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Good detail hear about the process if making the case - really interesting to read. Injection molding semi-liquid magnesium seems…quite difficult to say the le

Good detail hear about the process if making the case - really interesting to read. Injection molding semi-liquid magnesium seems…quite difficult to say the least! Tangentially, I wish there was some online resources for learning how best design for manufacture for things like laptops and cases. Contract CNC fabrication is really inexpensive these days until you need 10 iterations to fix your dumb mistakes.

zonkerdonker 3y ago
Thixomolding is an incredible process, I'm glad it's becoming more utilized. It really is the best for lightweight, strong, and super thin parts like laptop chassis. About 10 years ago I worked for a medical device company and we used thixo parts for a portable ultrasound system (think chunky laptop form factor). In my first few weeks, I had a proto part that needed a rework, so I chucked the thixomolded part into the bandsaw to chop it up, before the shop manager chewed me out for almost setting the shop on fire (who let this clueless engineer into my shop...etc etc). Magnesium dust is stupid flammable and burns incredibly fast and hot. There were only a handful of vendors in the world at that time that had the capability to mold the size of parts we needed, it's a vastly different process to casting other metals, in part due to the hazards of the material itself. Warning to all overly ambitious framework owners: careful if you decide to chop or drill into that case!
- liminalsunset 3y ago
  I'm wondering what the properties of thixomolding parts are like compared to casting compared to having the part machined out of a solid piece. One thing I personally noticed with these types of "cast-looking" parts is that they tend to fail in a brittle way and there's really not much ductility. I've seen many notebooks with Mg alloy casings that shatter when dropped, and I've always preferred the Apple unibody machined aluminum for this reason - if it's bent or drops, it tends to retain its integrity much better. Granted, aluminum doesn't tend to have all that much ductility before it too, breaks, but I've found it more robust.
  - zonkerdonker 3y ago
    Mag itself is not very ductile, and more prone to fractures than most AL alloys, with the tradeoff being overall higher yield strength. Depending on the magnesium alloy used for thixo, this can be mitigated somewhat, but you are correct in that almost every "casting" process will give you a less ductile part than the same alloy machined from a solid billet. So much of a metal's material properties come from it's crystalline structure, and how it's melted, formed, and tempered. Thixo tries to get the best of both worlds by using a slurry that is both a solid (containing the proper microstructures for desired material properties) and liquid to ease the injection molding. Machining from a billet of material guarantees consistent crystal structure, and is usually the go to when strength/appearance is a larger consideration than cost or weight. Billets can be formed very precisely and consistently, without consideration of the final product
- reaperman 3y ago
  > before the shop manager chewed me out for almost setting the shop on fire In his defense, an engineer should have known this. In your defense, we all have blind spots - we might know 98% of the obvious things and still get caught by a handful of them. That’s why supervision is so important!
Solvency 3y ago
Styrofoam. This is what auto body designers use to shape while designing forms.
- nomel 3y ago
  Not sure why this is downvoted. Carving away styrofoam is a great way to see what the real world form of something will be, especially considering there's a good chance you can fish it out of your trash. And, a hot glue gun mean you can put pieces back! For getting an idea, I like to play with clay, then move to CAD once something is fairly decided, with foam/cardboard mockups to get "real world" size feel. Then, a desk full of 3d printed mini versions, and then whatever final version.
  - mlyle 3y ago
    You can lay up composites (e.g. carbon fiber + epoxy resin) over a styrofoam mold and get nice results, too. (Just leave the styrofoam in).
baybal2 3y ago
> Tangentially, I wish there was some online resources for learning how best design for manufacture for things like laptops and cases. You are effectively asking for a disclosure of shop secrets. Even in cases of completely no-name factories, there will be so much of clever things nobody would put on a paper. One factory owner went nuts when we were going with inspection for a client in 2009, just because we clicked seemingly innocuous looking jig which was putting threaded inserts into mould. It later came out that nobody else anywhere had anything like that, and most factories rely on laborious process of manually putting inserts into the mould. There is so many unobvious things which 99% of people without actual manufacturing experience routinely overlook in ubiquitous items around us. I once been openning up dozens of laptop samples, and one in 100, from a noname factory had seemingly no ribs in its bottom cover, and seemingly nothing restraining it flexing, and sliding. Then, after days of hair pulling, the secret cracked.. nuts, and screws inside were not meeting orcompletely, but were suspended with preloaded fasteners, which used those few free millimetres of free travel for it.
claytonwramsey 3y ago
The fastest way to learn how to make machinable parts is to machine them yourself :). DFM is often a hard-earned skill. Unfortunately maker-spaces (the only kinds of places where you could get cheap access to good 3+ axis CNC mills) seem to have gone out of fashion. CNC mills in general cost about 5 digits just for the machine, and usually that again for the tooling. I think the closest one can get to learning some DFM without working on a machine would be watching machinists on YouTube. Back in the day NYC CNC was great, but I think they post more hype content these days. I'm far from an expert on the topic, but I spent a decent amount of time designing for and then fabricating stuff on CNC machines over the last couple years. To my knowledge, operations are cheap while setups are expensive: if you can design a part around a fixed orientation in a machine, it saves a lot of operator time.
- edrxty 3y ago
  You can get into cnc the diy route for between ~$2k and ~$8k depending on the amount of rigidity you want. There are conversation kits available for common import mills to make the process relatively easy but the control and wiring isn't for the faint of heart. I built one out of a PM-833TV and it's taken years to get working well, and I probably should have just bought a used HAAS at this point, but if you build it You Will Learn one way or another. Words of wisdom I wish I'd had: spend the money on decent over specced servos with ethercat. Don't skimp or you'll end up having to just redo stuff and it'll cost a lot of money. Do not buy stepper motors period.
  - justinclift 3y ago
    Let me introduce you to the PrintNC, a kind-of-high-end hobbyist CNC: * https://wiki.printnc.info/en/home https://wiki.printnc.info/en/home * https://github.com/threedesigns/printNC https://github.com/threedesigns/printNC * Discord invite: https://discord.gg/RxzPna6 https://discord.gg/RxzPna6 <-- extremely active CNC enthusiast discord It's "kind of high end" as it uses steel beams (not aluminium) for rigidity, so it's capable of driving some really powerful gear... fairly cheaply. :) The US$2k you mention above would indeed be the practical lower bound.

