Week 10/11: Mechanical and Machine Design - 2021 Fab Academy / Russian Wu

Assignment

Group assignment:
- Design a machine that includes mechanism + actuation + automation
- Build the mechanical parts and operate it manually
- Actuate and automate your machine
- Document the group project and your individual contribution
Link to Group Repository

Inspiration

PLA filaments are the main materials we used for 3D printing, but whenever we change the colors or print out something wrong the leftover couldn’t be used anymore. Base on this, we found a Filabot in our storage that ables us to recycle the leftover 3D print. But we need to roll it up to the spool manually, which might lead to uneven thickness. It might be a good idea if we have a machine to wind the filaments automatically and also tighten them.

We found two references on the Thingiverse: LYMAN FILAMENT SPOOL WINDER and Lyman’s Spool Winder Tweaks.

LYMAN FILAMENT SPOOL WINDER

Lyman's Spool Winder Tweaks

So a holder for the spool is necessary for our filament winder station, and I referred to Ultimaker 3.

It would be good if the holder can support the spool and be rotated by a screw. I referred to a snap joint that we learned from Week04 Computer-Controlled Cutting, and also found a reference from Snap-Fit Joints for Plastics. That I knew the snap joint should include a hook and leaning to the outside which helps to increase the tightness.

Modeling

Holder

Base on the measurements, I designed the holder in Fusion 360 and printed it with Ultimaker 3.

After taking the support off, besides some material shrunk problems which I will explain how I fixed in my Challenges chapter the holder fitted the spool so well and works as it should be.

Roller

Joint with station

Filament Winder Station

For the machine, we need a station as the body to install motors, a roller, and a spool. In order to design the station precisely and properly, the measurements for all the elements are critical here. I found a datasheet for the step motors from AliExpress, at meanwhile I measure the motor by myself in case that has some inaccuracies in the productions.

Add up some simulation components to visualize the machine in Fusion 360.

Also, don’t forget to assign dogbone to assemble all the components successfully.

From Week 08: Computer-Controlled Machining, I learned how to cut the wood with a CNC machine. To cut it I need to create a toolpath in Fusion.

Filament Winder Station Stand Part

This part is critical!! For engraving the pockets, cutting outlines, and drilling correctly, I used 3 different bits and 5 toolpaths to realize it.

Bit Size	Part
3mm drilling bit	Screw Holes
3mm milling bit	Pockets
6mm milling bit	Outlines

Drilling Screw Holes

Milling outlines

Engrave Pockets

Drill Screw Holes

Cut Outlines

Filament Winder Station Bottom Part

The bottom part is easier because I only need three cut-through pockets and outline. One toolpath and one 6mm milling bit can realize everything at once. The difference is my material, I selected a MDF wood from leftover that needs different Chip Load Values(Feed per Tooth) and Cutting feedrate because it’s softer.

And we assembled all the components successfully!!

Fixing with additional wheel and belt adjuster

The previous version couldn’t work because the cutting point of the belt wasn’t strong enough. And the wheels of the winder are too small to drive the winder properly. Therefore, I 3D printed a bigger wheel (pulley), with the standard of B300MXL. Timing Pulley Generator (unit: inch) help me to create the svg file, and I imported it into Fusion 360 to extrude it. Don’t forget to add tolerance for the shrink of filament.

I connected the belt with a staple and sewed it with a sewing machine that I learned from the final project. The result is strong enough and it wouldn’t stop the rotation. And add a piece of plywood to install another pulley to adjust the tightness of the belt.

Hero Video

Front side

Back side

Challenges

This was my first time to use Luzbot mini, however, the performance wasn’t really good. The support was printed failed, which led to some falls on the hanging part. The size wasn’t measured correctly, thus it didn’t fit our spool.

The worst was the printed direction couldn’t afford the horizontal force.

!! Solution: Changed the printing direction and increased the infill percentage to 80%.
The 3D printer couldn’t stick on the heating platform, which led to the prints detached and failed printing.

!! Solution: It might because of the wrong tools to take off the prints previously which led to the Thessalon platform was destroyed. Cleaning the platform gently and use some glue before printing would help the prints to attach to the stage.
The 3D printed result was shrunk and the support in the screw hole was hard to clean so that the screw couldn’t fit in.

!! Solution: I created a cube test model, in order to know how much it shrunk to add a shrink tolerance for our model.

The rubbing knife helped me to clean the screw hole really well.

A hot air gun, hammer and a piece of cylinder wood helped me to hammer the screw into our hole properly without any unnecessary hurt.
The support of our holder is too complicated to take off after 3D printing.

!! Solution: The strategy is that separating a model into two parts and connect it later.
The pocket engraved by the CNC machine was too small to fit the bearing. The drilling bit wasn’t really going through the materials.

?? Reasons and !! Solutions: The radius stock to leave was selected. The drilling function would left less than 1mm on the bottom of the stock. To drill through the whole material Bottom Height offset is necessary.

!! The little tip that saves my time!!:

If the material allows always locate it at the the END of CNC machine, which helps me to relocate my materials although I already took my material away from it.
The bearing and screw wasn’t tight so that the station was unstable.

!! Solutions: Electric retardant tapes helped me to fill up the gap between screws bearings.