Five axis machining probe configuration in the mold industry: cavity/electrode/deep cavity machining

Mold manufacturing is the most complex, high-precision, and difficult subdivision direction in the field of CNC precision machining. Mold processing, represented by injection molds, die-casting molds,

1、 Industry pain points

Mold manufacturing is the most complex, high-precision, and difficult subdivision direction in the field of CNC precision machining. Mold processing, represented by injection molds, die-casting molds, and precision stamping molds, faces the following core challenges:

1. Deep cavity measurement is difficult to reach: The depth of the injection mold cavity can reach 100-300mm or even deeper, and ordinary short measuring needles cannot reach the measurement point at all. Extending the measuring needle also faces the contradiction of decreased rigidity and increased triggering error;2.Complex surface contour verification: Mold cavities and cores have a large number of free-form surfaces (such as automotive interior parts molds and 3C shell molds), with form and position tolerances typically ranging from 5 to 15 μ m, and strict requirements for surface contour accuracy. Online measurement requires spatial multi-point detection in five axis linkage;3.Frequent electrode machining: Graphite/copper electrodes are used for EDM discharge machining, with shapes corresponding to the final cavity.. Each electrode requires precise measurement of the reference plane and discharge gap on the machine, and the machining cycle is highly dependent on online detection efficiency;4.Five axis RTCP calibration requirements: The accuracy of RTCP (rotating tool center point) of a five axis machining center directly affects the positioning accuracy of the mold cavity.. Conventional offline calibration is time-consuming and difficult to cover the full range of operating conditions. Online measuring heads for RTCP calibration have become standard in the industry.

2、 Key measurement requirements

Requirement dimension Specific requirements
——— ———
measurement depth ≥150mm， Adapt to deep cavity and deep hole characteristics
repeatability accuracy ≤0.5μm， Match mold precision tolerance
Needle measurement system Carbon fiber long rod/extension rod, high rigidity and lightweight
Five axis adaptation Support dynamic contact in the B/C axis swing angle direction
RTCP calibration Support five axis pendulum length calibration and rotation center calibration

Typical testing items:

  • Injection mold cavity: cavity depth, sidewall perpendicularity, bottom flatness, parting surface fit clearance;;
  • EDM electrode: positional accuracy of reference sphere/reference surface, height of discharge gap surface;;
  • Deep cavity sidewall: lateral displacement, bottom and side angles of deep holes/grooves;
  • Five axis machine tool: A/B/C-axis error calibration, tool runout (RTCP parameter) calibration.

    • 3、 Recommended products and parameter table

    3.1 Renishaw OMP400/RMP400 (Renishaw Corporation)

    OMP400 (infrared) and RMP400 (wireless) are the two main probes used by Renishaw for five axis machining of molds, with the same core sensing technology.

    parameter item OMP400 RMP400
    ——- ——– ——–
    2 σ repeatability accuracy 0.30 μm 0.30 μm
    communication method Infrared (modulated) Radio (frequency hopping)
    Needle interface LP2 (note: applicable to lathe turret or dedicated fixed station)/LP2 (note: applicable to lathe turret or dedicated fixed station) DD LP2 (note: applicable to lathe turret or dedicated fixed station)/LP2 (note: applicable to lathe turret or dedicated fixed station) DD
    Protection rating IP68 IP68
    Extended pole compatible ✅ (Supports up to 150mm extension rod) ✅
    Five axis adaptation Full angle trigger Full angle trigger

    Core advantages: OMP400/RMP400 adopts RENGAGE piezoelectric sensing technology, providingisotropic trigger consistencyin five axis swing angle measurement – that is, regardless of the direction in which the measuring needle contacts the workpiece (horizontal, inclined, inverted), the trigger signal responds at the same threshold, which is crucial for multi-point spatial detection of complex mold surfaces..

    The RMP400 wireless solution is particularly suitable for five axis machine tools with rotating workbenches or dividers. When infrared signals are obstructed by workpieces and fixtures in the processing area, wireless frequency hopping can ensure stable communication.

