nylonRigging

...LoL . .HaaHAHAHAHAHa .

What (wizcraft said ) .. slow down the rpm on moving through the thicker thicker materials and trying small adjustments like recommended . ( i no expert ) and It really hard to diagnose stitch problems without actually having hands-on and sitting in front of machine . So I will throw my guess in the mix . unless I missed it somewhere ? . your saying it just a 'Bottom-feed' Consew ? , but what model is it ? , and the needle 135x5 or a 135x17 or bigger ? You saying with 4 loose pieces of material, the top thread breaking, but how thick of a stack is it with 4 pieces ? this--> Assuming you already have proper Pressure-foot tension and thread tensions on Top and Bobbin thread ? , and also using the proper Needle size/length for your material ? I think your statement ..." I can rotate the machine by hand and all is fine ". is the giveaway . Your just asking your Machine to do to much . You may just be pushing the machine and needle to it's design limit, Plus . If just Bottom-feed model and not Needle-feed or Walk . with stacking the 4th piece of material on ? . And Nothing wrong with Bottom-feed and I still run 2 of them daily . Sometimes it is just plain hard for a Bottom-feed with keeping good tension and stitching on thick multi-layers . that is where a needle-feed or walk shines . hold multi layer materials firmer with stitching motion for no deflection and holding proper presser and thread tensions . .

( imho ) if looking for that edge over a everyday 550 watt, 4amp servo drive . Go for a ( Consew CSM3000 ) it a 750 watt and pulls 6amp, and It really improves the low rpm torque when your just bumping the needle threw some heavy or stiff materials with staying very smooth on the slow rpm light pedal pressing . it also has a couple accessory plugs for future position sensor .. with speed control on the on/off switch .. ' like your asking for ' . and break is released for easy moving of needle with hand . .

sent you PM ....thanks