3D Printed Screw Compressor - Part 1 Design

[Music] [Music] [Music] [Applause] [Music] welcome everyone to part one of my 3d printed screw compressor project um one of the things i've always found very interesting in uh automotive world is the use of superchargers and turbochargers uh to increase horsepower and where i've would love to make a 3d printed turbocharger it's really not feasible with the speeds that they have to reach but in other you know i think just as cool thing is a supercharger there's a bunch of different types of superchargers out there but one of the ones that i've been most fascinated with is the actual uh twin screw supercharger which uses asymmetric rotors to compress the air and create boost the mathematics behind these and how they're actually designed is fascinating and it's not an easy task by any means to actually design these types of rotors they've got their own design software they've got their own cfd software it's really its own little niche as to how these screw compressors work and so i found it very interesting over the past you know several months to learn more about these i'm not going to pretend uh that my modeling or fdm 3d printing is going to replicate the extremely tight tolerances that these types of compressors uh use but my my goal really is if i can just make something that's a cool display model it might make some cool noises and uh you know stretch goal of maybe potentially being an over engineered tire inflator someday if i get an sla printer i may try this again and see what results i can get with better tolerances also of note in case you're thinking about potentially making a 3d printed supercharger for your small engine from this design this particular model's rotor profile is not going to be ideal for use in a supercharger application also now amr makes an amr300 and there's an amr500 which are uh small superchargers for uh you know engines under two liters and they're less than 250 dollars uh us which is an unbelievable deal so before i launch into actually designing this in cad i want to just highlight a couple of different types of superchargers that often get mixed up of course there's the centrifugal supercharger which operates more like a turbocharger but the oldest type of supercharger that you would see out there is a root style blower and the difference is that a root style blower has rotors like this where both rotors are symmetrical and it's not actually compressing the air along its length like a twin screw compressor would it's actually compressing the air more like a fan actually it's just a high pressure fan so the inlets on this side and the exhaust is being on this side and they just spin throw the air out against the housing and force it out not unlike you might see in a oil pump in a car beauty of this design was it was very easy to manufacture and to design and didn't require you know the cnc type mills and things to manufacture but a much better design that came along is the twin screw supercharger and that actually compresses air a little bit differently so the air comes in at one end is actually thrown out against the housing and enforced in between the veins of the two rotors and compressed along the length of the screw and exhausted out the other side okay there's several different things to know about screw compressors there's a couple of different types based on how they're actually lubricated there's oil lubricated and there's actually dry screw compressors oil lubricated scoop compressors you know kind of like it sounds actually use oil for lubrication they typically inject oil somewhere along the length of the screw compressor and they use the oil for lubrication between the rotors as well as actually enhancing the ceiling between the rotors and it also the oil vapor itself is used to cool the air charge as it is being compressed one of the unique things about oil screw compressors is that they can achieve a much higher pressure ratio so that's essentially how many times they can actually uh compress the air the compressor with the better ceiling is able to achieve a pressure ratio of about 13 to one so that means if you have one psi on this side you're able to get 13 psi potentially out on the other side depending on the design so the other style of screw compressor is of course the dry screw compressor and they use this uh typically in smaller uh screw compressors left you know not industrial units they might use them you know for superchargers uh or for medical devices where they can't have oil vapor in the air being compressed the difference between dry screw compressors is typically they actually have a set of timing gears that actually keep the rotors separate from each other and they actually never touch so the gears essentially act as a synchronizer between the two rotors so there's a very very very small gap between the two rotors at any one time because a dry compressor does not have the oil to help that sealing they can really only achieve a compression ratio of about three to one so that's one psi in they might get three psi out and because there's no oil for cooling dry compressors typically use a charge cooler or some type to cool the air um to achieve higher pressure ratios with dry screw compressors there's typically multiple stages uh that feed into each other with uh like an intercooler in between another cool thing about screw compressors that is that the rotors are actually just gears um they can have