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CNC BasicBot Part 2: Motor Mounts

A lesson by Al Chirinian from TeachSTEMNow.com

The TSN BasicBot platform is designed with hobby servo use in mind for simple, reliable and inexpensive motion. Multiple holes the in motor mount region provide for variations in servo size and wheel placement. The servo mounts themselves form a major structural element of the BasicBot, together with the servo motors themselves to resist twisting forces. In this STEM lesson, we will guide students to successful CAM programming the servo mounts for machining on the CNC mill. The activity teaches students how to create pockets, contours, and creating new machine coordinate systems for part rotation. The written summary below highlights the CAM process. A more in-depth video is available at the bottom of the page. For students that do not have the benefit of a CNC mill, the part can be manufactured from plastic on a 3D printer as well.

Step One: Import the part

Import the .igs file into SprutCAM and drag select the entire part. Sew the faces together and select the transform button. Locate the Z axis to the top of the part.

 

 

Step Two: Pocketing

Click on the machining tab and create a pocketing operation.

 

 

Make sure that the edge tool on the upper part of the screen is active. Then hold the ctrl key and select the edges of the pocket. Double check that no segments were missed.

 

 

Go to the job assignment tab on the bottom left of the screen and choose add curves. The pocket will be created.

 

 

 

 

Click the run button and the toolpath will be generated. Look for the green check to appear.

 

 

The depth of the pocket will need to be adjusted in the parameters. Double click on the pocketing operation. Here you will select the endmill from your tool library, adjust feeds and speeds, as well as the pocket depth.

 

 

Before selecting the endmill, verify that the tool number corresponds to that in the tool library. Manually adjust if needed.

 

 

After adjusting the -Z value, the correct pocketing depth is achieved.

 

 

Exit parameters, click run again and look for the green check. Go to the simulation tab and run the simulation.

 

 

Step Three: Contouring

Create a 2D contour operation by going back to the machining tab. Go to finishing operations and find 2D contour. Holding the ctrl key, select the outer edges of the motor mount. Then within the job assignment tab, add curves as with the previous operation.

 

 

A path is generated around the servo mount. Choose the parameters for your endmill, feeds and speeds, depth of cut, and final cut depth. We are using .25 material in this case and run the endmill slightly over. You can elect to run slightly under the actual depth to stabilize the part and then knock it out, but this usually requires a bit of deburring.

 

 

Once the operation parameters are completed, click the run button to get the green check. Verify all is well with a simulation.

 

 

Step Four: Flip and Drill

This is a more advanced technique that will greatly benefit students, giving them the freedom to put all machining processes in one CAM program. Begin by rotating the part so the face to be drilled is oriented at the top. Create a hole machining operation. Click on the face and move up to the dropdown menu near the global CS tab. Choose the sense look vector option.

 

 

SprutCAM will automatically create a new Coordinate System, moving the axes so the Z is on the new ‘top’ of the part.

 

 

Next, go to the setup tab at the bottom left of the screen. Here we need to enable the machine setup parameters to recognize the new coordinate system.

 

 

Change the local cs settings to the new coordinate system name (probably local CS1 in this case) for Local CS, Workpiece CS, and Workpiece Setup.

 

 

Now to back to the job assignment tab. Select one of the faces in each hole that needs to be drilled while holding down the ctrl key. Click center and the holes will be recognized.

 

 

Click the run button and the green check will appear as the toothpath is generated.

 

 

Step Five: One More Time

There is one more hole to be drilled which means flipping the part again. Follow the same procedure as above, generating a new CS after selecting the new top face. Enable the coordinates on the machine setup tab, and select the hole. Click run to generate the toolpath.

 

 

At this point the simulation tab should indicate all green checks and the toolpaths will all be visible. Run the complete simulation to double check before machining. Students always get a kick out of the final simulations.

 

 

This completes the CAM process for the servo mounts on the BasicBot. These parts can be machined from Aluminum, plastic such as delrin or 3D printed. Using advanced manufacturing skills for genuine projects with long term educational value make STEM education an authentic experience with rewards that payoff all year long. For the complete CAM process in real time, check the video below.

Author: Al Chirinian

Original article

 

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