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Familiar With Manufacturing Processes? Need Help

Posted by Kai Hefner, Mar 23, 2020

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  1. Kai Hefner

    Kai Hefner Freelancer

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    Hey all.

    This whole virus thing has spiraled my studies out of control but it hasn't stopped professors from throwing projects at us. I'm wondering if you guys could help me out on something. I'm analyzing the manufacturing processes used to create a crank-case cover for a lawnmower.

    I already know that the part is created through die casting, then goes through some trimming (I'm pretty sure, correct me if I'm wrong), then something else to get that polished look. At first I thought it may have been hand-polished but the inside of the cover is also polished, and it has way too many curves for a human to be involved in that process.
    Does anyone know how they get that final polished look?
    Also: for the mating faces, are those decking lines? What machine would they use for the swirly lines?
     

    Attached Files:

    Road Race Build 892  2

    1998 Eagle Talon TSi AWD
    awd · manual · 2G DSM
    Loading...
  2. BLACK'98DSM

    BLACK'98DSM Proven Member

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    Yep, those are decking lines. I've never seen them polish the sidecovers, but I suppose they just use a hand polisher to keep it looking good until the first few times you use it.

    I've dealt with a couple of those 212's, so useless info about them can come your way if you need it...
     

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    1998 Mitsubishi Eclipse N/T
    fwd · manual · 2G DSM

    127  3

    2008 Tomberlin Crossfire 150R
    rwd · manual · Misc Vehicles

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    2008 Tomberlin Crossfire (325 swapped)
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    Dreams Realized and Kai Hefner like this.
  3. ThunderChild

    ThunderChild Supporting VIP

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    My assumption is it's tumble polished and then final machined on any flanged surfaces. IDK for sure though, maybe one of the fab guys can weigh in.
     

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    1992 Eagle Talon TSi AWD
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    1992 Eagle Talon TSi AWD
    awd · manual · 1G DSM
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  4. Kai Hefner

    Kai Hefner Freelancer

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    I'm comparing it to a crankcase cover that doesn't have the polishing. The GX200 has polishing on the inside. It could totally be a looks thing but why polish the inside?
    The other cover has decked mating faces but no swirly lines?

    edit: wrote before Thunder posted, tumble finishing makes sense since the inside is also polished?
     

    Attached Files:

    Road Race Build 892  2

    1998 Eagle Talon TSi AWD
    awd · manual · 2G DSM
    Loading...
  5. b00st3d

    b00st3d Freelancer

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    Looks vibratory or tumble polished to me as well. pretty common for this type of part.
     

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    1997 Mitsubishi Eclipse Spyder GST
    awd · automatic · 2G DSM

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    1998 Mitsubishi Eclipse GSX
    manual · 2G DSM

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    1993 Eagle Talon TSi AWD
    awd · manual · 2G DSM
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  6. 1990TSIAWDTALON

    1990TSIAWDTALON Moderator

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    I agree with @ThunderChild and @b00st3d on tumble polishing. Just watched some done on "How Its Made" and they toss those things in a drum full of ceramic rocks. If there needs to be a reason why the inside is so smooth I would say so it doesn't "hold" onto oil and lets it run off fast.
     

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    1998 Eagle Talon TSi
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    1990 Eagle Talon TSi AWD
    13.620 @ 108.460 · 1G DSM
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  7. rabenne

    rabenne Proven Member

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    Yes, nobody is hand polishing something like that in large scale operations. It is almost certainly vibratory polished or possibly tumble polished, but they seem big for tumble polishing.

    improving surface finish reduces chances of fatigue crack initiation thereby improving its total fatigue life... Could be why its polished. Or perhaps oil run-off is a factor, or both.
     
    Last edited: Mar 23, 2020

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  8. Kai Hefner

    Kai Hefner Freelancer

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    This is a great detail! Thank you.
    Might as well ask another question while I'm here. The inside of one cover has kind-of-like a guard for the cam gear (I circled it), I assumed it had something to do with getting oil to the gear. The other one doesn't. Anyone have any idea what this design might be for?
     

    Attached Files:

    Road Race Build 892  2

    1998 Eagle Talon TSi AWD
    awd · manual · 2G DSM
    Loading...
  9. BLACK'98DSM

    BLACK'98DSM Proven Member

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    I assume the Honda has it and the Predator doesn't. It's just to keep the oil on the teeth of the cam gear.
     

    Road Race Build 3K  10  25

    1998 Mitsubishi Eclipse N/T
    fwd · manual · 2G DSM

    127  3

    2008 Tomberlin Crossfire 150R
    rwd · manual · Misc Vehicles

    167  6

    2008 Tomberlin Crossfire (325 swapped)
    rwd · manual · Misc Vehicles
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  10. Kai Hefner

    Kai Hefner Freelancer

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    Yeah, the Honda has it and the (Powerfist I think) doesn’t. An important note is that the Honda cam gear is metal and the Powerfist one is plastic. Does It have anything to do with the cam gear material choice?
     

