[VIDEO] VFFS machine maintenance: How to change the knife blades on a stick pack machine

What are knife blades and what do they do?

First, let's talk about the cross-seal jaws.

A set of horizontal heat seal bars located in the cross-seal jaws creates the horizontal (cross) seal by pressing and bonding the film together between the heated seal bars of the closed jaw.

As bags are produced on a stick pack machine, each bag is still connected to the one created after it. To separate the bags, once per cycle the cutoff knife will move forward quickly from in between the cross-seal jaws, making a clean cut to release the current bag from the next one.

How to change the knife blades on a stick pack machine

CAUTION: Before performing a repair, be sure to follow your organization's Standard Operating Procedures for safety, lockout/tag-out, and PPE guidelines. Do not perform work in the machine compartment of an energized and initialized machine. Do not bypass any safety switches or relays. Failure to use caution while working on the machine by not using adequate safety procedures could result in injury or death. Only trained and authorized personnel should perform machine repairs. Viking Masek cannot foresee every instance where possible machine damage or an injury could occur. Work on the machine at your own risk. If you need assistance, schedule a service visit with one of our authorized technicians. 

To gain easy access to the shear blades, we first need to remove the cutting deck.

1. To remove the cutting deck:

1. Disconnect all the air lines and optionally installed sensor connections that connect the cutting deck to the machine. You may want to mark these for when you re-install the cutting deck, they are connected to the correct location.
2. Pull down and turn the quick disconnect pins that lock the cutting deck to its mounting bracket on the machine, to release the deck from the bracket.
3. With two people for safety, slide the cutting deck forward and lift it off its mounting bracket.
4. Place the cutting deck on a sturdy table upside down for easy shear blade access.

2. To remove the shear blades:

Warning: Blades are sharp, use caution to avoid injury.

1. With a 5mm hex wrench, loosen and remove the series of m6 bolts holding the shear blade to its pivoting mount.  The pivoting mount is spring-tensioned. While removing the bolts, press down on the back of the mount to keep the mount parallel to the shear blade, relieving the sideways pressure on the bolts. Remove both blades
2. With a 4 mm hex wrench, remove the m5 flat head bolts that attach the anvil blades to the cutting deck.
3. Install the new anvil and shear blades. When installing the new shear blades, push down on the pivoting tension mount while tightening the mounting screws to avoid cross-threading them. 
4. Once the blade is secured, check to ensure that the shear blade guide rides on top of the anvil blade throughout its full motion by manually engaging and disengaging the blades.

Note: It's a good practice to have a spare set of clean, sharp blades to install to minimize machine downtime. To order a spare set of blades, contact our parts department.

3. Re-install the knife deck:

Warning: Make sure your fingers are clear of the closing blades; severe injury could occur.

1. With two people for safety: Put the cutting deck back on the mounting brackets of the machine and seat the disconnect pins into the deck to secure it. Make sure the quick disconnect pins are fully seated, and the deck locks into place. Try sliding the deck back and forth slightly to check.
2. Re-connect the air lines and electrical connections removed in step 1.
3. With the machine energized and initiated, test the knife deck for proper operation with the test button on the PLS page (Allen Bradley), or the test button in test mode (Siemens).

Recommendation: Keep spare knife blades on hand

Over time, with use, the knife blade will get dirty or start to dull and you will notice a dip in cutting performance. Many packaging machine owners choose to have an alternate blade (or two) ready to rotate in to keep production going and minimize downtime. If you do not have a spare blade, contact your packaging equipment manufacturer's spare parts department.

Watch more packing machine maintenance videos

Check out the other videos in our VFFS Maintenance Quick Tips series:

How to set up the slitter blades on a stick pack machine >>

How to set up automatic film tracking >>

How to set up film registration & train photo-eye sensor >>

Stick to a comprehensive parts & maintenance plan

Machine preventive maintenance and managing your spare parts inventory effectively are two of the most important things you can do to ensure a long, productive life for your packaging line. Download our comprehensive VFFS machine preventive maintenance planner for daily, weekly, monthly, and yearly recommended maintenance tasks: