outer corners not sharp

Ive had to adjust my XY jerk and accel settings in Marlin and my corners are now kinda blobby looking rather than sharp. If i up the jerk and accel the corners look great but the machine will miss a step eventually while printing. I understand its the extruder lagging behind when the print head slows down for a sharp corner and ends up over extruding on the corners. But what can be adjusted to get things back to printing good corners?
Running a Prusa I3 with wades extruder.

Unfortunately, that's more or less one of the compromises that exist with this sort of printing. There have been attempts to compensate for this, but they are either not popular (the 'advance' algorithm that seems to be permanently labelled as experimental) or not generally available across different slicers (coasting might come under this category, but I don't have it in my slicers, so I'm not sure).

You can reduce the effect by

increasing the jerk. If you get missed steps at very low jerk settings there is probably another problem that needs fixing,

lowering the acceleration, so that there is more time for the extruder to change pressure,

reducing the print speed so that the ratio between the fastest and slowest speeds is less,

filleting the corners so that the print head maintains a higher speed.

I use the last approach whenever possible, but sometimes you need a sharp corner for functional reasons.

I did a lot of tinkering with parameters this evening and turned out i was over extruding by about 10% to start with. It got much better once that was set right.

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JamesK
There have been attempts to compensate for this, but they are either not popular (the 'advance' algorithm that seems to be permanently labelled as experimental) or not generally available across different slicers (coasting might come under this category, but I don't have it in my slicers, so I'm not sure)

From what little I've looked into the "advance" algorithm code, I think it attempts to create an extruder advance by very quickly jamming in extra steps at the beginning of a motion and then taking them back out at the end of the motion. Unfortunately, this usually results in the extruder skipping steps. Any sort of advance algorithm needs to be baked deep into the bowels of the motion planner (probably requiring a total rewrite of the motion code), or else implemented as a separate layer of timing control between the existing motion planner and the physical step pulse outputs (less daunting but maybe not so efficient). 'm too much of a programming has-been to implement either, but I'd be very interested in collaborating with anyone more facile with the guts of the firmware.

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LoboCNC

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JamesK
There have been attempts to compensate for this, but they are either not popular (the 'advance' algorithm that seems to be permanently labelled as experimental) or not generally available across different slicers (coasting might come under this category, but I don't have it in my slicers, so I'm not sure)

From what little I've looked into the "advance" algorithm code, I think it attempts to create an extruder advance by very quickly jamming in extra steps at the beginning of a motion and then taking them back out at the end of the motion. Unfortunately, this usually results in the extruder skipping steps. Any sort of advance algorithm needs to be baked deep into the bowels of the motion planner (probably requiring a total rewrite of the motion code), or else implemented as a separate layer of timing control between the existing motion planner and the physical step pulse outputs (less daunting but maybe not so efficient). 'm too much of a programming has-been to implement either, but I'd be very interested in collaborating with anyone more facile with the guts of the firmware.

Both Sailfish and RepRapFirmware implement working pressure advance algorithms. As you say, you can't just jam extra steps in at the start of extrusion and take them away at the end. For some moves, the extruder drive has to retract instead of extrude filament near the end of the move.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].