The Bicycle Helmet Project at IYRS
Kelsey Britton is the Composites Technology program manager and instructor at IYRS School of Technology & Trades in Newport, RI. We recently sat down with Kelsey to discuss her use of RhinoCAM as part of the curriculum in her Composites Technology class. Kelsey says that she uses many of the articles on the MecSoft Tech Blog to learn and teach her students how to be proficient in RhinoCAM. Here is a project by IYRS student Wyatt Jeffries recently completed in Kelsey’s class with the help of RhinoCAM.
The Bicycle Helmet Project
In this project, Wyatt manufactures a bicycle helmet using composite technology materials and techniques. The helmet design was loaded into Rhino 3D where the surfaces were used to design mold cavities. The mold was then used to create the composite fiberglass lay-up of the outer shell. It was also used as a fixture to machine the helmet’s foam inserts. The 3D model of the helmet is shown in Rhino below.
|“We chose to teach Rhino 3D to our students because of its dominance in the marine industry. RhinoCAM was a natural extension of that decision and honestly I love our RhinoCAM! I like the fact that its surface based. I can do just about anything with it. Also, the articles on the MecSoft Blog have been very helpful for setting up my curriculum. Every semester I feel that MecSoft supplies more ways to access support and that is huge for me.”
Kelsey Britton, Program Manager & Instructor
For this project right and left mold halves of the outer helmet shell were designed in Rhino using surfaces extracted from the original 3D CAD model. Only the outer shell needs to be represented by the cavity. Shown below is the right side mold cavity block. After the cavity block design is completed, RhinoCAM is used to create the toolpath strategies and the G-Code needed for the Fagor 8055 controller on the school’s Freedom Patriot 3 Axis CNC router.
In the left side image below we see the right half cavity mold. The four locators indicate which face is mated with the left side cavity. In the right side image we see a 2½ Axis Facing operation to level the parting plane and a 3 Axis pocketing operation for the four locators.
|(Left) The Rhino model of the left side cavity block mold is shown. (Right) We see the cavity block cut material simulation and in-process stock displayed in RhinoCAM. The parting plane and 4 locators are shown.|
Machining the Cavities with RhinoCAM
In the left side image below we see the cut material simulation and in-process stock results of a 3 Axis Horizontal Roughing toolpath strategy also referred to as Z-Level Roughing. Using a 12.7 mm diameter flat end millI, this strategy is used to clear out material from the cavity. Cutting parameters include a 0.6 mm stock allowance, an Offset cut pattern and a Mixed cut direction. The cutting tool works its way out from the center of the cavity at a 40% stepover distance. Each cut level begins with a 10 degree path entry and removes material at a depth of 50% of the cutting tool diameter. Arc fitting in each XY plane is also performed to maximize surface finish and accuracy.
|(Top Left) We see the cavity cut material simulation and in-process stock from the 3 Axis Horizontal Z-Level Roughing operation. (Top Right) We see the completed cut material simulation and in-process stock from the 3 Axis Horizontal Z-Level Finishing operation.|
In the right side image above we see the results of a 3 Axis Horizontal Finishing toolpath strategy using a 6.35 mm diameter ball mill. This toolpath strategy is also referred to as Z-Level finishing. Cut parameters include a Stock Allowance of zero, a Climb cut direction and a Stepdown of 1 mm between Z levels. In this strategy the steep side areas of the cavity are cut with the radius and sides of the tool. In the flatter areas, optimized machining is enabled which adds additional cutting paths utilizing the tip of the ball mill, all in one toolpath.
Each cavity block is made up of 6 levels of 10 mm thick MDF. The machined cavities are then visually checked, hand sanded where needed and the right and left halves are clamped together using the locators for alignment. To prepare the cavity for composite layup, 4-5 coats of epoxy resin are applied, then up to 600 grit sanding, buffing and polishing. The completed cavity is shown in the left side image below. On the right we see the fiberglass composite material placed into the cavity. The same cavity mold is also used as a fixture to machine the inner foam inserts of the helmet!
|(Top Left) The completed and assembled right and left side cavities, coated, sanded and polished. (Top Right) The composite fiberglass lay-up of the helmet outer shell.|
|(Top Left) Wyatt gives the mold cavities some last minute preparation. (Top Right) The final composite helmet and foam insert assembly.|
— Great job Wyatt! —
More about IYRS
IYRS School of Technology & Trades, located in Newport, Rhode Island offers marine industry classes on Composites Technology, Marine Systems, Boatbuilding & Restoration as well as Digital Modeling & Fabrication. To learn more about the IYRS programs we invite you to visit them online at iyrs.edu as well as on Facebook, Twitter and Instagram.