• 0 Posts
  • 35 Comments
Joined 2 years ago
cake
Cake day: June 23rd, 2023

help-circle

  • If I give you a free beer, you have one beer. If I give you the recipe, you can make your own beer. You do have to make your own open source beer or you can hire someone to do it for you or perhaps take you through the steps a few times until you’ve got it. With luck there will be a community of open source beer brewers with whom you can interact and improve those recipes.

    Free software is free until it isn’t! The illicit drugs industry works in a similar way (the first hit is for free).





  • Plus humidity is bad for your filament.

    I keep on hearing this but it does not check out for me.

    I have a Prusa 3S+, self assembled. I do not do a great deal of printing and go through phases. I did a flurry of prints during the pandemic and then it rested idle in our rather cold and slightly damp study for a couple of years. When I bought it, it came with a spool of silver Prusament which worked nicely. I then bought a spool of “Sunlu” filament (Chinese firm off of Amazon) and then a box of 10 colours of the stuff.

    I recently got the printer out and updated the firmware, re-calibrated it and so on. I’ve done several prints with filament that has been open to the environment for at least two or three years and its fine. I have done a print using some transparent filament which was unopened and that was fine too. The unopened stuff was vacuum shrunk wrapped so could not possibly be damp. The opened filament was stored in the original cardboard box in a slightly damp and unheated room.

    For me the main issues for a decent print are:

    • Adhesion on the plate. I actually used glue for a print for the first time recently
    • First layer calibration. If the first layer is wrong, the rest is wrong. You need to get the right amount of “squashing” to get a smooth bottom
    • Always clean the plate between prints - a squirt of EPA and a decent rub with tissue whilst the bed is heating up does the job
    • Keep the guide rails lubricated - Mine whined that all three axes were too tight or just wrong and yet the Prusa app to check belt tightness and forum and wiki advice said it was fine. Any engineer will tell you to lube up when in doubt - do it! X, Y and Z.

    I will try repeating a challenging print with filament that is way older now and see what happens. I printed a couple of tank models in red around four years ago. Both involved their turrets with the barrel facing upwards - that’s a lumpy cylinder about 4cm long and 2mm wide.

    I have seen some notes about PLA being hydrophylic (absorbs water) on the Prusa website’s official advice but I don’t personally think it is an issue and people are probably missing another factor or factors that is fucking up their prints. I think the filament dampness meme is “cargo culting”.

    PLA is heated to around 220C whilst being extruded so any water will steam off very quickly as water vapour - which is not even “wet”, well before worrying a print job.

    PLA is touted as bio-degradable and it is … eventually. It is extremely stable, despite being derived from corn starch. It really doesn’t seem to care about a bit of water hanging around. That’s why I can print new hinges for a plastic garden storage thing to replace the original ones and they last through winters and summers in the UK.

    So, if you think moisture is an issue for PLA filament used for 3D printing, why not do some experiments and then decide for yourself.

    I’m happy to be proved wrong.


  • gerdesj@lemmy.mlto3DPrinting@lemmy.worldMy new specs
    link
    fedilink
    English
    arrow-up
    4
    ·
    2 months ago

    That is superb. Sadly my eyes degrade faster than the frames wear out!

    I see you are on the John Lennon specials which makes it a bit easier to model. I haven’t worn circular specs since college (~1990) My current Tesco specials only have lens frame from the nasal bridge clips, over the top to about 5mm below the temple joints.

    Just a thought but you might like to investigate using spring steel for the arms and PLA just for the frames. You could create a jig for joining and heat the ends of the arms up with a brazing torch (kitchen supplies) and sink them into a suitable cylinder close to the temple joint. If you go all in you can make the straight part of the arm rigid and the over ear part flexible with careful heating and cooling and whacking with a hammer!

    Now, that metal work will be comfortable but might be a bit chilly. What about PLA tips over ear instead of steel?

    Anyway, great job. I’m very impressed.





  • If the boy has a gaming rig, then he also has a CAD workstation.

    I managed to get a dodgy copy of AutoCAD 2 running on my 80286 with an 80287 maths co pro that I persuaded my parents to buy me for Chrimbo. Sadly, it was a bit shite. The next version of AutoCAD needed a 32 bit machine with 32 MB (yes MB) of RAM. That was way out of my league.

    Depending on the age of the boy and given how long the little darlings are tending to hang around these days, a constructive bribery system in lieu of rent or pocket money enhancement might be in order 8)




  • I think we might be writing at cross purposes. The system you had for your mum obviously worked effectively for you and that is the important thing.

