10 Replies Latest reply on Oct 15, 2015 11:32 PM by Bo DO

    Hold part after adjusting part's position

    Bo DO

      Hi guys,

       

      I am designing a machine that used for assembly line. The machine working process as following:

      1. Operator places 3 parts in a jig with locktie.

      2. robot (hexapod form PI H-811 6-Axis Miniature Hexapod ) will pick up 1st part.

      3. Camera will take a picture, then calculate positions and orientations of parts.

      4. base on results of calculation, the haxapod will move part and place that part on a hole satisfying pre-defined tolerances.

      5. the hexapod then will move to 2nd and 3rd part to do the same process as 1st part.

      6. after adjusting 3 parts, heater will heat up locktie to fix 3 parts.

       

      the problem here are:

      1. I need a mechanism to hold 1st part in the positions and orientations that it  was adjusted, so the hexapod can move to 2nd and then 3rd.

      in the original idea, we use 3 hexapods, but it is not economic to use 3 ones (1 hexapod costs about 28k USD, then if we use 3, the machine will be expensive and our customer doesn't except that cost).

      2. so we have to design a jig to hold them, but the distance between parts are to small, like ~4mm distance between 2 adjacent parts (these parts are also small as well).

       

      So I ask you guys here for any idea on designing a jig like I mentioned or

      any others jigs/mechanisms that could help the machine work best.

       

      Sorry, I cannot attach any file because it's company confidential.

       

      I am looking forward for your feedback.

      thank you all

        • Re: Hold part after adjusting part's position
          John Stoltzfus

          If the part is steel you could use an electro magnet - Flat plastic or non magnetic materials use vacuum ??

          • Re: Hold part after adjusting part's position
            Jamil Snead

            I am having a hard time picturing what is going on. Is the part floating in space and needs to be held there? Or is the part resting on the object with the holes? Since the position is variable (based on the photo analysis) I don't see how any jig could work unless it was robotic, which then defeats the purpose of the jig.

             

            Maybe you can add a small heater to the hexapod to heat up the loctite of each individual part after placing it. At least to cure it enough to hold the part in place and then the big heater can fully cure it.

              • Re: Hold part after adjusting part's position
                Bo DO

                Thank you Jamil Snead.

                 

                The parts can be held in the holes placed manually by the operator then hexapod will do only adjustment or

                in a jig then hexapod will pick them up, place and adjust, whatever is fine. I just need a jig or even a robot like you mentioned, but the robot will need to be accuracy because the tolerance for the concentric between part and hole are 30um (0.03mm).

                 

                By the way, do you know any mechanism that has brakes ? I have an idea as following:

                I will design (or looking for if available) a manipulator that has 6DOFs (parts need to be free moved). At each joint of manipulator, I will place a brake and a motor (for initializing original position so the hexapod can pick the endeffector and then adjust). After adjustment, I will brake all manipulator's joint and hexapod will then release the endeffector, the result is the part will be held in the adjusted position.

                Correct my idea and give me a better if posible.

                 

                By the way, heating individual part is not possible because it would slow down the process.

                 

                Thank you.

                  • Re: Hold part after adjusting part's position
                    Jamil Snead

                    It seems to me that if you had a 6DOF manipulator then you might as well just use that for positioning the part in the first place and get rid of the hexapod. But I am guessing that would be too expensive since you said using 3 hexapods would be too expensive. So I'm trying to think of something that would be inexpensive.

                     

                    Building off of your 6DOF manipulator idea, you could possibly have one that had brakes only and no motors. The manipulator would start collapsed and the operator could load the part in and lock it to the manipulator, then the hexapod could grab the part and position it. Then the brakes could engage to hold the part in place while the hexapod moves on. Then after the adhesive is cured the operator could unlock the brakes and disconnect the manipulator and let it collapse again.

                     

                    Or along a similar train of thought, maybe the manipulator joints could just be friction joints that are stiff enough to hold a part, but still weak enough for the hexapod to move while positioning the part. After the adhesive is cured the operator could disconnect the manipulator as mentioned before and reposition the manipulator to the starting position and load in the next part.

                      • Re: Hold part after adjusting part's position
                        Bo DO

                        Thank you Jamil Snead.

                         

                        Now I am on the way implementing these ideas. Well, friction joints seem to be hard to implement: manufacturing ability, life span.

                        I am thinking more about locking and collapsing joints. Could you give me some examples?

                          • Re: Hold part after adjusting part's position
                            Jamil Snead

                            I didn't have any specific examples in mind, but I was just thinking you could use a brake like the kind that come on electric motors with brakes. I don't actually know for sure if you can buy them separately but I assume you can.

                             

                            You could also consider something like the felxible locking arms that are used to hold dial indicators.

                            I don't know if they make electric or pneumatic versions though.

                    • Re: Hold part after adjusting part's position
                      Avadhut Racharla

                      Hi Jamil,

                      Can you post Plan View of your layout if, you had put some arrangement of the parts and your Hexapod.

                      So we can  discuss, or have a brainstorm session, also for your part to fix position kindly specify geometry.  Round shape or some arbitrary shape.