Need Help! mates on scissor assembly are driving me nuts.


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    Default mates on scissor assembly are driving me nuts.

    I'm trying to do a scissor mechanism. When I add too many mates it locks up the scissor.
    this is my first design table and assembly design so there are likely to be lots of problems from me not following best practice.

    I tried to simplify the main assembly (x-axis assembly) by using multiple assemblies.

    The scissor mechanism is floating in its assembly. I did have a mounting screw to constrain it initially but it didn't seem to be helping so I deleted it.

    any help is appreciated to find out what is stopping everything from sliding as designed.

    I'm trying to upload the model but it's timing-out for some reason. ill keep trying.

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    Default Re: mates on scissor assembly are driving me nuts.

    hy solid is pretty good in such cases, and alows multiple conditions / restrains, etc, that are handled pretty well

    i guess this is the reason why we love solid, so to say

    time and bit of practice should help you setting mates faster

    i will explain for a "scissor" : think of a buterfly no kitting .. is the same as a buterfly, well , at least from my perspective

    you need 2 cilinders that are almost identical, coaxial and overlapped one cilinder is rigid / static, while the othre has this conditions :
    ... coaxial with 1st
    ... on face/ frontal on the face of the other

    in this moment the 2nd cilinder should rotate arround the 1st one, more exactly arround the simetry axis of the 1st cilinder

    this is key now you can build whatever arround those 2 cilinders

    to obtain a beautiful scissor , materialize those 2 cilinders like this :
    ... on one arm of the scissor, put an "extruded" cilinder
    ... on the 2nd arm, "extrude cut" same cilinder

    now you have those 2 cilinders materialized on solid shapes > go mate

    we are merely at the start of " Internet of Things / Industrial Revolution 4.0 " era : a mix of AI, plastics, human estrangement, powerful non-state actors ...


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    Default Re: mates on scissor assembly are driving me nuts.

    hollywood movie attached

    ps : i tried 2 look at ur files, but my 2012solid can not open them

    we are merely at the start of " Internet of Things / Industrial Revolution 4.0 " era : a mix of AI, plastics, human estrangement, powerful non-state actors ...


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    Default Re: mates on scissor assembly are driving me nuts.

    thanks for the effort, but without being able to open the assembly it is very hard to explain what is going wrong.
    The scissor mechanism is like this. mates on scissor assembly are driving me nuts.-scissor-mech-jpg

    It works by its self, but when matted to other parts it locks up. It will take 2 mates before locking. The first mate operates as expected. The 2nd mate is locked and further mates wont work, over defining the assembly.



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    Default Re: mates on scissor assembly are driving me nuts.

    i'll take a look asap

    we are merely at the start of " Internet of Things / Industrial Revolution 4.0 " era : a mix of AI, plastics, human estrangement, powerful non-state actors ...


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    Default Re: mates on scissor assembly are driving me nuts.

    just another hollywood movie

    i tried more out of curiosity ... maybe you can open those files, and check the mates, since your solid seems newer

    i think you did not succeed because you have declared too many conditions, while some were self-evident / implicit

    * * * * * * * * * * * * * * * * * * * * * * * *

    aaaaaaaa, i think i get it ... you have some problems when connecting other parts to this ... well, just share those parts, and i'll try

    we are merely at the start of " Internet of Things / Industrial Revolution 4.0 " era : a mix of AI, plastics, human estrangement, powerful non-state actors ...


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    Default Re: mates on scissor assembly are driving me nuts.

    actually, it may not lock, but only appear so ... for example try to use some dimensions over your final construnction, and see what happens when you change them

    if mates are ok, than you may be able to change parts position only by editing those dimensions

    we are merely at the start of " Internet of Things / Industrial Revolution 4.0 " era : a mix of AI, plastics, human estrangement, powerful non-state actors ...


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    Default Re: mates on scissor assembly are driving me nuts.

