Why does the weigh/fill machine need compressed air?

Posted by on

I received a very good question from a prospective weigh/fill customer today about why our weigh/fill machine needs an air connection and others do not.

This was my response:

Strictly speaking, an air connection is not mandatory. If you have one though, you’ll fill bags about 30% faster.

Roasting coffee isn’t necessarily all about speed, but packaging definitely is.

The fill chute gate is programmable to kill the momentum of the seed flow into the weighing hopper. With the gate, you can run a much faster rapid advance, slam the gate shut at the last possible second, and then dribble feed past it a couple of grams to top off the bag.

Without the gate, the rapid feed setting will overshoot your target weight. Your only recourse is to slow your rapid feed and step it down sooner to a dribble feed. This forces a longer cycle time to maintain accuracy.

Beyond that, for ground coffee, we also use air for the programmable pneumatic vibrator mounted on the underside of the discharge chute. This is set to vibrate the hopper every discharge cycle to eliminate ground coffee retention in the shallowly drafted 60mm diameter discharge.

We used that shallow draft to raise the outlet high enough so you don’t have to stoop to fill a bag. Then we made the outlet narrow enough to make it easy to fill even very small, single dose bags. It also pretty much eliminates the need for a bench top bag “shoe” tool to open the bag before filling.

Smart, right?

If you think of any other questions, give me a call.


← Older Post Newer Post →

Leave a comment



Notes from the Cupping Table: April 2024

April seemed to go by in the blink of an eye. Even with a break from our group roasting classes, our team stayed busy! A...

Read more

Engineering the New MCR-2E 2kg Electric Coffee Roaster

Years ago, when I first launched Mill City, we built electrically heated 500g and 1kg electric roasters. For a couple of our early years we...

Read more


Request a quote to get freight costs to have your equipment delivered to your location.

CALL (612) 886-2089

Our office team is available Mon-Fri, 9am-5pm (CT) and messages are monitored nearly around the clock.


Reach out to us via our contact page and we'll get back to you asap.