7. Computer-Controlled Machining
Hero Shot of the Week
Summary
Work Process
Calendar
| Date | To be done | What was done |
|---|---|---|
| Thursday | - 10h Local meeting | |
| Friday | - FabLab normal work | - PhotoShoot with the CNC |
| Saturday | - Documenting & Fusion file design | |
| Sunday | ||
| Monday | - Cutting & assembly | |
| Tuesday | - FabLab normal work | - Doing some documentation |
| Wednesday | - 11h Local - 12h Regional - 14h Global |
Introduction
Saco and Henk made an introduction. I also quickly presented Fusion Manufacture to the others quickly. I am no pro, I only know some of the basics.
General SAFETY
- investigate risk
- remove risk cause
- reduce risk effect
- use protection
Verify machine :
- integrity,
- cleanliness
- workspace
- rails
- surrounding
- inside (collet, mill)
- extractors
- fullness
- sucks correctly (nothing stuck in the pipes)
- wood dust + air + heat = fire or explosions
- Noise
- good noise
- VS bad noise
You need to know where are the:
- red button
- fire extinguisher
- fire blanket
- emergency exist
- FabManager location
Fixing your wood panel:
- position of your metal screws
- use nylon screws
Your safety:
- tied up hairs
- no ties around neck
- glasses (something can always fly your way)
It can be spined around the CNC and drag you around.
Match your collet size with your mill shaft size. But you first need to put the right collet into the machine head before inserting the mill inside to collet. Fasten the collet correctly. Too loose, the mill will fall out. Too hard, you wont be able to disassembly it later on.
Put the tools back where it is supposed to be!
Principles & Parameters
Important parameters:
- Cutting speed
- speed of the tool relative to the material
- Chip load
- Thickness of chip being cut away
Ways of milling
- Climb milling
- Conventional milling
Image source
Milling Path
- Step Over
- % of the milling bit that interacts with the material
- Spindle speed & cutting speed
-
\[ V_{cutting}= RPM * D *\frac{\pi}{60} \]
- too high -> burning wood
- too low -> splinters
-
- Feed Rate
-
\[ t_{chip} = \frac{V_{feed} }{n_{flutes} * RPM} \]
- too high -> high forces
- too low ->
-
- Generating toolpath
- GCODE
- GCODE is slightly different for each machine
- Selecting tools
- Fusion 360
- Corners
- Use DogBone (See image below)
CNC-Step High-Z S-1000/T
My FabLab's Tutorial that I am still working on.
It work zone is : 100 x 60 cm The head can move 11 cm in the Z axis.
More info on the sellers page
SAFETY
Fire extinguisher and fire blanket are next to the exit.
Our CNC is in an enclosure.
Before switching ON the CNC check the surroundings (inside & outside).
Clean it if necessary.
Move object that could cause issue (like the broom in front of the Fire Extinguisher)
In my case there was a little issue where one of the magnets of the door was off. So we glued it back.
You can also see on the image one of the sensors to detect if the door is closed or not
Than we need to check if the extraction is clean. (PS: if the head is not accessible: switch on the CNC, move the head, switch it off, continue the checklist)
Loosen the two screws maintaining the extractor head (second screw at the back)
Look inside.
You can take off the extractor tube if needed.
Not clean.
Shake it above a bin to get the stuck pieces out.
Than check the extractor itself.
Is the collector bag full ?
A safety feature is that when the doors of the case is open, the CNC wont move.
Personal SAFETY
The door handles are pretty close to each other. So when closing beware for your fingers. Mine are on the smaller side so I just get stuck between the handles...
When the CNC is running, we have plenty of ear protections
And glasses too even if the CNC is in an enclosure.
Collet & Mill
To change the mill (and the collet) you can unscrew the holder part with two Spanner key.
A collet can be change by popping out the previous one from the black holder and popping in the new one. The collet needs to be empty when doing a collet change.
The collet you should use depends on the diameter of the shaft of the mill that you want to use.
Generally the size of the collet is written on it but sometimes you get into this kind of situation:
The most important Mill parameters are:
- Shaft diameter
- Mill (cutting) diameter
- Flute (cutting) length
- Flute number
Switch On
Before switching ON, verify if the head motor is off.
To switch ON the CNC we first need to activate the badger.
Than verify if any of the emergency buttons are turned on. (LED on the main box will show a red light if there is an issue)
Also check the switch on the main box.
User interface
Program Interface
When you launch the KinetiC-NC program you are welcomed with the following screen.
You found yourself in the Program menu.
Here you can found the following submenus
- The four main menu
- A screen with the CNC heads movement. When launched there will be no data shown
- The menu where you can load your GCODE for the manufacturing
- The coordinates of the head. When you start the program, you will need to do a Reference so that the CNC knows where the head is.
- Status panel. This is where errors are shown.
When the door of the CNC is open you will get the following message in the Status panel:
The CNC wont move until the door is closed.