    3.2 Blum Z-Nano+TC52 (Blum Company)

    Blum Z-Nano is an ultra high precision tool alignment/measurement system designed specifically for Z-direction precision measurement; TC52 is a compact infrared probe from Blum, suitable for small and medium-sized mold machine tools.

    parameter item Z-Nano TC52
    ——- ——– ——
    repeatability accuracy 0.2 μ m (wired)/0.5 μ m (wireless) 0.4 μm
    Purpose Z-axis tool alignment+Z-axis measurement of workpiece 3D measurement of workpieces
    communication method Wired/Wireless infrared
    Protection rating IP67 IP68
    Application Scenarios Electrode Z high measurement, deep cavity bottom surface Measurement of cavity contour and sidewall

    Z-Nano’s core advantage: The extremely high repeatability accuracy of 0.2 μ m (wired) makes it irreplaceable in theEDM electrode Z-direction reference plane measurementscenario – the electrode needs to be accurately measured for Z-height before being clamped on the EDM machine, and Z-Nano is directly completed on the machining center, with errors controlled at the sub micron level, greatly reducing the number of discharge test machining times..

    TC52 core advantages: 0.4 μ m infrared probe, small size, easy installation, combined with TC52’s bidirectional triggering function, can complete multi-directional contact measurement in five axis mold processing..

    4、 Deep cavity measurement techniques and precautions

    4.1 Rigid balance of elongated measuring needle

    Deep cavity measurement inevitably requires the use of elongated measuring needles, but the relationship between elongation and measurement accuracy needs to be quantitatively grasped:

    Extended rod length Recommended measurement depth Stiffness attenuation ratio (relative to standard measuring needle) Suggest repeating precision discount
    :———- :———– :——————– :————–
    ≤50mm ≤ 80mm deep cavity ~5% No discount
    50-100mm 80-150mm deep cavity ~15% 10% off accuracy
    100-150mm 150-250mm deep cavity ~30% 30% off on accuracy
    >150mm Not recommended >50% Data for reference only

    Practical suggestions:

  • Deep cavity detection requires the use of carbon fiber extension rods: The elastic modulus/weight ratio of carbon fiber is four times that of stainless steel, and it has better rigidity at the same length;
  • Reduce the detection speed to 50% of the standard speed (usually from 300mm/min to 150mm/min) to minimize triggering errors caused by inertial impact;
  • After each replacement of the extension rod, the measuring needle length and ball diameter must be recalibrated, and the previous calibration data cannot be reused;
  • After the measurement is completed, it is recommended to conduct another retest in the opposite direction and take the average value to offset the unidirectional error caused by the bending of the extension rod.

    • 4.2 Treatment of coolant in deep cavities

    The bottom of deep cavities often accumulates cutting fluid, which has the following effects and countermeasures during measurement:

  • Impact: The cutting liquid film generates additional viscous resistance when in contact with the measuring needle, resulting in an error of 1-2 μ m in triggering delay.;
  • Solution: Before detection, perform a “blowing” action (using the machine spindle center blowing function or a program controlled cooling nozzle) to blow away the cutting fluid at the measurement point, wait for 1-2 seconds for the liquid to fall back and stabilize before measuring again;
  • Alternative: If the machine tool does not have a blowing function, the first measurement value can be discarded and the average of the second and third measurements can be taken – because the measuring needle has already broken the liquid film when triggered for the first time, and the results for the second and third times are more stable..

    • 4.3 Inverted/Side Wall Measurement Techniques

    The deep cavity of the mold often has inverted features (T-shaped groove, concave side wall), requiring the measuring needle to contact from a special angle:

    Feature type measurement method Required attachments Points to note
    :——– :——– :——– :——
    Verticality of side wall Probe along the Z-axis at multiple points on the sidewall Standard measuring needle Ensure that the triggering direction is consistent with the normal direction of the side wall
    Inverted concave surface Star shaped measuring needle or L-shaped measuring needle M2 star shaped measuring needle component Using the Inverted Measurement Macro Program
    T-shaped groove bottom surface Extension rod+90 ° angle measuring needle Corner adapter Angle error needs to be calibrated separately
    Deep cavity bottom surface Extended rod direct contact Carbon fiber extension rod Prioritize using RMP400 wireless communication

    4.4 Special considerations for graphite electrode measurement

    In EDM graphite electrode machining, the probe faces serious interference from graphite dust:

