CNC Mill Introduction

This is the content required for an introduction to our CNC mill - reading this does NOT replace the mandatory session with a tutor! It will make it a lot quicker though ;-)

If you need this introduction, please reach out to the following tutors: Sebastian, Luzian

Before you get this introduction, we recommend you get the Handheld Router Introduction and gather some experience, this will help you understand the machine much better. For CNC beginners, it is recommended that you start with the CNC router introduction and gain your first experience on the Workbee CNC.

Safety

Personal protection:

Dangers	Precautions
sharp, fast spinning bits (end mills or - rarely - certain router bits)	You MUST stay clear of the spindle when in operation You MUST unplug the spindle when changing a bit or touching the chuck for any other reason insert your mill as far as you can afford for maximum strength
the bit may break during operation, sending part(s) of it flying toward you	You MUST insert your bit as far as you can afford for maximum strength You MUST wear eye protection You SHOULD position the wooden or acrylic U-shaped box over the work area; the dust shoe also offers some protection You SHOULD NOT rapidly cool a hot bit by suddenly applying coolant - rather, cool continuously or do not cool at all
the bit can get extremely hot can potentially set sawdust on fire remains hot for a while after using	when you see smoke, immediately stop and re-think your tool settings - it might be spinning too fast or you could be feeding too slow! Are you sure your bit is sharp?
strong forces acting on the workpiece that might make it move	You MUST secure your workpiece properly - see CNC router workholding
the machine has no live sensors and will execute its code regardless of what gets into its way heat generated during improper use can even set the machine on fire	You MUST reference the machine to the workpiece (relative starting positions) before starting the router You MUST make sure your planned toolpath only passes through the workpiece and avoids machine or workholding parts You MUST monitor the CNC router closely when in operation You MUST keep an eye on the cables that come from above - are they securely out of the machine's paths? You MUST let end mills cool down before handling (risk of burning yourself)
powerful motion system can crush your fingers	You MUST stay clear of all moving parts while the machine is running
hitting "pause" or "stop" in a control program will still let at least the current line be executed	You MUST push the emergency shutdown button if anything goes wrong
lots of dust that could harm your health or settle down on machine parts, possibly hindering movements	When milling wood or plastics, you SHOULD use the dust shoe and connect a shop vac. When milling metal, you MUST NOT extract the metal chips with a vacuum. You SHOULD position the wooden or acrylic U-shaped box over the work area to reduce the risk of flying chips towards the user and to protect the rails.
When milling metal, hot chips can fly towards user	You SHOULD always place the U-shaped guardrail over the table. Even with the rail, chips can fly towards you. You MUST stay clear and you MUST wear eye protection.

Feed Direction

The feed direction at this CNC router cannot be influenced. Lots of CNC routers allow to set the feed direction using G-codes M3 and M4. On the Kress mill the router cannot change its spinning direction, it always use M3 (clockwise). The CNC router thus does push and climb cuts at the same work piece depending on your geometry.

Feedrate

The proper combination of rotation speed and tool advancement is determined by your bit and material.

• be cautions not to remove too much material at a time - several passes are usually necessary if you want to go deep
• advancing too slow can produce excessive heat, advancing too fast can cause the workpiece to chip and even damage the bit

Suggested Reading

Besides these safety notes, you should read about the different end mills (and router bits, if you want to try those) to know what you're doing! Different materials usually require different mills, and the feedrate depends on the mill as well as the type of material.

• our list of milling experiences - please also share what you find out!
• top milling tools for new CNC machinists
• G-Code fundamentals

Recommended Watching

• CAM, virtual setup: how to prepare your model and place it in a virtual workpiece in Fusion 360 (DE)

Demonstration

The tutor will show you these steps in detail:

1. Machine Explanation
   • Explain the main components of the machine
   • Explain the emergency switch vs. stop switch on remote jog wheel
2. Machine setup
   • turning the machine on and off
   • homing the machine (setting absolute "0" positions)
   • selecting the right bit
   • inserting a bit (note: unplug spindle!)
3. Fusion 360 setup
   • Draw a simple pocket
   • Set-up the machine in Fusion using files from Github (machine + post processor)
   • Create a tool
   • Set up a tool path
   • Export the tool path to USB
4. Setting up the workpiece
   • Securing your workpiece on the bench
   • How to protect the T-groove table
   • Setting the relative "0" position on your workpiece
   • connecting and turning on dust extraction (only for wood or plastic workpieces)
5. Execute the job
   • how to load and run the tap file from USB
   • tip: "cut air" first (remove bit and collet) to make sure coordinates are set up correctly
6. Cleaning & storage
   • Clean inside and outside the box with brush and vacuum cleaner
   • Storage below machine
   • Cover machine with sheet

Waiting List

This introduction takes longer than many others and usually can't be done spontaneously during regular opening times. If you would like to receive it, please add yourself to >> this list << and we will find a good time once a few members are on it!