    I was able to get your assembly to work how (I think) you intended. The problem was that you had too many mate redundancies. Solidworks is usually pretty forgiving about allowing multiple mates to constrain the same degrees of freedom. But having too many redundancies can really slow down the solver and even cause strange issues that are seemingly random and unexplainable. In these cases it doesn't always throw an error so it's up to you to figure out what is going on.

    In this specific example, I think the problem was mostly caused by the distance mates that constrain the way covers in the lateral direction. When you try to mate the holes in the scissor to the holes in the way covers you end up with multiple mates trying to constrain the lateral position of the way covers. Even though they should all solve in theory, they don't for whatever reason. The solution is to replace the distance mates of two of the way covers with parallel mates. This eliminates enough of the redundancy to make the assembly work correctly. Note that there are many other mate configurations that would also accomplish the same thing, so this is not the only solution.

    Understanding degrees of freedom and mates is a somewhat complicated subject and is worthy of review if you haven't done so for awhile. I've been using Solidworks daily for about 7 years now and I still get tripped up by mates on occasion.


    Oh, some other things I should mention:
    - there was a parallel mate in the scissor assembly that was totally unneeded, so I suppressed it.
    - It's generally a good idea to have (at least) one fixed or fully constrained part in an assembly, and then mate everything else to that part. It makes the solvers job a bit easier.
    - It's also a good idea to only use flexible sub-assemblies when you absolutely have to. This also makes the solvers job easier and reduces the number of mate redundancies.



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    Default Re: mates on scissor assembly are driving me nuts.

    thank you!
    is there a way to see what mates are redundant?

    The assembly started without the scissor setup and the distance mates were needed to constrain the slides at that time. Yes I could have chosen a number or other mates to do the same thing, but it is silly that you have to plan so far ahead with your matting strategy to prevent future parts messing the assembly up.

    The redundant parallel mate in the scissors was to prevent a impossible straight conformation that would occur when manipulating the assembly. Not necessary but it was making my life easier when manipulating the assembly.

    I wish it had a solutions solver like when you over defining sketches so you could choose and change existing relations to fix the issue.

    anyway thanks heaps for the help!



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    Default Re: mates on scissor assembly are driving me nuts.

    Quote Originally Posted by landslide1 View Post
    thank you!
    is there a way to see what mates are redundant?

    The assembly started without the scissor setup and the distance mates were needed to constrain the slides at that time. Yes I could have chosen a number or other mates to do the same thing, but it is silly that you have to plan so far ahead with your matting strategy to prevent future parts messing the assembly up.

    The redundant parallel mate in the scissors was to prevent a impossible straight conformation that would occur when manipulating the assembly. Not necessary but it was making my life easier when manipulating the assembly.

    I wish it had a solutions solver like when you over defining sketches so you could choose and change existing relations to fix the issue.

    anyway thanks heaps for the help!

    Sadly there isn't any tool for determining degrees of freedom outside of motion studies (which I've never really used). So finding errors comes down to process of elimination. Breaking things down into sub-assemblies based on motion is a good practice to minimize the possibility of errors. When they do occur i find it helps to start suppressing things to simplify until you find what it causing the problem. Also the basic mates tend to be more stable than the advanced mates. Width mate can be especially fussy, which is a shame because it's so convenient.

    A mate analysis tool would be awesome but I doubt it will ever happen.


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    Default Re: mates on scissor assembly are driving me nuts.

    Quote Originally Posted by landslide1 View Post
    is there a way to see what mates are redundant?
    there is an analisys that involves : position / static, speed&acceleration / cinematics , forces / rigidity , dimensioning, modeling in cad software

    that analisys is pretty simple, schematic : can you "play" with stuff from attached image ? if so, than this should lead to good mates, thus one shot, and not put you in the position to try several mates combinations

    you can design such a simple sketch in solid, and check the motion / if ok, than you can build the solid over it

    Quote Originally Posted by cygnus x-1 View Post
    Understanding degrees of freedom and mates is a somewhat complicated subject and is worthy of review if you haven't done so for awhile. I've been using Solidworks daily for about 7 years now and I still get tripped up by mates on occasion.
    keep up the good stuff

    please, can you recomend a monitor ? most part of the day i stay in front of one ... less brightness, less contrast, i replaced white backgrounds with gray, and so on

    onestly i wait for a monitor as an e-book-reader, but those are really slow, so no chance to use them as a computer screen kindly !

    we are merely at the start of " Internet of Things / Industrial Revolution 4.0 " era : a mix of AI, plastics, human estrangement, powerful non-state actors ...


