Three Problems That Remain With Offline Sample Inspection
The issue is not the performance of the measuring instrument, but the number of measurements and how the records are kept.
Sample Inspection Misses Sudden Height Anomalies
Height deviations caused by tool wear or changes in component lots occur suddenly and only for short intervals. With sample inspections performed once every few tens of minutes, these deviations slip through and flow to subsequent processes. Even when an anomaly is found, a decision must be made to either trace back to the previous measurement and re-inspect all parts, or discard them all together. If 100% inspection is performed, only the non-conforming parts can be discharged, minimizing the scope of rework.
Values Cannot Be Compared Without Determining a Reference Surface
Height is not an absolute value; its meaning changes depending on what reference the difference is based on. The reference is fundamentally different between a coordinate measuring machine (CMM) that measures on a surface plate and measuring a target on a line during transfer. If the target itself is tilted, the measured value will change even if the same location is measured. For inline implementation, it is first necessary to design what will be used as the reference surface, such as "creating a reference plane from surrounding surfaces" or "looking at the relative height of opposed heads."
Even If Measured, Judgment Cannot Be Made Without a Threshold
If the step height in micrometers that constitutes a NG is not determined, operations cannot run smoothly even if values are obtained. Thresholds should be set by calculating backward from the impact on subsequent processes (such as interference or functionality) and by measuring the actual distribution of non-defective lots to understand the current status. Without this procedure, the line will either stop due to over-detection or remain unchanged from the conventional state due to missed defects. This is an item that must be designed in conjunction with equipment installation.
4 Steps to Designing Inline 100% Inspection
Before selecting a sensor, determine the reference, tact time, environment, and judgment.
- 1 Determine the Reference Surface – STEP 1. Decide whether to set a flat surface around the target as the reference plane or to look at the relative height of opposed heads. Once the reference is determined, the effect of target tilt can be suppressed.
- 2 Match the Tact Time – STEP 2. Confirm whether measurement can be performed without stopping transfer. If a profile can be acquired during transfer using a method that does not require positioning, 100% inspection can be achieved without changing the existing tact time.
- 3 Account for Environmental Variations – STEP 3. During long hours of continuous operation, changes in ambient temperature appear as variations in measured values. By using a configuration that looks at relative values with respect to the reference surface, the system becomes less susceptible to environmental variations.
- 4 Determine Thresholds and Record – STEP 4. Measure the actual distribution of non-defective lots to set thresholds, and design the flow up to discharging NG products using judgment output. Saving measured values allows them to be used directly for understanding process capability and trend management.
Comparing Height/step Inspection Methods From the Perspective of 100% Inspection
They are compared not by measurement accuracy, but by whether 100% inspection is possible and whether the reference is stable.
Measurement frequency
LJ-X8000 Series (3D profile)
◎ 100% / Continuous
Point measurement displacement sensor
◎ 100% / Continuous
Contact height gauge
× Sample inspection
Coordinate measuring machine (CMM) (offline)
× Sample inspection
How to set the reference plane
LJ-X8000 Series (3D profile)
◎ Surrounding surfaces can be set as the reference plane
Point measurement displacement sensor
△ A separate reference point must be set
Contact height gauge
△ Assumes placement on a surface plate
Coordinate measuring machine (CMM) (offline)
◎ Coordinate system can be defined
Robustness against target tilt
LJ-X8000 Series (3D profile)
◎ Automatic correction with the position correction function
Point measurement displacement sensor
× Value changes if tilted
Contact height gauge
△ Depends on how it is placed
Coordinate measuring machine (CMM) (offline)
○ Can be corrected
Simultaneous acquisition of multiple points
LJ-X8000 Series (3D profile)
◎ Profile acquired all at once
Point measurement displacement sensor
△ Requires as many units as the number of points
Contact height gauge
× One point at a time
Coordinate measuring machine (CMM) (offline)
○ Can measure, but takes time
Step/Flatness
LJ-X8000 Series (3D profile)
◎ Captured as a surface and calculated from the reference plane
Point measurement displacement sensor
△ Results in a collection of points
Contact height gauge
△ Measurement points are limited
Coordinate measuring machine (CMM) (offline)
○ Measurable, but offline
Impact on tact time
LJ-X8000 Series (3D profile)
◎ Does not stop conveyance
Point measurement displacement sensor
◎ Does not stop
Contact height gauge
× Requires stopping and setup
Coordinate measuring machine (CMM) (offline)
× Removed from the line
Resistance to temperature drift
LJ-X8000 Series (3D profile)
◎ Minimal impact when looking at relative height
Point measurement displacement sensor
△ Affected by absolute values
Contact height gauge
○ Minimal impact
Coordinate measuring machine (CMM) (offline)
○ Requires a temperature-controlled room
Recording of judgment basis
LJ-X8000 Series (3D profile)
◎ Saves and outputs measured values and images
Point measurement displacement sensor
○ Measurement values can be output
Contact height gauge
× Relies on manual recording
Coordinate measuring machine (CMM) (offline)
○ Records are kept, but the number of items is limited
Reference Planes and Position Correction Are Key to 100% Inspection
Most of the reasons why inline implementation fails lie not in the sensor resolution, but in the instability of the reference. The LJ-X8000 Series can set a reference plane by fitting a flat surface around the target to a plane using the least-squares method, allowing evaluation based on the relative height from that plane. In addition, the 3D position correction function automatically corrects for target misalignment and tilt. Because the cross-section is acquired all at once, multiple points can be viewed simultaneously, allowing 100% inspection without stopping the transfer. Thresholds can be set in units of µm, and everything from judgment to recording is connected in the same configuration.
