Assemblies

After drawing several parts of a mechanical device, it is possible to bring them together as an assembly in Inventor and show how the parts move in relation to each other. The most important features to understand are the Constrain and Assemble tools. Constraints can force the faces of two objects to stay on the same plane or remain at a certain angle in relation to each other. They can also force parts to move at a given rate when when another part is moved. For example, a set of gears can have rotational constraints at a set ration so that when a small gear turns, a bigger gear will also turn so that the teeth will move at the same speed.

Assemblies can show people how a mechanism will move in the real world.

Creating Drawings from Parts

 Once a part is completed in Inventor, it is incredibly easy to transfer it into drawing form. Entire views can be produced with a single click, and dimensions can be placed without inputting values manually.

The image above shows half of the housing of a small blow dryer. To the left is a handle with text embossed on the top. At the center is the main compartment with a grill to allow airflow. to the right is the shaft that will direct air out. I placed an image of the part itself as a decal on the shaft.

The image below represents the same part, but it uses orthographic projection instead of a realistic isometric view. Their is a front view, a section view from the right, a section view from the bottom, and a section view from the left. The their are detailed views of the left section and the grill. It was difficult to get the section views to look right because I had to make the viewing depth so short that the curvature of the part would not be visible. It was also difficult to import the decal. I ended up placing it onto a power point slide and importing the slide.

Orthographic projections can be made much faster in inventor than AutoCAD because once the part is finished, the program knows what every view should look like.

Learning to Use Inventor

After working with AutoCAD for years, switching to Inventor was difficult. Although many of the tools and menus were familiar, there were just as many unfamiliar options. I had to learn how the new functions worked together with the tools I already understood. I had to learn how to handle 3D objects and constraints in Inventor.

The biggest difference between AutoCAD and Inventor is that all work in AutoCAD takes place on a single plane viewed from one direction, while sketches in Inventor can be made on any plane and viewed from any direction. The multiple planes of Inventor allow three dimensional objects to exist. A sidebar is necessary to organize the multiple sketches and extrusions so that the user can easily navigate their work. Three dimensional objects are most often produced by extruding sketches, the revolve, loft tool, and sweep tool can also produce three dimensional objects form sketches. Other tools like the hole tool and fillet tool can removed material from a shape. Because there are three dimensions, Inventor has more tools than AutoCAD and some of the tools shared by both programs do different things.

Another difference between AutoCAD and Inventor is that Inventor can dimensions objects after they are drawn. I can draw the approximate shape of a sketch and use three dimension tool to constrain the lines to the correct length. I can also constrain lines to be parallel or tangent to other features. Dimensions and Constraints make construction lines unnecessary in Inventor. instead of drawing two lines to position a circle, I can just draw the circle and constrain its position in relation to other features.

I enjoy creating 3D objects in Inventor, but I often find the software frustrating. It sometimes difficult to see and select the proper objects in 3D. If I make a mistake early on it is not easy to fix because many sketches may be dependent on earlier sketches, so deleting a sketch might mean I have to start over completely. If I don't do things the right way, I will run into problems later, so I need to take my time and think about the best way to move forward. In the graphic above, the plate connecting the base at the bottom to the ring at the top was difficult to draw. I knew how tall it was an how wide it was at the top of the base plate, but not at the bottom, so i had to draw it and extend it further afterwards. I initially forgot to extend it down, so there was a hole in the base right below it. I only realized my mistake when I was adding fillets to the edges and an error message displayed. Luckily, I could fix the sketch without starting over.

Once I understood the basic mechanics of the program, Inventor began to make a lot of sense. When I master the new concepts, it will be a powerful tool. Inventor can do for more than AutoCAD because 3D models actually replicate the shape of a part instead of showing profiles from single views.
        