zonkerdonker 3y ago

Thixomolding is an incredible process, I'm glad it's becoming more utilized. It really is the best for lightweight, strong, and super thin parts like laptop chassis. About 10 years ago I worked for a medical device company and we used thixo parts for a portable ultrasound system (think chunky laptop form factor). In my first few weeks, I had a proto part that needed a rework, so I chucked the thixomolded part into the bandsaw to chop it up, before the shop manager chewed me out for almost setting the shop on fire (who let this clueless engineer into my shop...etc etc). Magnesium dust is stupid flammable and burns incredibly fast and hot. There were only a handful of vendors in the world at that time that had the capability to mold the size of parts we needed, it's a vastly different process to casting other metals, in part due to the hazards of the material itself. Warning to all overly ambitious framework owners: careful if you decide to chop or drill into that case!

liminalsunset 3y ago
I'm wondering what the properties of thixomolding parts are like compared to casting compared to having the part machined out of a solid piece. One thing I personally noticed with these types of "cast-looking" parts is that they tend to fail in a brittle way and there's really not much ductility. I've seen many notebooks with Mg alloy casings that shatter when dropped, and I've always preferred the Apple unibody machined aluminum for this reason - if it's bent or drops, it tends to retain its integrity much better. Granted, aluminum doesn't tend to have all that much ductility before it too, breaks, but I've found it more robust.
- zonkerdonker 3y ago
  Mag itself is not very ductile, and more prone to fractures than most AL alloys, with the tradeoff being overall higher yield strength. Depending on the magnesium alloy used for thixo, this can be mitigated somewhat, but you are correct in that almost every "casting" process will give you a less ductile part than the same alloy machined from a solid billet. So much of a metal's material properties come from it's crystalline structure, and how it's melted, formed, and tempered. Thixo tries to get the best of both worlds by using a slurry that is both a solid (containing the proper microstructures for desired material properties) and liquid to ease the injection molding. Machining from a billet of material guarantees consistent crystal structure, and is usually the go to when strength/appearance is a larger consideration than cost or weight. Billets can be formed very precisely and consistently, without consideration of the final product
reaperman 3y ago
> before the shop manager chewed me out for almost setting the shop on fire In his defense, an engineer should have known this. In your defense, we all have blind spots - we might know 98% of the obvious things and still get caught by a handful of them. That’s why supervision is so important!

