Computer-Controlled Machining

This week we were tasked with an individual set of activities and group work. Working as a group, we needed to complete our lab's safety training and test a variety of settings on our lab's CNC machine. For our individual activities this week we were tasked with designing, milling on the CNC, and assembling something large.

We started the week off with our lab's safety presentation and a demo of the ShopBot CNC machine from Mr Dubick. We were given access to the lab's workflow which is what we are expected to use and have on us at all times while using the machine. We followed along with the workflow during the demo and had the ability to ask questions as we went. This was really helpful as this machine can be dangerous and it was nice to have someone very experienced with it teaching and guiding us along the process.

During the presentation/demonstration we learned about our start of day and end of day routines, and where the compressors are located. Then we discussed what safety equipment to wear and general safety instructions such as where to stand and not to stand and always working in pairs. We talked about using the nail gun to nail down our material and the safety benefits and general benefits of why we use plastic nails for this process. We learned where and how to turn on the dust collector and manage the many dust vents in our labs. Finally, we talked about performing an air cut at the beginning of our projects and why they're important, and how to use the Shopbot software to create a project. For a more in depth look at what our demo and safety training entailed, see my groups Week 7 page.

Introduction

Creating my puzzle shaped puzzle table was a fun and challenging experience. I have not used a CNC machine before this week. I have been around it since it is in the lab where I work and I had a project earlier this year that was cut on it for me, but I myself haven't personally ran the machine.

Our Labs Safety and Research Material

While looking through the workflow I noticed there were a ton of great links available for additional resources. There is a link to the ShopBot CNC handbook which was filled with valuable information for someone who has never done this before. I skimmed through a lot of the document on my own time, but I really focused on page 16 which was the Safety: A Few Basic Rules page. Also linked in our workflow document was a list of the bits that we have in the auto tool chamber, and I really liked that the document listed the suggested materials for each one. This really helped when I was setting up my tool paths.

Designing my Project

I wasn’t sure what I wanted to make at first, I had made some sketches for some random project ideas like a workshop in a box, a decorative display shelf, and a large storefront decorated doll display. While I do plan to possibly make some of these ideas in the future, I decided I would start a bit similar and do either an end table or bookshelf for my living room. As I looked up pictures of end tables and shelves for some inspiration I got more inspired to make a table as the shelves seemed a lot more plain then I was hoping for.

While looking at my apartment I really needed to visualize what the table would look like, where it would fit, and I really wanted something multipurposeful. I have a puzzle I started recently sitting on the living room table and it will live there until it's finished. Taking up the table isn’t ideal, but it's a good surface to work on and the lighting in the living room is really nice for puzzling.

This helped steer me in the direction of making a puzzle table, but of course I wanted something a bit more fun, so a puzzle shaped, puzzle table!

I designed the file using Fusion 360 and I had a handful of iterations before I was happy with my design. As you can see in my Fusion 360 file, I created 37 different pieces, bodies, while I was designing the table.



For the table there are two legs, 2 leg braces, the bottom table layer that you puzzle on, a middle rim, and a top piece that sits on the middle rim that covers the puzzle and creates an additional flat surface. The 3 part top allows me to puzzle, store and secure the puzzle, and still have a surface to use as an end table or project space when I'm not puzzling.

The Puzzle Top

Bottom Piece

Version 1 (shown): Inset finger joints for leg attachment.
Version 2: The design I cut. I removed the inset channels and cut the finger joints all the way through.

Middle Piece

Version 1: Four interlocking pieces that can easily be removed if an additional table is connected.
Version 2: The design I cut. A solid frame piece.

Top Piece

Version 1: A solid puzzle piece shape.
Version 2: A topper piece of a thin edge to allow for sitting on the middle rim.

The Legs

Version 1: A solid frame like design. Meant to slide into the channels on the table top. Could potentially be used as additional puzzle surfaces if disassembled.
Version 2: An open frame design.
Version 3: Open frame design with finger joint connectors.
Version 4: U-shaped leg with finger joint connectors and multiple through holes spaced at 1 inch apart to connect leg braces. I 3D printed this version so I could visualize where I like the leg braces.
Version 5: U-shaped leg with my chosen through hole locations and channels for the brace to sit in
Version 6: This is the one I cut. U-shaped leg with my chosen through hole locations, but I removed the channels. Not pictured, I adjusted the finger joints to be half inch to match the changes I made to the table top, instead of .125in deep.

