11 Replies Latest reply on Nov 19, 2014 1:38 AM by Jared Conway

    Setting up Vacuum Simulation

    Patrick Hands

      Hi,

       

      Im new to this so I hope someone out there can help me as I am quite stuck. I am designing a duel manifold for an end of arm tool for a six axis robot which is aimed to reduce the tubing entering this tool. I have attached some images of the manifold so you can visualize it. The highlighted pink section is to be a vacuum manifold where the one inlet on top is joined to a vacuum manifold to draw a vacuum through the 4 outlets on the bottom. This bottom will be then sealed with a gasket to a base creating an air tight lock. there is then 16 individual nozzles attached to the base fed by this vacuum to pick up light plastic objects.I want to run a simulation to visualize the flow in the manifold and measure the draw at in each of the four areas on the base to see are they equal. You can ignore the curved tubing as that has a different function which I have already solved.

       

      How would I go about setting this problem up?

       

      I have attached a step file incase anyone needs a better look.

       

      Hope you can Help

       

      Patrick

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        • Re: Setting up Vacuum Simulation
          Chris Michalski

          If I understand correctly what you would likely want to do is a flow simulation with 1atm outside of the cavities and a low pressure at the end of the tube/port.  You will need to define the distance this part is away from the surrounding parts.  The flow will be much different when in open air vs if it is 3mm from a flat plate.  The resistance to flow from the environment in will dramatically affect the uniformity from branch to branch.

          I would make an open top box - length and width the same as your block and mate it below.  The depth should be the distance from the surface supporting your plastic parts will be.  (you may need to run this parametrically to vary that height to ensure that as the system approaches the surface the flow remains uniform).

          Then set the interior side walls of that box as boundary conditions at 1atm (assuming that exposed to true ambient).  Leave the bottom as this needs to be a solid surface without air flowing through it.  Then set a BC of however much pressure at the suction connection.

            • Re: Setting up Vacuum Simulation
              Patrick Hands

              Hi Chris,

               

              Thanks for your reply. I understand what your getting at it alright I think. Ill just attach these two images as well just to make sure you fully understand the problem and the same set up will work. These images shows the base (in transparent) and the nozzles. You can see how the curved manifold I told to ignore attaches directly to the nozzle and flows down the center. The vacuum then fills in on top around this. Does this paint a clearer picture? the end of this nozzel is what picks up the plastic parts.5..PNG4.4.PNG

                • Re: Setting up Vacuum Simulation
                  Chris Michalski

                  Okay... so pink seals to transparent view the dark grey gasket and the pink cavity draws a general vacuum?

                  Then the transparent tubing draws a further vacuum to lift the plastic parts until they seat on the upper surface of the pink cavity?

                   

                  Or is the single feed of the pink for makeup air as the little tubes draw a vacuum?

                    • Re: Setting up Vacuum Simulation
                      Patrick Hands

                      The pink cavity draws a general vacuum.

                       

                      The transparent tubing can be ignored still as this is a complete different dosing system.

                       

                      the vacuum will draw up through the pink cavity from the four out lets as seen in the first message. the manifold is joined to the transparent base with the dark gasket between them. each outlet on the bottom will draw a vacuum up four nozzles until the plastic parts are stuck to the nozzles. the tool then transports the parts to another station where the vauum shuts on and the parts fall off.

                        • Re: Setting up Vacuum Simulation
                          Chris Michalski

                          I must be missing something. 

                          Is that green gasket one continuous sheet with a hole over each plastic part?  So the pink butterfly is a vacuum cavity but sucks through 4 holes, 1 above each plastic part?  Perhaps a cut through one of the plastic parts to verify that.

                          Or are the wireframe parts at the bottom the nozzles and not the plastic parts that will be picked and dropped.  I just want to make sure I understand what comes apart to help setup where your boundary conditions are.

                            • Re: Setting up Vacuum Simulation
                              Patrick Hands

                              Try these images chris I took away most of the stuff and have just left the manifold the gasket and the nozzles. So remember the gasket seals the base to the manifold. The gasket also has the butterfly removed and the base has the same indent. the vacuum draws from the top and causes a vacuum to fill this void inside the butterfly. the four nozzles are inside this butterfly and they have holes in the top of them as seen in the images which run though the nozzle. The vacuum travels through these holes. so basically the vacuum draws from the top, fluids the butterfly, equalizes between the four nozzles and then draws up each so i suppose the top is one BC and each nozzle is going to be another?

                               

                               

                               

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                                • Re: Setting up Vacuum Simulation
                                  Chris Michalski

                                  Yes, if these are all bolted together and sealed then your exit BC would be the negative pressure or at the top of the butterfly port and your inlet would be the pressure at the holes for each nozzle.

                                   

                                  Now that I understand the entire situation: what are you trying to solve for?  Because once a part is picked up, the flow through that nozzle will decrease due to increased resistance because of the close gap, and the flow through others will increase so the negative pressure would increase at the others until all nozzles are stuck to a part and the highest negative pressure is achieved.  Even if they are not completely uniform, the negative pressure will increase with each part attached right?

                                  But if your vacuum pump is volume limited then that could be your exit BC (max flow rate out) to determine the velocity and pressure at the nozzles.

                                    • Re: Setting up Vacuum Simulation
                                      Patrick Hands

                                      Right we on the same page now at least.

                                       

                                      Yes you are correct when one part is picked the flow will decrease in this nozzle and increase in the others. but the system shoud pick 32 parts simultaneously and transport them before dropping them. We have this technology already in the plant I design for and it works. I am just changing the manifold design so need to make sure it dosn't effect either.

                                       

                                      What I need to check is that once the vacuum starts that I am getting the same negative pressure at each nozzle and the value of this pressure to ensure it is enough to lift the plastic components I want to.