Introduction

The core of Equator is a set of parallel motion structures: three linearly driven struts (P/Q/R three-axis) lift the motion platform, with Hooke hinges connecting the two ends of the struts. Each strut only bears pure tension or pressure and does not transmit bending moments; The linear encoder scale is directly mounted on the strut, and the driving point and feedback point are the same source. The whole machine has no screw, no belt drive, and no Z-axis column. The base and top are both castings instead of granite.

1. Original text: Why is Equator not a scaled down version of a CMM

1.1 The cost of Cartesian structure: rigidity relies on “large components”, which bring inertia

The mobile structure of traditional coordinate measuring machines and machine tools is Cartesian series parallel: columns, beams, slides, and spindle boxes are nested layer by layer. To maintain a stable spatial position of the probe at the end of the stroke, each suspension link must be sufficiently rigid – the beam must be thick, the cross-section must be large, the guide rail must be long, and the support must have weight. So several iconic components appeared: a large section granite workbench and guide beam, heavy-duty cast iron columns, and thick sliding seats.

This technical route is extremely clear in geometry: the three directions are not coupled with each other, one axis moves while the other two axes remain stationary, the error model is easy to linearize, and compensation is also easy to do. Its cost is hidden in two physical quantities: mass and hysteresis.

Mass determines inertia, and inertia determines acceleration and stabilization time. The heavier the carriage, the smaller the acceleration obtained by the same motor thrust, the slower the residual vibration attenuation after the probe reaches the target point, and the greater the fluctuation of contact force during scanning. Hysteresis is even more concealed: a heavy structure undergoes elastic deformation when subjected to force, and the deformation cannot be fully restored after the force disappears. The error presents a hysteresis loop with the loading direction. This hysteresis loop is almost invisible under unidirectional light load, but in bidirectional scanning and frequent reverse comparison measurements, it will seep into the results in the form of micrometers.

When explaining the design starting point of Equator in official documents, it is precisely this point that serves as a comparison: traditional Cartesian structures rely on large granite shafts and heavy castings to ensure rigidity, but this approach itself introduces limitations in terms of hysteresis and inertia.

1.2 The opposite route: replace “relying on large components for hard support” with “relying on structural axial force”

The mechanical characteristics of a series structure are that the end load needs to be transmitted to the foundation through a long cantilever chain, and each section needs to use bending stiffness to resist the moment. The material utilization rate is very low – most of the cross-sectional area is used for bending resistance, not tensile compression resistance.

The parallel structure has reversed this chain. Three struts point directly from the fixed end towards the motion platform, each of which is a two force rod: it only receives force in its axial direction, and the hinges at both ends do not transmit bending moments. The force state of a two force rod is pure tension or pure compression, and the material is uniformly stressed along its entire length. The axial stiffness provided by the same cross-sectional area is much higher than the bending stiffness provided by using it as a cantilever beam. This is the fundamental reason why parallel mechanisms can achieve higher structural stiffness with lighter structures – short load paths and simple load forms.

Meanwhile, the deformation of the strut is a tensile and compressive deformation along the axial direction, which belongs to a repeatable elastic behavior; Compared to the bending hysteresis of a large cantilever, the loading unloading curve of axial tension and compression is much cleaner. This is the true value of ‘only subjected to tension and compression’ in the metrological sense: not just high stiffness, but more predictable stiffness behavior.

1.3 Three linear drive struts (P/Q/R axis)

The three axes of the Equator are not called X/Y/Z, and the official letters are P, Q, and R. This is not a naming convention, but a recognition of the structural fact: the true degrees of freedom that can be independently driven in the machine are the lengths of the three struts. P. Q and R each correspond to the expansion and contraction of a straight driven strut.

By understanding this, many descriptive myths are automatically dispelled.

Firstly, the three “axes” of the machine are not perpendicular to each other in space, they converge diagonally from the fixed end onto the platform. Therefore, there is no such serial action as’ move X first and then move Z ‘, and any movement of the target point is the result of three struts simultaneously changing length and working together to complete it.

Secondly, X/Y/Z is calculated, not fabricated. The raw quantity read by the control system is the position of three struts, which are then converted into the spatial coordinates of the platform center based on geometric relationships. The straight line drawn by the probe in the workpiece coordinate system is usually a curve in the support space.

