I have attached the basic design. to get the briquttes without break.
To make them harder i Think you need to add very small adhesive type of additive.
Well if it up ---- > down process then it will have the top area to be lesser than lower area .
As when the die returns it can easily get away without breaking the corners.
The Variation of the top and bottom can be handle with close proximations
Well Bro Seems that You did nt add any kind additives to Strengthen your briquette.
As per i think you have to add some additives at mixing stage.
This will strengthen the briquette and make it hard.