Should engineers do parts drawings?

      Product engineers can draw impressive sketches. But should they be expected to write code? November 15, 2000

Question
I have a question on integrating CNC code with engineering design in the woodworking industry. I am working on setting up engineering standards and CNC machining for a new company and am looking to link the two the best that we can. We are getting a Biesse or Komo machining center and will be using RouterCIM with AutoCAD 2000.

With companies that I worked at in the past, we always made production drawings and then a person outside of the engineering department took those drawings and re-drew all parts to be run through RouterCIM, where they were finally put to the CNC. I realize that this will still have to happen, but I would like to have the engineering department make the part drawings for the CNC. How does your company do this and what are your experiences with making this process efficient?

The last company that I worked with made the exact same product as we will be making (high end custom work, seldom in production runs or repeats). We tried Cabinet Vision Solid and it fell on its face because the amount of time spent doing the custom work with it was not worth having the CNC code come out the other end. We generally have lots of custom metalwork, plexiglass and other hardware that CV does not handle well. It was cheaper to pay someone to re-draw the parts (and sometimes faster).

Most of the CNC dealers that we have met with say that 90% of similar custom market companies still re-draw their parts. So what is the best way to do this? What is your process from creating production drawings through parts being cut?

Forum Responses
The main reason, albeit a poor one, that parts are drawn twice is accountability and accuracy, or lack thereof.

There is no good reason CAM software can't filter layer names to convert to code, or usable layer names can't be used in engineering to create correct code from the beginning. The fact of the matter is, it seems, most companies would rather put up with the political and practical inefficiencies of drawing parts twice than to do it right once.

There is usually a collective groan from the engineering department when they are brought into the discussion concerning the electronic accuracy of their drawings and the idea of converting these to CNC code. They take too many shortcuts that don't produce accurate drawings, only "sketches". This is normally multiplied by the number of individuals doing the drawings--it seems everyone has a different set of shortcuts that produce flawed drawings that can't be used without being cleaned up.

That's why it is so prevalent to have someone redraw the parts to be converted to code--they were never drawings to start with, only "sketches" done in CAD.

It can be done and is best done by having the engineering department in charge of the post processing to code--it sort of puts them in the hot seat. It puts control where it belongs (not in the other guys hands), manufacturing, in this case. If one department is in charge of creating and delivering accurate code to the machinery, the finger pointing in minimized to say the least.

This also means someone in the engineering department has to understand what is required to correctly run the parts, and data flow should be in one direction. By that I mean if the CNC code is not right, the program should not be corrected on the floor, a change notice should be sent to engineering and the problem corrected. Nothing is quite as wonderful as having 6-8 programs that could be what you need to run, and having to guess until you get the right one.

Stringent guidelines must be in place and adhered to in engineering and manufacturing segments, and the manufacturing segment should be looked upon as an extension of engineering, working with each other instead of being at odds with each other. It takes a lots of commitment to run a tight ship like this, but it certainly increases efficiency tremendously. If everyone involved is not committed to the idea and methodology, it will not work, period. Then you will be back in the same boat as the majority, redoing "sketches" to drawings to create code for the machinery.

It is not that it is faster or more efficient to have someone do the drawings again--it's more than likely the drawings were never accurate enough to use to post code. I love it when I am sent programs to post to code from time to time and there is a disclaimer that the drawing is for visualization only.

Sorry to be so long here, but I work as a systems integrator and I see this kind of thing all too often, doing the drawings 2 times, (or more).



For what it's worth, CV's newest build has been total re-engineered on the CNC code end of things. The logic used to create and write the geometry has been re-engineered, as I understand. I have not installed and used it yet--this is just what I have been told.


I know what you mean by sketches. We went from a sloppy draftsman to an ace recently and now I can pull DWG files into Alpha CAM and tool up fairly quickly. Accuracy is everything! But I do redraw a bit.


The comments below were added after this Forum discussion was archived as a Knowledge Base article (add your comment).

Comment from contributor A:
For what it's worth, I do this every day. I am the designer/engineer where I work. I make 3D models of all our products in AutoCad for customer approval and use those drawings in a more detailed version as shop drawings and to program our two CNCs. As for the accuracy of the models, they are right on because they have to be. Makes my job a lot easier to do the whole process from start to finish.



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