Hi Everyone.
I have an issue with my Fluent RGA lifting the lid off my petri plates.
The vectors are all correct to retrieve the plate (with lid) from my stack, but when it moves to lift the lid off for picking I get an “object not gripped at source location” error. Even though it did lift the lid off. This seems to be a terminal error and I then have to start again. I have reduced the grip force to lowest possible to hold the lid, but still get the error.
What percentage is your force?
Also have you tried to adjust your grip delta? (Basically the ± for a tolerable grip range)
Also the definition is decent correct? (including those in the robot vectors)
Lids of Petri dish plate are quite flexible when you apply force while gripping, perhaps you bend the lid while gripping and therefore the force threshold may not be reached within the expected move range. Try to reduce the Force attribute of the petri plate lid labware definition as low as possible (perhaps around 10%) or check a slightly higher or lower grip position on the labware. Tecan has ‘special’ RGA fingers for petri plates, do you have these? The very bottom part of the fingers that gets in contact with the labware is made of metal and thicker in front and back so it better fits the round shape of a petri plate (instead of the straight bottom part with the small rubber pads)
Hi @Rowland, are you using an Execute Single Vector command to pick up the lid? What you are likely experiencing is the gripper reaching the close distance prior to the RGA reaching the grip force. Either the force or close distance will likely need to be adjusted, or potentially a combination of both.
Hi everyone.
Thank you for your responses.
@luisvillaautomata
Grip force is currently 10% and the grip delta is 5mm. I have been working with the predefined definitions for the RGA.
@Snowball
The lids are bending while gripping. I have tried reducing the grip force. I will try adjusting the grip position to a little higher so that there is more resistance. I am using the petriplate fingers. I see that there is also a ledge above the rubber pads. I had thought of trying to close to a point then list to have the lid resting on the rubber pads.
@EricScheitz_Tecan
Yes. I’m using the Execute Single Vector command. it is part of a loop where plates are brought to the petriplater then returned to a different stack as well as from the stack to the Pickolo and back to another stack. (In one side and out the other). I’ll have a look at the close distance and make adjustments there as well.
Hi Rowland,
10% force is less than I would unusual use. Increasing it might help.
Also if you grip closer to the “frame” of the plate/lid, it will flex less and then be easier for the griper to detect the lid
This has helped me before, I hope it will help you
Thank you. I’ll try increase the grip force as well as grip closer to the top “frame” as you suggest.
I second this, usually 30-60% is the sweet spot. When I go too low, it also throws this error.
Hi @Rowland
I use the pretriplater, too. Also with Single Vectors.
For VWR and GreinerBioOne labware I work with 5% grip force for the lid. I close the gripper to 90mm. That works fine for me.
If it continues to be a problem you can remove the lid, move the plate, then place the lid back after the plate is at its destination. I have to do this in certain situations where reliability is paramount
Hi Everyone.
Thank you for your input.
I will change the gripper close position to 90mm as well as to see if increasing the grip force will help.
Unfortunately, our plates are in a stack that is not accessible as we have a BSL2 hood that makes it difficult to get to the stack once the door is closed.
What’s your opinion on the pickle system? We’re looking to get one in 2025.
Hi @rhcole
I have been happy with the Picolo system. We have it set up with two fluorescent lamps for screening. The only issue I has was in the early days of testing, where we’d loose coms and the robot would stall picking. We solved this by not using a hub for the USB connection to the Picolo and disabling powermanagement for the all USB ports.
Did you resolve this issue? Another cause of your error could be if the bounding boxes are not defined correctly.
Hi Joe.
It was a system glitch where Tecan had to change something when the RGA stops for the next command. I then had to refine the grip force, speed and width.