Category — Machine Design

CAD Exchanger is a new program written by Roman Lygin designed to ease CAD model interchange by providing file viewing and translation for a variety of 3-D CAD formats.

The beta currently supports importing, viewing, and exporting IGES, STEP, STL, and Open CASCADE BRep files; in the future, more formats will be supported.  It is based on Open CASCADE; it is currently free but not open source.

CAD Exchanger does not currently support measuring.  I prefer that the CAD Exchanger team concentrate on adding and improving its file translation abilities; there are already fine free solutions for measuring STEP files.

I tried CAD Exchanger using the same Norcomp HD26M model I used with other CAD programs.  The user interface does not currently support drag-and-drop.  The HD26M model loaded in a reasonable time; 3D performance (rotate, zoom, pan) is good, even on a laptop with crappy Intel graphics.  CAD Exchanger provides a nice selection of pre-defined views.  I didn’t try exporting.

Here is a picture of CAD Exchanger in action:

HD26M model in CAD Exchanger

Why am I interested in viewing and measuring STEP files?  Because I can make a better automation PCB if I can use STEP files.  Mechanical engineers, of course, like 3D models they can import and use in assemblies, but I am mainly concerned with PCBs.

There are a variety of standard 3D file formats, including IGES, STEP, 3D PDF, STL, VRML, ACIS, and 3D PDFs.  The most common formats for electrical components are IGES, STEP, and, recently, 3D PDFs.  My experience is that STEP files typically import with fewer problems than IGES; 3D PDFs are very nice for viewing parts, but unless the file creator took the proper steps, cannot be used for measuring.

My uses for STEP files include:

• Viewing parts.  I can’t synthesize 3D parts in my head from a set of 2D drawings, and sometimes it’s very useful to see what a part looks like.   I really like to have real parts to play with, but that’s not always possible.
• Sometimes the manufacturer’s 2D prints do not give all the information I want to create my PCB component shape.  I can get any dimension I want from a STEP file.
• It’s very easy to screw up PCB connectors.  Doing a quick assembly of the PCB and components lets me verify that my drill sizes are correct, check for cable orientation, and such.

Since I am not doing any heavy duty mechanical design work, I did a bit of research into free MCAD programs that can view and measure STEP files, and preferably create small assemblies.  I found one program specifically designed as a STEP file viewer, IDA-STEP.   The free version of IDA-STEP does not measure.

However, most free MCAD programs can import and then measure STEP files.  I took a quick look at five different programs, listed below.  CoCreate PE is my favorite of the bunch; it seems the best match for a non-mechanical guy like me.

1. CoCreate PE
2. PowerSHAPE-e
3. Alibre Design Xpress Note: since Alibre has dropped STEP import from Design Xpress, it is no longer a good choice.
4. IDA-STEP
5. Acrobat 3D PDF
6. CAD Exchanger (a program to convert between CAD file formats, but it also works as a viewer)
7. CADFaster|QuickStep is another CAD file viewer with free and paid versions; when I get time, I will give it a short test.

Note that the free versions of MCAD programs exist primarily for marketing reasons, and the terms can (and have) changed at any time.

There are other free Mechanical CAD programs that might be able to read STEP files, including:

• Medusa4 Personal, which runs on Linux and Windows, but can’t export data and all drawings are marked.
• Kompas-3D Light, which cannot create assemblies.
• Autodesk Inventor LT, which cannot create assemblies.

CoCreate Personal Edition is the free version of the CoCreate CAD program.  CoCreate PE requires an Internet connection every 3 days, can import IGES, STEP, DWG, and DXF files, export STL and VRML files, and is limited to a maximum of 60 unique parts per assembly.

You can drag and drop STEP files onto CoCreate.  It has a pretty complete set of pre-defined views.  Performance on my system is snappy.  I found measuring easy.  Hmm, so far pretty short and sweet – that’s because I like it.  It’s my favorite of the four programs I’ve tried (CoCreate, Alibre, PowerSHAPE, IDA STEP) – it seems the most intuitive to me, and was definitely the easiest to use to measure parts.

Note that like all other free CAD programs, the terms may change in the future.  For example, PTC (the current owner of CoCreate) had a free CAD program called Pro/Desktop that was later dropped (IIRC, the current users were given a five year license).

Measuring HD26M with CoCreate

PowerSHAPE-e is the free version of Delcam’s PowerSHAPE CAD program.  It has all of the functionality of the PowerSHAPE program, except that you can only save files using the encrypted PowerSHAPE-e file format, which cannot be read by any other CAD software (including PowerSHAPE).  You can use the Delcam Exchange program to save in another file format; I believe the cost is £200 (~$300) per file.

The Exchange software provides CAD file translation for a very large number of CAD file formats.  Importing the files is free, but exporting to another format costs money (currently £34 (~$50) per file for non-PowerSHAPE-e files).  The Exchange software can be run stand-alone, or from within PowerSHAPE-e.

You can set a variety of import options when directly importing STEP files using Exchange; there are no options when importing using PowerSHAPE-e.  However, you cannot measure parts in Exchange.

