CNC Toolpath Coding

Project For
Carleton University
Year

Fourth Year (2021)

Key Focus
  • CNC
  • Fusion 360
  • Toolpath Coding
  • 2D and 3D Toolpaths
  • Group Collaboration
Project Length
2 weeks

“This project introduced us to 3D cam toolpath generating software to create a small 3D part to be cut on a CNC mill”.

This project was assigned for Carleton University’s fourth year course Advanced Studies in Manufacturing Technology. It was a 2 week group project where we were required to create 3D tool paths using fusion 360s milling options. This part was then cut on a CNC mill. The part had certain mandatory features to challenge us to cut different elements such as a flat bottom pocket and convex and concave features, among others.

01 Creating the Part

Initial Meeting

This project had a unique challenge as we completed it as a group of three during the COVID 19 pandemic, so all meeting were done virtually via zoom. We started by listing off the different features required and create our part with that in mind. We also had a size requirement for the part, and were given a stock piece to build off of. We decided to create a mini skatepark with the different elements.

An angled surface
A flat bottom pocket
A convex feature
An angled surface
A flat bottom pocket
A convex feature
A concave feature
A hole (through or blind)
A fillet
A chamfer
A straight sided protrusion
Some engraving (text or a symbol)

02 Toolpath Creation

Toolpath 1 

3D Adaptive Clearing

We started with a 3D adaptive clearing with a 1/2″ flat end-mill to clear most of the extra stock. The geometry selection was the stock contours and most of the default settings were left the same.

Toolpath 2

3D Adaptive Clearing

Next we did a 3D adaptive clearing with a 3/16″ flat endmill to clean up some of the stock in the pocket as the 1/2″ endmill was too large to fit. For the geometry we selected the bottom edge of the pocket.

Toolpath 3

3D Horizontal

We used a 3/8″ endmill on a 3D horizontal path to finish the horizontal surfaces of the part. No geometry was selected. The path left 0.02″ of radial stock and smoothing was turned on with a tolerance of 0.01″.

Toolpath 4

3D Horizontal

Much like toolpath 2 we used the same toolpath type with a 3/16″ flat endmill to reach into the pocket. The geometry selected was the bottom edge of the pocket and the same radial stock and smoothing selections as toolpath 3 were used.

Toolpath 5

2D Contour

We used a 2D contour to finish the horizontal edges of the path with a 3/8″ flat endmill. We selected all the features with flat horizontal walls for the geometry and turned smoothing on with a tolerance of 0.01″.

Toolpath 6

2D Chamfer 

We used a 2D chamfer toolpath on the box element to create a chamfer using a 1/8″ 30 degree chamfer tool. The geometry selected was the top edge of the box. The chamfer width was 0.04″ wide and smoothing was turned on with the same tolerance as prior.

Toolpath 7

Engrave

We used an engrave toolpath on the text to with a 1/8″ 30 degree chamfer tool. We selected the text and made the top clearance height -0.2″ to create the engrave.

Toolpath 8

3D Contour

We used the 3D contour tool and a 1/4″ ball endmill to cut out some of the features. We turned on rest machining so the tool wouldn’t touch parts where there is no stock left. We also turned on avoid features and selected some features we didn’t want this toolpath to cut such as the hole and convex feature. We turned on the smoothing feature and changing the ramp angle from 2 degrees to 10 degrees.

Toolpath 9

3D Ramp

We used the ramp path and a 1/4″ ball endmill to cut out the fillet feature. We found this did the best job to cut out the curve. We also turned on smoothing with a 0.001″ tolerance.

Toolpath 10

3D Parallel 

We used the 3D parallel path and a 1/4″ ball endmill to cut out the both the ramp and concave feature. We turned on contact boundary point for a better finish and smoothing. We selected those two features as the geometry. We had a stepowver of 0.02″ which gave a nice finish.

Toolpath 11

3D Scallop

We used the 3D scallop path and a 1/4″ ball endmill to cut out convex feature. We turned on contact boundary point for a better finish and smoothing. We selected outline of this feature for the geometry. We had a stopover of 0.015″ to get a finer feature. Initially we had collision problems with this feature so we roughed it out in toolpath 8.

Toolpath 12

Drill hole

We used a 5/32″ drill tool to start the hole for our part. We selected the hole feature for the geometry. We set the bottom height to the desired depth of the hole and made sure to not cut into the safety sheet.

Toolpath 13

Circular 

Finally we used a circular tool path with a 1/4″ ball endmill to enlarge the size of the hole. We selected the hole as the geometry.

03 Cutting the Part

Our professor cut these pieces on the CNC and showed us via zoom so we could see how the foam cut and how efficient our toolpaths were.

04 Final Model

05 Takeaways

This project was a good start to learning about creating toolpaths and fusion 360s milling features. This was the first time any of my group members have creating milling toolpaths so it was a little bit of trial and error for us to figure out what the best paths for different applications. With the covid 19 pandemic we also had the challenge of working remotely. We worked mostly through zoom with one person controlling the fusion model and screen sharing so the other group members could provide assistance. For certain areas where we got stuck, we would take an evening to ourselves to try to find solutions and regroup to share what we learned. Overall, this project taught us a lot about CNC milling and 2D and 3D toolpaths.