Sit down and torch the soleus.
Bent knees shift the work to the soleus, so chase a deep stretch and a tall finish.
With your knees bent and pinned under the pad, the gastrocnemius goes slack and the soleus underneath has to press the load alone. The machine's fixed path lets you focus entirely on the two things that grow calves, a deep stretch at the bottom and a tall, paused finish at the top. It earns its place because the soleus does a huge share of lower-leg work and almost nobody trains it directly.
Knee angle. Straight legs let the big gastrocnemius drive the movement, bent knees hand the job to the soleus underneath. They are different muscles, which is why complete calf training includes both.
You are probably loading too heavy and bouncing out of the mid-range. Drop the weight, let the heels sink into a full stretch at the bottom, and press to the tallest point you can hold for a beat.
Calves recover fast and the soleus especially tolerates frequency, so two to four sessions a week is reasonable. Consistency over months matters far more than any single brutal session.
