SHOPBOT GURU PAGE

This page contains content authored by David Carr, Agnes Chang, and possibly others.
Page moved to content archive 1/18/2011 by Daniel Fourie MAS.863 Fa '10

What kinds of materials can the ShopBot mill?

What types of bits can the ShopBot use?
What does the ShopBot operating software do?
How does PartWizard write part files for two-dimensional designs?
There is a collect of very detailed descriptions of various aspects of the shopbot from CSU-Pomona here.

How do I make a toolpath for the ShopBot / how do I generate ShopBot part (.sbp) files?
To make tool paths for the ShopBot, you'll need to use their "Part Wizard" program to export ShopBot part files that have the .sbp extention. Part Wizard saves information about the design and toolpaths as .art files, and generates .sbp files for the ShopBot Control software to read. You must save the .art files you created in Part Wizard in order to modify any designs or cutting files.
When Part Wizard first opens, click on "Create New Model" to get the following screen:

Set the width and height to the material you are working with (e.g. a 4-by-4 sheet of MDF is 48" x 48"); set the thickness to be slightly more than the thickness of the material to ensure that the shopbot cuts completely through (that's why we have sacrificial layers of wood underneath.) For example, if you are working with 1/2" MDF, set the thickness as 0.6". Set the Material Z Zero to "Top of Block" and just double-check that the Units are set to the units you are using.
On the main screen, the right side is your piece; where you place your paths on this white "material" is where the ShopBot will cut. Import your .dxf file and use the default settings in the dialog that appears:

Use the toolbox on the left to edit your paths; you'll basically only need to use the Select and Transform tool. The bottom left corner of the screen maps to the corner of the ShopBot bed that is closest to the power switch. When you have the paths laid out to your satisfaction, click on the Toolpath tab at the bottom left of the screen and you'll see your toolpathing options:

For general purposes, you'll want to use Profile, which will look like this (these were my settings for my rocking chair):

Select the tool you want to use, etc. When finished with all your settings, click on Calculate: Now at the bottom of the screen.
If you get errors, you'll want to check your vector paths. Minor problems can be fixed back in the Assistant screen, but I found that for most cases, I needed to fix the .dxf file. If everything goes smoothly, you'll see bright pink lines indicating toolpath, and arrows indicating travel direction on your screen.

Click on Save Toolpath.

Select your toolpath from the right-hand side and click on the Save... button at the bottom right to export your toolpath to a .sbp file.

How do I turn on the ShopBot?
The ShopBot is powered by two switches.

The box will turn on the machine (that moves the head along the 3-axes), and the big switch on the wall turns on the spindle (that rotates the bit.) On top of the box is the emergency panic stop button unit.

How to I setup the ShopBot?
First put your material on the bed and secure your piece using clamps. Make sure the extended end of the clamps are pointed down so it doesn't get in the way of the ShopBot head. If clamps aren't strong enough (and in many cases it isn't) you'll want to use screws, nails, or sit on your material when its cutting in order to hold it in place.
Load your part file using the bright green button:

To set the origin, hit the key K on the keyboard, and use the arrow keys to move the ShopBot head along the x- and y-axes. (The page up and down buttons will move the head along the z-axis, but you can automate the z-axis calibration in the next step.) When you are done, go to the Zero menu and select Zero axes (X & Y):

To automagically set the z-origin, click on the button to Zero Z-axis (using zeroing plate):

The computer will then give you instructions on the screen, but basically, locate zeroing plate and alligator clip located on the side of the ShopBot head:

Pull it out and plate it directly under the bit, and clip the alligator clip to the head as such:

Hit Ok on the screen and the ShopBot will sense and set the safe z-distance.
Before you cut, remember to turn on the vacuum, whose main body is located to the left of the ShopBot:

Just flip the red and yellow switch on its side:

Now go to File -> Part File execute. Remember to hold on to the emergency stop button just in case.

How do I change tools / change bits on the ShopBot?
First, you'll need to lower the vacuum hood by loosening the screw at the back of the ShopBot head:

Then, you'll need these two wrenches:

You'll see that the head has two sections, colored appropriately to match:

Use the silver one to hold the top in place and twist the bottom with the other wrench to loose grip on the bit.

How do I use the ShopBot to mill / how do I use Mill Wizard?
See Daniel Cardoso's documentation here.

What are good feed rates for the ShopBot
In 1/2 inch MDO/Plywood, here are some good settings to start with:
1/8 inch mill, .25 inches deep - 100 ipm, 50 ipm plunge
1/4 inch mill, .25 inches deep - 75 ipm, 30 ipm plunge

Do I want to climb cut or conventional cut?
It depends. In general, "non-oriented" materials like plywood and MDO respond better to conventional cutting. Solid wood and wax seem to like climb cutting.

My holes are not round!!! What do I do?
There is backlash in one or more of the machine axes. Most likely the stepper motor plates need adjustment. See one of the class staff to show you how to adjust these.

My holes are rounder now, but they're still ~.003 out of round.
Unfortunately, there is some residual backlash even after the axes are readjusted. To deal get even better precision, you need to preload them. When cutting your precision holes, grab the spindle housing with your hands. As the cutter moves around the hole, apply generous force to push the mill into the material. This will take up the backlash and give you a the best hole possible.

Important!
If your endmill looks like this, your speeds and feeds are wrong, and you are probably about to start a fire! Triple check your settings!