Computer Controlled Machining

Table of Content

Assignment:

Group Work

Test runout, alignment, speeds, feeds, and toolpaths for your machine

Individual Assignment:

Make Something Big

What I made this week

1. Context

My day job back in Bangladesh

I work part-time as a CNC operator at a woodworking company in Bangladesh. I mostly handle day to day CNC operations, finishing/polishing and inventory management. And they let me use the factory tools for my personal projects as well.

Before Fab Academy, I couldn't design my own files. I was dependent on instructables or thingiverse for Designs. I hope to start designing my own work after I return back.

The CNC I work on,
p.s, That drill machine does not stay there, just wanted to take a photo and kept it there, don't judge me.

The CNC I run there is a 4ft x 4ft KingCut XPro. As the name sugeggests, it is chinese and also runs a quite primitive firmware. It definitely is not as accurate, powerful or big as the ShopBot at Fab Lab CEPT. These are some of my work for Dovetail.

Some of my previous Machining Work

Oak Clock

This wall clock was made on a 12" oak plank and then finished with linchseed oil.

See how the wood texture can come alive just by using a finish.

Wooden Food Trays

Wooden food trays using dense wood like Beech, Teak and Birch. I usually use Bees Wax for organic and foodgrade finish.

Interesting design patterns like this can be generated using toolpath manipulation. Example is this Beech Wood tray.

Beech Wooden tray, Pocket cut with 0% overlap and ballnose bit

Making organic curves like this wooden tray is time consuming on a CNC, We usually cut in 2D and then use the sander to get interesting designs like this.

Teak wooden tray, our premium item with exotic wood

Game Arcade Cabinets for Fab Lab IUB

These 6 gaming arcades were made for Fab Lab IUB. Since we didn't have an 8x4 CNC back then, we used a CNC from a local woodworkshop to cut these.

Large scale orders like these game arcades can be automated easily by sending the designs to local wood factories. If your CNC has a routine running, it's much more financially feasible to outsource the order to neighbouring CNCs that are free. This ensures maximum utilization of resources among the community.

Making Game Arcades for Fab Lab IUB, Got them cut from a local factory with a 8x4 CNC

Semi Assembled Game Arcades at Fab Lab IUB

Cat Furniture:

These Cat Posts were made partially on the CNC router with 1" plywood bases. The carpetting and ropes are all made of cotton.

Mini, a happy Customer using cat posts made by me

CNCs are not just for wood and boards. You can create proper furniture just by covering them with carpetting. Besides, I just wanted to show off my adorable cats. :3

My Startup back at home

My Startup, WiFi Picchi, at home is based on community internet, where I used these very attractive looking boxes as housing for the router and additional electronics. Besides, they act as good advertisement as well.

Boxes for my Community Internet Startup back at home

You can create very cheap and professional looking enclosures for your projects just with a CNC. Have a look at my startup adventure while you're at it.

Random Machining Projects

You can create very accurately spaced drill holes on a CNC, Such as this drill bit organizer I made using scome scrap Pine wood & this pegboard I made with pallet wood.

If you're as bad as me with the chisel and the saw, you could use the CNC to make complex joinery like how I tried with this teak mirror. I wish I had taken better photos of this one before selling it.

What Paid for my Fab Academy Tuitions

Infact, my Fab Academy Tuitions were paid from going to many community product showcasing events hosted by Made in Bangladesh.

A CNC in my opinion is one of those machines, that will never be a lost investment. If you buy it, you will most definitely get returns.

Community buy/sell events that paid for my Fab Academy course

2. Machine Specs

I was really excited to be working on a 8x4 CNC and a ShopBot at that. First thing I did was I checked the Machine specs, the cam options and the softwares available to us.

