We recently added a new product to the syn webstore. Its a 4 pack stepper driver heat sink kit. These are not needed with TinyG or grblShield when using motors up to about 2 amps per winding. However at 2 – 2.5 amps you really should be using at least the heat sinks and possibly a fan as well. You can pick them up for $5.99 for the first month. After which the price returns to normal $6.99.
We are using these heat sinks for the v90 Probotix mill we have. We have some beefy stepper motors on this machine. These little heat sinks help get that extra out of the drivers.