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Big Blue Saw Blog General Updates

Prototyping and Working with Acetal Parts

This is part 2/2 in a series of guest posts from Jay Doscher.

In the previous article we worked on designing a part on the computer. We sketched out the part on graph paper, designed it in Visio, then printed it out to make sure it fit on our project chassis. It will take a couple weeks or so to get the parts in the mail, and we're going to pick up the project after getting the parts back. You can see the paper print out below where we printed it out and cut it out on paper from last time.



It's especially important to make sure all your holes are where they need to be- this can get tricky on complex shapes. As you can see here we have printed out several holes. We can use a hobby knife to cut those out or simply poke out the holes with a pencil in a pinch.



As you can see above, we've taped the part to the project frame. (3M painter's tape works great for this exercise.) Here's a picture of the whole project with several of the parts taped to the frame. It looks a little bit messy, but it shows us exactly how it will all line up.



When we get the parts in the mail, it's important to check the parts individually- in this case it's easy to stack them up and sure enough, they are all in good shape. You can see a photo of one of the finished parts below. One important thing we did for this project was leave the screw holes a little smaller than needed- this meant that when the parts arrived, we could start testing with smaller screws, then drill out the holes to the size we needed. Since there is a high amount of precision from the part design, we can use the existing holes as guides for the larger diameter screw holes. This means the location of the holes stays very accurate even though we are drilling them out by hand.



You'll notice that all the holes line up exactly where we want them, and that the part matches the paper design we did a couple weeks before. One important advantage to working with ABS plastic is that it's easy to work with if we need to change small things. As you can see in the picture below, the part on the right has a couple new additions- we have drilled holes to make spots for some stand off screws, making room for a Raspberry Pi B+.

You can also see how the parts sitting next together show that they can interlock together. This would be extremely difficult to do without prototyping them in paper first, and would likely require very expensive software. Instead, we can rest easy knowing our parts will fit on our frame, just as we expect.



Finally, you can see the finished parts installed on the frame. The parts fit great, and as you can see they fit on a variety of places on the frame thanks to the versatile design. It's important to note that this process works the same for most plastics and even some metals. We could easily place the same order but use aluminum instead. It's important to take into consideration the different materials' properties, since tolerances and other attributes change with different materials types.



We hope you have found this article helpful. You see the full project build gallery over on the Polyideas website here. There you can find other projects that use the same process for prototyping with paper, then using Big Blue Saw to make the ideas a reality.

Designing Parts for Acetal on the Computer

This guest post is from Jay Doscher. Part 2 of this series will appear next Friday.

Getting Started

Designing parts for a custom project can be a daunting task if you've never tackled it before. There are many unknowns and unanswered questions- and there is a risk that things might not turn out the way you planned. This guide will attempt to answer many of those questions and help you get started. The first thing to realize is that there are many steps to do before actually placing an order. The first step is thinking of the idea or problem in your head that you want to solve. Some good questions to start with are:

  • What material will I want to make the part out of?
  • Does this part need to fit with any other existing parts?

Design Software

There are many CAD programs out there, and they vary wildly in price. I'm a big fan of going with what you already know and already have available, and for me that means Microsoft Visio. It's not the best or the cheapest, but the ideas and concepts will be the same for just about any design software you choose. There are many free tools out there, and you can find links to them here.

Rough Sketch

To start, let's say you have an idea for a part, and you're pretty sure you want to use plastic as your material. While there are many engineering aspects to part design, we're going to assume it's a plastic bracket for a hobby project. We also know that this part will have to fit onto an existing project frame. Here's a picture of the project frame that we're starting with:



Now we know that we're going to want a plastic part, and that it will be mounting to the corner or side of this frame. Let's start with some basic graph paper to sketch out the part. Don't worry too much about getting the measurements exactly right, but for this example we're going to assume one graph paper square is two centimeters. We start by drawing out the frame that we need to fit into:



Now that we have drawn the frame design in pen, let's sketch some ideas we have for the frame:



Now we have two ideas: one is a panel that covers the full side and another is a small corner bracket. Now we're ready to move into software.

Part Design

Instructions on how to use Visio or any of the other software tools is out of the scope of this tutorial, but we'll walk through the basic steps to get our sketch converted into a shape in software. First, let's draw a rectangle that is our outside shape; for this project, we know it's 18cm x 30cm.



An important lesson for ordering parts is that larger parts usually cost more than smaller parts. Additionally, it is usually cheaper to get multiple quantities of a part than it is to order individual parts. That's why for this project we're actually going with the smaller corner bracket rather than a panel for the whole side. If we designed a panel, we would have to order unique parts for each side, and we would find out for our project that only the sides are the same. The top, bottom, front, and back are actually different sizes. Since we're using a smaller corner bracket, we can actually order multiples and use them on all sides- even on other similar projects that have the same corner design.

For this project, I need to cut out a corner to make room for other parts; here you can see I've created a rectangle and a triangle in the corner for this part. Each is a basic shape in Visio.- notice I am using the triangle's 45 degree angle to set the shape for my corner. If you can't see it now, don't worry- it will make more sense in a bit. Note this is only for the corner part I need to design around.



Now that we have a custom shape for my corner parts, I can bring in the other basic shapes for my part, using the outside rectangle from the first step as a guide. Now my layout looks like this:



Now we are ready to draw the outline for the full panel part-- the larger of my two planned designs. I'll use the line drawing tool again to draw the shape, using the existing shapes as a guide.





