Some time ago, Protech received a request from one of its partners: “Can you construct a handle from a design sketch?” The handle was first to be manufactured as a prototype and later in a smaller production of 5-piece handle. The final production of handles should be 100 pcs. per year. The handle should be light and therefore aluminum was the suggested material.
Our partner wanted the handle to have a smooth surface to facilitate cleaning. The requirement meant that we could not make the product light in the form of ribs and holes on the outside of the handle. The first construction took 12 hours from sketch to finished CAD file and was performed in the integrated CAD / CAM system TopSolid’Design. After finishing construction, we did CNC programming in TopSolid’CAM and began machining. The finished handle was really good, but required a lot of manual work. We removed the handle from the milling block, fixed it and then blew the whole surface clean. The pre-milled handle weighed 187.5 grams .
The milling time of the first handle was quite long. This is to be expected when it comes to milling the first prototype, as it often requires some adjustment and reprogramming of the NC code before the machine operator is completely satisfied. The first milling took 8 hours and cost incl. materials, CNC programming and machining time totaling 807 euros . Subsequent milling of a handle took 1 hour and 25 minutes and there is probably a lot more you can do to reduce the time in the machine. In the table below you can see costs and production time for some different production volumes.
After analyzing the weight and production cost of the milled aluminum handle, we asked ourselves this question – why not use additive manufacturing and manufacture a hollow stainless steel handle? The requirement for the handle was that the insert part should be in metal, but not necessarily in aluminum.
We chose to manufacture the hollow handle in stainless steel (316L), instead of aluminum, as the machine cost of producing with additive manufacturing is significantly lower in stainless steel than aluminum. The production capacity for additive manufacturing in stainless steel is also significantly greater than in aluminum. The original handle construction was made whole with a wall thickness of 1 mm. We even added a small hole to be able to get excess powder out of the handle. It took less than 5 minutes in the CAD system to make these two adjustments. In order to 3D-print a complete handle, we were forced to add support structure. The generation of the support material is a relatively automatic process. The generation of the support material for the complete handle took 15 minutes . It took 43 hours and 11 minutes to print the hollow handle in our Xact Metal XM200C .
Removing the support material after 3D printing with Metal Powder Bed Fusion (Metal-PBF) is in many cases a time consuming job. For an item similar to our handle, most are removed manually. The 3D print of the hollow handle was really good and with a weight of 112.2 grams . The weight of the handle was close to the target of less than 100 grams, but the cost per. handles were too high and productivity became too poor. Although one could use a machine with a larger build volume and thus print several items at a time, productivity was still too low.
The challenge was to lower the weight of the handle without compromising on the design requirements. The insert itself should be in metal, but what happens if you combine plastic and metal? With a two-part construction, the handle itself could be made of plastic which would lower the weight of the entire handle drastically. Reconstruction of the handle into a two-part product took 8 hours .
The actual handle part of the two-piece item was designed so that it could be 3D printed in carbon fiber reinforced Nylon ( Nylon 12CF ) in our Stratasys 450mc 3D printer. The mechanical properties of the material are unique and the item was printed with an internal so-called Lattice structure. Ten handle parts were distributed on the 3D printer’s construction board and were printed in 7 hours and 36 minutes . A single part took 1 hour and 10 minutes to print and had a total weight of 25 grams .
The insert portion of the handle was designed to shorten print time and the need for support material. Ten insert parts could be packed on the building board in our Xact Metal XM200C and it took 125 hours and 10 minutes to print. Removing supporting materials and completing each topic also took time. Each item was then glass blown to obtain a smooth surface. One insert took 17 hours to print and weighed 60 grams .
The two-part handle eventually gained a total weight of 85 grams , which meant the lowest weight and lowest production cost for all variants of handles produced in the project.
By using additive manufacturing and innovative construction, the result is products that weigh less and cost less to produce. Design for additive manufacturing challenges designers to think in other directions, but can result in better products than with traditional production technology – think additive manufacturing.
The table shows costs and time for production of 1, 10, 25 and 100 pcs. of the different handle variants.
The costs shown in the table are the actual costs in Sweden. Of course, the cost can vary from country to country. Manual labor is a large part of the cost of the different variants of the handle construction and the cost of manual labor varies quite a lot between countries. The table shows costs and these are not the actual prices of a manufactured handle. Companies that manufacture products always put a margin on their production costs. The margin that is imposed varies greatly in the different companies. Therefore, the actual price of a product can vary a lot.
All the conclusions drawn in this project are based entirely on geometry. Another product with a different construction may well result in different conclusions.
Protech has been given permission to publish this project to inspire others to think about how their products can be manufactured. The project can be used freely and models as well as underlying calculation data can be requested by Anders Brask (Contact information can be found below).
Reduced weight on a product saves costs, reduces a product’s climate footprint as well as its transportation costs. Additive manufacturing is going to play an important role in changing the way products are manufactured.