Uber Design U180 - part casting

thingiverse

I've been following the RC groups thread for the incredibly powerful Uber Design U180. I saw my buddy fly the U180 the other day. It looks super cool and crazy fast. I was hesitant to jump in due to the comments of parts breaking during crashes. In the thread people were talking about trying to mold motor mounts and mid plates from actual parts. Previously, I tried to mold from 3D printed parts and found it frustrating. Background: Creating 3D printable molds in CAD software is a hassle. The steps are well-known. However, for every iterate of the part you need redo the whole mold making process. I was really happy to find Jason Webb's OpenSCAD script which does much of the heavy lifting. Check out his project http://www.thingiverse.com/thing:31581 There is also further info on his website. http://jason-webb.info Updates 6/19/2016 – I created two versions of the bottom plate with different thicknesses (beefy and skinny). I also created a jig to drill the carbon fiber rods so it can be joined together with nylon zip ties. I designed a small support to secure the ESCs to the carbon fiber cross bars with zip ties. The assembly of the Uber went well and I'm happy with the end result. See attached photos Give them a try and send feedback. 4/26/2016 - The casting approach required the recreation of Theledman's original design to be mold release friendly. The current designs are coming out of the casting well and the molds have been reusable with no wear. All designs are dimensionally accurate for the motor mount holes and 10mm OD/8mm ID Carbon Fiber Tube. I created three different designs to address various approaches to the inner cross section connection to the motor mount. Design 1 is most similar to Theledman's design but requires the drilling of a hole for - 6mm OD/4mm ID Carbon Fiber Tube Looking to minimize the amount of post-casting work, I thought creating a boss was a better approach. Then I found jolars' remix and my assumption was confirmed http://www.thingiverse.com/thing:1406948 Design 2 includes a boss for the - 6mm OD/4mm ID Carbon Fiber Tube. (The STL file has –sb- in the name for small boss) Design 3 includes a boss for the - 10mm OD/8mm ID Carbon Fiber Tube. (The STL file has –bb- in the name for big boss). Note pay attention to the changes in his BOM which uses all 10mm OD CF tubing Of all the designs, I believe that either #1 or #3 are the best approach going forward. Decision criteria. If you want to use the original BOM and are willing to drill the hole, go with Design 1. If you are looking for more durability and are willing to switch to all 10mm OD CF tubing, go with Design 3 All the necessary files are included so you can remix or tweak on your own. Print Settings Printer Brand: RepRap Printer: Prusa i3 Rafts: No Supports: No Infill: 20 Custom Section Casting steps After the mold are printed. Coat both side with Smooth-On XTC-3D and allow to cure overnight. Put a very small clay gasket around one half of the mold. This will help make sure you have a leak-proof seal and will make it easier to get the molds apart. Apply two coats of the Smooth-On Universal Mold Release Spray on the other half of the mold, allowing for proper curing time between applications. When to remove the part. After a lot of trial and error, wait until the Urethane is cured but not fully hardened so you can get it out of the mold without distortion. I've found my parts are ready between 1 ¼ and 1 ½ hours. You can gauge its hardness by leaving a small amount of Urethane in the mixing cup to check its progress or by depressing a small Exacto knife into the material at the pour hole. If it's too soft, wait a few minutes before pulling off the second half of the mold. After you pull off the top half of the mold, check the Urethane consistency. The material should feel like a stale gummy bear. If it's too soft, wait a few more minutes before attempting to remove the second half of the mold. To get the second half of the mold off, gradually work around the part until it pops out. Take your time. Do some basic part cleanup with a pair of side cutters. You are looking to remove any big pieces of excess Urethane. I clean up around pour hole but leave the fine detail cleanup until after it's cured to avoid distortion. Once the part is released, put the parts in the stove at 150F for a couple hours.