Box that opens itself via Bluetooth - how to produce mechanical parts - Page 1
Forum section: electronics / projects

author: TheCamel
author_rank: Newbie
timestamp: May 20, 2014, 03:25:35 pm
content: Hi,I'm currently designing a project of a box that can be remotely opened via Bluetooth. It is built around the BL600 module and uses servos to actually open the box through levers.I am quite seriously thinking of selling this project once it will be finished (probably using crowdfunding). While I now have a quite good idea of how the production of the electronics is made, I have no idea of how to get mechanical parts done and assembled.So my question is: do you have useful links or past experiences that could help me understand the process of actually getting mechanical parts done (the levers will probably in plastic in my case) and electronics and mechanical parts can get assembled together to form the final product?Thanking you in advance,Benoît V.

author: josem
author_rank: Regular Contributor
timestamp: May 20, 2014, 04:18:43 pm
content: I thought about making an app controlled box (via BLE like yours) myself but haven't had time to go back to it.My plan was to go with box made of laser cut parts (probably acrylic, Bluetooth gets cranky going over MDF) and then a servo and/or solenoid for the lock.There are many freely available plans for laser cut jewellery boxes on the the web. Could be a starting point.

author: ajb
author_rank: Super Contributor
timestamp: May 20, 2014, 06:07:45 pm
content: Quick tip: If you add your location in your profile it will make it much easier for people to give recommendations for suppliers based on where you're located.Mechanical design is a whole discipline unto itself, not unlike electronics design. Just as with an electronics design project, you need to start with some basic questions:-How big should the box be?-What do you want the box to do, functionally?-How strong or durable does it need to be?-How do you want it to look?-How many are you making?If the box is fairly large, wood may be the most economical option. If it needs to be especially durable, then metal (if the box is large) or perhaps a glass-filled plastic (if the box is small) could be best. If you want a very nice looking product, you'll need to consider finishes. For metal, this means a surface treatment + anodizing, or powdercoating, for wood it'll be sanding & staining, or for plastic painting. For a small box you could do acrylic, but assembling acrylic in anything but a rectangular prism with interlocking edges can be tricky (involving solvent welding or bending). That said, acrylic is cheap, laser cuts very nicely, and there's a lot of info out there on using it to make enclosures. There are some services that will do laser cut acrylic to order, or you may have a local hackerspace where you could do it yourself. If you're going to eventually make a couple thousand, then injection molding becomes viable, but the setup costs are significant. You may also be able to find a ready-made box to which you can graft your locking mechanism.

author: TheCamel
author_rank: Newbie
timestamp: May 20, 2014, 08:12:09 pm
content: Thank you for your replies.I think I was a bit unclear in my first message. I already know how I want the box to be made, using wood. You can find a diagram of my project in attachment (to give you an idea of the size, it will roughly be 5cm long, like a ring box). What I was wondering is how to get the mechanical arms done: in which material and with what process?

author: Unknown
author_rank: Unknown
timestamp: May 21, 2014, 12:59:14 am
content: Seems like the sort of thing you can buy off-the-shelf as a sub-assembly. Have a look at hinged lid supports or stays at somewhere like McMaster-Carr for inspiration. Then all you need is a coupling to your servo shaft or horn.

author: Mechatrommer
author_rank: Super Contributor
timestamp: May 21, 2014, 05:00:27 am
content: finding a good mechanical engineering site was a dismay for me, only found few dormant sites. perhaps sites like instructable will help? and few details such as how big and heavy the box? how fast or slow it can be, where the lever should be or should not be etc will result in different mechanical mechanism involved.

author: GeoffS
author_rank: Unknown
timestamp: May 21, 2014, 05:08:34 am
content: It depends on how many of these you plan to build and how much you plan sell them for. Having custom parts made in small quantities will be expensive. Typically stays and supports for a jewellery box would be made of brass, mostly for appearance.Have you worked out the torque required from your servo to lift the lid on your box? That would be more important than just what material to use for the mechanism.Consider spring loading the hinge to compensate for the weight of the lid and mechanism.

author: zapta
author_rank: Super Contributor
timestamp: May 21, 2014, 05:57:24 am
content: Search Google for Useless Box, it also open with a servo.Sent from my Nexus 5 using Tapatalk

author: pickle9000
author_rank: Super Contributor
timestamp: May 21, 2014, 06:27:57 am
content: There are many professional and semiprofessionals around that could help for little to no money.- Local technical school, ask a staff teacher if it could be a quick after-school project. Offer pizza.- Go to a local supply house. That is a place that sells metalworking tools or raw materials. Metalworkers are very skilled and can often come up with a nice simple mechanical solution. You may even luck in to a free design in the hopes that they will get to build the item.- Build it yourself.

author: Yago
author_rank: Frequent Contributor
timestamp: May 21, 2014, 12:17:29 pm
content: Move the servo to the other corner near the hinge.Then one single arm with a roller on the end will do the job.I would be looking at R/C model suppliers, they have lots of linkages and rollers..servos..etc.

author: Stonent
author_rank: Super Contributor
timestamp: May 21, 2014, 04:36:26 pm
content: How keen are you on making sure the box can't be opened physically?

author: free_electron
author_rank: Super Contributor
timestamp: May 21, 2014, 05:15:09 pm
content: things like this are easy to make in a program like illustrator.simply 'unroll' the contour of the box then draw castellations across the edges.send the file to an epilog lasercutter. done. it'll fit like a charm. you can set the illustrator grid to the thickness of the wood.i do a similar approach with plexiglass. works like a charm.if you want a metal box simply waterjet the plates, bend em on a brake and then either spotweld or weld.to make a very nice box with a perfectly matching lid : make a fully closed box first. then simply saw the top off.

author: TheCamel
author_rank: Newbie
timestamp: May 21, 2014, 08:00:39 pm
content: Thank you for all your suggestions, I'll look for them.I was already thinking of using springs to reduce the needed amount of force coming from the servos. I don't know yet how much torque I would need but I will look for it.About the amount I am planning to manufacture, I would say a few hundreds.It is quite important that the box can be opened, for operations such as changing the battery or access some configuration buttons and switches I plan to place on the PCB.