Chasing Micrometres with the best Ball Screws

แชร์
ฝัง

ความคิดเห็น • 565

  • @Made2hack
    @Made2hack 5 ปีที่แล้ว +1736

    You should always use a granite surface plate desk, even in the kitchen! I sleep on a granite surface plate to make sure I get the most precise dreams ever, to within 3 microns.

    • @reps
      @reps  5 ปีที่แล้ว +285

      < Insert Rick & Morty True Level Scene here >

    • @DeDeNoM
      @DeDeNoM 5 ปีที่แล้ว +49

      It also straightens out the back

    • @brainfornothing
      @brainfornothing 5 ปีที่แล้ว +5

      ​@@DeDeNoM ...Or make a "C" with your column, if you sleep over your side. Cheers !

    • @bill605able
      @bill605able 5 ปีที่แล้ว +4

      @@DeDeNoM Raises hell with the "roids" tho!

    • @subzeronitro4686
      @subzeronitro4686 5 ปีที่แล้ว +7

      @@reps EVERYTHING IS CROOKED! REALITY IS POISON! *LAMBS TO THE COSMIC SLAUGHTER*!
      I've seen that scene at least 5 times this week because it keeps popping up in TH-cam for me.

  • @jayjaytronics8358
    @jayjaytronics8358 4 ปีที่แล้ว +58

    Hey Marco, the Steinmeyer ball screws are induction hardened as well (only the threads up to a few mm depth into the material). They also start as rolled part but then they get precision ground to fit to the pitch within tolerance (as low as a few µm). Of course the abrasive grinding will heat up the thread but they balance the cutting depth to control the soft-annealing. So no worries - they will hold up fine.

  • @krackpack1
    @krackpack1 5 ปีที่แล้ว +7

    I just love how you worked that ad right in there. Smooth as butter i didn’t see it coming and then BAMM like a freight train.

  • @cajone7591
    @cajone7591 5 ปีที่แล้ว +170

    That's going to be one hell of a PCB etcher

    • @nothanks7752
      @nothanks7752 5 ปีที่แล้ว +52

      the worlds most expensive dickbutt plotter

    • @you_just
      @you_just 4 ปีที่แล้ว +2

      Can’t wait to see the 1:100000 scale city that he etches.

  • @cocosloan3748
    @cocosloan3748 5 ปีที่แล้ว +62

    Marco we see so much stuff in your videos we cant find nowhere else..TY.

    • @Audio_Simon
      @Audio_Simon 5 ปีที่แล้ว +5

      And cant afford haha!

  • @Chizu015
    @Chizu015 5 ปีที่แล้ว +3

    Finally a new video! I'm so happy to see your CNC machine coming together😍 can't wait to see those beauty in action

  • @danaolson2871
    @danaolson2871 4 ปีที่แล้ว +5

    Thank you so much. You saved me a lot of time. Going to replace my end bearings and get that Tiny FPGA kit now! Excellent.

  • @matthyslaubscher8151
    @matthyslaubscher8151 5 ปีที่แล้ว +3

    More, please sir! One of my favorite channels.

  • @rickypotter3103
    @rickypotter3103 5 ปีที่แล้ว +2

    Finally, a new video!! I was getting really tired of watching reruns and can't seem to get my fix anywhere else! I just got my MK3 Extended last week and already started my collection of cheap Chinese knock-offs….I'm in too deep already and obsession/fascination with Micro Reps isn't going away..one video every couple months just won't suffice!

  • @vasyapupken
    @vasyapupken 5 ปีที่แล้ว +74

    bearing blocks on linear rails must have a certain amount of preload to give you accuracy and rigidity under load.
    that's why a new linear blocks don't slide freely and have some amount of friction.
    (and that used rails from industrial machines slides freely just because they are WORN OUT and lost their preload. that's why they was removed and replaced with new ones)

    • @reps
      @reps  5 ปีที่แล้ว +21

      Sounds all correct! The banggood ones however have an uneven friction and seem to get caught on some high spots. And since hobby stuff is the only area where you would consider used rails anyway I think even the most worn-out ones will be easily good enough? Maybe I can find a way to actually measure my worn-out Rexroths ...

