Week 9 Assignment - Mechanical design

This is part 1 of 2

Group project page

The official lecture notes are found here.
Videos of the lectures can be seen here.
The assessment criteria can be found here.
Relevant tutorials can be found here.

Goals

Assignment

Make a machine, including the end effector, build the passive parts and operate it manually. (week 1 of 2)

Ø 40 mm Ball launcher files

	Fusion360 ping pong ball launcher Step file assembly of the ball launcher DXF-cutsheet complete launcher PDF-cutsheet complete launcher
	Fusion360 full assembly, CAM and cut sheet Full assembly and cut sheet in STEP format

Video of manual mechanical test

Youtube link for higher resolution

Connection to final project

We used linear rails with integrated rack and pinion drive for our motion system in the group project. They were milled from POM on on Hank - A shopbot fabbed CNC machine made by Jens Dyvik as part of the Fabricateable machines project.

Video of Hank milling motion system

My final project was making a next generation fabricateable machines CNC machine with similar linear rails as used here, but made from aluminium and with improved glide blocks. See my final project page for more details.

Jakob log

Meeting #1 23/03/2017

Attending, the whole local Fab Academy class from Verket Fab Lab

Hanne Eriksen
Jakob Nilsson (me)

Agenda

What to build
We brainstormed and came up with these ideas

Precious plastic machines
Analog arcade/carniaval game
Window writer pen bot
Coffe serving robot
Motorized platform for the 3D scanner

window-writer pen bot

analog arcade game

When to build

Staurday
Monday after lunch
Tuesday
Wednesday is spare.

How will it work

Possibly a moving ping-pong ball shooting cannon with (moving?) hoop targets.
Perhaps a motion sensor thorugh the window (or a photon-webserver for smartphone interaction).
We want a nice looking display that can be added to over time

How to log the work

We will log our individual work on our pages and present the project on the class page.

Tasks after the meeting

Both: Think of fun features for the game in the window to the next meeting
Jakob: Fabricate axis with Instructor Jens
Hanne: Create a page for the machine building project on the class page
Both: Meet again on Saturday to decide what to build and start making it.

Ping pong gun - prototyping

Also know as the end effector of our machine :)

I designed a test launcher in Fusion360, it uses small metal springs to fling the ball out of a square tube when the trigger is released.

It took three attepmts to get it working, the first two were to weak to be assembled. I used the fitting "comb" from Week3 but since I used scrap pieces the thickness varied.

We tested the working prototype together and concluded that these improvement were neede

Squarer tube
Straight spring mounting
Wider clearance to carriage
Wider clearance to arms
Press fit is not suited to this application.
More abrubt release
Centered release mechanism
Latching release mechanism

Upgraded launcher

I implemented the improvements listed above in the fusion model

It worked satisfactory so I locket it together with hot glue.

Later bug discoveries

After using it for many tests we had two problems. The first one was that the slider (made from 4 mm 3-layer plywood) broke, and had to be replaced with a new 6 mm version. The second one is that the the trigger mechanism sometimes failes to latch onto the slider, this is due to horisontal play in the slider relative to the barrel. UPDATE! I fixed this problem by gluing in a stopping plate from some scrap plywood at the point where the blue arrow in the picture above starts.

Fabricating the main body

The assembly and the cut sheet layout in fusion360.

We CAMed and milled the main body together!

Milled and test-assembled

Mounting axis to launcher

I spent a day with Instructor Jens Dyvik and his self fabricated CNC machine, "Hank". The goal was to get the CNC working well enough to mill linear axis that we could use to automate the ball machine. We ran into some software/controller problems that we could not work out so Jens had to finish the axis milling without me.

When we milled the main body we also milled axis mounting blocks and an arm to connect the axis plate to the trigger. I mounted them to the launcher and then the launcher to the main body.