickness"))
(setq InnerBendRadius MetalThickness)
(setq Length1 (getreal "\n Enter Outer Length 1"))
(setq Length2 (getreal "\n Enter Outer Length 2"))
(setq TheWidth (getreal "\n Enter the width"))
(setq NeutralInnerOffset (* KFactor MetalThickness))
(setq NeutralOuterOffset (- MetalThickness NeutralInnerOffset))
(setq NeutralBendArcRad (+ NeutralInnerOffset InnerBendRadius))
(setq Length1Neutral (- (- Length1 NeutralBendArcRad) NeutralOuterOffset))
(setq Length2Neutral (- (- Length2 NeutralBendArcRad) NeutralOuterOffset))
(setq ArcLength (/ (* pi 2 NeutralBendArcRad) 4))
(setq DevLength (+ Length1Neutral Length2Neutral ArcLength))
(setq HalfArcLength (/ ArcLength 2))
(setq DistanceToFold (+ Length1Neutral HalfArcLength))
(setq TheOrigin (getpoint "\n Pick a point for the development"))
(command "UCS" "n" TheOrigin )
(if (tblsearch "layer" "MED") (command "layer" "s" "MED" ""))
(command "_rectangle" "0,0" (list DevLength TheWidth))
(if (tblsearch "layer" "dim") (command "layer" "s" "dim" ""))
(command "_dimlinear" "0,0" (list DevLength 0) "0,-50" )
(command "_dimlinear" "0,0" (list 0 TheWidth) "-50,0" )
(command "_dimlinear" "0,0" (list DistanceToFold 0) "0,-25" )
(command "-text" (list DistanceToFold 20) "" "90" "BEND UP 90%%D")
(if (tblsearch "layer" "hid") (command "layer" "s" "hid" ""))
(command "_line" (list DistanceToFold 0) (list DistanceToFold TheWidth) "")
;;;;;;;;;;;;;;;NOW DOING THE TEXT TO ENABLE CHECKING THE INPUT DATA;;;;;;;;;;;;;;;;;;;;;
(command "layer" "s" "Defpoints" "")
(command "UCS" "W" )
(setq apt (getpoint "\nInsertion Point for Text: "))
(setq TheText "Data for this development input as follows: ")
(setq MetalThicknesss (rtos MetalThickness))
(setq Length1s (rtos Length1))
(setq Length2s (rtos Length2))
(setq TheWidths (rtos Thewidth))
(setq booText (strcat TheText "\nThickness: " MetalThicknesss "\nLength 1: " Length1s "\nLength 2: " Length2s "\nWidth : " TheWidths "\nK Factor Used is 0.4"))
(command "UCS" "n" apt )
(command "-mtext" "0,0" "200,-100" booText "")
(command "UCS" "W" )
(command "layer" "s" "0" "")
(princ)
)
Happy developing!
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