Now we'll copy this shape to a new page, and you can see the basic shape below:



Now that we've gone through the basics, you can use this same simple approach to build more complex shapes. You can use this same approach for drawing drill holes or other holes of just about any shape. For this project, we just want some holes for mounting screws. You can see in the photo below I've made a small square with a circle in the middle. The circle is for screw holes. The square gets used to keep it in alignment with the rest of the shape. I copy and paste them together, then remove the square before ordering.

It actually took several hours and attempts with paper to check for errors, but this is what the shape ends up looking like. Be prepared to print on paper, cut them out and check multiple times. This is why we use paper for prototyping! It's cheap and easy to correct.



Now that we have a shape we're happy with on the computer, let's print it out. We can cut it out using some scissors and check to make sure it fits the frame. For larger designs such as the panel, they may not fit on a single sheet of paper, so we can draw a large "X" in the middle of the design. Then we can line up the two sheets of paper after we cut them out. Since I am using a smaller part, I can copy and paste so I have multiple parts per printed page. Note that when you place the order, you'd only want one. Then change the quantity on the order at checkout.





As you can see above, we've cut out the shape for the smaller part. This will let us use the same part on various places throughout the frame. On the bottom, the shape can even interlock to create a solid panel. Now that we've tried the part out for one piece, let's tape it to the frame. (3M painter's tape works great for this exercise.) Here's a picture of the whole project with all the parts taped to the frame. It looks a little bit messy, but it shows us exactly how it will all line up.





Let's go back into our software and make sure we have a clean drawing. We don't want any excess shapes or lines- just the part and any holes we want to have cut. Here you can see the part is on its own page. From Visio, we'll export the page as an AutoCAD Interchange (DXF) file. Note: Make sure that your drawing only has the shapes you want cut and nothing else on the page. You can see in the screenshot below we've done this. When you're ready to save it, first save your original in the Visio format, then click File, Save As..., and select a folder to save it in, then click the drop-down box and select "AutoCAD Interchange".





Now we're ready to order! We'll navigate to the Big Blue Saw website and click the button for Upload and Order. The next steps are pretty easy!
  1. Click the "Choose File" button and find the DXF file you just exported.
  2. After you've selected the file, click "Upload".
  3. The part should upload and look like it does below: PIC
  4. From here, we are free to select a material type. For our case, we're going to select "Black Acetal Plastic 0.125", or 1/8".
  5. The next screen shows pricing, where we can choose our quantity. Because we are going to use the same part all over our frame, we will save money through a higher volume of the same part, instead of having unique parts for each part of the frame.
  6. From here we can finish ordering our part.
You can see the full project build gallery over on the Polyideas website here.

Sale on aluminum: October 29-31

$

You can save big on custom aluminum parts with our sale that runs from Wednesday, October 29 through Friday, October 31. During the sale, all orders placed online for aluminum 6061 in 0.125" (1/8" or 3.2 mm) thickness will receive a quantity discount, no matter how small the order.

For example, our control panel example part will cost just $25.70 in quantity 1 during the sale, a savings of 72%. Our butterfly example part will cost just $9.20 in quantity 1, a savings of 90%!

Upload your design now to get started.

7 New Thicknesses of Stainless Steel Available

7

If you love parts that look good and last a long time, take a look at our latest additions in stainless steel. When you use our online quoting system and choose Stainless Steel T-304 material, you now have 7 new thicknesses to choose from:

Inches Millimeters Gauge
0.0180.4626
0.0240.6124
0.0300.7622
0.0360.9120
0.0481.2218
0.0751.9114
0.1353.4210

This is in addition to all the old thicknesses: 0.06", 0.09", 0.12", 0.125", 0.1875", 0.25", 0.375", 0.5", and 0.75", meaning we now offer 16 standard thicknesses of 304 stainless steel.

If you're having trouble deciding on the thickness of your part, here are a few common items and their thicknesses for comparison.

InchesMillimeters
Dollar bill0.00430.1092
#9 Standard Razor Blade0.0090.2286
#12 Heavy Duty Razor Blade0.0120.3048
Credit Card0.0300.76
CD, DVD, or Blu-Ray Disc0.0471.2
US Dime0.0531.35
US Penny (Cent)0.0601.52
US Quarter0.0691.75
US Nickel0.0771.95
Canadian Polymer Banknote0.0040.091
Canadian 10 Cents0.0481.22
Canadian Cent0.0571.45
Canadian 25 Cents0.0621.58
Canadian Dollar0.0691.75
Canadian 5 Cents0.0691.76

As always, just let us know by e-mail if you're looking for a material or thickness that's not listed in the online quoting system.

Stainless Steel and Aluminum Savings August 20-22

Sample Aluminum & Stainless Parts

We will be having a sale on waterjet cut aluminum and stainless steel parts from Wednesday, August 20, through Friday, August 22. Any order placed online for 1/8 inch thick aluminum 6061 waterjet cut parts will automatically receive a large quantity discount. As a bonus, we've got a brand new thickness of stainless steel 304 that we're also putting on sale: 0.135" (10 gauge).

Take advantage of this sale to get a great price on those parts you've been putting off ordering. You can also use this sale to try out a new design or building technique without spending a lot of money.

Get ready for the sale by uploading your design to our online quoting system today.

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