ShopBot PRS Alpha 96-48 closed loop

Nominal Cutting Area	96"x48"x6"
Total Movement Area	102"x50"x8"
Footprint	L120"x W79"x H67"
Step Resolution	0.0005"
Linear Cutting Force	Approximately 150 lbs
X and Y axis Drive System	Rack and Pinion
Z axis Drive System	Rack and Pinion
Positional Accurace(no load)	+/- 0.003in
Max Spindle Speed	24000 RPM
Spindle Horsepower	3 Horsepower

The CNC I work on is definitely not as big as this, but the best feature about the shopbot to me is it's Z height. None of the CNC's I ever worked with had a working Z height of more than 4 inches, maybe because we really don't have good machines back in Bangladesh. But a z height of 6 inches would definitely open up new doors for me.

Cam Software

Functions:

Generating toolpath
Basic Design manipulation

Opinion:

Didn't like it at all. very basic functionalities. Feels like a budget version of vcarve. I will try Fusion's CAM tool since I always wanted to try that and my CNC back home doesn't have a supported post-processor for that.

Functions:

Communicate with Control Box
Basic CAM preview

Specs:

Software Version 3.8.42
Running OpenSBP open command software (this is the post processor we'll need for fusion)

3. Bits & Collets

The collets we have at our lab are Imperial ER-25 collets which came originally with ShopBot. They were in dire condition when we got our hands on it. Some good old fashioned scrubbing with wd-40 helped with solving that. From the wear and tear, I would assume the 1/8" collet gets used alot and it was almost destroyed. The Bigger ones look like are not used much in this lab.

The bits that were given to us for this week were the following: (from left to right)

1/8" 4 flute straight Endmill
A surprisingly long 1/8" 4 flute straight Endmill
1/8" ballnose

2x 1/4" 4 flute straight Endmill
1/4" ballnose Endmill

4. Design Selection

I am not good at design, or atleast I was not. But I learned to use fusion 360 and learnt the basics of 3D and 2D designing in our Computer Aided Design Week.
I wanted to show off what I learnt a bit and ended up selecting this mesmerizing yet complex Iris Lamp Design by Jonathon Odom.
But I guess I overestimated my newly learnt design skills a bit. But still.... imagine a BIG version of this amazing lamp!

5. Complexities

I started with downloading John's design files, including his f3d file in fusion 360. But his design was full of missing reference sketches, dimensions were missing. I tried to make the iris design myself, but I couldn't figure out the inner and outer diameter ratio, the curvature of the arms and the fillets on the iris petals....

Broken references all over the design, dimension sketches missing

It was a full scale disaster, I had the cut files ready but I could not reproduce them myself. I asked my regional instructor about referencing someone's work, and he said I need to reproduce or modify atleast 60% of the original work. Which seemed quite impossible at the moment.

6. Design Selection again

It was Saturday and I still could not figure out Jon-a-Tron's designs. So I had to do a strategic retreat and shift to an easier design. I searched for easy fusion 360 furniture design and this simple octagon table came up. I just took a reference imageand started to design it by myself, applying what I learnt about Fusion360 in the past few weeks.

This time I decided not to look at the design files at all and make it by myself.

7. Designing in Fusion 360

I will be using Fusion 360 to design my table. Here are the reasons why I chose fusion360:

I am slowly getting familiar with all the features of Fusion360, all my weekly projects were done on it so far.
My low spec laptop runs it smoothly. It takes about 3 mins for grasshopper to compile one command for me in rhino. I certainly took a hint from there.
I would love to learn AutoCAD if I get the time, but maybe not for this week.

> Making the table top

To make the table top, I used reference designs from my Parametric Construction Kit design. I used the same logic to make the table top.

I first made a triangle with fingerjoints on one side and extruded them. I used a circular pattern to generate the top octagon. I'll

Using rectangular Pattern to generate the finger joints

Using circular Pattern to generate the top with 8 parts

> Adding Parametric Finger Joints

Generating the finger joints parametrically was quite difficult at first. But I used rectangular pattern to generate them with each having same size and spacing. I followed this youtube tutorial by The Hobbyist Maker to do it.

>Making Legs

To make the Legs, I just used a simple sketch, extruded it and used the Combine tool to cut out the finger joints using the table top I already made.

