Delcam PowerSHAPE 2010 – Part 4

Here are the links to Part 1, Part 2 and Part 3.

In this part I am going to try and create a simple model in PowerSHAPE 2010 – a Lego block. Considering that is a prismatic part with no complex surfacing involved, I am assuming that it should be easy.

I started by creating a 2×1 rectangle and extruded it by 0.5. The PowerSHAPE menu has a drop down called “Object” where all geometry and feature creation commands reside and are quite easy to find. Yes, I used the word “feature” and you will soon see why. I used Object > Line > Rectangle to create a rectangle and Object > Solid > Extrusion to extrude it to a block. I could have also used the nice and big toolbar buttons. But that is something I usually do after I am done familiarizing myself with the menu.

This is the base of the Lego block. Next I needed to create the pins that sit on top of it. So I proceeded to create a circle using Object > Arc > Full. I clicked on the top face of the block and sure enough a circle appeared. Next I needed to accurately position and size it. Exactly how I was supposed to do that didn’t seem obvious to me, which is precisely why I should have read the tutorials first. Anyways, after fiddling around a bit I figured that if I double clicked the circle an Arc Properties dialog box popped up which let me specify the center and radius of the circle, among other things. So I set the center to (2.5, 2.5) and a radius to 2.

Next I wanted to create a 4×2 rectangular pattern using the circle. I saw an icon on one of the toolbars that looked as if it wanted to be clicked by someone wanting to create a pattern, but I could not find any menu item mentioning the word “pattern” in the Object drop down or any of its sub menus. After some searching I found Edit > General Edits > Create Pattern which popped up this Pattern Edit dialog box.

Pretty straightforward. I entered 2 rows and 4 columns and a pitch of 0.5 for both and ended up with 8 circles on the top face of the base.

I used Object -> Solid ->Extrusion to extrude the circles by 0.2 to get the 8 pins.

Just when it looked like things were going on smoothly, I found myself in a fix. I wanted to apply fillets to the top circular edges of the pins. So I used Object > Feature > Fillet. When I clicked on the edges that I wanted to fillet I kept getting an error message saying “Please pick an edge on the solid“. I thought I was doing precisely that. But the error message kept popping up. While struggling with this error I accidentally picked the edge of the base box and noticed that the error message didn’t pop up. As it turns out, contrary to the impression that I got from the image above, PowerSHAPE created the eight pins as individual solids disconnected from the base solid. Now in PowerSHAPE, only one solid can be “active” at a time and the base solid was the active one and not the pins whose edges I was picking. That’s why I was receiving the error message asking me to pick an edge on the solid. I think an error message like “The edge you picked is not part of the active solid” would have been more helpful.

Anyways, instead of making each pin active and filleting them one by one, I decided to add the pins into the base with a boolean union, since that was what I wanted in the first place. So I used Object > Feature -> Addition to add the pins into the base which left me with only one solid in the model. I applied a fillet of 0.05 to the top circular edges and got this nice looking Lego block.

There was one last thing remaining. To make it a real Lego block I needed to shell the solid by removing the bottom face. I did that using Object > Feature > Hollow which resulted in my first model in PowerSHAPE 2010.

I know that all solid modelers have a model sectioning feature to let you inspect the model internally. I found it at View > Dynamic Sectioning.

While I was modeling I noticed a window on the left of the screen with a tree populate itself as I modeled. It looked like PowerSHAPE was keeping track of the things I was doing. By the time I finished modeling the tree looked like this.

Actually, I edited the tree a little. The items in the tree were just numbers starting with 1. In my opinion, not very helpful. The only way to know the type of a feature is by looking at the icon. I am not sure why Delcam does not use names like “Fillet 1″, “Extrude 2″, etc. like other MCAD systems.

Anyways, so now I know that PowerSHAPE has a feature tree. So is it a feature based parametric solid modeler? We will find out exactly that in the next part.

  • http://worldcadaccess.typepad.com/ ralphg

    Real LEGO bricks have ribs underneath to hold the pins of the second brick in place.

    For what it’s worth, I was able to model a LEGO brick with AutoCAD in 1990.

  • http://worldcadaccess.typepad.com ralphg

    Real LEGO bricks have ribs underneath to hold the pins of the second brick in place.

    For what it’s worth, I was able to model a LEGO brick with AutoCAD in 1990.

  • http://www.deelip.com/ Deelip Menezes

    The wall thickness is 0.05 and is equal to the distance from each pin vertical cylindrical surface to the edge of the brick. So I figure that a block sitting over another will fit snugly. Of course assuming that the manufacturer is going to mess up on the plus side, it will be more of an interference fit, which is what Lego blocks are all about.

    If this is not how Lego does it, then maybe I should patent this design ;-)

  • http://www.deelip.com Deelip Menezes

    The wall thickness is 0.05 and is equal to the distance from each pin vertical cylindrical surface to the edge of the brick. So I figure that a block sitting over another will fit snugly. Of course assuming that the manufacturer is going to mess up on the plus side, it will be more of an interference fit, which is what Lego blocks are all about.

    If this is not how Lego does it, then maybe I should patent this design ;-)




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