different uh ratios of lobes like three to five ratio four to six four to four and because there's their gears uh like for example these two would be a ratio of three to five but this one would have to rotate five times for every time the female would have to rotate three and in this particular case it's a four to six ratio different numbers of lobes are useful for different purposes there are lobe arrangements that are ideal for oil or just dry compressors so lobe arrangements are better at moving high volumes of air and some for achieving higher pressure ratios this particular screw compressor is a kind of a middle-of-the-road 4-6 lobe design that can be used in oil or dry with a decent pressure ratio also because these are just forms of gears of course you can create a helix this one here is twisted about 330 degrees over its length and this is twisted 220 degrees over its length now what's interesting is unlike a normal spur gears the the actual twist angles have to follow the same ratio as the lobes so for the screw compressor we're building it's going to be a four to six ratio with something called a stasic end profile and a 330 degree main rotor twist angle and using stasic's non-patented design i know that's a mouthful and i won't go into all the technical details of how every type of screw charger is designed but all that means is essentially the rotors themselves are asymmetrical to each other as well as the actual lobes are asymmetrical in design go ahead and include a link to a grad paper written by stasic that covers this in more detail and the mathematics behind these rotors i think that's actually one of the most fascinating things if you're actually a math person is to go see how they actually develop these rotors [Music] so [Music] [Music] so i think the easiest way to do this is to be able to walk through the design in cad starting off with the rotors and kind of working our way out so to design the rotors themselves stasic has some great grad papers on his non-patented designs as well as some other designs and what i did is i went into c sharp and actually created a program that i've actually lost over the years but it actually creates an svg file that can be imported into fusion 360 and actually turned into a sketch so once you have the profile it's pretty straightforward from there you just actually are doing a sweep with the profile over an access and putting a twist angle on it the one thing that i found out from some earlier prototypes was that getting the clearance between these rotors and the housing is very difficult to do in one go and i ended up printing out multiple copies of these housings which would take you know 50 to 100 meters of filament every time i did that so the design approach i've taken now is to actually have a liner that the rotors actually come in contact with and this is inside the housing so there's not too much unique about the liner other than it's fairly easy to be able to reprint and also allow me to test different materials for the rotors and for the liner itself the only thing that you have here is on the actual air intake is just a little divider that helps with the efficiency of the compressor itself so next up is the actual outer housing so this surrounds the rotors themselves right here is the intake port so this is where the air comes into the compressor and over here is the actual exhaust port and what actually happens is these rotors actually spin this one goes this direction so it'll go clockwise and this one goes counterclockwise it actually throws the air against the outside of the housing and i don't know if you can see this but actually as it comes into the port here it's actually open on the top half of the housing here so that the air can actually wrap around the rotor and it actually matches the profile that the rotor cuts as it's spinning so it can suck the air around about i'd say that's about 80 percent or so of the rotor now i'm not sure mathematically if that's accurate but i based on pictures i saw this is roughly what i was seeing in other screw compressors it's the same way with the actual inlet and the outlet uh the inlet is roughly uh three times as big as the in surface area as the outlet this is again based on pictures that i saw i'm not sure what the actual mathematics are behind this i couldn't find uh any information on this it's actually really hard to find information on screw compressor design it's a very proprietary type information and the companies that actually manufacture these don't really share their their information with the general public too much so now that we've actually got the housing here i'll actually bring in we'll call the actual ends here so the intake end we've got some bearings some o-rings and the exhaust and then i'm going to go ahead i'm actually going to switch back to the design view here so that i can slice this in half and show you the uh the guts of the housing and actually going to hide the rotors here so this is what the guts of the housing look like it's pretty straightforward what i've done here is actually just have some 608 skateboard bearings on either end i do have two on the exhaust side because these are actually the rotors themselves are helical gear so there is some axial load and in real screw compressors of course they use some sort of thrust bearing i have some o-ring seals on both ends uh on this end it's just a single o-ring seal because this isn't really the high pressure on