CAD Craft

A resource to CAD Craft specialists, and a showcase of my work — in both material and virtual worlds

Archive for manufacturing

CAD Tips: Sweeps

In engineering design of machined parts, there is often a misunderstanding of meaning when someone uses terms like ‘economical or low cost design’. Conditioned to think of cost in terms $$, many often overlook the factor of time, most significantly in the context of machining steps — operations, iterations, repeated passes, etc. Whatever we can do as designers to reduce the number of operations & iterations in the machining process saves $$$. This is what time study engineers do — analyze ways to streamline a task process. For instance making a series of circular features concentric — even when this may not be crucial to the design — can significantly assist those in the machine shop & inspection area to more swiftly and effectively complete their tasks.

One of the features which sometimes befuddles folks is the Sweep(in SolidWorks), whether an extrusion or cut. I will address some tips in this area. However, it is important to keep in mind that it is a mistake to presume that just because you can design a 3D model, it can be machined. It is also true that a feature you apply in a CAD design may not be able to be machined in an analogous process. For instance, a sweep along an edge of a circular part is a fairly simple lathe operation. However, a sweep along a polygonal part is more complex.  For some machining systems, working their way around a 4, 5 or 6-sided part is not so challenging.  For others, it is a harrowing issue. Allow me to reiterate: CAD is not a stand alone tool/premise/concept — it was always conceived as a partner in CAD/CAM = “Computer-Aided Design” & “Computer-Aided Manufacturing(or Machining)”.  Once you have completed your model and submitted it to the shop, they must go through a process of conversion to their CAM software to program their CNC machines to actually do the work.

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CAD: Process & Technique

Some users and others are coming to CAD fairly recently, and may be unfamiliar with its origins, how it got to be what it is today. Having been in the design field since well before its introduction, I thought I might be able to share some insights. This is pertinent because in many instances, the actual process and mindset one needs to bring to the CAD process is ensconced within the process of its evolution.

For an iteration of the technological/corporate developments is CAD, I have found The History of CAD to be an exceptional resource. One of the keys I found intriguing was in his section on 1970-1980, where Bozdoc asserts:

“MCS was founded in 1971 by Dr. Patrick J. Hanratty. Since the day it was founded in 1971, MCS has enjoyed an enviable reputation for technological leadership in mechanical CADD/CAM software. In addition to selling products under its own name, in its early years MCS also supplied the CADD/CAM software used by such companies as McDonnell Douglas (Unigraphics), Computervision (CADDS), AUTOTROL (AD380), and Control Data (CD-2000) as the core of their own products. In fact, industry analysts have estimated that 70% of all the 3-D mechanical CADD/CAM systems available today trace their roots back to MCS’s original code.”

I consider this to be important because, as many CAD polyglots will tell you, there are certain challenges which seem largely identical across certain types of CAD apps. This is also pertinent in that it further underscores the veracity of the premise that what you learn — in terms of technique/process — on one system is generally mappable to others.

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