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Redesign? Retool? Snow Problem

Dec. 1, 2011
Software helps design a new collapsible snow shovel
The collapsible snow shovel is designed by Senior & Dickson Ltd. for portability.

At this time of year, it’s wise to be ready for foul weather, at home and on the road. You may not want to shovel snow, but it’s good to have the right tools when the need arises. With a two-hinged handle, the Senior & Dickson collapsible shovel is designed by the plastic molding company with the aid of Vero Software specialty CAD/CAM tools, primarily for motorists. The manufacturers also expect the folding design to become a preferred tool at home, with its interchangeable shovel and fork heads.

Senior & Dickson Ltd. is an English producer of plastic injection and rubber moldings, as well as diecastings. By combining its experience with injection molding, toolmaking, and rapid prototyping, it develops concepts like the collapsible snow shovel from concept through to working prototypes and on to production tooling.

The VISI CAD/CAM suite was instrumental in the design of the shovel’s head configurations, specialized handle, and 3D 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.

Senior & Dickson technical director Chris Hodgson explained the advantages of moving toolpath creation from the office to the shop floor. "We moved the 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 best to machine an insert or electrode." The electrodes are extracted directly from the 3D inserts by the CAD office and passed to the shop floor for manufacture. The graphite electrodes are machined using Hurco Ultimax VMX50 machining centers (50×26×24-in. machining envelope) and then sparked into the tooling using an Agietron 3U cavity-sinking EDM machine.

The injection mold tooling for the shovel head was designed using the VISI Mould program, and then manufactured from P20 pre-treated steel. H13 hardened steel was used to form the handle and hinge molds.

VISI Modelling played an important part in the design of the original handle, and later in the process of strengthening it, by allowing senior design engineer Karl Freeman to add ribbing to the existing model. It also simplified the step of applying changes to the tooling inserts. Based on the industry-standard Parasolid kernel, VISI provided complete flexibility for constructing, editing, deforming, and repairing complex 3D data.

Chris Hodgson said that after running trials on the first prototype Senior & Dickson designers chose to add cross-ribbing to the shaft, to give it greater sideways strength, and to 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,” Hodgson offered. “You can simply jump back into the design process any point – you’re never stuck with a model that you can’t alter.”

Once the model had been finalized, the 3D tooling was designed using VISI Mould, 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 that is widely used and fatigue-resistant.

The shovel concept began with a wooden handle, but Senior & Dickson quickly concluded that this was impossible because of the angle required for it to connect to the head. At that point the designers turned to VISI to design the model for a molded handle. “We looked at using a cranked handle, and followed on from that with a folding design to make it much more convenient to store. At around two kilos the shovel is extremely lightweight, and with the folding handle it fits inside the smallest postage bag, keeping post and packaging delivery costs down for online customers.”

The VISI CAD/CAM suite was used to devise the CNC toolpaths, and is run on the shop floor.

When full production is underway the shovel is likely to be available though many retail stores and DIY/home improvement chains.

Chris Hodgson said that before switching to VISI from another high-end CAD/CAM software, he sometimes waited two or three weeks for tooling designs to be complete. I the snow shovel project, VISI reduced that time to just three or four days. Karl Freeman pointed out that VISI’s speed and ease of use means the Senior & Dickson design office is producing higher-quality work now, with fewer staffers.

Both agree that Senior & Dickson would not be as successful without using VISI, which they say gives them a competitive edge.

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