Saturday, April 17, 2010

The disappearing draftsman, slips and trips, and DS and DIMLO

First, The Disappearing Draftsman. Last week I had an interesting viewpoint explained to me by an engineer I'm working with. He had gone ahead and done his own PID's, but needed me to knock them into shape so that they would be presentable, which took a day to do. I'm not sure how long he spent on them, I would imagine at least 4-5 days.

He explained that he found that he could use Autocad as a faster, easier way of producing a sketch of what he wanted than doing a hand sketch. Plus there was an added advantage that the draftsman was only required to do a short "tarting up". The last place he worked, there was a proper drafting department, and they were probably grumpy that he was doing part of their work.

Here at his new work, there is no drafting dept (only me, 2-3 days a month!). So he has to manage somehow.

I have done a few PIDs, but would hardly call myself an expert, so I was interested to hear his take on how they should be done. He reckons, at the quotation stage, you just insert symbols, and leave it at that. You do not use symbols with lots of hidden attributes so that at a future date you can extract a full Equipment List from the job.

The generation of tag numbers, he said, should be the preserve of the Electrical guys, who make a large database. When they have done their thing, and the job is a go, then you can put the tags on.

Slips and trips: I recently had a reasonably complex design to draft. It was a "bag massager".
I came unstuck in one of my drawings: the 20mm plates welded onto a 100x100 axle, somehow got moved by 100mm, this was only in the detail drawing- the main ass'y drawing was correct.

Which made me think: could this have happened in Inventor? Probably not. But I'm stuck with Autocad, so what could I do to prevent this happening again? My only idea is that I make it policy with any assembly to xref in all the parts.

DS and DIMLO: Yet another engineer, at a different plant, has arrived, and he seems keen on doing his own drawings. That is OK by me, because less time working=more time living. He seems pretty good, just a little polishing required in the dimensions department. Namely, he had large arrows and tiny text on his dimensions.

I explained to him the system I use-but I'm not sure he was at all in favour of it, which is to use 2 lisp routines, DS.lsp to set the text height and DIMLO.lsp to insert, then erase a block that has most dimensions styles a mechanical draftsman might need.

In the past done I have done things differently-see a previous post about zero height text.

Here are the two routines:


;This routine sets up for text to be right height
;By Bill Le Couteur
(defun c:DS()
(setq skale (getreal "Please enter the plotted scale: "))
(command "-style" "STANDARD" "ARIAL" "0" "1" "0" "" "" )
(tblsearch "style" "R1")(command "-style" "R1" "ARIAL" "0" "1" "0" "" "" ""))
(if (tblsearch "style" "R1-25")(command "-style" "R1-25" "ARIAL" "0" "1" "0" "" "" ""))
(if (tblsearch "style" "R2")(command "-style" "R2" "ARIAL" "0" "1" "0" "" "" ""))
(if (tblsearch "style" "R5")(command "-style" "R5" "ARIAL" "0" "1" "0" "" "" ""))

(setvar "MIRRTEXT" 0)

(setq the_textsize (* skale 3))
(setvar "textsize" the_textsize)
(setvar "dimassoc" 2)

The nice thing about this is if you have an existing drawing an someone has used the style R5 say, then you can change that at the same time as well.

Here is DIMLO.lsp

;This routine sets up for dims and text;
By Bill Le Couteur
;imports a dummy block containing a set of dimension styles
(defun c:Dimlo()
(command "-insert" "c:/cad/library/symbols/dimension styles" "0,0" "1" "1" "0")
(command "erase" "l" "")

A very simple routine-I have no idea why Autodesk don't have a magic button that does all this...

Of course, many will argue that you need to set up your prototype drawing nicely, with all the needed scales and the text the right size, and this is correct, except what happens when you change scales? As well, if you purge the drawing your nicely setup scales that are not used are ditched, so if you want to use a 1:20 dimension style, it won't be there.

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