Choosing a gripper mechanism

Femme_physics

So we need to make a gripper in Solidworks only for this object



Our current goal (as per our professor) is to focus on our gripper mechanism.

My classmate suggested the following for the gripper final grip mechanism



The idea being that at the end of this straight movement that closes the gripper 2 jaw parallel effectors attached at the tip of this mechanical mechanism grab the object. We thought it's best for both sides of the gripper to close in a straight motion as this would increase accuracy, as opposed to a Two Jaw Cam Actuated Rotary Gripper...which mean they will be closing in an angel and decrease accuracy.



What do you think of the idea so far?

I like Serena

Well, how does it look... sexy!

As for the idea of a linear gripper... do you have a drawing?

Femme_physics

Better yet, I have a video! :)

http://www.youtube.com/watch?v=Ttsp7LJMDdo

I like Serena

Nice video. ;)

So are you finished already?
Or is there more to come?

Femme_physics

No, it's just a suggestion. I wanna see if it can be improved, or if it's a good idea overall. We're still beginners on the issue, so every feedback counts. Do you have a feedback? :)

I like Serena

Should your gripper operate in 3 dimensions?
How would your gripper be fixed in a frame?

Did you already google for grippers? Trying to find a picture of a gripper that matches your object?
And perhaps one that will look sexy in SolidWorks?

Personally, I thinks it's more important that it looks sexy than that it is a functionally correct gripper.

I like Serena

Btw, is there anything I can get you for your birthday?

Femme_physics

LOL, well the current design is pretty sexy

Yes, it's 3 dimension. But, I guess you can just imagine the 2D construct with volume, or width.

Yes, I googled for gripper, mostly we realize that the 2 jaw parallel gripper is good since it uses less friction than flat friction grip, therefor less energy. My issue is the gripping mechanism, not the actual gripper design. It looks ok, but I'm just a starter so can use the feedback :)

Femme_physics

Aww yea what u brought last time just for uppers ;)

j/k! Your forum help is the best gift I can ask for!

I like Serena

Well, the forum help is for free, so that does not count.

So you'd like something to match cybergrrl?
Well, that alone already gives you +25 intelligence points, let alone the charisma points.
I'm just wondering what more uppers I can get you...?

OldEngr63

Just a few comments about the whole thing.

1. The problem statement apparently does not specify the direction that gravity wills act on the combined gripper/object assembly, not does it specify the actions that the assembly must be able to make. This makes it difficult to determine just how the gripper must hold the object and how firmly the grasp must be. For example, can it simply scoop the object up in a shovel and dump it out, or must it pick it up in one orientation, carry it, and reorient it before placing it at the final position. How fast does it have to function; will dynamic loads be a consideration?

2. It appears that you have not made use of any of the features of the object to help secure the hold of the gripper on the object; shaped jaws could certainly help, but the closing/opening motion must not allow for a jam.

3. Your gripper design looks really bulky. Often the gripper needs to insert a part where there is not a lot of room for the gripper. You might want to look at ways to stream line the design. (Make your two operating wheels coaxial, so that they appear one over the other in the side view, for starters. I think you might think you might want to look at other mechanisms as well.)

4. In your second figure, the on labelled Fig 1, what appears drawn as a spring is labelled "cam." I cannot see it being anything other than a spring.

5. Remember that done properly, the grip/release motion is really very small. What you have drawn generates a very large motion which is easy to see, but far too big to be serviceable. Think about the sizes that are really needed, and the motions, and corresponding cycle times that could be achieved with them.

Femme_physics

It has to work in numerous such conditions and be able to adapt.

I agree, it's awfully bulky. Although, in reality, it would only open up 30% larger than the object it needs to catch (from each side), in my solidworks video it opens up really wide. It was an initial sketch idea.

I don't see a spring in our design. You might be confusing the "Cam" from the "CamStudio" software I used to record.

As I said my video was overdoing the grip. We did think of a less clumsy mechanism, which I'd like to present:

http://www.youtube.com/watch?v=zKtcw...ature=youtu.be

Any thoughts?

berko1

Both designs are based on rotary movement converted to linear motion. You may think of using a linear actuator (Pneumatic or Hydraulic) to drive your design in some sort of scissor motion.. Just a thought..

OldEngr63

This is really not a design spec, and there is no way to say whether a particular design meets it or not. This is especially true with respect to the dynamic loading/cycle time considerations.

The use of a rack and pinion, with the rack perpendicular to the main system axis, is going to make it very difficult to ever achieve a compact design. Why not a rack parallel to the axis, driving a wedge to clamp onto the object (much like a Jacobs drill chuck)?

Femme_physics

The idea is indeed to use a linear actuator in our design to drive both gears :) We discounted scsissor motion because direct linear motion for grabbing seems more accurate, don't you think?


Our part weighs 7.3 gr. Not sure about using Pneumatic or Hydraulic. We need to grab the part on the area marked in red, so we figured an electric one would best serve this purpose. No?

Well, it has to be designed to grab that SPECIFIC part, in that specific area marked in red. The part weights 7.3 gr and made out of AISI steel 1040. It has to be able to pick it and place it elsewhere.


I wasn't sure about your comment at clause 1, I'll try reanswering it:

Doesn't gravity always act down?

Oh, I see what you mean.Yes, it's for pick and transfer.


How can you grab the object with a wedge exactly?

I like Serena

How about a sliding gripper?
Something like this:

Femme_physics

Well, that's essentially what we've made so far in the last solidworks animation (imagine that at the end there are 2 jaw grippers like in your pic. The difference between my idea and your pic is:

A) Mine drives the end-effectors directly. Suppose I could mount on the rails grippers like yours.




B) Yours doesn't show internal design