# Lecture Notes

## Wednesday - Neil time!

Press F in KiCad during tracing to `automaticly` finish the trace


Open loop cnc machine

Closed loop cnc machine


### Materials
Tri fold cardboard - Doesn't machine well
Ridgit foam insulations
MDF - machines smoothly - can be very toxic
MDO - better MDF
OSB "constructieplaat - recycled wood - eco friendly

### Flute
2 than one flute mills 
The more flutes to smaller the bites the drill takes so the smoother the result is.

fewer flutes when removing a lot of material.

Flutes can have different coatings. Coatings can significantly extend the lifetime of the `end mill`

Different bits for center cutting and not center cutting

center cutting lets you directly go into the material
Non center cutting is to clean the cuts.


Need to watch which way you're drilling it will have impact on the holes and cuts

### Cutting materials
Down cut leaves loose material around the hole
up cut destroys the bottom if you're going through the entire material at once

doing a combination can give you the benefit of both and leave a clean hole.



Machineries handbook

Chip load - how fast you let the tool spin/cut while moving. Too fast is bad too slow is bad. There is a sweetspot


For heavy metal machinery you need lubricants. For other stuff not really



### locking the material in place
machining vise - good
bar clamps - need a lot and to distribute the holding force
vacuum bed - The vacuum hold the material down - need periodic maintenance because the holes can get clogged


### Sacrificial layer
Set to Z=0 

Bolts can get loose on the shopbot.

### Dust
You need a dust collector because the cnc machine will create a lot of dust. If there's dust around the lab something is wrong.


### Modification
flexible designs - Flexure
Steam bending - Big box of steam to soften wood and shape it.


Japanese wood joints
https://www.thingiverse.com/thing:169723


### Tool paths
Kerf - Offset by tool diameter

Runout - The tool may not be attached straight to the machine so it will create sloped cuts


climb - cleaner cut but harder on machine - for finishing
Conventional - To start out with is easier on the machine. Is more rough

2d top down
3d
4d Can curve the tool during cutting
5d all degrees of freedom




prototype by 3d printing or laser cut before you do the cnc job


Shopbot - Vcarve


### Safety
Sharp material can fly out
Material can get very hot - Fires
Splinters


Always wear safety glasses
Shoes no crocks or sandals
Hair in a knot
Ear protection


Never reach into a running machine
Never do large format machining alone
You want a second pair of eyes and ears always check each other
Need to be well prepared

Know how to turn the machine off before turning it on


Before you start milling all the documentation has been done.



### Extra notes
If you set the RPM too low it can't calculate the toolpath. For some reason when you change the rpm the the starting point changes when cutting a line.

Pocket allowance = offset

When doing the corners of a cut with filet. You need to double click the corner.

Check the grain of the wood. One side works better than the other.
TODO: add this to main docs