You have used your Dyson too long without thorough cleaning - Here's how.
Obtain a torx screwdriver, or a set of torx bits, you will need to select the correct size when you come to remove the screws. They are all the same, so you will need only one.
Take the radix catridge off the machine as if to empty the clear plastic sucking container. (From here on your hands get dirty).
Firmly pull out the inner conical funnel. Here it is removed. (Note I am showing photos of the cleaned device).
Next remove the three torx screws. You can see the recesses these are hiding in in the above picture they are the holes without nozzles. The screws are self tappers screwed into plastic, and are easy to undo.
Remove the lower part of the housing and its rubber sealing ring.
Note the orientation for when you put it back together. The above photo shows the lower bell housing opened away from the top part as if opening a door. It's pretty hard to put them together incorrectly so don't worry too much.
You now need to remove two further screws which are recessed into the sides of the inside of the housing. Their positions are easy to find as they are the only recesses large enough, and match up with two curves on the outside of the housing. They are at the left and right in this picture.
Next you need to remove the handle at the top of the radix housing that you normally use to pick up the device.
Remove the two screws deep in the tubular holes you can see at the right of this picture.
Then slightly lift the end of the handle at the end where you removed the screws.
Next use a screw driver to push the other end of the handle off the housing away from the end where you just removed the screws.
This picture shows the handle pushed out (or ready to be re-attached)
Finally remove the screw revealed by removal of the handle.
You can now lift off the top housing revealing the wormy looking cyclone device This is where most of the **** builds up.. Lift this off and clean everything out thoroughly with water.
Make sure everything is clean and dry!!!!
Re-assemble in reverse order.
Now your Dysin is restored to original sucking power.