Mating to a curved slotted hole in solid works

[ryanmech]

Gidday,

I am using both 2001 and 2001+.

I am trying to model a spigot mating with a 'curved' slotted hole(ie the parts rotate about another centre and are restained by the curved slot). The spigot needs to be able to move in the slotted hole but be restrained by the ends of the slot, so that i can confirm the design. The slotted hole is situated on some cable chain, that rotates through a certain angle (yet to be confirmed). I have tried several ways and found that it could be done for a couple of links if i mate the inside surface of the slot with the outside surface of the spigot (cam tangent mate), but when i do this for ~50 links i get an over defined error/fully defined error.

if there is way of getting around this, it would be bloody good, if you could give me an answer in detail as although i have a pretty good handle on the basics i have only spent 20+ hrs on solid works.


Cheers

Ryan

 

[josephv]

Hello Ryan,

You can try this:

Starting in SolidWorks 2001Plus, when you MOVE a component there is an option called PHYSICAL DYNAMICS, select this and you can simulate complex motion (without complex mates).

From the SolidWorks Help:

With Physical Dynamics enabled, when you drag a component, the component applies a force to components that it touches. The effect is to move or rotate contacted components within their allowable degrees of freedom. The dragged component reacts to a collision by rotating within its allowable degrees of freedom or by sliding against a constrained or partially constrained component to allow the drag to continue.

cheers,

Joseph

 

[TheTick]

One possibility as far as constraints:

I've used this when a part has to follow a non-linear but predetermined path, such as a curved slot centerline:

1.)Make a sketch of the centerline, part with the slot.
2.) Extrude a surface from this sketch
3.) Mate the axis of the bolt (or spigot) to the centerline surface with a coincident mate.

It's a little roundabout, but it may help you skirt the learning curve for physical dynamics if time is an issue.

Gravity is a harsh mistress.

 

[JNR]

Here's another idea if those don't work for your situation. Actually two ideas. Cam-mates are great....but! Obviously if a profile consists of (or is derived from) of several geometric entites end to end, you can't mate to all of them at the same time. In your case, it sounds like at least four arcs in the sketch creating the boundaries of the slot. A composite curve will not work because the resulting surfaces are still separate(!?!). Try superimposing a single spline curve along the entire profile - you have to make sure it is actually on the other entities by relating the points (which can be tricky). The resulting surface will allow you to do a cam-mate. The only thing you have to worry about is that the spacing of the spline points has to be closer where the radius is smaller OR where changes in curvature exist -particularly straight line tangent to arc. You'll get it with a little trial and error. It is not perfect, but REALLY close.

The other interesting trick I used some time ago was to get a sphere to mate to this type of cam surface. I actually added a very narrow (.001) cylindrical surface entity the same diameter as the sphere in the sphere part. Since a cylinder mate works, it performed what I needed. (You can hide the surface if need be.)

 

[ryanmech]

Thanks JNR, The Tick and Joseph,

I had already tried the collision detection/physical dynamics approach, but with ~50 links in my chain with one end of the chain fixed and the other on a floating part and then moving the floating end takes an bloody long time. The concentric mates at the pivot point and the physical dynamic collision detection of the spigot agianst the slotted hole all seem to be fighting each other. I currently have only tried physical dynamics with spigots mating with slotted holes on both sides of the chain, so i will try it with only one side having the slot, this will hopefully increase the speed by two fold.. Also i found that the spigot needs to be smaller in diameter than that of the slot otherwise it introduces restaint all the way along the slot travel instead of just at the ends... To make this work i think i have to simplify the situation as far as possible..

I had tried The Ticks idea of mating the centre of the spigot with the surface of the slot centre line, it did restrain the centre of the spigot to the surface of the extrusion but it did not restrain the spigot to the end of the slot..I obviously had an error as i had wanted to mate the centreline of the spigot to the surface i had extruded of the centre line of the slot as a coincident mate, therefore the centreline of the spigot should not have left the surface??? I will try this on a stright slot..

I will try JNR's trick after i have sorted if i can do it another way. I will have to check out how to sketch a spline over a path first..


Cheers

Ryan

Ryan.coatsworth@mooring.co.nz

 

[josephv]

Hello Ryan,

Your approach seems good. Like you said simplifying will help.

If motion simulation is critical you may want to consider some add ons:

1) COSMOS Motion

2) Motion Works

I believe they can simulate chains, but it would be good for you to get an evaluation copy first.

cheers,

Joseph

 

[ryanmech]

Joseph

I have cosmos motion and are doing a few tutorials to get the hang of it..

but i hadn't heard of motion works untill now.. I will look into that..

cheers
Ryan Coatsworth

ryan.coatsworth@mooring.co.nz