    • @mariusb6035
      @mariusb6035 5 ปีที่แล้ว +7

      @@reps I've recently bought some used miniature Bosch rexroth linear guides (size 15, 4 bearings, 2x330mm rails) from ebay, alongside 500 steel bearing balls. Had to replace the old balls and even replaced the new ones multiple times until I found a "good batch" of those cheap balls that were running smoothly with slight preload. All in all this costs me 120€ compared to new ones from Bosch for over 500€

    • @michaelkelly3158
      @michaelkelly3158 5 ปีที่แล้ว

      @@mariusb6035 How do these Bosch rails compare to Hiwin rails? Only ever heard of Hiwin rails being used in high end CNC applications.

    • @mariusb6035
      @mariusb6035 5 ปีที่แล้ว +3

      @@michaelkelly3158 the original Bosch rails are very similar to hiwin rails. You'd have to compare lifetime, friction or other technical properties in a specific use case. Just saying "these are better" is impossible. As long as you get new brand name rails (hiwin, Bosch, SKF, Schneeberger,...) you should be good to go for any hobby project.

    • @jubjuber1
      @jubjuber1 5 ปีที่แล้ว +3

      I have some cheap Chinese linear rails in a 20mm size. They run kind of rough but don't seem like it's specific high spots. Do you think taking them apart and cleaning would help smooth out the motion? I kind of suspect it's small particles in side the carriages are causing it to stick

  • @l3d-3dmaker58
    @l3d-3dmaker58 5 ปีที่แล้ว +43

    YESSS! I freaking LOVE your videos!!!

  • @avejst
    @avejst 5 ปีที่แล้ว +1

    Nice to hear from you again
    Thanks for sharing👍😀

  • @Vidz0022
    @Vidz0022 5 ปีที่แล้ว +1

    Thank you for the unfiltered sharing of information. It is quite refreshing.

  • @brad2678
    @brad2678 5 ปีที่แล้ว +5

    thank you for the lesson in angular contact bearings

  • @jon_raymond
    @jon_raymond 5 ปีที่แล้ว +3

    A new video from Mr Reps makes my day.

  • @maxk3673
    @maxk3673 5 ปีที่แล้ว +79

    Oh finally a new video. 😀

    • @ZeroMass
      @ZeroMass 5 ปีที่แล้ว +1

      Just found this channel... Been binge watching since : )

  • @scottjackson2812
    @scottjackson2812 5 ปีที่แล้ว +48

    Your videos are usually pretty funny, but that joke at the end about rails getting replaced preemptively in industrial settings was hilarious.

    • @adisharr
      @adisharr 5 ปีที่แล้ว +4

      Bigger companies do this all the time. Regular maintenance is important when your Nestle and bottling 10's of thousands of water bottles a day.

    • @MarksmenTM
      @MarksmenTM 5 ปีที่แล้ว +1

      @@adisharr
      I am not sure if you have ever replaced a ball screw, but it doesn't sound like it.

    • @SystemsPlanet
      @SystemsPlanet 4 ปีที่แล้ว +2

      Can you please explain the inside baseball joke to the non players?

    • @panaxion
      @panaxion 4 ปีที่แล้ว +6

      @@SystemsPlanet Most industrial machines (outside Germany at least) get run to death, rarely get the love or greasing they should.

    • @siggyincr7447
      @siggyincr7447 3 ปีที่แล้ว +1

      Depends a lot on the application, but most companies will replace ball screws when it starts causing problems. If it's in a machine that NEEDS to run without a hitch, consumables will generally get replaced or at least checked for wear on a predetermined schedule. I used to work for a company that would always have a maintenance crew scheduled for holidays so they could do that sort of thing without creating excessive downtime.

  • @lvxleather
    @lvxleather 2 ปีที่แล้ว

    Your videos are awesome, I can't believe I hadn't discovered these sooner, bravo.

  • @davidliddelow5704
    @davidliddelow5704 5 ปีที่แล้ว +223

    When you go below 1um accuracy you start getting weird effects like the heat from your body causing thermal expansion.

    • @operator8014
      @operator8014 5 ปีที่แล้ว +29

      I want to see someone use laser interferometry to measure the position to kick off the next generation of hyper accurate making.

    • @CNCGuy
      @CNCGuy 5 ปีที่แล้ว +18

      @@operator8014 Your in luck I happen to be in charge of the cnc department of Infinity Drain. We have brand new AMS Loader from Amada paired to our 4kw Laser. The Loader uses just that to tell where the pallet traverser is and to also measure sheet material thickness.

