Biomek Guide

Streaming Biomek

Friday, August 24, 2007

Drops at top of well after pin tool aspirates liquid

This post was from David Carter

Pin Tool Position error in 384 well plates and solution
We had a problem with pins scraping on the edge of 384 wells, leaving droplets of liquid on the edge and depositing less than needed.

Discovery: Slowed the robot down to 10% (Instrument/ Hardware Setup/ Pod 1/ Additional settings/ Speed limit 10%)
Tripped the light curtain with the tips down. Shining a flashlight on the wells showed the pins were front and slightly left of center; pressed against the well edge. Several pins did not fully fall into wells during slower descent.

Possible Cause: labware definition was incorrect

Discovery: Manually moved head to determine good central position (Instrument/ Manual Control/ Advanced/ Pod 1/ Moved Right 0.02 then another 0.03. Moved back -0.05 then another -0.05 by typing numbers directly into fields rather than using arrow keys. Remember minus sign)

Solution: Edit labware definition (Project/Labware Type/ double click on in this case AB Gene 1055 384/Wells_1/Well offset changed from x=1.245 to 1.295 y=0.845 to 0.755)
After fix, tips hit center and day's work completed.

Outstanding problem: On 8/24/07 when writing up this post, x and y numbers had defaulted back to 1.245 and 0.845. Don't know how to make changes stick.

Outstanding problem: I think the labware definition offsets refer to distance from top left corner of plate, but we had wedged the plate bottom-right to eliminate the little bit of slop in placement. Should we always push the plates back and left instead?

Possible alternative: Framing error. I did not try re-framing the deck, which is running fine in all other applications.

end of post

1 comment:

Andrew Defries (Cutler Lab) said...

Hi David,

Thanks for the post. I discovered the same thing yesterday and re-defined my plate definition. I’ve had no problems with drops as of yet, so the definition still works. In general when people are doing really detailed work they should sit down and double check if their labware is defined properly. I don’t know if the labware was fine to begin with and if it went off due to a deck shift, or if no one knew that the drops were being created all this time.