the intake end and on this end we have uh double o-ring seals is yet to be seen whether or not we actually develop another enough pressure to actually need two o-rings on there uh the other purpose for these is potentially you know sometime in the future i might play with actually filling the ends with oil so that they can have additional lubrication for the bearings and on this side i'll actually show you the timing gears let's go ahead and show those so these two timing gears have the same ratio as the rotors themselves and so what i'll do is i'll actually set it up so that there's a minimal amount of play between the rotors and the gear should actually keep them separated at all times now for a small compressor like this and with fairly you know lubricative material like plastic you don't necessarily need these gears and i may play with uh not having them in place later uh but for now i just wanted to do it because it's kind of cool and we'll see what actually happens in the end so again we have just the shafts coming through here this is a mains driven compressor which is a fairly typical design for these compressors and what that just means is that the male rotor is the one actually with the input and i'll go ahead and show the rotors again so that you can actually see this is the input rod here and i'll show the intake cover itself so this will be where the actual power comes from the motors and actually drives the rotors themselves um i'll have a set of pulleys here that i'm still working on the design for and a couple of motors up here that uh will actually drive those with a big gt2 timing belt i think that'll work the best they'll be kind of belt driven just like real superchargers and cars are i also added a uh you know for fun because it's cool a velocity stack i'm sure that will probably do almost nothing let's see what else do we have on here here at the exhaust and um i do have the ability to adjust the thrust so essentially essentially have some caps that can be uh printed at different tolerances to actually change the preload on the rotors uh the bearings themselves and then those will just screw in with three m2 screws into some brass inserts i used brass inserts on all of this now i know there's gonna be a lot of people out there worried about uh you know this exploding on me but the reality is you know being a dry compressor and even if i play with injecting some oil you're never going to you know realistically see more than let's say 40 to 60 psi if i'm extremely extremely lucky this housing is very overbuilt i did everything with five walls on the prince so you could literally i can stand on this housing and it doesn't even flex um there's nowhere even at the thinnest parts between the rotors and the ends and the caps there's nothing with less than uh i think 12 walls it's the thinnest it gets so there's very very little safety concerns i have with this particular design from you know an explosion type standpoint and i'll be printing all the housing out of pet g which again that just adds a little bit of extra protection so this side here is the exhaust this is designed to actually match the profile of the rotors as you can see to maximize the pressure or to minimize sorry the pressure loss as it's actually exhausting the gas out but on top of here i'll actually have a elbow essentially that's just a 90 degree turn that transitions between that strange shape at the outlet of the compressor to a more rounded shape and then to this i'll actually bolt with a put a o-ring in there and then i'll actually have an air port so that i can thread in uh some sort of fitting so that maybe i can you know stick a pressure gauge on this and see what kind of pressures we're going to get out of it so right now i'm about halfway through printing all the parts everything is being printed in pet g i did some small scale tests as you could see with pla and they almost immediately began to melt so hopefully the pet g will hold up enough to get me through the actual testing of this model i know that later i'll probably have to reprint the rotors out of delrin or nylon 12. but i want to go ahead and just see what kind of performance i can actually get out of this before i go invest in more expensive materials realistically i've got a probably another couple days of printing left i found the slower that i print the better the accuracy and uh honestly i have over one kilogram of pet g just in this housing itself so it's definitely very strong next video i'm hoping to be able to start fitting all this together and maybe see if we can fire this thing up let me know in the comments if you have any good ideas for ways to test this thing's performance i hope everyone enjoyed this format i know the trend on youtube right now is just to skip to the end and show the project working all in one video but my hope is that walking everyone through the design will help people appreciate more about how these machines actually work and realistically these uh i wouldn't be releasing videos very often if i uh only skip to the end anyways if you like this video please hit that like button and uh if you want to see more content like this please consider subscribing thanks [Music] [Music] [Music] so you

Channel: Indeterminate Design

Views: 51,077

Keywords: supercharger, rotary screw compressor, twin screw, blower, 3d printed, compressor, air compressor

Id: jVPjSDNfAfk

Length: 22min 14sec (1334 seconds)

Published: Sun Aug 02 2020