You can drag and drop STEP files onto PowerSHAPE-e.  One nice feature are all the pre-defined views – just click on the icon to spin the part into that orientation.  However, I had to look up how to manually rotate a part: you have to hold down the middle mouse button.  Part manipulation speed is good.

You use the calculator to measure.  When measuring, PowerSHAPE-e seemed a bit behind where I wanted it to be; it might need a faster system than my Athlon 2800 + older Quadro card

Viewing HD26M connector with PowerSHAPE-e

Update 6/24/09: Alibre wants to keep Design Xpress secret, and has removed several of the pages linked to below

Update 8/7/09: Alibre has removed STEP file import from Design Xpress, so it’s no longer useful as a STEP file viewer.  (OK, you can import STEP files during the first 30 days, but after that, you’ll have to pay or find something else).  Go here for or my latest MCAD news posts.

Alibre Design Xpress is the free version of Alibre Design.  It is significantly less capable than Alibre Design Standard.  Limitation include only 5 unique parts per assembly, no advanced modeling tools, and no advanced drawing functions.  Alibre has a feature comparision here.  However, Xpress can still do a lot, including create assemblies (many free versions can’t), import and export files in various formats [import DXF, DWG; export STL], be used professionally, and create 3D PDFs.

With the free version of any proprietary software, the terms can change at any time.  My Design Xpress license allows 25 5 [changed when updated to V11] unique parts per assembly.  Until recently, the normal Xpress limit was 10 unique parts; now it is 5.

In any case, Design Xpress makes a fine STEP file viewer [for 30 days].   You can drag and drop STEP files onto the Xpress Control Panel (but not a part or assembly window), or use the Import menu or button.  This brings up the Import dialog box, which controls how the STEP file is imported.

Alibre 11 STEP file import options

STEP files don’t always import correctly, so it’s good to have these options available.  Note that these options do affect how quickly the part is imported.

I tested Alibre using the same Norcomp HD26M part; it imported without a problem.   I rotated, panned, and zoomed the part without problems.  Since I often end up with the part at weird angles, I appreciate the View–>Orient–>To Plane… menu which snaps the part view back to a plane.

I found measuring a little tricky at first, mostly because what I thought I was selecting wasn’t what I really was.  I was viewing the part looking straight at the front; when I rotated the part a bit (as shown in the picture below), I easily selected the features I wanted.

The Linear/Pairs measurement options takes the first mouse clicks after you select it; I could not figure out how to reset the points being measured without closing and re-opening the measure dialog.  So I had to be careful where I clicked the first two times.

HD26M STEP model in Alibre Design Express

The German company LKSoft makes a a free STEP file viewer; the current version is IDA-STEP V4.  The free version does not allow measuring; measuring, printing, editing, importing, and exporting are extra cost add-on modules.

IDA-STEP is an unusual STEP viewer, because it is written in Java (possibly using the Eclipse RCP), and because it is oriented towards PCB design – just take a look at the available components at the LKSoft store.

I spent a little time playing around with it using the STEP model of the Norcomp 180-026-103 HD26M connector.  It seemed to work well; rotating the model was fast.  I wish I could drag & drop STEP models onto IDA-STEP.   As noted, the free version is restricted to viewing; it does not allow measuring.

HD26M in IDA-STEP

I’ve noticed that Adobe’s Acrobat 3D PDF files are becoming common.  For example, I’ve seen 3D PDF models at Tyco Electronics and Norcomp.

The best about Acrobat 3D?  Since it’s been built-in to Acrobat Reader since, IIRC, 7.07, all you need to do is click on the link, and (assuming your browser has Acrobat setup correctly) the model appears in your browser.  If you click on this link to a Norcomp 180-026-103 HD26M connector Acrobat 3D model, you should see similar to this:

HD26M connector shown by Acrobat Reader 9

The 3D PDF format still isn’t a replacement for STEP or IGES files.  The biggest issue for mechanical designers is that, as far as I know, you cannot import 3D PDF parts into a MCAD program and use them in an assembly.

Another problem is that it’s not always possible to measure 3D PDF models.  Suppose I want to know some distances that are not documented on Norcomp’s 180-026-103 2D PDF drawing.   I cannot measure using Adobe Reader 9 and Norcomp’s model, since Norcomp did not enable analysis when they created the model.  If I have Acrobat Professional 7 or later, then I can measure (and can enable measuring for Acrobat Reader by enabling analysis and saving the modified PDF).

When the 180-026-103 model has measuring enabled, Adobe Reader 9 can measure like this (click for a larger image):

Measuring HD26M with Acrobat Reader 9

I found it a little hard at first to get Reader 9 to measure what I wanted, but it did get easier with practice.

Another problem is that measurements are in “model units”.  For the 180-026-103 model, the model units appear to be inches, but I know that because I know how big a HD26M connector should be.

So right now 3D PDF is an interesting technology, especially for documentation, but I’ll be downloading STEP files for my designs.