    Road Race Build 892  2

    1998 Eagle Talon TSi AWD
    awd · manual · 2G DSM
    Loading...
  11. BLACK'98DSM

    BLACK'98DSM Proven Member

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    Either the plastic doesn't need as much lubrication, or since it's a cheap engine they're saving every last ounce of material they can. Could be both.
     

    Road Race Build 3K  10  25

    1998 Mitsubishi Eclipse N/T
    fwd · manual · 2G DSM

    127  3

    2008 Tomberlin Crossfire 150R
    rwd · manual · Misc Vehicles

    167  6

    2008 Tomberlin Crossfire (325 swapped)
    rwd · manual · Misc Vehicles
    Loading...
    ThunderChild, rabenne and Kai Hefner like this.
  12. 1990TSIAWDTALON

    1990TSIAWDTALON Moderator

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    Solomon knows his small engines, so I am going with him on that question.
    Thanks Sol!!!
     

    Street Build 4K  29

    1992 Eagle Talon TSi AWD
    14.74 @ 117.04 · 1G DSM

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    awd · manual · 1G DSM

    749  18

    1967 Chevrolet Camaro RS
    rwd · automatic · Misc Vehicles

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    1998 Eagle Talon TSi
    fwd · manual · 2G DSM

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    1990 Eagle Talon TSi AWD
    13.620 @ 108.460 · 1G DSM
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  13. Lucky13

    Lucky13 Supporting Member

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    As for your mating surfaces I'd imagine you'd machine them in a mill of some kind with a fly cutter or endmill ( thus the swirly lines ).
     
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  14. motomattx

    motomattx Proven Member

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    Those swirly lines are from being milled flat on a cutter, the smooth one looks to me like it is cast in the "lost wax" casting method, the other looks like its die cast.
     

    Drag Race Build 4K  24

    1995 Mitsubishi Eclipse GST
    fwd · manual · 2G DSM
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  15. Kai Hefner

    Kai Hefner Freelancer

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    Thanks guys!
    Have one more part I need you guys to look at. How do you think this starter cover is manufactured?
    Looked like pretty thin sheet metal. Are all the holes just stamped out, and then the part is thrown into some bending machines?
     

    Attached Files:

    Road Race Build 892  2

    1998 Eagle Talon TSi AWD
    awd · manual · 2G DSM
    Loading...
  16. Kai Hefner

    Kai Hefner Freelancer

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    Calgary, AB, Canada
    The design of the starter cover for the nicer motor is much more complex (has some heat-sinks or something on it). Anyone have any idea how this was made?
     

    Attached Files:

    Road Race Build 892  2

    1998 Eagle Talon TSi AWD
    awd · manual · 2G DSM
    Loading...
  17. BLACK'98DSM

    BLACK'98DSM Proven Member

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    Holes punched first, then pressed or stamped in to shape, then painted.
     

    Road Race Build 3K  10  25

    1998 Mitsubishi Eclipse N/T
    fwd · manual · 2G DSM

    127  3

    2008 Tomberlin Crossfire 150R
    rwd · manual · Misc Vehicles

    167  6

    2008 Tomberlin Crossfire (325 swapped)
    rwd · manual · Misc Vehicles
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  18. Kai Hefner

    Kai Hefner Freelancer

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    Thank you for the info Sol!
    I'm looking for specific machines/manufacturing processes that were used to create these things. From the previous replies, the best ones were the ones telling me about tumble finishing and milled on specific machines. i.e. I want to know how they punch the holes, I guess stamping into shape isn't too diverse in terms of machines, and possibly what kind of painting technique they use? Just normal spray-on? Anodizing?
    I'm having doubts that the GX200 one is stamped into shape because of those heat sinky looking things.
     

    Road Race Build 892  2

    1998 Eagle Talon TSi AWD
    awd · manual · 2G DSM
    Loading...
  19. BLACK'98DSM

    BLACK'98DSM Proven Member

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    At the fab shop I used to work at, there was a machine that sprayed the parts we sold. It was like a smaller scale robot that paints cars. An electric gun on a swivel, and you programmed the size of the part into the computer like a 3D model.

    It could be different for each company though, I'd try doing some research on that.
     

    Road Race Build 3K  10  25

    1998 Mitsubishi Eclipse N/T
    fwd · manual · 2G DSM

    127  3

    2008 Tomberlin Crossfire 150R
    rwd · manual · Misc Vehicles

    167  6

    2008 Tomberlin Crossfire (325 swapped)
    rwd · manual · Misc Vehicles
    Loading...
  20. motomattx

    motomattx Proven Member

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    wampum, Pennsylvania
    That part is just painted with enamel paint, anodizing is only done on aluminum or titanium it cant be done on ferrous metals, those parts start out as flat metal then it is punched then formed to the right shape and trimmed to the final dimensions.
     

    Drag Race Build 4K  24

    1995 Mitsubishi Eclipse GST
    fwd · manual · 2G DSM
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