vertical vs. horizontal machining center

[BobM2]

What are the advantages to suing a horizontal machining center over a VMC? There must be some because HMCs are much more expensive. I can't see that they would cut any better or faster.

 

[Iskit4iam]

I can offer two reasons for choosing an HMC over a VMC. The rotary axis is more robust on the HMCs. If you have large workpieces requiring rotation it is much more difficult to do in the VMC. The second is pallet change time. There may be some VMCs with fast change times but the HMCs are usually much faster. The fast pallet change allows loading inside machining time.

Several years ago I inherited a project. The project included a large Mazak VMC. As envisioned, 12 fixtures would be mounted on two pallets to eliminate set up time. This machine replaced a dedicated drilling machine that had a two hour set up time. When I indicated to the vendor that I wanted duplicate fixtures on each pallet they told me it would be slower because the pallet change time was about 30 seconds, while load time was only 15. The second pallet's only function was the ability to put more fixtures on the machine. We replaced the VMC with an HMC (6 second pallet change time), added a tapping operation that eliminated another machine and an additional six hour set up, designed a fixture that could adapt to each size we needed inside machine time and used the rotary axis to align the tapped threads to the cross holes. Added an induction heat treater to the cell and cut through put time from 16 weeks to two hours. Needed the HMC to make it work.

 

[EnglishMuffin]

One other important difference is that in general, horizontal machines have better chip evacuation properties.

 

[BobM2]

Thanks to the both of you!

 

[EdDanzer]

We have both a VMC and a HMC. The HMC will do larger size parts with creative fixtures and sheet metal removed. Chip evacuation when deep hole drilling is much better, but can be worse when boring.
Most horizontals will be more ridged because they are heaver and have larger slide ways for travel size. Part of the increased cost is because of better construction.