Unit Type vs Stack Type Flexo | A Real-World Selection Guide

The Most Expensive Mistake is Buying the Wrong "Skeleton"

In my 20 years of configuring printing lines at Newtop Machinery, I've seen a recurring pattern. Clients come to us asking: "How much is a 6-color machine?"

This is the wrong starting point. A 6-color Stack Type Machine and a 6-color Unit Type (Inline) Machine are completely different beasts. Choosing between them isn't about budget or color count—it's about your production reality.

One fits in a garage; the other needs a warehouse. One is perfect for double-sided burger wrappers; the other is the king of self-adhesive labels. Today, I’m going to share the internal logic we use to recommend the right structure to our clients, stripping away the marketing fluff.

1. The Truth About Stack Type: The Efficiency King

Many competitors describe Stack Type presses as "entry-level" or "old school." I disagree. They are specialized tools for specific jobs.

In a Stack press, the print stations are stacked vertically, one above the other.

• The "Space Saver" Reality: If your factory is in a city center with high rent and limited floor space, Stack is your savior. A 6-color Stack press might only need a 4-meter footprint length, whereas an equivalent Unit type needs 10+ meters.
• The "Double-Sided" Secret: This is where Stack type truly shines. Because of the web path, we can easily configure it for 4+2 or 3+3 printing (front and back) without complex, expensive turn-bar systems. For products like shopping bags, woven sacks, or wrapping paper, this is the most cost-effective structure.

The Limitation: Gravity exists. Ink drying distance between colors is fixed and relatively short. This makes it challenging to run high-coverage process jobs at ultra-high speeds without trapping issues.

2. The Reality of Unit Type (Inline): The "All-in-One" Factory

Unit Type (often called Inline) presses lay the stations out horizontally. This is the standard for the modern label industry.

• Modular Flexibility: The biggest advantage isn't printing; it's converting. Because the machine is long and horizontal, we can insert UV dryers, hot air, cold foil units, and die-cutting stations anywhere in the line.
• Registration Stability: For high-precision labels, Unit Type Flexo Presses (especially Servo-driven ones) offer better control over material tension between stations compared to older mechanical Stack presses.

The Limitation: It eats up floor space. You need a long, straight production hall. Also, changing from 6 colors to 8 colors later usually means physically extending the machine frame, which is a major project.

3. "How We Do It": Matching Structure to Your Product

When a client sends us a sample, we don't look at the colors first. We look at the application. Here is our decision matrix:

Scenario A: The "Fast Food" Supplier

Product: Burger wrappers, Sandwich paper, Flour bags.
Requirement: Cheap, fast, often simple logos, printing on both sides.
Our Recommendation: Stack Type. Why? You need to print thousands of meters of thin paper cheaply. You don't need complex die-cutting inline. The Stack press allows you to print Front/Back in one pass with a compact machine footprint.

Scenario B: The "Brand Label" Converter

Product: Shampoo bottle stickers, Wine labels.
Requirement: 4-color process images, gold foil, varnishing, and die-cutting.
Our Recommendation: Unit Type (Inline). Why? You cannot achieve this finishing quality on a Stack press. You need the long drying path for UV inks and the ability to add rotary die-cutting at the end of the line.

Scenario C: The "Heavy Duty" Industrial Sack

Product: PP Woven sacks for cement or rice.
Our Recommendation: Stack Type. These materials are tough and thick. The vertical structure of a specialized Stack press handles the tension of woven fabrics much better than a standard label press.

4. Avoiding the 3 Common "Rookie Mistakes"

In our experience, buyers often regret their choice because of these three oversights:

1. Ignoring Ceiling Height: Buyers measure the floor but forget the height. Stack presses are tall. We've seen clients having to cut a hole in their factory roof to fit the drying tunnel.
2. Overestimating Stack Capability: Trying to print high-end, photo-quality cosmetic labels on a mechanical Stack press. While possible with great skill, keeping registration tight is a constant struggle compared to a Servo Inline press.
3. Underestimating Inline Length: An Inline machine isn't just the machine; you need space for the unwind roll, the rewind roll, and the operator to walk around. A 10-meter machine needs a 15-meter room.

Conclusion: Let Your Product Dictate the Machine

Don't buy a Stack press just because it's cheaper. Don't buy a Unit press just because it looks modern. Buy the structure that solves your specific production bottleneck.

Still unsure if your product needs a vertical or horizontal setup? Send us your factory layout and product sample. Our engineers will simulate the production line for you—free of charge. Contact Newtop Machinery today.