The Make Unique Command in NX8

The “Make Unique” command is an extremely useful new ability that is now available in NX8. A good way to describe it is a way of dealing with the situation that arises when you have an assembly with a number of components that you first thought would be all identical, then you subsequently found it necessary to make some of them different. For example, if you have a table that has four identical legs, and then you decide that two of the legs should have casters on them so you could just tilt the table and roll it away. 

Now in NX8 you can use the Make Unique command. All you do is select the two legs that you want shortened and select the command. You are prompted to enter a new component name. In this case “Table led Shortened” was chosen. Then you make the shortened leg the work part and chop off the end of it where the caster will go. Finally you assemble the casters onto the end of the shortened legs and you’re good to go.

The Make Unique command can be found in the Assemblies / Components menu. To give it a try download the Make Unique Table assembly. It is a zip file that contains the original table assembly plus the caster. You will have to shorten the two legs by 3.25 inches.

table.zip (954 KB)

Components of Great Design in NX8

When opportunity meets preparation there is the potential for great success. For great success in the consumer products arena, human need is the opportunity. The preparation is thousands of hours studying mechanical and electrical engineering as well as the human needs themselves. On the engineering side, school is not nearly enough. One must have spent years playing with mechanical stuff, taking things apart, breaking things, all to develop a keen sense of how things work. On the human side, one must be self-aware, as well as keenly aware of others.

Years ago, a friend of mine had the pleasure of watching the great Wayne Gretski warm up for a hockey game. My friend watched as Wayne practiced some kind of crazy round the back, without looking impossible shot. As some point during the game, everything was just how Wayne envisioned it. He worked his crazy move, and achieved a goal. I think most super athletes are to some degree freaks of nature, but their preparation is years in the making. I think good engineering is the same way. A good design engineer has a heightened sense of the physical world, a mechanical ability, which was probably apparent when they were just 2 or 3 years old. For the fortunate ones, that sense is nurtured and augmented with and years of practice, and then engineering school. When an opportunity comes in the form of some new need for a product, all that aptitude springs into action and a product is created.

I was reading a book one day by Stephen King, an author known for horror/suspense novels but this was different in that it was an auto biographical work. Some of it gave clues into his writing technique which directly relate to good product design. In the book Stephen King wrote that he keeps a notebook with him where ever he goes. When he sees something, some interesting portion of human nature, he writes it down. Later when he’s writing a book and he wants to add realism and depth to a character he will include the detailed behavior that he witnessed. In the book The Shinning, one that Stephen is most famous for and later became a movie, I remember a scene where one of the characters, an old guy, blew his nose into a handkerchief, then looked inside to see if there was anything interesting. Although I read the book almost 2 decades ago, I still remember that detail because it’s interesting. I feel that in order to realize a detail like that Stephen must have been very aware. I cannot speak for the author but is seems to me that such a small detail would not have struck him as interesting unless he himself like most of us had this nutty little fascination with what comes out of one place or another on our bodies.

I believe that good design comes from constantly noticing what people do so you can give them more of what they want. A Kindle e-reader is a great example. It speaks to the way people read. Reading is special because when we read we create much more of the story with our own imagination and notions then when we watch TV or go to a movie. If you spend a lot of time reading books or watch people who do you may gain a sense of the minimalism of it all. It’s just you and the pages. It’s the smell of them and the sound as you turn them and hold the book in one hand as you prop yourself up in some comfortable position. You want to be comfortable, perhaps even recline so you are not distracted from doing the creative work. People talk about curling up with a good book. The e-readers that have the e-ink don’t light up, and they don’t weigh much. The black letters on the light grey back ground offer an experience that is more book like then their app running, back lit, handle with care, counterparts. Even though when you turn the page on an iPad™ you can see a little graphic that simulates a page being turned, you still don’t necessarily get as much of the book feel as you get when using the Kindle.

Another example is the latest ice cream scoop from Tupperware. Even this simple device is made great by an attention to detailed human behavior and feelings. The fact is, the way ice cream is consumed has changed over the last little while along with the actual ice cream itself. The new ice cream may have chunks of frozen Heath bar in it or heaven knows what else. It’s probably much more dense than ice cream used to be and it creates much more resistance to the scoop. People who eat gourmet ice cream are likely to grab the pint right out of the freezer and have at it. Designers at Tupperware noticed all this when they innovated their new ice cream scoop. It has a bit of a point on the end, and a handle that feels like it came off of a construction tool. You can grip it tight and strong, but effortlessly put a great deal of force onto the scoop tip. Simultaneously they gave it an elegant look using stainless steel inlays. They really did a great job.

