Taking Toolpath Creation out of the CAD Office
The VISI suite of CAD/CAM software was instrumental in designing the head configurations, handle and 3-D tooling, along with the CNC toolpaths for a the collapsible shovel.
With its two-hinged handle, the collapsible shovel is designed and manufactured by plastic molding experts Senior and Dickson with the help of CAD/CAM tools from Vero Software.
While the snow shovel is primarily aimed at motorists because of its handy folding design, the manufacturers also expect it to become an essential tool for helping householders keep their driveways clear of snow and other debris with its unique interchangeable shovel and fork heads.
Senior and Dickson are specialists in plastic injection, rubber moulding and die casting. By linking their experience of injection molding, moldmaking and rapid prototyping, they readily develop ideas from concept through to working prototypes and on to production tooling—as demonstrated by the snow shovel project.
The VISI suite of CAD/CAM software was instrumental in designing the head configurations, handle and 3-D tooling, along with the CNC toolpaths. All design work and electrode extraction is performed in the CAD office while toolpath generation is carried out on the shop floor next to the milling machines.
Chris Hodgson, Technical Director, explains the advantages of taking the toolpath creation out of the CAD office. "We moved CAM onto the shop floor as the machinists are closest to the action and can react immediately without having to wait for the design team. They know what tooling is available and how to best machine an insert or electrode."
The electrodes are extracted directly from the 3-D inserts by the CAD office and passed to the shop floor for manufacture. The graphite electrodes are machined using Hurco Ultimax VMX50 machining centres (50"x26"x24" machining envelope) and then sparked into the tooling using an Agietron 3U cavity sinking EDM machine.
VISI Modelling was key in both designing the original handle and then strengthening it by allowing Senior Design Engineer Karl Freeman to add further ribbing to the existing model and easily apply the changes to the tooling inserts. Based around the industry standard Parasolid kernel, VISI provides complete flexibility to construct, edit, deform and repair complex 3-D data.
Hodgson says after trialling the first prototype they chose to add cross ribbing to the shaft to give it greater sideways strength and apply larger radii to remove a localized stress point that caused part failure during stress testing. “This was very easy to do in VISI because the software is not constrained by rules or a previous design history. You can simply jump back into the design process at any point—you’re never stuck with a model that you can’t alter.”
Once the model was finalized, the 3-D tooling was designed using VISI Mold and then manufactured from P20 pre-treated steel for the shovel head, and H13 hardened steel for the handle and hinge. The shovel handle and folding mechanism are produced using a high-performance polycarbonate and the shovel head is produced using a recycled polypropylene, which is commonly used and resistant to fatigue.
The shovel concept began with a wooden handle, but Senior & Dickson quickly realized that this was impossible because of the angle required for it to connect to the head, and turned to VISI to design the model for a molded handle.
“We looked at using a cranked handle, and continued from there with a folding design to make it much more convenient to store. The shovel is extremely lightweight, and with the folding handle it is an ideal size for keeping delivery costs down for online customers.”
Focusing on the relationship with Vero, Hodgson says before switching to VISI from another high-end software system, it often took 2 or 3 weeks to produce tooling, but VISI has reduced that time to just three or four days. A fact echoed by Freeman, who also points out that VISI’s speed and ease-of-use means the design office is now producing more high quality work with fewer members of staff.
Both agree that Senior & Dickson would not be as successful without using VISI, which they say gives them a competitive edge. The company has been in business since 1981 and provides an extensive service of design and manufacture to a number of major clients that includes Hotpoint, Spear and Jackson and Stewart Golf. “We do not specialize in any one particular area,” comments Hodgson. “But thanks to VISI, we master them all.”
For More Information:
Senior & Dickson Ltd
Negative stock shutoff can help you make better molds in less time. Here is a clear definition and description of the process. While the concept is fairly simple, the implementation can be challenging.
While both hot runner and cold runner systems have their benefits, for design flexibility as well as reduced cycle times and costs, hot runner systems will probably be the better choice.
The world of CAD offers many alternatives to shops that want to use the latest 3-D technology for their mold design. This article looks at the benefits of the various approaches and offers some tips on choosing the most appropriate one.