I haven’t had time to test most of these, but here are some ideas for installing Subversion and Trac:

• Read the manuals carefully and do a manual install. In my experience, Subversion isn’t too hard, but getting Trac working can take some tinkering.
  • The Subversion and TortoiseSVN manuals are excellent (if you’re a Windows user, you may find the TortoiseSVN manual more useful, since the Subversion manual is all command line).
  • I’ve found the Trac documentation a little harder (more spread-out, probably because it’s all wiki pags), but for Windows the key is the TracOnWindows page. I’ve found it useful to browse the TitleIndex list – you can find some stuff you’d miss otherwise.
• Try installing Trac 0.11 beta – it’s supposedly simpler to install (I haven’t tried yet).
• Try the TOW (TracOnWindows) project installer. I haven’t tried it yet; on the plus side, it’s a single installer for Trac, Subversion, and dependencies, and it’s been updated recently so the versions are current. OTOH, it appears to want to install everything in a fixed location (C:\TOW).
• You can try a VMWare Appliance (using the free VMWare Server) with Subversion and Trac already installed. I’ve looked at this; most appear to be somewhat out of date (e.g. Trac 0.9x), and for licensing reasons always use a open source OS (Linux, BSD) which might not be the best choice for everyone. Similar appliances might exist for the competition.
• You can use a hosting service with an installer (such as Webfaction) – that really does make installation easy, but upgrading can take a bit of work.
• It’s worth considering installing to a virtual machine (whether on Linux, Windows, etc) so you can move the Trac server around, or just to experiment without installing lots of programs on the host OS.

Finally, it’s always important to setup the server correctly, with the desired access rights and user log-ins.

Tony

Updated 1/23/2008 with AMP socket connector part numbers (which some people find easier to hand assemble than 3M, but they are more expensive), and a bit more on MCAD.

A list of the parts and resources needed for the FP-SMC-1 Interface PCB. The Phoenix parts are available from a number of sources, including Digikey, but Mouser (who I will use) and Online Components sell them in small quantities.

Software:

1. Eagle PCB. I’ll be using the Light version (free for non-commercial, $49 for commercial).
2. Viewmate from PentaLogix, which is a free Gerber viewer.
3. Alibre Design Xpress which will help check the mechanical side of the PCB (free). If time allows, I’ll cover other options for checking the mechanical fit of the PCB.

Board Houses:

1. Sierra Proto Express
2. Possibly SparkFun/BatchPCB (can be cheaper for 1 PCB)

Bill of Material for circuit board (excluding PCB):

1. 4 Pin Header 10 pin (2×5) AMP 5102321-1
2. 1 Pin Header 26 pin (2×13) AMP 5102321-6
3. 15 Phoenix ZFK3DS 1,5-5,08 Terminal Block (Part Number 1704415)
4. 1 Phoenix ZFK3DSA 1,5-6,08 (click on Additional Products) End Terminal Block (Part Number 1704554)
5. 3 Phoenix ZFKDS 1,5-W-5,08 Terminal Block (Part Number 1706714)
6. 1 Phoenix ZFKDSA 1,5-W-7,62 (click on Additional Products) End Terminal Block (Part Number 1706730)
7. 2 Phoenix UMK-FE DIN rail feet (Part Number 2970031)
8. 2 Phoenix UMK-SE 11,25 side elements (Part Number 2970002)
9. 2 Phoenix UMK-BE 45 base (Part Number 2970015)

Bill of Material for cables:

1. 8 IDC Socket Connectors 10 pin (2×5) 3M 89110-0101 or AMP 1658621-1
2. 8 Strain Reliefs 3M 3448-89110 or AMP 499252-5
3. 2 IDC Socket Connectors 26 pin (2×13) 3M 89126-0101 or AMP 1658621-6
4. 2 Strain Reliefs 3M 3448-89126 or AMP 499252-3
5. Ribbon cable 26 conductor AWG 26/28 0.050″ pitch (available from 3M and others, length depending on your need)
6. Ribbon cable 10 conductor AWG 26/28 (available from 3M and others, length depending on your need)

Tony

This series describes how to have a PCB made for factory equipment from start to finish using a real board. I am not going to concentrate on the details of the PCB layout software (there are plenty of tutorials available for that), but instead cover details such as getting the right output out of the PCB layout software.

I am going to design a PCB that could be useful in a machine, using components I like. You should be able to learn from this example to design your own low cost board. The PCB will be designed to interface a Panasonic FP0 or FP Sigma PLC to a SMC pneumatic manifold. I am naming the board FP-SMC-1.
The board interfaces 16 PLC outputs to a SMC 26-pin header manifold. SMC uses this design on various manifolds that can have up to 12 stations, and each station can use 1 (for single acting) or 2 (for double acting) outputs. In my board, I use up to 8 stations; all of them can be single or double acting.

The board interfaces 16 PLC inputs to terminal blocks, so you can have two limit sensors (extended, retracted) for each pneumatic cylinder.

The board has a four power terminals, two +24V and two GND. Providing extra 24V and Ground connections allows the board to power another board.

The board mounts on a Phoenix UMK DIN-rail holder. I have successfully used the UMK series before. Phoenix also provides 3-D models, which is useful.

I will be using Eagle PCB to create the schematic and layout the PCB. I will be using Sierra Proto Express as the board house. I plan on investigating the creation of a 3-D board model.

Tony