At its best a good design is a caring and accommodating conversation between the designer, the manufacturer and the user. The language is the shape and features that are predicated on the common experiences and belief system that they share. A personal story illustrates this perfectly. I had the pleasure of biking through France once. I was riding through a park in Paris and I saw some elephants. I stopped because I’ve always been fascinated by these intelligent and gentle beings. As I approached I was amazed to find that these two elephants were out in the open with no attendant. Even more astonishing was the only thing that kept them from wandering off was a thin nylon tape that was stretched around four trees to make a makeshift pen. Perhaps it was foolish, but I moved right up to the tape and stood there with the bike between my legs. One of the elephants came right over. He raised his trunk, gently put it on my helmet, and took a huge elephant inhale. This was followed by a delightfully stinky elephant breath ex-hail that cascaded through the breather holes of my helmet and down the back of my neck. Next our eyes met and I reached out to pet the trunk. His hair was course, like wire, and as I pet it he backed away ever so slightly. I backed off and then he got comfortable again. He took his trunk and started to play with the break handle of my bike. I sensed what could only have been curiosity and intelligence of this magnificent creature. When it was time to go, I reflected on how impossible the entire experience would have been in the United States due to our litigious protect you from yourself nature. As much as I love the design of American cars, particularly cars like the Ford Mustang and the Chevy Camaro, I don’t like a certain aspect of them. I don’t like an automatically locking door, or a seat belt beeper that won’t shut up if you don’t have your seat belt on. I prefer what I see as the European “don’t be an idiot or it’s your own fault” attitude. When you drive a BMW, you lock your doors if you want, or not. You wear your seat belt because it’s a smart thing to do, not because it’s the only way to get the car to shut up. The social contract of Europe, which is not as litigious as the US, had a direct effect on the design. The perception that here in the US you can sue any one, for anything, at any time has a negative impact on the design.

The best designs are the ones that are derived from the highest and best human sentiments. The designs that are a result of the ethic of service and community are the ones that really please customers in the end.

Source: nxtutorials.com

The Positive Thing about Negative Numbers in NX8

It may seem like a small thing but in NX8 we now have the ability to move geometry around in a sketch using a negative number. But it’s really significant because there are a lot of situations where sketched entities are on one side of a line or datum axis and are dimensioned in a way that they need to be moved to the other side.  This now works for angles two. If you have a line that is tilted 18 degrees from the horizon and you want to be able to move it below the horizon, all you have to do is type -18.

Figure 1. Model built from sketchwie positive 18 degrees

Figure 2. Model built from sketch with negative 18 degrees

In the image above one can see how switching the sign on an angular dimension can actually change the angle of a corresponding model face. This part also utilizes the pattern feature command. The holes all along the perimeter have been created using the “Pattern feature” command. For the first time in the history of versions of NX, it is now possible to pattern holes along a path without them being separate solids.

The Positive Thing About Negative Numbers in NX8.zip (138 KB)

NX8 Synchronous Modeling “Edit cross section”

Synchronous modeling is an amazing technology. It’s like a great big “Get out of jail” card for CAD modeling. As amazing as parametric modeling is and as powerful and stable as the NX CAD system is, there are times when parametric models with a multitude of features begin to do things that the original model creator just failed to anticipate.  Also, when models are being edited by someone other than the original creator they may not understand the way a model has been created. This can cause the editor to make a parametric change to the model that effects something other than was intended.  Like anything else that has a lot of moving parts the model can get “jammed” up. When a model becomes all jammed up and a designer would normally spend a huge amount of time deciphering a list of features that are refusing to regenerate properly, they can switch to a synchronous modeling technique and in a few seconds get a model to do just what they want.

Synchronous modeling is also great because a majority of the commands are fully parametric. When you use the “move face” command or the “reuse” command, the parametric expressions that you enter are stored in the expressions list just like any other parametric command. You can comment them, edit them and re-name the variables just like any other command.

There are those who criticize synchronous modeling because they think it may lead to sloppy modeling technique.  The common wisdom is that if you use synchronous modeling it will lead to a confusing model because faces of solids can end up in different places then where the sketches would normally place them. The example that is used is that of a simple extruded rectangle that forms a rectangular box. Then a subsequent move face is imposed on the top of the box. The finished product then has a top face that is no longer controlled by the sketch and extrude alone. Although there are CAD users that would be confused by this, anyone who is familiar with synchronous modeling would be able to click through the various features and figure this out in a heartbeat. In fact, the parametric synchronous modeling commands are very similar to many of the commands that have been accepted for years. For example, the “offset face” command, the “draft” command, the “trim” command. All these commands are capable of having a similar effect on the above mentioned block, as the synchronous modeling “move face” command. In the end analysis, any command that is extremely powerful also has the power to confuse and confound the untrained user. Innovators are usually in a race against time. In this continual race we must be given the most powerful tools and we must gain the wisdom to use them well. We can only do this by great training, experience and making a mistake every now and then.

New power has been added to the “Edit cross section” synchronous modeling command in NX8. It can now be used in the “History ” mode. The command allows a user to create a datum plane that intersects a solid, then where the plane intersects with the surfaces of the solid, sketch curves are created. Once the sketch curves are created, the solid surfaces can be manipulated by placing dimensions and constraints on the sketch curves. This like many of the other synchronous modeling commands is very powerful. It can allow a user to redefine the design intent of a model. This is a blessing to those who are aggressively trying to create transformational designs that are innovative and get to the market first. It is a technique that enables those who bravely transcend the status quo.