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    Default Re: mates on scissor assembly are driving me nuts.

    Quote Originally Posted by deadlykitten View Post
    keep up the good stuff

    please, can you recomend a monitor ? most part of the day i stay in front of one ... less brightness, less contrast, i replaced white backgrounds with gray, and so on

    onestly i wait for a monitor as an e-book-reader, but those are really slow, so no chance to use them as a computer screen kindly !


    I don't use any special sort of monitor, just a basic 23" LCD. I do tend to use a lower brightness and contrast but I've never had any significant problem with eye strain, so for the most part I don't do anything beyond that. In a past life (before I learned Solidworks) I actually spent more time in front of a computer than I do now, and I used to set white backgrounds to tan/grey, which does help as well. The standard color scheme in Solidworks doesn't seem to lend itself to a dark background so I never messed with it. I also occasionally save screen shots of models to use for documentation, and solid white background makes this work better so I just leave it at that.


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    Quote Originally Posted by landslide1 View Post
    thank you!
    is there a way to see what mates are redundant?

    The assembly started without the scissor setup and the distance mates were needed to constrain the slides at that time. Yes I could have chosen a number or other mates to do the same thing, but it is silly that you have to plan so far ahead with your matting strategy to prevent future parts messing the assembly up.

    The redundant parallel mate in the scissors was to prevent a impossible straight conformation that would occur when manipulating the assembly. Not necessary but it was making my life easier when manipulating the assembly.

    I wish it had a solutions solver like when you over defining sketches so you could choose and change existing relations to fix the issue.

    anyway thanks heaps for the help!
    Not sure what this accordian was going to do in relation to your assembly but here's a fixed set of constraints you needed. There was nothing defining a fixed point on the accordian and nothing to drive it. It will confuse Solidworks when it's in a flexible state in the top assembly and sub assembly. Take a look at the last few constraints.

    Your "way design" and "way cover" assemblies many mates conflicting with eachother. For example you have concentric mates on holes on parts that are also defined by distances. It works fine until you try moving stuff and SW chokes. If you can make yourself some planes and mate to planes rather than distances you can cut about 2/3 of all those mates. And don't forget to define (not fix) one part. I usually go right across TOP to TOP FRONT to FRONT and RIGHT TO RIGHT where I can after inserting my first part.

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    Default Re: mates on scissor assembly are driving me nuts.

    Quote Originally Posted by cygnus x-1 View Post
    I've never had any significant problem with eye strain
    hy i do have ... i am on cnc's, and when i write code i have to be carefull at each char, and this means that my eyes focus more comparing to when using cads

    interesting is that i had glasses from a good doctor arround here, until some young girls poped up here for a base control, and said that i don't have protection against monitor, so they offered to fixed that, if i pay, of course and so i did, but they did not tell me that my lens will be replaced, so i received new lens that i could not use ,,, after a few seconds my head was going crazy ...

    i decided to use those, so i started to get used to them, but when i droped them off, my head / eyes started seriously hurting ... it sucks

    i contacted my original doctor, just to find out that he is away now, in a better place

    well, that's nothing compared to friend of mine that drinks a bit 2 much, and he drops / smash his glasses pretty often through local pubs maybe i should learn from him

    Quote Originally Posted by warrenb View Post
    For example you have concentric mates on holes on parts that are also defined by distances
    i thought of such things, but ... nice from you being patient to check others work

    we are merely at the start of " Internet of Things / Industrial Revolution 4.0 " era : a mix of AI, plastics, human estrangement, powerful non-state actors ...


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mates on scissor assembly are driving me nuts.

mates on scissor assembly are driving me nuts.