  • Dust Protection: Graphite dust is conductive and abrasive, and the standard probe seal ring has a 50-70% shortened lifespan in graphite environments. It is recommended to use probes with dust covers or purchase dust prevention kits.;
  • Communication reliability: Graphite dust absorbs and scatters infrared signals – under the same operating conditions, the infrared transmission distance is attenuated by 30-50%. It is recommended to use a radio solution (RMP400) or install an auxiliary infrared repeater.;
  • Needle life: Graphite material has 2-3 times higher wear on ruby balls than steel parts. It is recommended to check the diameter of the needle ball every 200 electrodes and replace the worn needle in a timely manner.;
  • Cleaning frequency: On the graphite processing line, the probe body and receiver should be blown with compressed air every shift to prevent dust accumulation from affecting the seal..

    • 5、 Comparison of Five Axis Plans among Various Brands

    5.1 Renishaw Solution (RENGAGE Series)

    Dimension Details
    :— :—
    Core Product OMP400 (infrared)/RMP400 (radio)/RMP600 (high-precision radio)
    accuracy class 0.30μm / 0.25μm
    Five axis calibration Support A/B/C axis swing length calibration and provide A901 series macro programs
    Extended pole support Maximum 150mm carbon fiber extension rod
    Needle interface LP2 (note: applicable to lathe turret or dedicated fixed station)/LP2 (note: applicable to lathe turret or dedicated fixed station) DD unified interface, rich accessories
    Maturity of the plan ★★★★★★ – The highest coverage rate in the global mold industry
    Typical Customer Da Wei Makino, DMG MORI, Makino

    5.2 Bloum Novotest Plan

    Dimension Details
    :— :—
    Core Product TC52 (infrared)/Z-Nano (wired)/TC55 (high-precision)
    accuracy class 0.4μm / 0.2μm / 0.3μm
    Five axis calibration TC series support, requires the use of a dedicated calibration ball
    Extended pole support Maximum 80mm standard extension rod
    Needle interface Blum dedicated interface, non universal M4/LP2 (note: applicable to lathe turret or dedicated fixed workstation)
    Maturity of the plan ★★★★ – High market share in the European mold market and fast growth in China
    Unique Advantage Z-Nano 0.2 μ m wired – irreplaceable in EDM electrode Z-high measurement

    5.3 Marpos Plan

    Dimension Details
    :— :—
    Core Product VOP40P (Piezoelectric Infrared)/MIDA Series
    accuracy class 0.25μm
    Five axis calibration Provide MIDA five axis calibration cycle
    Extended pole support Maximum length of 100mm
    Needle interface M4 compatible (universal interface)
    Maturity of the plan ★★★ – The automotive mold industry is widely used, but there are relatively few universal molds
    Unique Advantage Piezoelectric trigger zero wear, with significant advantages in mass production

    5.4 Selection Comparison Summary

    evaluation dimension Renishaw Maine lobster Marposs
    :——– :—— :—- :——
    Precision ceiling 0.25μm（RMP600） 0.2 μ m (Z-Nano wired) 0.25μm（VOP40P）
    Five axis calibration ecology best moderate moderate
    Deep cavity adaptation Best (maximum 150mm extension rod) moderate moderate
    Graphite environment Optimal wireless solution Need to strengthen dust prevention Need to strengthen dust prevention
    cost-effectiveness moderate best Medium to high
    Technical Support (Domestic) Good Good moderate

    6、 Actual Processing Cases

    Case 1: Deep cavity processing of injection molds for automotive interior parts

    project Details
    :— :—
    workpiece Automotive dashboard injection molding cavity (P20 steel)
    Deep cavity depth 180mm
    machine tool DMG MORI DMU 80 P (five axis)
    Probe scheme Renishaw RMP400 (wireless)+LP2 (note: suitable for lathe turret or dedicated fixed station) DD extended type+carbon fiber extension rod 130mm
    Measurement Item Depth of deep cavity bottom, verticality of side walls, and positional accuracy of parting surfaces

    Effect data:

  • Before renovation: Each offline item is sent for three coordinate inspection, with a feedback cycle of 4-6 hours and a defect rate of approximately 8%
  • After renovation: online full inspection of key dimensions, real-time compensation for knife repairs, and a reduction in defect rate to 1.2%
  • Control the depth deviation of the deep cavity bottom from ± 12 μ m before the modification to ± 3 μ m
  • The RTCP calibration cycle has been increased from once a month to once a week (using RMP400 online calibration, each time only takes 5 minutes)

    • Case 2: Batch Processing of EDM Electrodes for 3C Shell Molds

    project Details
    :— :—
    workpiece Graphite electrode for mobile phone shell mold (30 specifications)
    Number of electrodes Approximately 2000 pieces produced per month
    machine tool Fanuc RoboDrill alpha-D14MiB5
    Probe scheme Blum Z-Nano (wired 0.2 μ m)+TC52 (0.4 μ m)

    Effect data:

  • The measurement time for electrode reference surface Z height has been reduced from a total of 3 minutes/piece offline and online to 8 seconds/piece online
  • The number of discharge gap trial machining times has been reduced from an average of 3 to 1, saving approximately 15 minutes of EDM time per piece
  • The electrode repair rate has decreased from 15% to 3%
  • Recovering the investment cost of the probe within 3 months

    • Case 3: Die casting model core five axis precision machining

    project Details
    :— :—
    workpiece Die cast model core of automobile engine cylinder block (H13 steel, HRC 48-52）
    Processing machine tool Da Wei Makino DA300 (five axis)
    Probe scheme Marposs VOP40P (0.25 μ m piezoelectric)+MIDA probe
    Measurement strategy Measurement of allowance before precision machining → measurement of contour after precision machining → closed-loop correction

    Effect data:

  • Core critical dimension (diameter ø 50 ± 0.008mm) CPK increased from 1.2 to 1.8
  • Five axis linkage profile stability within ± 5 μ m
  • The lifespan of precision machining tools has been extended by 30% (due to more accurate residual detection, avoiding empty cutting and overcutting)

    • 7、 Configuration plan

    Plan A: Injection mold/die-casting mold deep cavity five axis machining line

    “`Machine tool: Five axis vertical machining center (Da Wei Makino/DMG MORI DMU series)Probe: Renishaw RMP400 (wireless, avoid signal obstruction)+LP2 (note: suitable for lathe turret or dedicated fixed station) DD extended probeTool setter: Renishaw NC4+Blue laser tool setterDeep cavity accessory: Carbon fiber extension rod (100-150mm)“`

    Detection process:1.RTCP calibration (first piece/week): RMP400 completes five axis swing length calibration with a dedicated calibration ball (including A/C axis rotation center measurement, about 5 minutes)2. After rough machining of the cavity, measure the depth of the deep cavity bottom and the verticality of the side walls using RMP400 and an extension rod (approximately 20 seconds per hole)3. After semi precision machining, perform multi-point detection on the surface (distribute points along the tool path, 4-8 points per section, approximately 40 seconds)4. Precision machining completed → Confirmation of final contour and parting surface position (approximately 30 seconds)

    Plan B: EDM electrode machining dedicated line

    “`Machine tool: High speed graphite carving and milling machine (Fanuc RoboDrill/Makino)Measuring head (workpiece): Renishaw OMP400+LP2 (note: suitable for lathe turret or dedicated fixed station) (trigger force 0.5N)Tool setter (Z-direction): Blum Z-Nano (wired, 0.2 μ m)Probe (Z-direction fine adjustment): Blum TC52“`

    Detection process:1. After rough milling the electrode shape, measure the position of the electrode reference ball using OMP400 (approximately 10 seconds)2. After precision milling the bottom surface, the Z-Nano measures the height of the electrode Z (sub micron level, about 2 seconds), and the data is automatically written into the EDM machining program3. After precision milling the discharge surface, TC52 measures the tolerance of the discharge gap surface (about 8 seconds)4. Generate electrode detection reports for all measurement data and transfer them to the EDM station along with the material flow

    Plan C: Periodic Calibration Plan for Five Axis RTCP Accuracy

    “`Calibration tool: Renishaw RMP400+Ø 25mm calibration ball (calibrated sphericity ≤ 0.5 μ m)Testing program: Renishaw five axis calibration macro program (A901 series)“`

    Calibration Items:1. Center position error of each rotating axis (swing length parameter)2. RTCP linkage accuracy (circular/conical interpolation trajectory detection)3. The compensation values for the reverse clearance of each axis are automatically written into the machine parameters

    This solution does not require a dedicated laser interferometer, and can achieve five axis accuracy through the use of RMP400 probes and standard balls. Regular calibration on the machine is recommended to be performed once per shift/week.

