Meet the Machine

Used Haas UMC-750SS: The Super Speed Is in the Trunnion

Read the Haas spec pages for the UMC-750 and the UMC-750SS side by side and most of the lines match. Same 30 by 20 by 20 inch travels. Same 30 hp spindle making 90 ft-lbf at 2,000 rpm. Same 500 mm platter, same 660 lb load rating, same rotary torque, same brake torque.

Then you reach the trunnion speeds. The UMC-750 tilts and rotates at 50 degrees per second. The SS tilts at 170 and rotates at 179.

That is the biggest gap on the sheet. The Super Speed package does raise the spindle speed and the rapids, but the biggest multiple on the spec sheet is in the two rotary axes, and on a five axis machine those are the axes that set the pace of every reposition.

Same Machine, Faster Axes

Here are the two machines as Haas lists them today.

Every row that measures force or size is identical. Every row that measures time is faster on the SS.

The Super Speed Is in the Trunnion

On a three axis mill, rapids and tool changes are most of the time the spindle is not cutting. On a five axis trunnion machine there is a third item: the platter tilting and turning to put the next face of the part in front of the tool.

In 3+2 work, where the trunnion indexes to an angle and locks while the spindle cuts, every face change is a tilt or a rotation. At 50 degrees per second, a 90 degree tilt takes about 1.8 seconds at rated speed. At 170 degrees per second it takes about half a second. Multiply that by every face, on every part, on every shift.

In simultaneous five axis work, the rotary axes move while the tool cuts, and the machine has to coordinate all five axes along the toolpath. Faster rotary axes are less likely to be the axis that holds the feed back when the tool angle changes quickly.

The hardware behind that speed has changed over the years. Haas's service document RD0078 says the earlier UMC-750SS used roller cam rotaries on both axes, where the earlier standard UMC-750 used an HRT450 and an HRT310 rotary table, and that the current reboot version of the UMC-750 uses cycloidal rotary drives. Know which version you are buying before you compare it with anything else.

Resell CNC Take

The SS earns its premium on parts with lots of faces and short cuts, where the trunnion is moving as often as the spindle is cutting. On a part that spends twenty minutes in one orientation roughing steel, the SS and the standard UMC-750 cut at the same torque, and the faster rotaries save you seconds on a long cycle. Look at how often your parts reposition before you pay for the speed.

What the SS Does Not Change

Torque. Both spindles are rated 30 hp and 90 ft-lbf at 2,000 rpm. The SS spins faster, it does not pull harder.

Rotary strength. Haas lists identical continuous torque on both machines, 2,240 ft-lbf on tilt and 1,854 on rotation, and identical brake torque, 2,000 and 900 ft-lbf.

Load. Both platters are rated 660 lb, and both drop to 200 lb with a pallet pool fitted. That rating covers the vise and fixture as well as the part.

Size. Same travels, same 27 inch maximum part swing, same 4 to 24 inch range from spindle nose to platter.

Two 2022s, Two Spec Sheets

We have two 2022 UMC-750SS machines on the floor, and their listings do not describe the same machine.

One lists a 12,000 rpm spindle, a 500 mm platter and a 50+1 tool changer. That matches Haas's current UMC-750SS page. The other lists a 15,000 rpm spindle, 150 degrees per second on the trunnion, +110 to -35 degrees of tilt and a 630 by 500 mm T-slot platter. That matches the launch coverage of the SS, which described a 15,000 rpm spindle, a 40+1 changer, a 150 degree per second roller cam trunnion and a 630 by 500 mm table.

Haas's current page lists +120 to -35 degrees of tilt, 170 and 179 degrees per second, a 500 mm platter and a 30+1 changer. So the UMC-750SS name has covered at least two sets of specifications, and a model year alone will not tell you which one is in front of you.

The fix is to identify the machine, not the listing. RD0078 gives the tells: the current reboot version has a smaller operator door that rides behind the enclosure, an external coolant tank and a front mounted pendant. The earlier version has a large door that rides in front of the enclosure and an integrated coolant tank. Then read the spindle nameplate and the rotary ratings off the machine.

The Numbers Underneath

These are Haas's current published figures for the UMC-750SS. For an earlier build, pull the spec sheet for that serial number.

Which Control You Are Getting

Both of our 2022 machines are listed with the current generation Haas control. What matters on a used five axis Haas is less the control generation than the options turned on inside it.

Look for Dynamic Work Offsets and Tool Center Point Control, which let the machine track a part's position as the trunnion moves and keep the tool tip on the programmed path. One of our 2022 machines lists both. On the other, confirm them at the control. Also check program memory, high speed machining, and whether wireless probing is fitted and working.

U.S. Parts and Service

Haas Automation was founded by Gene Haas in 1983 and builds its machines in Oxnard, California. Service runs through its network of Haas Factory Outlets across the United States. More on the company in our Haas brand profile.

Two on Our Floor

2022 UMC-750SS, 12,000 rpm. 50+1 side mount tool changer with CT style grippers, 300 psi through spindle coolant, programmable coolant nozzle, 95 gallon coolant tank, Hennig chip disk filtration conveyor, rotary scales, Dynamic Work Offsets and Tool Center Point Control, 1 GB program memory, WiFi, HaasConnect remote monitoring and HaasDrop.

2022 UMC-750SS, 15,000 rpm. Listed with the 150 degree per second trunnion and a 630 by 500 mm T-slot platter, rotary scales, Haas WIPS-R wireless probing, through spindle and programmable coolant, 95 gallon coolant tank, chip conveyor, auto door and oil skimmer.

Inventory changes, so check the Haas brand page for what is available today.

Used-Market Value

The SS premium. New, the SS costs US$47,000 more than the standard UMC-750. How much of that survives on a used machine depends on whether the buyer's parts use the speed.

Version. Reboot or earlier, and which spindle and trunnion ratings the machine actually carries.

Five axis options. Dynamic Work Offsets, Tool Center Point Control, rotary scales and probing. A UMC without them is a much harder machine to put to work.

Tool capacity and coolant. A larger magazine and high pressure through spindle coolant suit a machine built for many tools and short cycles, so count them in the price rather than as extras.

What to Check on a Used UMC-750SS

Identify the version. Door, coolant tank and pendant position, per Haas RD0078.

Confirm the numbers on the machine. Spindle speed from the nameplate, rotary speeds from the control, and a pocket count on the tool changer.

Run both rotaries at full speed. Through full tilt and several full rotations, listening for noise and watching for hesitation, then check brake engagement.

Probe the rotary centers. A five axis machine that has been crashed or moved can lose its rotary center calibration, which shows up as features that do not line up between faces.

Add up the platter load. Vise, fixture and part against 660 lb, or 200 lb with a pallet pool.

Read the hour meters and alarm history, and confirm which options are active in the control.

Who Runs One

The UMC-750SS suits a shop cutting small to medium aluminum and other free cutting parts with many faces, the kind of work where the trunnion repositions constantly and cycle time is measured in minutes. For heavy roughing where each orientation is held a long time, the standard UMC-750 cuts with the same torque for less money.

We made the case for why more shops are moving to five axis in 5-Axis Is Becoming the New 3-Axis and 5-Axis Is a Geometry Shift, and for a different Haas approach to five axis, see our piece on the Haas VR-8 gimbal head.

Frequently Asked Questions