The two questions that decide it
Ask two things about the part mix. First: on average, how many separate set-ups does a part need today? Second: what percentage of the shift is the spindle actually cutting? If the answer to the first is three or more and to the second is under 60 percent, a horizontal with tombstone fixturing is usually the right investment. If parts need one or two set-ups and change every week, a vertical is more productive per yuan spent.
How the two architectures differ in practice
| Attribute | Vertical (VCN) | Horizontal (HCN) |
|---|---|---|
| Faces per set-up | 1 (2–3 with a trunnion or 4th axis) | 4 faces of a tombstone, plus top |
| Chip evacuation | Gravity-assisted, good in pockets | Excellent — chips fall away from the cut |
| Reach into deep pockets | Better, tool points down into the cavity | Limited by tombstone depth and tool length |
| Fixturing cost per part | Low (vise, soft jaws, plate) | High (tombstone, multi-station, hydraulic) |
| Floor space per spindle | Compact | Larger, plus pallet pool and load station |
| Unattended potential | Moderate, with a pallet changer | High, with a multi-pallet pool |
| Best batch size | 1–500, high mix | 500+, repeat part families |
Why horizontals keep the spindle busier
On a vertical, the operator loads while the machine waits, and the machine waits again while the operator measures. On a horizontal with a pallet pool, loading happens on a separate station while the spindle cuts. That structural difference — not spindle speed — is what moves utilisation from 50 percent to 75 percent.
The arithmetic: a vertical cutting 45 minutes in every 60 produces 45 minutes of value per hour. A horizontal with a pallet pool cutting 52 minutes produces 52. Over 4,000 hours a year that is 4,700 extra minutes of cutting — around 78 hours — before any consideration of multi-face fixturing. Add three-face machining in one set-up and the gap widens further.
Where verticals still win outright
- Deep cavities and mould work — the tool approaches from above and can reach into a pocket that a horizontal physically cannot address.
- High-mix, low-volume job shops — a vise and a fixture plate change in ten minutes; a tombstone does not.
- Large single parts — a 1,200 mm plate belongs on a vertical with a big table, not on a pallet.
- Budget-constrained entry — the same money buys a larger vertical envelope or better options.
Where horizontals win
- Part families with features on several faces — housings, valve bodies, brackets, pump components.
- Repeat production above a few hundred a year — the tombstone cost amortises and the set-up count falls.
- Lights-out running — the pallet pool is the mechanism that makes unattended machining work.
- Aluminium and cast iron at volume — chip evacuation down and away is a genuine quality advantage.
The mistake buyers make
Buying the horizontal for the machine and not for the fixturing. A horizontal without a tombstone strategy is an expensive vertical with worse reach. The correct way to evaluate the purchase is as a package: machine, pallet pool, and the tombstone set for the first two part families. If the package does not show a payback in the same five-line model used for fixtures, the horizontal is the wrong answer regardless of how good the machine is.
Machine options that actually change the outcome
On the vertical side, a trunnion or a 4th axis converts a one-face machine into a three-face machine for a fraction of a horizontal's cost, and is often the highest-return option in the quotation. On the horizontal side, pallet count matters more than spindle taper: two pallets enable lights-out, six pallets enable a weekend.
Liuzhou Dongben Machinery Equipment Co., Ltd. is an authorized Mazak distributor based in Liuzhou, Guangxi, and specifies the machine, the pallet system and the tombstone set as one proposal — because the machine alone does not decide the cost per part.