For example, a vessel is created in a simple way. A block is created whose walls are drafted, then the shape is blended, then shelled.  A designer later finds out that the wall on the right has to be moved out and tilted to meet up with another portion of the assembly.

Figure 1. Ordinary creation of a vessel

The Synchronous modeling “Edit cross section” method is chosen for its ability to edit shapes in an extremely flexible and powerful sketch based way. A center datum plane is created and the “Edit Cross Section” command is invoked.

Figure 2. Center datum plane is created and the Edit Corss Section command is invoked

The two surfaces of the wall on the right are selected, then the datum plane. The sketch button is selected and the intersection curves of the walls and datum plane appear. The user can then use a variety of sketch commands to create a new construction method for the vessel. In the case bellow, a gage point that measures one inch below the top surface is created. The gage point is also moved such that it is 9 inches away from the left edge and the two intersection lines are angled 30 degrees. The two surfaces of the solid wall change position in order to comply with the sketch.

Figure 3. The shape of the vessel is edited using the Edit Cross Section command

Figure 4. The finished product

Congratulations to the NX8 software development team at Siemens. Synchronous modeling is a truly amazing invention. It saves an incredible amount of time in the design process and allows designers to focus on their design more than the foibles of CAD commands.

vessel.zip (73 KB)

Source: nxtutorials.com

Model the rose bush of Broccoli

There are many shapes that are exceedingly difficult to represent with CAD. Ordinary things like a stalk of broccoli or even the shape of a rose bush are common place yet exceedingly difficult due to the varied and “humaniform” nature of their geometry. These shapes are also difficult due their intricate nature and the degree to which everything is different. Capturing these shapes is near impossible. The shape of cedar shingles on a house or large screen panels are also difficult due to shear number of surfaces that are present even when it’s the same shape over and over again.

Figure 1. Cedar shingles on a shed

In these situations many engineers that are defining product definition data are forced to resort to the use of notes on a drawing to define the shape. They can’t model it. In some cases such as those that involve injection molding a standard texture note is enough. Below is a texture that can be specified from the MoldTech company. www.mold-tech.com SED 25020.

Figure 2. A swatch of the Mold-tech SED 25020

A designer will create the overall shape of a product and the injection molder will cut the mold. Then the mold will be sent to the texture people such as Mold-tech who will use one of several proprietary processes that will produce the specified texture on that shape. It’s worked well for many years but it takes some of the control away from the designer who is forced to rely on the mold maker’s judgment and standard catalog of textured shapes.
All of this creates a problem. When defining a new product it is not always easy for a designer to know what’s available without an extensive set of samples from the mold preparation that they happen to choose. Also, due to the fact that textures that are non-standard are difficult to apply to new surfaces especially when they are highly sculpted, designers limit their designs to fit the CAD tools and the textures that they have available. This is an intrusion on the creative process. The design should be driven by the needs of the user alone, not the needs or constraints of the computer program that happens to be employed or the texture house that happens to be selected. And what happens when the part will not be injection molded at all.
There are a few solutions that can be employed. One such solution is to provide a swatch, a small portion of the overall surface with the fully defined pattern or texture on it. This will inform manufacturing of the overall geometric thrust, without creating a massive and cumbersome file.
Another solution is to try to define a mathematical equation that drives the geometry so that you actually create the shape. It can be a bit difficult especially for those who’ve been out of school for a while. Many of the textures that you can achieve with mathematical formula are the result of alternating sinusoids. As shown in figure 2.

. A solid model of a screen

Figure 3. , the equations to create the screen

The model of the mesh shown above is available for download. It’s called meshmodel.prt and you may find it in the “models” section of NXTuroials.com.
Another techniques that you can use when you have a sculpted piece of geometry and you want to actually model the specific geometry is using the Point set command along with Associative copy. First you distribute points on the surface in a pattern that represents the locations of each repetitive portion of the geometry. Then you create a solid that you will serve as a cutter. Using the associative copy command, you duplicate the cutter all along the point set. Then you subtract all the cutters and voila, your pattern is done. For more info download the part file called “patterns on a surface.prt”

Figure 4. A surface with a texture created by the Point set and Associative copy command

Yet another way of creating highly repetitive geometry is using the instance along a guide curve technique. For example, you can create a simple revolved body and placing under it a spiral shaped curve. Then project that spiral along a vector straight up onto the body so you have the spiral shaped curve superimposed on top of the surface. Next you place some sort of cutter solid at the beginning of the curve and use the instance geometry command with the along guide curve option. See the exercise below:

Step 1 Create a revolved feature

Figure 5. A Revolved Solid

Step 2 Create a spiral curve

Figure 6. A spiral sketch on the bottom of the solid

Step 3 Project the spiral up onto the face of the surface

Figure 7. A spiral projected onto a surface

Step 4 Create a sphere at the end of the spiral and instance it along the curve. In this case there are 240 copies of the sphere, evenly distributed along the curve.

Figure 8. Spherical cutters distributed along a projected helix

Step 5 The face of the original shape was offset with a small negative offset, then all the spheres were subtracted.

Figure 9. The spheres are subtracted from the larger solid

Source nxtutorials.com