Products for Inline 100% Height and Step Inspection
This is an inline profile measuring instrument that can acquire cross-sectional shapes all at once and make judgments based on the relative height from the reference plane.
Supports Replacement From Offline Sample Inspection to Inline 100% Inspection — LJ-X8000 Series
2D/3D Laser Profiler
The ultra-high-definition measurement of 3200 points/profile represents the cross-sectional shape in detail, quantifying indicators such as height, step, width, and angle. Because the cross-section can be acquired all at once simply by projecting a line laser, the heights of multiple points can be measured simultaneously in a single image capture. From the acquired height data, a flat surface around the target can be fitted to a plane using the least-squares method and set as the reference plane. By evaluating based on the relative height from that reference plane, a configuration can be achieved that is less susceptible to how the target is placed or changes in ambient temperature.
Because height images are hardly affected by surface printing, patterns, or colors, judgments can continue to be made using the same criteria even if the appearance varies. The stray light suppression function works against multiple reflections and diffuse reflections that occur on shiny metals. The 3D position correction function eliminates the need for positioning, and when combined with the automatic target detection function, inline 100% measurement and inspection can be achieved. Inspections can be set up simply by choosing from approximately 30 types of profile measurement tools, such as step, width, cross-sectional area, and angle. It also supports discharging NG products via judgment output and saving measured values and images using the FTP server function.
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Inquiries regarding inline 100% inspection of height and steps
Application Examples of Shifting From Sample Inspection to 100% Inspection
Conventional sample inspections are replaced with inline 100% inspection using height data.
Height Inspection of PCB-Mounted Components
Inspects the height of components mounted on a PCB. Since the surrounding PCB surface can be used as a reference, judgments can be made based on relative height without being affected by how the target is placed.
Gap and Step Measurement During Vehicle Assembly
Measures the gap and step of the assembly part simultaneously. Even targets with large height differences can be imaged stably, allowing step management to be performed inline.
Crush and Crack Inspection After Pressing
This is an example of replacing a process where the presence of crushes or cracks was conventionally judged indirectly by weight variation with 100% shape inspection using height images. This is an example where the effect of 100% inspection is clearly demonstrated.
Frequently Asked Questions Regarding Inline 100% Inspection of Height and Steps
It is the reference plane. Height only has meaning as a difference from the reference. Deciding first whether to set a flat surface around the target as the reference plane or to look at the relative height of the opposing heads will solidify the subsequent design.
Yes. The 3D position correction function recognizes misalignment and tilt to automatically correct them. Furthermore, by evaluating the relative height against a reference plane created by fitting a surrounding flat surface using the least-squares method, judgments can be made with almost no effect from how the target is placed.
Changes in ambient temperature appear as fluctuations in measured values. By configuring the system to judge based on relative height from a reference plane rather than absolute values, it becomes less susceptible to environmental changes.
Yes, they can. Because a line laser acquires the cross-section all at once, multiple points within the field of view can be measured simultaneously with a single image capture. There is no need to line up multiple point-measurement sensors.
After calculating the required level backward from the impact on subsequent processes and functions, measure the distribution of non-defective lots to understand the current situation. Setting the threshold at a level that differentiates from defective products can suppress both over-detection and missed detections.
By specifying a flat surface around the target as a range, the height data of that range can be fitted to a plane using the least-squares method and set as the reference plane. Since this is available as a standard function, there is no need to prepare additional software. From then on, judgments are made based on the relative height from this plane, allowing evaluation under the same standard even if there are changes in how the target is placed or in the ambient temperature.
Yes, they can. Measured values and images can be saved using the FTP server function, which can be used as they are for understanding process capability and trend management. Records can be kept while discharging NG products based on judgment output.
If you tell us about your target and current inspection method, we will propose a configuration including the reference plane and tact time. Please request a catalog or contact us using the inquiry form.
- 2D/3D Laser Profiler LJ-X8000 series
2D/3D Laser Profiler
LJ-X8000 series