The Leg Braces

Version 1: A simple straight leg brace
Version 2: The one I cut. A puzzle piece shaped leg brace. Not pictured, I corrected the mismatched finger joint sizes.

Testing my Design before Cutting

3D Printing

Since my design was made in Fusion 360, I decided to export my finished pieces as .obj files and 3D print them. I scaled the design down to 10% from the original size to quickly print my test pieces in about 30 minutes. This allowed me to visualize where I wanted the leg braces, how everything looked together, and see how the top pieces interacted.

Exporting my Design

To get my 3D model ready for aspire I needed to create a DXF file. I created components from all of the bodies I was using and created a sketch plane the size of my wood. I was suggested to use the arrange feature in the Manufacturing Workspace, but I couldn't actually find the arrange tool, so I went back to the Design Workspace. I used the Arrange tool found in Solids > Modify > Arrange. I selected my shapes and then chose my new sketch plane as my envelope.



The tool arranged the pieces decently, but it put a bunch of the pieces sideways or upside down. I reoriented the pieces using the Arrange tool and got the pieces arranged how I wanted them. Next I created a new sketch and used the Project tool to create a 2D projection of all of my pieces. From here, I exported my file as a .DXF to bring into Aspire.



For any files or parts I changed or missed, I was able to quickly right click on the sketch for that part and choose the export as a DXF option. If there were multiple sketch items on that sketch I just deleted what I didn't need when I brought it into Aspire.

Setting Up my Design in Aspire

I started by creating a new project and setting the job size. I set the width and height to 96 x 48 which was the size of the wood I was provided and I set the thickness to 0.475 which was the average I measured from my 0.5in thick wood.



I brought in my DXF file and rearranged any pieces I wanted to add in or remove, such as removing the four interlocking pieces for the middle top part and bringing in the solid middle piece.



I selected each part individually and used the join tool to create a solid vector. For all my parts that have interconnecting pieces I went into the Fillet menu and added either a dogbone or a T-bone depending on what fit in the small spaces. While I was still in the 2D part of Aspire I also duplicated one of my holes to create a tester hole for fit.

I selected my pocket cut on the table top and set up a Pocket Toolpath using the Drill bit listed below. I then selected all of my outside cuts and set up a Profile Toolpath using the Drill bit listed below. I also created a test cut for my hole using the Profile Toolpath.

Bits used in my project:

Pocket:

ATC Tool Location: 6

ShopBot Description: 1/4 2 Flute Ballnose Bit (13576)

Manufacturer Link: Onsrud 52-280B

Outside Cuts:

ATC Tool Location: 8

ShopBot Description: 1/8" 1 Flute Straight Bit (13728)

Manufacturer Link: Onsrud 61-040

Testing the Offset

The first set of cuts I made, after an air cut to test my locations, was one of the straight leg braces and a hole sample. I cut the straight leg brace and the hole using the settings in the Profile Toolpath I set up for my project. This was done to test the fit of my joints. This test was very important because I quickly learned that all of my parts and holes which were designed for 0.5in thick wood (before I had a chance to measure the wood I was given) did not fit well together. There was a lot of wiggle room in the first test.

I was suggested by Mr Dubick to add in an offset to determine the perfect fit for my pieces. I went back to my Toolpath and added in an offset of 0.005. This test still had wiggle room so I cut a new hole at 0.01.



I continued to cut new holes with varying offsets until I found that 0.025 was a perfect fit.

Cutting the Pieces

The pocket cut took about 31minutes and 35 seconds which I was not expecting. This was the longest cut time of any single part in the cutting process.



Cutting all of the remaining outside cuts of the remaining pieces took a total cut time of 39minutes and 47seconds. Due to the layout I had set, I decided to cut the two remaining pieces inside the middle puzzle frame and then cut all of the rest of the pieces. I added tabs so I think it would have been fine, but at the time, I was unsure if those pieces would potentially wiggle or move causing an issue with the rest of the cuts.

Finishing and Assembling

Week 7 Files

In my repo is a zip folder containing files for my week 7.