    POTS provide(s|d) a fixed point of reference - your address is registered against the number for 999 etc; it provides power for a handset or device; Its been like that for a lot of decades! These are cast iron guarantees. A POTS line has guarantees, enshrined in UK law, that mobile etc does not have. POTS is circuit switched (well it was) which means there is a physical path between the ends for the duration of the conversation.

    So, by old school, I mean that you currently have important guarantees about telephony in the UK that will evaporate in future. In 2025 or so, we in the UK will have finished migrating from our old school POTS copper lines and will enjoy our smart new SoGEA lines instead. Single Order Generic Ethernet Access. Instead of an emulated circuit switched line we will use VoIP across the entire country. Nothing wrong with that but it probably won’t have the guarantees that POTS had.

    Red Care is no more - BT have dropped it on the floor as of Feb this year which may indicate that things are not well with our future comms promises. The general system that Red Care was one product of is still available.

    This is the important point: Promises (in law) that we used to be able to rely on for comms may (will) be binned.


  • In the UK at least, the POTS (Plain Old …) copper phone lines carry an electrical current as well as signals and can power the handset. There are certain guarantees about this so that in an emergency your phone will still work so you can dial 999 (our original emergency number) or 112. Our fire regulations require something like 30 minutes before things should start failing. In the real world, you get out immediately and use your mobile.

    We have an emergency alarm monitoring system used by businesses. Its generally known as “Red Care” which was a brand run by BT (British Telecom). You have a small device connected to a phone line (and powered by it) and it will monitor your fire detectors and building access control systems and a 24 hour manned monitoring centre will notify you in the event of an emergency. Nowadays, these devices will use your wifi and internet connection. Sometimes: old school is best.



  • Which distro do you use? Ubuntu, Debian, Arch and Gentoo have packages and I’ve no doubt that most others do too. On Linux you should not have to go to random websites and download stuff and faff around - use the built in distribution packages. If you are not sure what you’ve got try this at a command prompt and read the output:

    $ cat /etc/os-release
    
    

    As a last resort, you can run tcpdump on nearly anything and dump to .pcap, transfer that and then open that in Wireshark. Note that modern Windows has a OpenSSH client and server available so getting files around via scp is a doddle. Windows can even do NFS too and there is of course Samba - but CIFS/SMB can be tricksy.


  • Errm, Wireshark. Please bear with me.

    Wireshark is a shining example of an open source project completely and utterly crapping on the closed source competition. As a result we all benefit. I recall spending a lot of someone else’s money on buying a sort of ruggedized laptop with two ethernet ports to do the job back in the day.

    Nowdays, I can run up a tcpdump session on a firewall remotely with some carefully chosen timings and filters and download it to my PC and analyse it with Wireshark.

    OK, all so convenient but is it any use?

    Say you have a VoIP issue of some sort. The PCAP from tcpdump that you pass to Wireshark can analyse it to the nth degree. Wireshark knows all about SIP and RTP (and IAX) and you can even play back the voice streams or have them graphed so you can see what is wrong or whatever. That’s just VoIP, it has loads of other dissectors and decorators built in.

    So what?

    The UK (for example) will be dispensing with boring old, but reliable, POTS (Plain Old Telephony System) by 2025. Our entire copper telephony and things like RedCare (defunct soon) will go away.

    We are swapping out circuit switching for packet switching. To be fair, a lot of the backend is already TCP/UDP/IP that is shielded away from us proles. When SoGEA (Single Order Generic Ethernet Access) really kicks in then the old school electric end to end connection will be lost in favour of packet switching, which never fails (honest guv).

    If you are an IT bod of any sort, you really should be conversant with Wireshark.



  • Nextcloud is simply software that runs on something. You might use DNS to find the something that your Nextcloud runs on … or not. A domain can cost as little as say £10/year (no details given - loose costing provided!) but you say you don’t want one.

    You could do some weird stuff involving something like this: Your clients update a database on the server with their current IP address(es) and the server reciprocates in kind regularly.

    For an internets conversation, both sides need to know IP address, protocol, and optionally port; for both ends. For example, a webby conversation might involve:

    My end: 192.168.100.20/24, tcp port 2399 -> NAT -> 33.22.4.66, tcp port 2245 Remote web server: 99.22.33.44/37, tcp port 443

    Now, provided both sides are warned off about changes to addresses and port numbers on a regular basis, then comms will still work.

    Say, your home external IP address changes, then your browser writes that new address to the remote server and comms continue. Provided one end knows all the details of the other end at any point in time and can communicate local changes then we are good.

    000000000000000000000000000000000000000000000000000000000000000000

    Maybe not. Lookup: Dynamic DNS.