Mushroom Substrate Bagging Machine: Sizing a Drive for Hard Accel and Decel

The machine fills bags with mushroom substrate — the blended, fermented compost that grows the crop. It is a single machine doing four jobs at once: conveying material, metering it, filling the bag and compacting the fill so the bag is dense enough for sterilisation and inoculation downstream. The barrel across the middle of the machine houses the metering mechanism.

Inside that barrel is an auger — a screw conveyor. Its rotation pushes material from the bottom of the hopper to the discharge outlet, and the amount delivered is a function of how many turns it makes. That makes portion control an electrical problem rather than a mechanical one: count the turns, or run the auger for a set time, and every bag comes out at the same weight.

The duty cycle is what makes the drive selection interesting. The auger has to fill, then reverse to clear, and it does this continuously through a shift. The machine's specification called for forward running at 50 Hz and reverse at 30 Hz, with acceleration in 0.30 s and deceleration in 0.10 s. A 0.10 s deceleration on a screw full of compost is an aggressive demand — the drive has to absorb the kinetic energy of the auger and its load quickly, and it has to do so thousands of times a day.

The motor is a 7.5 kW, 1500 rpm machine drawing a full-load current of 14.2 A. Yolico specified a YD280T4-11G/15PB rated 25 A. The drive is deliberately well above the motor's nameplate current, and the reason is the application rather than a safety margin: a duty that reverses and stops this hard needs current headroom that a drive sized at exactly the motor amps would not have. This is the same logic that applies to any indexing or metering axis, and it is worth stating plainly because oversizing a drive for a steady fan or pump is waste, while undersizing one for a hard-ramp indexing duty is a warranty claim waiting to happen.

Commissioning was straightforward and is worth recording because the parameter set is a template for this class of machine. The drive runs on terminal command with a multi-speed frequency reference. Acceleration is 0.30 s and deceleration 0.10 s, with the time unit set to 0.01 s so those small values can be entered. Terminal DI1 is forward, DI2 reverse, DI4 selects the multi-speed step. On site the machine runs stably at 50 Hz forward then 30 Hz in reverse, and the motor responds quickly to the aggressive ramp profile. The recorded current, output frequency, DI1 and DI2 signals confirm that the drive is delivering the profile the machine was designed around.