I'm looking into making a type of feeder arm, probably 2 axis, that will have a vacuum gripper on the end of it and have searched on google but not knowing what to search for is proving to be a problem.
I was wondering how the gripper knows when to turn on to pick a small piece of paper up off a stack of paper, I could add a sensor at the top of the stack of paper to accomplish this but when the top of the stack starts going down the sensor will stop working as the gripper will be above the top of the stack. I could complicate the design by adding an elevator to keep the top of the stack at the same height for the gripper but there must be a more efficient way of telling the gripper to keep moving until it hits the top of the stack but not sure how or what to search for.
I did see something about a pressure sensitive resistor but looking at them I don't know how you would use it with a vacuum gripper. I also saw proximity sensors which I use in a couple other projects I have done but they read metal surfaces or magnetic fields and since this is paper I don't know how it would detect it.
Any nudge in the right direction to accomplish this is appreciated.
Try and think out of the box
Look at how printers move paper?
Use a roller ?
Blow it off with air ?( direct or in tube )
It’s worth saying what the project is and why you want to do it
Search "pick and place vacuum"
No criticism at all but...
Is forum becomming an everything fix institution? A design bureau? An alternative 911?
"How do I cut gras", "cook a certain dinner"?
It's getting tireing being notified for questions type "mama help".....
Are you thinking of a printer like my HP printer? It keeps raising the end of the stack of paper until the rubber rollers actually move a page into the throat of the feeder. The sheet blocks light, so the printer knows to engage the rollers in the rest of the path.
It certainly has been a kitchenful of Stone soup recently.
Thanks. new to me!
@hammy I have a hot glue dispenser and would like to use a little arm to pick up a paper disc and set it down underneath the dispenser. I'm trying to do something cheaper than buying an expensive robotic arm to move pieces underneath the dispenser. After the paper disc has glue on it I will use the same arm to drop a small plastic disc on top of that.
I bought a cheap vacuum gripper off eBay a long time ago and it was simple enough to turn the pump on and pick things up with it using my hand as the feeder arm, but what I was looking for is how a robot grabs something with a vacuum gripper without slamming into the piece it is picking up, do they have proximity sensors or pressure gauges in the vacuum gripper or some other way that would help answer my question.
@JCA34F I did search pick and place but couldn't seem to find anything but parts to buy without and explanation of how it's used.
@Railroader when I was learning how to use Arduino years ago this forum was an immense help with helpful people handing out advice on any problem someone would have, they gave crumbs to help someone work their way through their question so they could learn more but since covid snarky remarks such as your's have led me to not want to ask question's on here anymore.
@Paul_KD7HB I thought there would be a way of telling the feeder arm to go to the paper stack without slamming into it with some type of sensor the way a robot arm would do it, which I have no idea how a robot arm does it. I thought about putting the stack on an elevator of sorts but was hoping for something simpler.
This issue here might simply be that you think robot arms have some kind of built in sensing feature as a general category. This is not correct! A typical robot arm will absolutely smash through whatever, or destroy itself trying to reach, anything it's programmed to. They don't have a generic sensor that defects pressure and has an understanding of the external world. They are just a bag of motors position encoders and limit switches in a useful configuration with a microcontroller for processing gcode, as a general rule.
Maybe some of the advanced ones have over-torque protection but it's not a generic feature of the class or anything like as fine as what you'd need for this project.
Thanks @jaguilar84, I see them picking up things in videos all the time and just thought they must have something that helps them not slam through the object they are picking up. I see designs for grippers with force sensors but can't seem to find a company that sells vacuum grippers with force sensors. I was hoping to get a nudge to something but maybe I'm looking for something that doesn't exist.
Will depend a lot on what type of vacuum gripper you have. Is it possible to mount a microswitch near the gripper to detect the paper? Can you monitor the vacuum and detect the change in vacuum when the paper is gripped? Can the gripper be mounted so that it is free to move vertically, then just lower the arm as low as needed for the bottom of the stack of paper?
I can tell you that the pick and place machines I had used a vacuum pin to pick up components to place then on circuit boards. The height of the pin was stopped when it contacted the top surface of the component and it knew that because the sudden vacuum increase. Part of the initial programming was to either input the height of the component or let the computer determine the height when first being programmed for that board, which was more convenient.
I don't know the details about how vacuum p&p machines work but there are probably a lot of ways to skin this cat. I have no idea the engineering behind this but you have proof by example that it is possible in the sense that real pick and place machines exist. Dig in to the problem and I am convinced you'll find something!
@david_2018 I didn't think of a microswitch next to the gripper but when I try to lay the paper back down the microswitch will already be actuated.
Not sure about your second suggestion.
I started thinking about your last question when I came across load cells to detect strain on the gripper, could be a possibility.
@Paul_KD7HB I haven't seen and vacuum grippers with pins yet in my searches but it kind of goes with david_2018 and using microswitches, I will continue searching.
Thanks
Elevators are pretty common solution for simplifying the and optimizing the motion of the arms. You can feed the stack up to a limit switch. Alternately, you could put a sensor somewhere else, on the gripper to measure the distance to the stack or above the stack to measure the height of the stack, and compute a stopping point for the arm.
Just by way of an FYI, in most such cases the robot is controlled in one of two ways:
- If it's a demonstration, the path that the robot is taking might have been created by moving it to each desired endpoint manually, recording the endpoint, then having a computer or the robot recalculate the movements so that the optimal paths can be used. The robot can sense its position in 3-space down to a very precise location, which is necessary to complete programmed tasks, so it can also remember desired endpoints.
- In industrial settings where a robot arm is part of a manufacturing line, either the work pieces are positioned very precisely, or the robot is receiving information from the sensors in the manufacturing line about the position of the workpiece so it can manipulate it.
- In academic settings, people are working on feeding robot arms information through cameras and ML. This is probably also happening in some industrial settings but I guess it is less common. I'm not an expert this is just some background knowledge I picked up while designing a lego robot arm that could do kinematics and inverse kinematics.
Any chance of a picture or at least a drawing of what you envision?
How about monitoring the pressure and stopping the arm when the pressure changes (as I assume it will when the suction port is blocked by the paper).
Trying to be charitable, I think the problem is the way a lot of people are learning how to do "electronic stuff" these days. Back when I (and I assume you) learned, we'd learn basic stuff like how simple circuits work and how to wire them together safely. We'd add to that body of knowledge over time as we tried more and more advanced projects. So, it was pretty easy to identify where the gaps on our knowledge were and what to do to learn to close them.
When you learn starting from pretty advanced topics like most YouTube videos and tutorials show (cuz who wants to learn silly stuff like how to light an LED with a battery and a resistor), then you miss a lot of the earlier, more basic steps. Stuff that seems obvious to us, like "add a microswitch to the vacuum head so it can detect the top of the stack" is no longer obvious since the videos skip over those details.
At least, that's my theory for now.
So, OP. You need a detector on your gripper. It can be as simple as a microswitch that triggers when the the gripper goes down and hits the top of the paper stack.
Well written! In the old days the start was learning basics and then figuring out what the knowledge could be used to.
Nowdays new people start from the other end, thinking everything can be made. Just throw some libraries into the melt.
Getting knowlledge in measuring technics is also extremly valuable.