cakephp 3.0 query not take required result

$table = TableRegistry::get('Mechines');
 $mechines = $table->find()->select(['Mechines.id',
              'sum' => $table->find()->where(['purchases.mechine_id' =>                         'Mechines.id'])->func()->sum('purchases.qty')
                ])->join(['purchases'])->group('Mechines.id')>toArray('assoc');
        var_dump($mechines);
        die;

SELECT m.*,(select sum(p.qty) from purchases p 
                WHERE p.mechine_id=m.id) AS numberOfFills,
                (select sum(p.qty*p.cost) from purchases p 
                WHERE p.mechine_id=m.id) AS revenue FROM `mechines` m