Design for Manufacturing - Project to Product by Modifying Off-the-Shelf Cases -- Episode-651

In a past element14 presents episode, Clem created a Universal Debugging Screen. This project sparked interest and many, many queries about its availability as an actual product! Well, what a good opportunity to investigate how to do that, in this episode Clem investigates enclosure options and how to customize them to turn a project into a product with items from Hammond Manufacturing. 

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Design for Manufacturing - Project to Product by Modifying Off-the-Shelf Cases -- Episode-651

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Occasionally, a project posted on the internet prompts people to respond with questions about its availability as a kit, or as a product for purchase. One such project is the Universal Debugging Screen made by Clem in a previous episode of element14 presents. The universal Debugging screen turned out to be a handy tool for quick checks of serial data while working on a project. You could liken it to using a multi-meter that you can quickly whip out to check voltages or amperage. This handy device instantly shows you data flowing on the serial bus in letters and numbers, not variable voltages and in a human readable form. 

While Clem’s initial version consisted of leftover parts from previous projects (which demonstrates the value of keeping a stockpile of components around). A kit or product would need to be built from available still manufactured parts or designed with purpose. In the journey to transition from project to product, Clem has changed key components. Most notably of these are that Clem switched the user interface from individual buttons to a single rotary encoder. This change with a completely new form factor allows the device to be used one-handed in an ambidextrous manner by those who are left or right-handed. 

While Clem analyses the available approaches to a customized case, Clem explains how individually 3d printing case parts for such a project would consume too much time and introduce an element of risk due to quality control, especially having to do so at scale from a small business setup. 

Instead, the best approach has been decided to modify a ready-made enclosure as it would control costs and make certification of the final product much easier. After reviewing what products are available, Clem decided to use a handheld case from Hammond Manufacturing. With a penchant for it being blue in colour, having fancy soft over-moulding and a battery hatch that will fit a very specific purpose in the design! 

The battery compartment in the off-shelf enclosure is designed to hold a 9V cell block or 2 AA batteries. While Clem could run the device on a single 14,500 Lithium-Ion cell that fits the compartment, he decided to place a ‘pouch LiPo’ into a remining cavity in the enclosure and use the battery hatch to store the breakout cables needed to operate the device. A handy approach to keeping everything together and accessible for the user. 

While using the enclosure as a basis for the design, Clem proceeds to leverage the manufacturer supplied data sheets and specifications into a combined workflow of FreeCAD (Ondsel version) and KiCad to design and derive the ideal PCB shape to make sure that all the components tightly fit into the desired enclosure. Using Boolean subtraction to generate case versions with the required cutouts and ensuring to test out multiple ways of producing the modified cases ‘in house’. While designing the changes to the enclosure, Clem notes that eventually it would be more economical to order the cases pre-modified from the manufacturer or similar service to be able to produce the product at scale, using CAD designs can ensure that the measurements taken are appropriate to be passed on for such changes. 

The same data can also be used to create instructions for machines accessible to the casual and more professional maker. A simple way would be to just 3d print the modified parts and combine them with the readymade enclosures. Clem recommends that resin printing should be considered for this approach due to its high level of detail and accuracy as well as sturdiness (given the right resin is used). Unless you have a specifically designed resin for this purpose (such as MayerMakes Engineering Resin – totally not a product placement). Though after assessing these options, Clem instead focuses on the less common methods such as laser cutting and CNC milling. 

Using Lightburn to generate the instructions for a Fiber laser engraver, and a CO2 laser, Clem highlights the difficulty in choosing the right method as it greatly depends on the material that is being cut (while emphasising safety and user protection). The milling CAM that Clem uses is generated with the FreeCAD Path workbench and executed by a tiny 3020 CNC router commanded by LinuxCNC. to exactly position the cutouts in respect to the already manufactured enclosure holders and mounting templates were used that reference the machines 0,0 home position to allow for repeatable cuts. 

While the Laser approach showed promise, it demonstrated that it needs a lot of experimentation, appropriate masking, and preparation to find the ideal settings to prevent damage and repeatable results. The CNC milling yielded a usable result from the first try from the perspective of cut quality, but the enclosure shifted due to the cutting forces imposed on it, so this approach needs a better prepared workpiece mount. 

Overall, Clem has demonstrated that this part of design for manufacturing is only one in many steps you will need to consider when taking a project into a marketable product. Iteration and testing is still significantly important, and Clem shows that even on a small scale, you can create the necessary adjustments to move onto producing at scale. 

Links and Downloads:

• Case Files for all versions
•  All-Purpose Debugging: A Practical Universal Screen with LCD Displays -- Episode-631  

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