    • @brianjensen5200
      @brianjensen5200 5 ปีที่แล้ว +22

      @@operator8014 already done. We use those at my work. Picometer accuracy. It's a pain though, as in Australia this accuracy encoder systems requires defence approval. We had one system fail, and I had to arrange approval from ministry of defence to be able to send it back to the manufacturer for repair.

    • @evildrome
      @evildrome 5 ปีที่แล้ว +3

      @@brianjensen5200 Does everything run in a temperature controlled oil bath? I saw a video from Mitutoyo and that's how they keep their master leadscrew at a fixed temperature when screw cutting.

    • @brianjensen5200
      @brianjensen5200 5 ปีที่แล้ว +4

      @@evildrome no our motion stages are in free air. We keep the technical hall under 1K temperature deviation and encoder feedback loop controls the rest

  • @LitchKB
    @LitchKB 5 ปีที่แล้ว +3

    Good humour and technical knowledge. Subbed.

  • @sansdecorum4600
    @sansdecorum4600 4 ปีที่แล้ว

    Excellent breakdown and explanation with valuable tips and tricks for the aspiring CNC machine builder. Thank you. Subscribed.

  • @gregfeneis609
    @gregfeneis609 4 ปีที่แล้ว +6

    6:04
    When a ballscrew shaft is ground, the metal can already be very hard prior to grinding and the resulting screw can be far superior than a ballscrew that gets some hardening in its roll forming process.

  • @WhoIsTheEdman
    @WhoIsTheEdman 4 ปีที่แล้ว +1

    I'm really glad I'm subscribed to this channel. I feel like the humor here is within the same vein as This Old Tony.

  • @Iceteavanill
    @Iceteavanill 5 ปีที่แล้ว +2

    Nice to see some SMC stuff in the video. I have never used anything from them other than pneumatics but i got a tour around one factorie and they do make very high quality stuff....

  • @CaskStrength777
    @CaskStrength777 5 ปีที่แล้ว +15

    I could listen to you say "steinmeyer ballscrews" over and over on repeat endlessly. I wish I had your voice, fantastic vid

    • @jenskapmeyer2579
      @jenskapmeyer2579 2 ปีที่แล้ว

      That's how we Germans say it ... 😀

  • @1959Berre
    @1959Berre 5 ปีที่แล้ว +2

    The lubrication sounds are very inspiring. Fruits & vegetables are good for you, Marco!

  • @CyborgPandaBaby
    @CyborgPandaBaby 3 ปีที่แล้ว +3

    I know it's been a while but at my job we have what is essentially a large pair of calipers to calibrate cinema cameras. In order to discover and correct for long distance accuracy we use the distance traveled and revolutions of the motor. It uses a belt and pulley along with a very nice absolute encoder. We note the error (difference) of where it ended up vs the target and use the encoder resolution as well as the revolutions of the pulley. So if the machine was 0.015" off we would use that distance multiplied by the ticks/mm of the encoder (a constant), divided by the number of revolutions made during the move. This would give us a long range error correction value that the machine can compensate with. Essentially the number of encoder ticks it should increase or decrease by with every revolution of the pulley. I believe a similar calibration technique could be used with a ball screw mechanism.

  • @divyajnana
    @divyajnana 5 ปีที่แล้ว +2

    As usual, a hilariously instructive video, thank you MUCH!

  • @lazyh-online4839
    @lazyh-online4839 5 ปีที่แล้ว +2

    I think it's important to note that the final hardening comes just before grinding (which happens after rolling in the case of rolled ball screws) and so the effect of surface hardening is minimal compared to the higher precision and therefore tolerances of purely ground ball screws.

  • @fredio54
    @fredio54 3 ปีที่แล้ว

    Came for the precision, subscribed for the humour! Nice and dry, just how I like it.

  • @MCsCreations
    @MCsCreations 5 ปีที่แล้ว +1

    Pretty amazing stuff, man! 😮

  • @ForensicCats
    @ForensicCats 5 ปีที่แล้ว

    Beautiful, thanks for sharing.

  • @SYLTHECRU
    @SYLTHECRU 5 ปีที่แล้ว

    Love your commentary!