Creating the Finger joints using the Combine tool

Extruding the Legs from a simple sketch and using circular pattern to create 4 of them

> Making the Side Covers

I created a simple sketch for the side covers as well. And used same techniques to generate the finger joints and then used circular pattern to create four more of them.

Making Fingerjoints with Rectangular Pattern

Using Extrude to mirror the same finger joints on the other side

Using combine to create finger joints on top

Design Output

A360 embed:

Download F3D A360 Link

> Adding Dogbone joints with a script

Now that I was done with the design, I had to start thinking about the Milling features. I knew I had to add Dogbone joints to it. And I have some 45 degree angles on my legs which would take a long time to cut. It was already Sunday and I had to cut it fast, so I decided to do that part manually by sanding it. To Add the dogbone joints, I used a Fusion360 plugin called Dogbone. Github repo for Dogbone can be found here.

8. Laser Cutting a half Scaled Model

I laser cut a half scaled model first before milling it. I used 6mm cardboard and the scale was half of the original. I exported DXF files of the three components from Fusion and cut them seperately.

I accidentally made the dxf out of an older version backup, it didn't have the top notches

But it was a quick fix,I quickly cut the proper file just for the side covers.

Scaled down model:

Download Laser Cut DXFs:

Top.dxf Leg.dxf Side.dxf *note that these files dont have dogbones on them

9. Material Selection

I chose to go with the cheapest material available to me. Which was 12mm MDF. Since I was living here in India all away from home, I had to be stingy with my budget. The lab did not provide us with a sheet of material as promised since we are all scholarship students here.

I would honestly prefer some Plywood for this design, since I did not put any horizontal support on the bottom region. But I had to make do with what I had.

10. Generating Toolpaths in Partworks

I took the .dxf file generated from Fusion 360 and opened it on Partworks to generate the toolpaths. I did try using fusion 360 to generate the toolpaths, but it seemed like alot of work and I was running out of time for this week.

I made two toolpaths, one for inside profile cut and the other for outside profile cut using the 1/8" upcut bit. The toolpaths generated are of .sbp format. Make sure your unit is matching your control box software. For us which is in inch.

Tool Parameters

3mm upcut 4 flute bit
Pass Diameter: 3mm
Step Over: 40% of diameter
Spindle Speed: 12000 rpm
Feedrate: 0.79 inch/sec
Plunge Rate: 0.79

11. Fastening the Material

I fastened the material on the sacrificial board using 1" screws and made sure the screws weren't in the toolpath by keeping them on the edges.

One corner of the Sacrificial board was damaged

Fastened two Screws to the side to fix that

12. Opening & Tightening the Collet

The Collet nut needs to be opened and closed using a spanner and a wrench. Rotating them 'towards' eachother should tighten it while rotating them away from eachother will tighten it.

13. Sending Files to the Shopbot

Sending the .sbp files to the machine is done by the ShopBot Control Software.

14. Zeroing and Cutting

Zeroing can be done using the control box software, make sure to check all the limit switches. After that we're all ready to cut. Read all the warning pop ups and turn the spindle on when the popup for that comes up. Rest of the job is painfully slow and nervewracking at the same time (if anything goes wrong). If all goes well, you should have your cut parts ready.

Zeroing using the Shopbot control software

Clean cuts means feedrate settings were okay

15. Cleaning, Sanding and Finishing up

I took out all the cut parts, sanded them lightly and pressed fit them together. Some of the parts needed a bit of glue but the rest of the table was good to go.

16. Hero Shots

17. Learning Outcomes

There was not much for me to learn this week, although this was my first time working on a Shopbot. Funny thing is I found my cheap Chinese CNC more easy to work with than the ShopBot.
Partworks is not a good CAM software, I need to learn how to use Fusion's CAM tool. I couldn't use it this week for the time constraint. Back home I am not able to use it because the post processor for it is not supported by Fusion.

18. Downloads

Software

Fusion360
Partworks (paid software, license bought under CEPT University)
Shopbot Control Software