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