  • @brainfornothing
    @brainfornothing 5 ปีที่แล้ว +5

    Always interesting ! In my experience, too much precision is useless, because, at the end, the total deflexion of the structure, leadscrews, the motor head, the tool, etc. is very significant, but, of course, "too much precision" is better than "meh!". I'm saving money for the parts of my next CNC router. Thanks for sharing !

  • @nonyabidness4479
    @nonyabidness4479 5 ปีที่แล้ว +1

    Holy Bleep. Awesome video!!! Awesome technical detail and heavy with the lols. Nightmare fuel lol.

  • @marcdraco2189
    @marcdraco2189 3 ปีที่แล้ว +1

    Precision engineering with German precision dry humour. God I love this guy!

  • @anthroponym568
    @anthroponym568 5 ปีที่แล้ว

    super valuable information, thank you

  • @YuureiInu
    @YuureiInu 5 ปีที่แล้ว +1

    Linear rails have different amount of preload and various combinations of seals that will affect how easy they slide.

  • @Flornmonk
    @Flornmonk 2 ปีที่แล้ว +1

    I understand NOTHING but I can't stop watching.

  • @fibranijevidra
    @fibranijevidra 5 ปีที่แล้ว

    Technical, and pretty funny. I love your style and hard German accent.

  • @evans5756
    @evans5756 2 ปีที่แล้ว

    You are such a knowledgeable and funny guy.

  • @4.0.4
    @4.0.4 5 ปีที่แล้ว +8

    That tiny FPGA thing... I didn't knew such a thing existed! That's the size of an Arduino nano!

  • @Greeninja13
    @Greeninja13 5 ปีที่แล้ว

    To measure long distances you could attach levers to the encoder. It's the same technique that people used back in the day to convert large movements into small ones for precise machining. You'd be trading micrometer precision for mm or cm precision though.

  • @torinstorkey
    @torinstorkey 4 ปีที่แล้ว

    I love the shot at 3:37 where you can see a die with all the traces allong it.

  • @Mavi222
    @Mavi222 5 ปีที่แล้ว +9

    I was just pooping and was searching for some video to watch on the meantime.. And then I saw that you uploaded a new video! That was the best poop I had this year, thank you!

    • @reps
      @reps  5 ปีที่แล้ว +7

      Good to know!

    • @cfeigel
      @cfeigel 5 ปีที่แล้ว +7

      Er . . . too much to know.

  • @humanhiveanomaly
    @humanhiveanomaly 5 ปีที่แล้ว +32

    Had no idea FPGAs could be so adorable. I need to dust off some micro-controller unworthy projects and exchange some financial details with Elektor.

    • @AttilaAsztalos
      @AttilaAsztalos 4 ปีที่แล้ว +4

      Elektor: "only 0 left"
      Me: "oh great... fuck my life."
      My wallet: *quiet sigh of relief*

    • @rusticagenerica
      @rusticagenerica 4 ปีที่แล้ว

      I can confirm that in 2025, FPGAs will go beying Kittens in the minds of serial-video-watchers.

  • @michael-gary-scott
    @michael-gary-scott 5 ปีที่แล้ว

    OMG this channel is awesome!! Subbed!

  • @hugoboyce9648
    @hugoboyce9648 3 ปีที่แล้ว

    Whoa that SMC card motor is just so cool!

  • @you_just
    @you_just 4 ปีที่แล้ว +4

    3:10 when your hardware is so precise that your nut has bolts inside it

  • @mailamaila5918
    @mailamaila5918 3 ปีที่แล้ว +1

    Funny , ohh the humor , most excellent content. This is exactly the info I was looking for as I'm currently trying to repair a TL-1 Lathe : )

  • @TouYubeTom
    @TouYubeTom 5 ปีที่แล้ว

    keep the good work up!

  • @circuitsandcigars1278
    @circuitsandcigars1278 5 ปีที่แล้ว

    I used to work with these in laser trimmers and C02 lasers. The C02 had a 200 pound polished slab of granite that everything was mounted on

  • @thiscommentwasposted262
    @thiscommentwasposted262 4 ปีที่แล้ว

    Very good video! It made me feel dumb, but motivated me to learn this stuff!

  • @melgross
    @melgross 3 ปีที่แล้ว

    Very good. I like your sense of humor too.

  • @johnjacobjinglehimerschmid3555
    @johnjacobjinglehimerschmid3555 4 ปีที่แล้ว

    Another great vid. Subscribed!

