What's better Linear Ways or Scraped Ways ?
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  1. #1
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    Default What's better Linear Ways or Scraped Ways ?

    I figure the forum needs a new subject. Here is a magazine article I contributed too back in 2015.

    Scrape to the point | Cutting Tool Engineering

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    They did not mention hydrostatic ways.

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    The ultimate must be scraped linear ways, with flaking on all the rolling elements and rails.


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    Good survey article apparently intended for design staff and supervision unfamiliar with the comparative merits of linear bearing systems.

    While the article couldn't cover everything (hydrostatic bearings, alternative lining materials, machine tool survey, buy Vs build, prep for rebuild, etc), it omitted scraping assembly joints for correcting alignment and scraping bearing surfaces for geometry and fit. A good tech writer could have synopsized these sub-topics in a single paragraph - enough to plant a nugget in the mind of a technical decision maker.

    Most folks with only a vague knowledge of scraping are unaware its niche applications, including accurizing the mounting surfaces intended for linear bearing assemblies. It would be beneficial if the decision makers were at least aware of these refinements and of source material, bibliographies, etc for further study should they be so inclined.

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    People hand scrape linear bearing mount surfaces or even bearing locknuts...

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    Quote Originally Posted by RC99 View Post
    They did not mention hydrostatic ways.
    Landis cam grinders have the kind that are pressurized. Is that hydrostatic or hydrodynamic ?

    Whichever, they are the coolest. Makes everything else look like junk.

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    Obviously, the correct answer is the one wot Richard says!

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    Quote Originally Posted by EmanuelGoldstein View Post
    Landis cam grinders have the kind that are pressurized. Is that hydrostatic or hydrodynamic ?

    Whichever, they are the coolest. Makes everything else look like junk.
    It's a little counterintuitive, but hydrostatic is pressure fed, hydrodynamic is when the movement of the mechanical elements induces a lubrication wedge between bearing surfaces.

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    Quote Originally Posted by Milland View Post
    It's a little counterintuitive, but hydrostatic is pressure fed, hydrodynamic is when the movement of the mechanical elements induces a lubrication wedge between bearing surfaces.
    My mnemonic is that hydrostatic is pressure fed as a way to keep static pressure.

    Quote Originally Posted by Forrest Addy View Post
    Good survey article apparently intended for design staff and supervision unfamiliar with the comparative merits of linear bearing systems.

    While the article couldn't cover everything (hydrostatic bearings, alternative lining materials, machine tool survey, buy Vs build, prep for rebuild, etc), it omitted scraping assembly joints for correcting alignment and scraping bearing surfaces for geometry and fit. A good tech writer could have synopsized these sub-topics in a single paragraph - enough to plant a nugget in the mind of a technical decision maker.

    Most folks with only a vague knowledge of scraping are unaware its niche applications, including accurizing the mounting surfaces intended for linear bearing assemblies. It would be beneficial if the decision makers were at least aware of these refinements and of source material, bibliographies, etc for further study should they be so inclined.
    Damn glad to see you around, Forrest!

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    Isn`t the development in tooling dictating linear ways ???

    Peter

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    Application Specific.

    Do you need a robust machine to take heavy cuts.

    Or a fast light duty machine to lay carbon fiber.

    Kind of like on Saturday morning, you would like a pick up truck to take yard wast to the dump, but then Saturday night you would like a sports car to go out and chase the ladies, or dudes......

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    Quote Originally Posted by Peter from Holland View Post
    Isn`t the development in tooling dictating linear ways ???

    Peter
    that's an interesting thought. or could it be that since linear ways are becoming more prevalent, that cutting tool design is being optimized for use on machines with linear ways to take advantage of the advantages of those way systems and to minimize the disadvantages of them.

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    The best and biggest names in machine tools still use a mix of both. Mazak is entirely linear guides as far as I know. But Okuma uses box ways on the lathes and linear guides on the mills. Similar for Mori Seiki.

    Some companies like Doosan use box ways as a selling point claiming rigidity. Others like Brother use linear ways using speed as a selling point.

    I think we will see both for years to come.

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    Quote Originally Posted by ewlsey View Post
    I think we will see both for years to come.
    ...horses for courses.

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    Imo,
    Linear guides are taking over, eventually accounting for most-all typical contact-bearing machine tool uses.
    I believe linear guides are 90% of machine tool ways, in 2019, by new machines made in units.

    I doubt any manually scraped contact surfaces in machine tools will be relevant in 10 years, == 2029.
    Machine-ground surfaces similar to todays scraped surfaces might be used in some very specialty apps by 2029.

    Clar(ification):
    I did not belittle the scraping skills and quality and results achieved here by many in PM in many cases, at all.

    I just opined that it will not be commercially relevant past maybe 1(-2)% or less of cases, by 2029.

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    The added benefit of the linear ways is the comparatively lightning fast rebuild time.

    That is one of the reasons I bought a Brother.

    Don’t get me wrong, I learned scraping to rebuild some of my old machinery, and I am a rank amateur, but it takes FOREVER comparatively.

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    Another vote for a well designed hydrostatic system.

    Regards Tyrone.

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    Perhaps linear motors will take over
    Do these have seperate ways BTW ??

    Peter

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    Quote Originally Posted by Peter from Holland View Post
    Perhaps linear motors will take over
    Do these have seperate ways BTW ??

    Peter
    So far the linear motors I've seen just provide propulsive force, not axis direction or stability. So they've using linear rails to provide that.

    Now in theory they should be able to do both, but the force required to be stable in all six axis while under cutter load or movement directive would likely be energy prohibitive, unless we got a practical superconductor for the drives.

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    Quote Originally Posted by Peter from Holland View Post
    Perhaps linear motors will take over
    Do these have seperate ways BTW ??

    Peter
    Yes separate and in bigger sizes they do not like box or conventional ways due to huge attraction force which will clamp down these type setups.
    Bob


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