Solvency 3y ago

Styrofoam. This is what auto body designers use to shape while designing forms.

nomel 3y ago
Not sure why this is downvoted. Carving away styrofoam is a great way to see what the real world form of something will be, especially considering there's a good chance you can fish it out of your trash. And, a hot glue gun mean you can put pieces back! For getting an idea, I like to play with clay, then move to CAD once something is fairly decided, with foam/cardboard mockups to get "real world" size feel. Then, a desk full of 3d printed mini versions, and then whatever final version.
- mlyle 3y ago
  You can lay up composites (e.g. carbon fiber + epoxy resin) over a styrofoam mold and get nice results, too. (Just leave the styrofoam in).

baybal2 3y ago

> Tangentially, I wish there was some online resources for learning how best design for manufacture for things like laptops and cases. You are effectively asking for a disclosure of shop secrets. Even in cases of completely no-name factories, there will be so much of clever things nobody would put on a paper. One factory owner went nuts when we were going with inspection for a client in 2009, just because we clicked seemingly innocuous looking jig which was putting threaded inserts into mould. It later came out that nobody else anywhere had anything like that, and most factories rely on laborious process of manually putting inserts into the mould. There is so many unobvious things which 99% of people without actual manufacturing experience routinely overlook in ubiquitous items around us. I once been openning up dozens of laptop samples, and one in 100, from a noname factory had seemingly no ribs in its bottom cover, and seemingly nothing restraining it flexing, and sliding. Then, after days of hair pulling, the secret cracked.. nuts, and screws inside were not meeting orcompletely, but were suspended with preloaded fasteners, which used those few free millimetres of free travel for it.

claytonwramsey 3y ago

The fastest way to learn how to make machinable parts is to machine them yourself :). DFM is often a hard-earned skill. Unfortunately maker-spaces (the only kinds of places where you could get cheap access to good 3+ axis CNC mills) seem to have gone out of fashion. CNC mills in general cost about 5 digits just for the machine, and usually that again for the tooling. I think the closest one can get to learning some DFM without working on a machine would be watching machinists on YouTube. Back in the day NYC CNC was great, but I think they post more hype content these days. I'm far from an expert on the topic, but I spent a decent amount of time designing for and then fabricating stuff on CNC machines over the last couple years. To my knowledge, operations are cheap while setups are expensive: if you can design a part around a fixed orientation in a machine, it saves a lot of operator time.

edrxty 3y ago
You can get into cnc the diy route for between ~$2k and ~$8k depending on the amount of rigidity you want. There are conversation kits available for common import mills to make the process relatively easy but the control and wiring isn't for the faint of heart. I built one out of a PM-833TV and it's taken years to get working well, and I probably should have just bought a used HAAS at this point, but if you build it You Will Learn one way or another. Words of wisdom I wish I'd had: spend the money on decent over specced servos with ethercat. Don't skimp or you'll end up having to just redo stuff and it'll cost a lot of money. Do not buy stepper motors period.
- justinclift 3y ago
  Let me introduce you to the PrintNC, a kind-of-high-end hobbyist CNC: * https://wiki.printnc.info/en/home https://wiki.printnc.info/en/home * https://github.com/threedesigns/printNC https://github.com/threedesigns/printNC * Discord invite: https://discord.gg/RxzPna6 https://discord.gg/RxzPna6 <-- extremely active CNC enthusiast discord It's "kind of high end" as it uses steel beams (not aluminium) for rigidity, so it's capable of driving some really powerful gear... fairly cheaply. :) The US$2k you mention above would indeed be the practical lower bound.