  • @gizish
    @gizish 5 ปีที่แล้ว +1

    Nice video! And thank you for the nice tips!
    But are you sure you're going to enjoy those microns with the rigidity of steel frames? Have you considered filling granite on the voids?

  • @giannebaron6139
    @giannebaron6139 5 ปีที่แล้ว

    Yesss another upload

  • @PabloMuerteUno
    @PabloMuerteUno 5 ปีที่แล้ว

    Informative and entertaining. Many thanks

  • @GGG965
    @GGG965 5 ปีที่แล้ว

    Beautiful video mate:)

  • @spicemasterii6775
    @spicemasterii6775 4 ปีที่แล้ว +4

    German precision oozing out of this video. I had a German accent for an hour after watching this. Love this channel! Subscribed!

    • @bendito999
      @bendito999 4 ปีที่แล้ว

      Precision wood block table

  • @thaibinhphamdinh1299
    @thaibinhphamdinh1299 5 ปีที่แล้ว +1

    Here in Vietnam we can get those linear rail and ball screw second hand for dirt cheap. They are often disassembled from old machines. Just got a pair of unused IKO LWA15 rails and NSK 1602 ball screw for like $40. $200 can get you a nice 400w servo with driver from Japanese brand like Yakaswa.

  • @TTBOn00bKiLleR
    @TTBOn00bKiLleR 4 ปีที่แล้ว

    this is really informative

  • @erwinz5926
    @erwinz5926 10 หลายเดือนก่อน

    best video ever. inspired me to study engineering and will build a machine.

  • @DudleyToolwright
    @DudleyToolwright 3 ปีที่แล้ว

    Very informative. Thanks.

  • @ridermak4111
    @ridermak4111 4 ปีที่แล้ว

    I have never learned so much while laughing so hard.
    Precision comedy dude. 🧐😂

  • @youthised58
    @youthised58 4 ปีที่แล้ว

    Great video!

  • @JT-ee1ii
    @JT-ee1ii 3 ปีที่แล้ว

    Informative and hilarious!

  • @weerobot
    @weerobot 5 ปีที่แล้ว

    Awesome Work....!!

  • @MichaelAaronBerger
    @MichaelAaronBerger 5 ปีที่แล้ว

    I love your videos dude.

  • @nobytes2
    @nobytes2 5 ปีที่แล้ว

    One way I could think of measuring long distance movement, would be measuring rotation shaft movement vs fixed point via laser distance sensor.

  • @stonecraft745
    @stonecraft745 5 ปีที่แล้ว

    My first video, instantly subcribed! Thanks!

  • @HalleyRai
    @HalleyRai 4 ปีที่แล้ว

    thank you youtube rabbit hole...found this amazing channel

  • @JamesNeave1978
    @JamesNeave1978 3 ปีที่แล้ว +1

    The qualifying test for becoming a marine artificer in the royal navy in the 1970s was to build a miniature metal lathe.
    By hand from scratch, to a maximum accuracy of so many thou.
    Apparently creating those jack screws and whatever they made to run along it is tricky.

  • @opendstudio7141
    @opendstudio7141 5 ปีที่แล้ว

    You need to give your narrator a raise in wages. What a great voice.

  • @HH-xf9il
    @HH-xf9il 5 ปีที่แล้ว +3

    For the love of god I hope you've picked up Fusion by now :)
    Cool videos, keep it up !

  • @charlieabbot3649
    @charlieabbot3649 4 ปีที่แล้ว

    Only you could make ball bearings and vertical axis travel sound humorous.
    Nicely done.

  • @henrychan720
    @henrychan720 5 ปีที่แล้ว

    A simple laser interferometer can be used to measure accuracy over long distances. All you have to do is to program maybe an arduino to count how many times the interference pattern cycles. The accuracy may not be great because you can't really properly calibrate it but it should be super precise, as long as you don't loose count.

  • @akshaykumarvyas
    @akshaykumarvyas 5 ปีที่แล้ว

    since you live in germany, you can get mineral castings for the cnc machine done from EPUCRETE or now called RAMPF.

  • @crosby3108
    @crosby3108 4 ปีที่แล้ว +1

    Your hilarious great job I learned allot

  • @teamidris
    @teamidris 4 ปีที่แล้ว

    Yep, turning the nut is tricky. It takes a while turning it back and forth to be ‘happy’ again. For a while it was trying to force out the plastic seal. At one end the plastic seal is held in by two tiny grub screws.

