A Sabre 400 running an Acramatic 2100 (the control model is 2100, not 1200) drops to a crawl at the corners of the rectangular slot cycle and does not react to feedrate override. Override scales the programmed feed. A corner speed that override cannot move is being set by something other than the programmed feed: a corner or plunge feed inside the cycle, an exact-stop at each corner, a block-processing limit, or a machine acceleration/deceleration limit. The checks below separate those four in order. The evidence gives no parameter numbers, so read every value from the control's own screens and manuals.
Check 1: Compare actual feed with programmed feed on straights and corners
Prerequisite: the slot program runs in single-block or dry-run mode with the tool clear of the part.
- Display the actual feedrate readout while the cycle runs the slot.
- Record the actual feed on a long straight and at each corner.
| Reading | Meaning | Next |
|---|---|---|
| Straight matches programmed feed, corners drop | Corner-specific limit | Check 2 |
| Straight is also below programmed feed | Feed is capped globally (override at a low setting, feed-limit mode, or axis rapid/feed limit) | Verify the override switch position and any feed-limit mode, then repeat Check 1 |
| Actual feed follows programmed feed everywhere but the machine looks slow | Programmed feed is low | Read the feed fields in the cycle (Check 3) |
Check 2: Test whether override moves the corner speed
Gate: Check 1 shows a corner-only drop.
- Run the slot at three override settings, for example low, 100% and high.
- Record straight and corner actual feed at each setting.
If straight speed scales and corner speed stays fixed, the control is imposing the corner speed itself. The cause is either a fixed corner feed written into the cycle or a machine-level decel/corner limit, and override scales neither. Go to Check 3. If corner speed does scale but stays proportionally low, the programmed corner feed is simply set low. Fix it in Check 3.
Check 3: Read the feed entries and corner handling in the cycle
Open the rectangular slot cycle screen and list every feed-related entry (roughing, finishing, plunge, and any corner or approach feed). Confirm the entry names in the Acramatic 2100 programming manual rather than assuming them.
| Finding | Action |
|---|---|
| Separate corner/approach feed entry set low | Raise it to the cutting feed, rerun Check 1 |
| Single feed entry, already correct | Go to Check 4 |
Check 4: Isolate exact-stop behavior from the cycle
A control in exact-stop or in-position mode decelerates each axis to zero and waits for the following-error band to close before the next block. On a slot, that happens at every corner and looks like a dramatic slowdown that override cannot affect, because the time is spent waiting, not feeding.
- Write a short hand-coded program with the same slot geometry, straight linear moves at the same feed, with no exact-stop code active. Confirm the exact-stop and continuous-cutting mode codes for this control in the programming manual.
- Run it at the same override and compare corner actual feed with the cycle.
| Result | Meaning | Next |
|---|---|---|
| Hand-coded slot holds feed through corners | The cycle's generated blocks force the stop or use different motion mode | Use the hand-coded (or expanded) toolpath for production, or select a cycle option that rounds corners |
| Hand-coded slot slows the same way | Limit is in the control or machine, not the cycle | Check 5 |
Check 5: Test for block-processing starvation and cutter-comp segments
If corners are made of many short segments (small corner radii, cutter compensation, or arc approximations), the control can consume blocks faster than it can process them and it slows to avoid starvation. Estimate with a derived relation, using feed F in mm/min and block length L in mm:
block time (s) = L / (F / 60)
required: block time >= control block-processing timeRead the block-processing time from the control documentation, not from a guess. If corner blocks fall below it, the options are a lower corner feed, larger corner radii, or fewer, longer segments. If block lengths pass, the limit is the machine acceleration setting (Check 6).
Check 6: Review axis acceleration and corner parameters, then apply and verify
Corner speed on a contouring machine is bounded by axis acceleration and the allowed corner deviation. Those values live in the machine parameters set by the builder. Back them up before touching anything and change them only with the machine builder's guidance, because they protect the drives and the mechanics.
- Save the current parameter set and record the acceleration and corner-related values you will change.
- Change one value in the smallest step the builder documents.
- Rerun the Check 1 measurement at 100% override. Confirm actual corner feed rose and the servo following-error display stays within the limits given in the manual.
- Cut a test slot in scrap. Inspect the corner for overshoot, chatter marks, or oversized corner radius against the drawing.
- Repeat the Check 2 override sweep. Corner actual feed now scales with override at every setting, with no fixed floor, and the scrap slot measures to size.
FAQ
How do I tell if the Acramatic 2100 is in exact-stop at slot corners?
Run a hand-coded slot of the same geometry in continuous-cutting mode and compare corner actual feed with the cycle. If the hand-coded path holds feed and the cycle does not, the cycle is stopping at corners.
How do I find out why feedrate override does nothing at the corners?
Sweep override across three settings and log straight versus corner actual feed. Straights that scale while corners stay fixed mean the corner speed comes from a fixed cycle feed or a machine limit that override does not scale.
How do I check whether small corner segments are starving the control?
Compute block time as L / (F / 60) for the shortest corner block and compare it with the block-processing time in the control documentation. If block time is shorter, lengthen the segments or lower the feed.
How do I change the machine acceleration parameters safely?
Back up the parameter set, change one value by the smallest documented step, and follow the machine builder's guidance. Recheck following error and cut a scrap slot after each change.
How do I verify the corner slowdown is fixed?
Run the slot at 100% override and read the actual feed at each corner, then repeat at a higher and a lower override. Corner feed that scales with override and a scrap slot that measures to size confirm the fix.