Jog/Setup Interface
In the second menu you will be able the move the head.
Your first step will be to home the head so that the CNC knows where it is located. You can use button 3 for that.
- These are onscreen buttons to move the head in the three different axis.
- With this button you can tell to the CNC to do a homing. (Execute a reference drive with all axis to referencing the machine)
- With those two button you can set the Zeros for the X and Y axis for your CNC machining. (Reset axis to 0) These zeros refer to your Fusion GCODE zero position.
For number 1. you can also use the Numeric keypad (numpad) numbers to move around the head.
| +y: 8 | +z: 9 | |
| -x: 4 | +x: 6 | |
| -y: 2 | -z: 3 |
Custom Interface
It is in this interface that you will found the Z0-finder with mobile tool length program.
You need this program to 0 your Z axis with the button stored on the side of the machine.
Make sure to do the Zero at the same place as it is setup in your Fusion GCODE.
After you did the Z axis Zero, put back the button and make sure that the cable is not in the way.
My File
To create a Red Heat Lamp Post.
Making it parametric
I lost so much time to find this equation:
- s is the length of any side
- n is the number of sides
This equation gives you the distance from the center point of a regular polygon (all sides same length) to one of it vertex.
Now my file really can be parametric.
Usage of Dogbones
Articles explaining the principles behind the dogbones:
Plugins for Fusion 360:
- Two pages referencing the same github project: More elegant CNC dogbones & Dogbone
- Nifty Dogbone for Autodesk® Fusion®
- needs $
Somehow I cannot make the DVE2000 DogBone addon work. It does not want to recognize the face that I need to correct.
...
I just complained in here and now it works...
Joins
After thinking I wont use any complicated joints. If need be I will use glue.
I will first make the holes a little smaller than use a lime if need be.
Than glue.
I know.
I should first do like with the laser and calculate the CNC kerfs equivalent.
(The step-over if I understood it correctly)
GCODE
I will use a d=6mm mill from ShaperTools with 2 flutes.
For the toolpath I used the following tools:
- Face to flatten the wood and get to the hight that I used in my CAD
- 2D Pocket to make the bigger holes
- Bore to make the smaller holes
- 2D adaptive to make other holes
- 2D Contour to cut out the parts
So in fusion I checked the simulation if everything look OK.
It did.
I only forgot to check ONE thing.
...
The time.
Now I have to sit and watch 3h of milling...
I am sure I could have better optimized the time / cutting.
Cutting
To prepare for the cutting I just screwed the wood into the martyr.
Than for the parameters I used what I was told for that kind of wood.
While cutting I noticed that the wood powder was not sucked up by the vacuum. So I opened the door of the case (yeah, it puts the milling on pause ^^) and checked myself.
In the end I opened up the vacuum itself.
The tube itself was plugged up with wood stuff.
I cleaned what I could.
But I think I should also open up where the motor is to see if there is anything inside that should not be.
My clothe became white in the process.
So much manga chapters read while being next to the CNC.
I did not manage to finish before the recitation. Put my CNC on pause while listening to the recitation. Unfortunately my headsets are not strong enough and so if I continue cutting while listening, I wont hear a thing.
The scariest part of cutting was when the CNC wasn't making any noise.
No noise is scary.
Well...
I made a calculation mistake somewhere.
The tabs that I put into my GCODE aren't there...
Thankfully nothing happened.
And my nose started to bleed...
WHY ?! I WAS JUST SITTING FOR MORE THAN 2h !!!
So I think I know why. I cleaned the extractor without a mask. I sniffed all the wood powder which desiccated my nose so it started bleeding (after a time delay).
Assembly
Forgot to take an image of the components out of the bed.
Anyway.
It seems that sometimes I am missing 1-2 mm to really fit.
So I took a file to make it press fit (and a hammer).
And I did not realize how small one of the part was, so now I am unsure if the lamp will fit on that part or if I need to redo it.
I need to redo it...
I made a miss calculation...
Back to the drawing board. Back to the cutting. At least its only one piece.
The locking mechanism works great:
Finishing
Now I just need to find some chemicals to finish the surface.
I also need to install the lamp socket and the electrical cable. I am also wondering if I should install a switch onto the cable or onto the lamp post itself ?
Learning Outcome
So it wasn't my first time doing CNC machining. But it was my first time doing it alone... (I wasn't alone in the FabLab)
It was a little scary to launch the cutting without knowing if I really did all of the GCODE correctly. And it happens I did it correctly but not optimally.
Digital Files and Links
Assignment Check
- group assignment
- do your lab's safety training
- test runout, alignment, fixturing, speeds, feeds, materials, and toolpaths for your machine
- individual assignment
- make (design+mill+assemble) something big (~meter-scale)
- Done
- extra credit: don't use fasteners or glue
- Done (for now)
- extra credit: include curved surfaces
- make (design+mill+assemble) something big (~meter-scale)