  • @y2ksw1
    @y2ksw1 5 ปีที่แล้ว +1

    Those forbidden dreams of precision 😄

  • @DrakkarCalethiel
    @DrakkarCalethiel 5 ปีที่แล้ว

    Excellent video about a thing that gets ignored quite often.

  • @lawrencewalraven5137
    @lawrencewalraven5137 4 ปีที่แล้ว

    Great video thanks

  • @alexcweiner
    @alexcweiner ปีที่แล้ว

    this is excellent

  • @forbiddenera
    @forbiddenera 5 ปีที่แล้ว

    That tiny fpga looks f*n cool !

  • @joejane9977
    @joejane9977 5 ปีที่แล้ว

    this video after i watched made me feel screwed with. thanks for the fun times excellent video

  • @mattnsac
    @mattnsac 5 ปีที่แล้ว +75

    Made with carbon metal not a trace of cabon wood LMAO

  • @I3urnHard
    @I3urnHard 5 ปีที่แล้ว

    died during the sound sample ... you are tearing me apart ... marco :3

  • @sv3glx
    @sv3glx 5 ปีที่แล้ว

    At last sir... A New Video!

  • @Lux158
    @Lux158 5 ปีที่แล้ว +1

    For testing longer range you could Mount an standing plate and Drive the carige against it..

  • @IngeBall
    @IngeBall 4 ปีที่แล้ว

    Hypnotizing!

  • @namAehT
    @namAehT 5 ปีที่แล้ว +1

    FYI: You should look into Klipper if you are interested in interfacing a regular threaded OS with a realtime OS. Klipper is a 3d printer software that does all the heavy lifting on a computer (usually a Pi) and then uses one or more microcontrollers to schedule and execute commands.

    • @reps
      @reps  5 ปีที่แล้ว +1

      Yeah, cool project. I think Cetus is also based on that principle

    • @namAehT
      @namAehT 5 ปีที่แล้ว

      @@reps I honestly think it's the way forward for 3d printing as opposed to using STM32 based boards with webUI addons like the Duet. Plus it can be infinitely scalable. Want to have two Y-axis gauntries with two X-axis carriages with two independent extruders each? Slap a few cheap reprap boards together and hook them up to a Pi and install Klipper on everything.

  • @tamurhaq
    @tamurhaq 4 ปีที่แล้ว

    I actually shuddered when you rotated the ballscrew with abrasive in it

  • @cosmoalien12345
    @cosmoalien12345 3 ปีที่แล้ว

    1.07 luckily you didn't fall on the staircase behind ... hahaha

  • @halasimov1362
    @halasimov1362 3 ปีที่แล้ว

    You are an asset to humanity.. and futue A.I overloards alike!

  • @milithemuffin4534
    @milithemuffin4534 5 ปีที่แล้ว +1

    That's some quality hardware! I'm only worried a bit about this Z axis, it looks going to be 2-3 times longer than spacing between rails, this will amplify load on the rails, and then amplify deflection at the tip of an end mill even more. I might be overthinking it but i'd be tempted to make something like Okuma double column machining center.

    • @reps
      @reps  5 ปีที่แล้ว +1

      Valid point!

  • @wolf3o3rok
    @wolf3o3rok 5 ปีที่แล้ว

    Hello, it's my first comment here.. First of all love your channel...So I am writing aboute the "el chepo chinese linear rails" i've bought some more then a year ago.. Frustrated over the laggy performance, etc... Solution disassemble the carriage submerge in alcohol (to clean some wierd oils inside) reassemble, greas up... It worked for me... Still going strong after a year or so of modernet to heavy use..

  • @MrJme3192
    @MrJme3192 3 ปีที่แล้ว

    Looking for my first cnc machine. What will you suggest to look for when selecting a complete out of the kit cnc machine? BTW, love your video very informative.

  • @o0julek0o
    @o0julek0o 5 ปีที่แล้ว +1

    Hahahahahhaah, "avoid things like this" I'm hecking crying 😂😂😂😂😂😂

  • @ArtyomGalstyan
    @ArtyomGalstyan 4 ปีที่แล้ว

    top-level hobbyist