    8、 Selection suggestions

    1.Frequent deep cavity (cavity depth>100mm)→ Renishaw RMP400 wireless+LP2 (note: suitable for lathe turret or dedicated fixed station) DD extended measuring needle, wireless communication can avoid infrared signal attenuation problems in deep cavities;2.Batch production of EDM electrodes→ Blum Z-Nano (0.2 μ m wired) is paired with OMP400, with Z-Nano responsible for Z-high benchmark measurement and OMP400 responsible for overall contour measurement – the two complement each other and cover all requirements;3. Five axis calibration requirements: Renishaw OMP400/RMP400, combined with specialized calibration macro programs, is currently the mainstream solution for five axis RTCP calibration in the mold industry, with mature ecology and complete technical data;4.Budget sensitive small and medium-sized mold factories→ Blum TC52 (0.4 μ m)+Z-Nano combination, excellent cost performance, and Blum’s technical support response in China is fast;5.Graphite electrode processing→ It is necessary to choose a radio communication solution (RMP400), as graphite dust severely attenuates infrared signals; Simultaneously installing a dust cover for the probe to extend its lifespan;6.High hardness quenched die steel (HRC>50)→ It is recommended to use a piezoelectric probe (MarposVOP40P), which has a small and constant triggering force and reduces the wear of the hard alloy probe.

    Data source:

  • Renishaw OMP400 Product Manual (H-2000-5067-03-A)
  • Renishaw RMP400 Product Manual (H-2000-5068-03-A)
  • Renishaw Five Axis CNC Machine Tool Calibration Scheme Manual (H-5650-5003-02-A)
  • Technical Specification for Blum TC52/Z-Nano Series Products
  • Blum LaserControl LC50 DIGILOG (Analog Continuous Scanning Technology, Non Simple Switching, Thousands of Dynamic Data Acquisition per Second, Can Achieve Dynamic Filtering and Micro Diameter Tool Detection in Splashing Cutting Fluid) Laser Tool Alignment System Manual
  • Marposs VOP40P Product Technical Specification
  • The actual case data in the article comes from the customer implementation project statistics of Ningbo Jiangce Technology from 2022 to 2025

    • This article has been independently reviewed by Ningbo Jiangce Technology. If you need professional services, please contact us.

    ⚠️

    Dynamic safety of deep cavity length measuring needle

    When using a measuring needle with a length of ≥ 75mm, the inertia of the five axis high-speed movement may cause the internal mechanism of the probe to trigger incorrectly. must:

    -Limit the positioning acceleration of the probe (it is recommended that the feed rate of G01 be ≤ 2000mm/s ², and the fast moving speed of G00 be reduced to 50%)

    -Select

    Carbon fiber extension rod

    (Compared to stainless steel rods, it reduces weight by 40-60%)

    -Set a safe movement path in the macro program called by the probe to avoid collision with the deep cavity sidewall

    Appointment Presentation& Technical Support

    Ningbo Jiangce Technology Co., Ltd.On site demonstration, technical consultation, or evaluation of probe repair solutions

    📞 < Service Hotline: 157-5780-7400/132-2194-1413📍 Shipping and repair address: Ningbo City, Zhejiang Province (please call for detailed address)⏱️ < Response Commitment: 24 hour response time, with the fastest arrival within 8 hours (in the Jiangsu Zhejiang Shanghai region)

    The technical parameters of this article are based on the official product manuals and technical specifications of Renishaw, Marposs, and Blum. Part of this article is based on the maintenance and service data organized by Ningbo Jiangce Technology. Please refer to the official manual of the corresponding model for specific configuration and compatibility. This article does not constitute a disparagement or comparative conclusion of any third-party product, and the third-party software/systems mentioned in the article are compatibility statements. If you need professional repair services, please contact Ningbo Jiangce Technology Co., Ltd.