CNC Router 101

Class presentation here: 

https://docs.google.com/presentation/d/1z0J3msKjeNkzQOtDGowYq-WXv3sUo-WxrOoSAq3kXHk/edit?usp=sharing

3DHubs CNC Design: https://www.3dhubs.com/guides/cnc-machining/

CNC Router Fees

At the CNC Router

Basics of How It Works

ink_part_vcarve.png

     Design                                    Create Toolpath             Run the CNC

     ( CAD Software )                 ( CAD / CAM program )         ( Machining Software )

CNC = Computer Numerical Control

Specifically a Computer Numerical Controlled  Router

The computer controls the machine, telling the motors where to move the router and how fast it rotates

Parts of the CNC

How to Turn It On

Spindle Warmup Routine

Needs to be done if you are the first one to use the machine that day

Safety Considerations

In the Classroom

SlideShow

https://docs.google.com/presentation/d/1ZZJPgDvorbs5rYXwNcsdP4EbCp53vzvXbybJh5fe0TE/edit?usp=sharing

Workflow

ink_part_vcarve.png

     Design                                    Create Toolpath             Run the CNC

     ( CAD Software )                 ( CAD / CAM program )         ( Machining Software )

CNC Bits (show block with different bits in it)


Step 1: Design - CAD Software

The CNC Router 101 class goes over 2D Design using Inkscape.

With a 2D design, a 3D part can be created by controlling the depth of the cut.

Design Considerations

Step 2: Create Toolpath - VCarve

To access the MakerSpace version of Vcarve 12 to run on MakerLabs' CNC Router, follow these steps:

Open your vector file in VCarve

Job Setup

Job Size (X & Y)

Material (Z)

Units

Leave everything else as the default

Tool Setup

Cutting Parameters

Types of Cuts

Note: When cutting through material, set the depth of the cut to 0.02” deeper than the material (Z) thickness


**Special Note: For VCarve version 10.5, it will generate multiple pockets if multiple tools are listed.  

IE. In the image shown, it will generate .04" pockets for both the .5" and .25" endmills listed.  If you only need 1 pocket to generate, remove the tool from the list that is not applicable.


Feeds and Speeds


Tool Number

Passes

Climb vs Conventional Cut

Climb Cut: the rotation of the router bit pushes into the material

Conventional Cut: the rotation bit pulls off the material

Note: every material and end mill is different and they should be tested to determine the best finish

Tabs

Tabs are pieces of material left behind in profile cuts when the material is cut all the way through. Tabs should always be used and ensure that the pieces will not move, break, or fly away throughout the rest of the cut.

Tab Sizes

Tab Placement

    Note:

Ramps

Exporting your File


Step 3: Clamp Down Methods

Material can be secured in a variety of different ways. If you can rip material off the bed, so can the machine.

Screws

Use screws through a sacrificial part of your material. Make sure the screws will not get hit while running the job.  You can damage or break a bit if hitting a screw.  

Clamps

Material can be clamped directly to the bed using regular wood clamps.  Be careful with clamp placement to avoid running the tool into the clamps.

Cleats

Wood cleats can also be made from scraps of wood. Cleats are a block of wood with a rabbet (groove on one side), and can be used to hold down material on each side. The rabbet height should be slightly less than the material height, allowing it to pull down tightly when screwed in place.

A thin, slightly flexible strip of wood can be used on varying material thicknesses. Glue a smaller strip across it, which will butt against the material to prevent slipping.

Jigs

Press-Fit Jigs

A press-fit jig provides good holding power and can be made quickly and accurately using the Shopbot.

This is a good solution for holding small work pieces, extra-thick stock, or if the material has already been cut to its final size and there is no room for screws.

Shown here: two pieces of MDF have been glued together and pocketed out to hold this piece of hard- wood. The jig is screwed to the table, then the work- piece is pressed in.

A similar method can be used where blocks of wood are tightly screwed to butt up against each edge of the material to hold it in place.

Door Stop Jig

This method is good for repetitive processes where you need to switch out materials of the same shape and size.

Blocks of wood are butt up against two edges and screwed into place. A third block of wood is screwed into another edge at and angle, and a door stop shaped piece of wood is wedged between the material and the angled block. This allows for quick and easy removal of the material, while keeping it secure.

The ideal angle for the wedge is 110 degrees.

Step 4: Run the CNC - ShopBot

Quality Assurance - Air Pass

An air pass is where the CNC follows the motions of your toolpath “.sbp” file but does not cut the material. The X & Y directions are properly zeroed with respect to the material but the Z direction is zeroed above your material so that the lowest point does not touch the material.

Run an air pass in between steps 6 & 7 above.

Using the Desktop CNC

- Bring RED computer + connect CNC to it through USB. Make sure the connection is stable.

- Connect both to a power source, that is not being shared with the big CNC

- Turn the CNC on with the switch on the right corner by moving it upwards. The control box on the side will light up.

- Open Shopbot in the RED computer

- Clamp your material and zero axes

- Feed rates cannot be greater than 2"/second on this machine.  The Desktop CNC cannot move as fast as the CNC Router table, and will skip steps if it is pushed to move too fast.

- Spindle speed is set manually through the dial on the control box . 

- Proceed to run file.

FAQ’s

Where is the larger, detailed command window of Shopbot?


How do I change from mm to inches and vice versa in Shopbot?

Strange Error messages you do not recognize and google doesn’t help

Reload default configuration file

Runtime Error 13:

Delete C:/ProgramData/Shopbot/Shopbot 3/shopbot.ini

Reopen Shopbot

In pop-up asking for configuration, select file (in folder alpha) for ShopBot PRSAlpha 96x48 - double check the z-height settings

The toolpath is cutting inside & outside the line

Check if all the vectors are a closed path. If not, "weld" or "join" all the lines together.

If spindle stops in the middle of cutting and the following message appears:

         ShopBot No Longer Being Recognized!

        "An error is occurring that could not be corrected. You will need to exit, check all cables, then restart the software. Tool Location may no longer be accurate."

Take a photo of where your zeros are.

        Restart the Shopbot software.  Zeroes should still be accurate.

        Modify your Vcarve file if necessary to start where the machine left off.

Parameter Error:

Parameter Value Above Range for VS -- Setting to Upper Limit (304.799995422363)!

This error means the file is set so the jog speed is greater than 300mm per second.  This is faster than the CNC can safely move and the speed will need to be adjusted to a lower speed.  If you do not click OK on the error message within 20 seconds the application gets stuck and you have to restart the whole ShopBot and start over.

       

Resources

Free project files:

https://www.toolstoday.com/t-tool-videos

https://www.shopbottools.com/explore/projects


More Feeds and Speeds:

http://www.harveytool.com/cms/GeneralMachiningGuidelines_17.aspx