Why Do Shops Ask for TCP or RTCP Support Specifically When Shopping for a 5-Axis Simultaneous Control?

Because without it, every tool length change forces you to recompute and reload a program's offsets by hand, and that's a nonstarter for real simultaneous 5-axis work. TCP, Tool Center Point control, sometimes called RTCP for Rotation around the Tool Center Point, lets the control keep the tool tip at the programmed position in space while the rotary axes swing underneath it.

What's actually happening without it

It's not subtle once you see it happen.

On a simultaneous 5-axis move, the two rotary axes aren't just tilting the part. They're rotating it around pivot points that typically sit somewhere other than the tool tip. Rotate a trunnion ten degrees and the part's surface moves in X, Y, and Z simultaneously, not just angularly.

Without TCP, the control has no idea that's happening from a tool-tip perspective. The linear axes execute exactly the coordinates in the program. If those coordinates were calculated for a 100 mm tool and you've actually got a 102 mm tool in the spindle, the tip ends up in the wrong place by an amount that depends on the rotary angle at that instant, not a fixed offset you can dial out with a single number.

With TCP active, you tell the control the tool length once, and it does the real-time trigonometry to keep the programmed tool-tip path correct regardless of which combination of linear and rotary motion gets it there. Change tools, touch off the new length, and the existing program runs correctly without re-posting anything.

Why this matters more for simultaneous work than 3+2

In 3+2 positioning, where the rotaries move to an angle, lock, and the cut happens as a conventional 3-axis move, you can get away without TCP by baking a fixed offset into each setup. The rotary angle doesn't change mid-cut. True simultaneous 5-axis has the rotaries moving continuously while cutting, so there is no single fixed offset to bake in. TCP isn't a convenience there. It's the thing that makes the toolpath match the CAM model at all.

What to actually verify when shopping

A spec sheet says 5-axis. Confirm what that actually means.

Ask whether the control's TCP implementation handles both rotary axes simultaneously or just one at a time. Some older or lower-tier control packages advertise 5-axis capability but only apply tool-length compensation cleanly through a single rotary, which limits you to head-head or head-table configurations rather than full trunnion work.

Ask how the control handles a tool-length change mid-program versus requiring a restart. And run a known test part, a feature with a documented nominal location, through the machine before trusting TCP on a production job rather than taking the spec sheet's word for it.

CNC machining at DigiForge runs 3-, 4-, and 5-axis milling and turning in metals and plastics, with ISO 2768-m as the standard tolerance down to ±0.01 mm where a feature calls for it, and a 3-week standard lead time with a 1-week rush option. Whatever the post-processor and control are doing with TCP on a given job, the part gets checked against the print either way.