Auxiliary Views

     Auxiliary views are used to show the true lengths parts of objects that do not have faces parallel to the normal three viewing planes. Auxiliary view are folded up from a normal view into the viewing plane. In the image shown above, the view at the center shows a front view of the object. The object curves upward at each end. The top view shows the the object as seen from the top, but the features at the ends are contorted due to the fact that they are viewed at an angle. the circles have become ellipses, and lines do not show the true length or angle of the surfaces of the part. The three views on the sides help show the true lengths and shapes of the angled features. Features that would be contorted in a normal view are dimensioned in an auxiliary view instead. The view to the far right is a secondary auxiliary view, because it is folded up from another auxiliary view. The auxiliary views in this drawing are partial auxiliary views, because they do not show the entire object. Sometimes, a short break line is used to show where the object would continue if it were shown.
     Without Auxiliary views, tedious trigonometric calculations would be necessary to find the actual lengths of features at angles, and dimensions might have to be drawn to hidden lines more often, and features would not be dimensioned in their primary view.

Sectional Views: Is the glass half empty, half full, or half sectioned?

     In the sectioning unit, I learned about full and half sections,  and revolved and removed sections.
These methods of sectioning bring clarity to drawing by giving a view of the inside of an object without the use of Hidden lines. Hidden lines can become confusing in complex drawing. Sectional views are an intuitive way of avoiding this confusion.
     Half and full sections essentially cut way the front quarter or the front half of an object so that the features of the back half of the object can be seen directly. A cutting plane line indicates where an object has been cut, and which part of the object has been removed from the sectional view. The section line appears in a different view than the sectional view. In the sectional view, section lines are drawn at a 45 degree angle to the surfaces of the drawing wherever the part is cut by the section. These lines are about 1/16" apart. The differentiate surfaces that are flush with the cutting plane from surfaces that are recessed. In full sections, an entire view will be cut by the cutting plane. In half sections, only half of the view is cut by the section view. In the drawing above, The view on the right is in half section.

     Revolved and removed sections are sectional views of specific regions of an object. A revolved section appears inside a normally drawn object. Part of the object is broken away, and the sectional view shows what the object would look like if it were cut away and rotated ninety degrees. Section lines are used on the foremost surfaces. Usually, features of the object behind the revolved section are ignored in the section. In a removed section, a section of a part of an object is shown in a view on its own.  Notes are used to show where the cutting plane is and which view shows the section made by that cutting plane.
     These types of sectional views, as well as other types are used often to make parts easier to understand, and to show the true shape of the inside of a part without hidden lines.

Dimensioning Styles

     In this unit, I practiced dimensioning parts, and learned several methods of dimensioning drawings in AutoCAD. I used tabular dimensioning and rectangular dimensioning, and I created a tabular drawing.
     Tabular dimensions include every piece of information necessary to create features on an object on a table. A table can display the size, the location, and other information about many features without becoming confusing. To dimension the holes in the anchor plate above., I gave each hole a label that corresponded with a row on the graph. Each row gave the diameter of a hole, as well as the X and Y coordinates based on the origin indicated in the graph. Because the holes went all the way through the plate, the Z coordinate was given as THRU. In the notes section, I provided information about the type of finish for the edges of each hole.
     With the rectangular dimensioning style, every dimension in a view starts at one leader line, and extends to its own leader line. Each dimension is stacked on top of the last, starting with the smallest dimension, and finishing with the largest dimension, which is often the overall length of the part.
      The tabular drawing I created gave the dimensions of four parts with one generic picture that isn't to scale. I dimensioned all the features and replaced the numerical values with letters. The letters corresponded with columns on a table that was created in Excel and copied into AutoCAD. Each row of the table gave the numerical values for the dimensions of one of the four parts. This method allows designers to dimension many similar parts using one picture.
      With these new dimensioning styles I will be able to dimension complex parts faster and with fewer confusing dimension lines. My personal favorite was the tabular drawing, because the dimensioning style makes sense, and is very effective for dimensioning a large number of similar objects.
    

First Blog Post

This is a blog created to display completed work from my Survey of Engineering Graphics course. I this course, will learn how to "express, plan, specify and evaluate ideas through the language of technical drawing." In other words, I will learn how to use autocad, as well as other engineering related techniques. I hope that by the end of this class, I will have gained proficiency in CAD, and will be able to continue leaning more complex techniques with the software.

I chose to take this class becuase i have the eventual goal of becoming an Architect, or working in some related field. Leaning to use CAD is an important step in the process of becomimg an architect. The skills learn in this class could be applicable throughout my career.