VLM vs ASRS: Which storage system fits your warehouse?

What is a VLM?

A Vertical Lift Module is an enclosed automated storage unit that uses your building's ceiling height instead of floor space. It stores inventory on trays inside a compact column and brings the right tray down to the operator at an ergonomic pick height — so nobody is walking the aisles or climbing to reach stock.

Best suited for:

• Spare parts storage — keeping a wide range of parts organized and easy to retrieve without dedicating floor space to shelving.
• Manufacturing — delivering components and tooling to the line without sending operators to a separate parts room.
• Maintenance operations — giving maintenance teams fast, traceable access to the part they need, when they need it.
• Tool management — tracking which tools are stored and issued, cutting down time spent searching or reordering.
• Healthcare and lab inventory — storing smaller, high-mix items like supplies and lab materials in an organized, traceable system.
• Space-constrained facilities — sites with limited floor space but available ceiling height.

Compared with open shelving, VLM's main advantage is floor space — it stores inventory vertically in an enclosed column instead of requiring open aisles and ladder access, recovering space that traditional shelving would otherwise use for the same inventory.

For long, flat or bulky goods such as bars, profiles and panels, ICAS also offers the MAXI VLM.

How a VLM Works

Most VLMs follow the same basic cycle for every pick or put request:

1. Request — An operator requests an item at the unit, or the request comes through from a connected WMS.
2. Locate — The system identifies which tray holds it.
3. Retrieve — An internal mechanism retrieves the tray from storage.
4. Deliver — The tray arrives at an access opening at a comfortable working height.
5. Pick or Put — The operator picks or places the item, and the system updates the inventory record.
6. Return — The tray returns to storage, ready for the next request.

What is an ASRS?

An Automated Storage and Retrieval System is a broader category — typically a racking structure served by cranes, shuttles, or robotic retrieval mechanisms that move pallets, totes, or cartons in and out of storage automatically.

Best suited for:

• High-volume distribution centers
• Operations needing very high throughput
• Facilities storing palletized or cartoned goods at scale
• Businesses planning significant future growth

How to decide

1. What are you storing? Small parts/tools lean VLM; pallets/high-SKU cartons lean ASRS.
2. How constrained is your floor space? If floor space is the biggest constraint and ceiling height is available, VLM often wins.
3. What's your throughput requirement? Very high pick/put rates at scale typically favor ASRS.
4. What's your growth trajectory? ASRS is often designed with future scale in mind; VLM units can be added incrementally.
5. How much do accuracy and traceability matter? If every pick needs to be right and every item traceable — spare parts, tools, regulated supplies — VLM's tray-to-operator workflow is a strong fit.
6. How much time goes into walking and searching? If operators spend a large part of their shift walking aisles and hunting for small items, a VLM brings the stock to them instead — cutting travel and search time.

Whichever way you lean, check ceiling height early. A VLM needs enough clear height to be viable, and the exact requirement depends on the unit, so it's worth confirming your building's specifics with our team before deciding.

The short answer

There's no universal "better" system — it depends on what you're storing, how much space you have, and how fast you need to move. Many ICAS clients in Singapore run both in the same facility: VLM for parts/tools, ASRS for high-velocity palletized storage.