Thirdly, the three struts determine the platform’s pose, including three positions and three postures. Three fixed length constraints lock the degrees of freedom of the platform in a determined state, which is the meaning of ‘parallel constraints’. There is also a Parallel constraint mechanism in the official component diagram, which functions in conjunction with this constraint logic and is part of the structural integrity.

1.4 Hooke hinge: Why must it be at both ends

The strut must become a pure two force rod, provided that neither end can transmit bending moment. If a fixed connection or overly tight pin is used at the end, the strut will be forced to bend when the platform tilts, and the pure tension compression premise will immediately fail, causing all the stiffness advantages in the front to collapse.

Hooke hinges provide two orthogonal degrees of rotational freedom, while not allowing rotation along their own axis or transmitting bending moments. There is one support pole at one end, and the platform can pitch and tilt, while the support pole still only experiences axial force. This is the complete logic of the combination of “three struts+two end Hooke hinges”: the shape of the rod is responsible for tension and compression, and the degrees of freedom of the hinge are responsible for ensuring only tension and compression.

In the official component diagram, item 8 is written as Upper pivot/Hooke’s joint, which simultaneously carries the dual functions of “geometric pivot positioning” and “rotational degrees of freedom”. The spatial position accuracy of the hinge point directly determines whether the platform pose conversion is correct – if the hinge point coordinates in the conversion model do not match the actual object, even the most accurate readings of the three struts will be converted into an incorrect platform position. This is a special requirement for assembly accuracy in parallel structures, and it is also one of the watershed points in maintenance logic between it and Cartesian structures.

1.5 Grating mounted on strut: Drive point and feedback point are of the same origin

The position feedback link of the traditional series structure is very long: the motor rotates once, passes through the deceleration, coupling, screw, and nut before going through a section; If the grating is installed at the end of the screw, it measures the screw angle; If installed on a workbench, it measures the displacement of the workbench, but the driving point is still upstream. Regardless of the arrangement, there are several movable links between the command and the actual situation – the twisting and thermal elongation of the screw, the gap between the coupling, and the crawling of the guide rail.

Equator directly installs the grating on the driving strut. The motor is pushing this strut, and the ruler is also measuring this strut. There is no transmission link in between, feedback is the state of the drive itself, and the two are of the same origin.

From an error perspective, this arrangement simultaneously suppresses three types of problems.

Abbe error perspective. The Abbe principle states that when the measurement axis is not collinear with the measured axis, the deviation between the two will be amplified into measurement error, and the amplification amount is proportional to the offset distance. In traditional structures, there is often a large offset distance between the grating and the probe; The grating on the strut is basically aligned with the axis of the strut, measuring the same axial displacement, and the offset is pressed to a minimum.

Return perspective. The return error comes from all transmission pairs that have gaps and friction. The strut drive does not have a layer of rotation to a straight line, so there is no error source of reverse clearance; The remaining reverse differences mainly come from the small gaps and friction of the hinges, with completely different magnitudes and structures.

Delayed perspective. The ruler is directly attached to the load-bearing component, and the deformation caused by tension and compression of the component is read by the same ruler. This means that structural deformation is not ‘ignored’, but enters the reading – the ruler on the same strut reads the overall length, and the elasticity of the structure itself is contained within this length, rather than being hidden between the ruler and the moving point.

1.6 Conversion Logic from P/Q/R to X/Y/Z (Qualitative)

Don’t push formulas, only talk about logical chains.

The starting point of the chain is three known quantities: the position of the hinge point is fixed, and the distance between the hinge points is constrained by the length of the strut. Given the current length of the three struts, the pose of the platform relative to the fixed end is determined – this is the function of geometric constraints and a typical feature of parallel mechanisms that are difficult to solve in the forward direction and easy to solve in the reverse direction: it is relatively easy to calculate the length of the three struts when the platform reaches a certain point; Conversely, to determine where the platform is based on the length of only three struts, it is mathematically necessary to solve a system of nonlinear equations.

The reason why the correct solution is difficult is that the constraints of the three struts are coupled with each other in space: changing the length of one strut, the displacement of the platform is not only in the direction of that one rod, but also simultaneously adds rotation and translation. The constraint equations of three supporting rods are nonlinear when combined, and usually require iterative solution.

This conversion has three direct consequences for practical work.

Firstly, the coordinates of the hinge point and the length of the strut are two inputs of the same model, and any inaccuracy on either side will contaminate the conversion result. The coordinates of the hinge point depend on assembly, and the length of the strut depends on the grating reading – both are verifiable and re established objects.

Secondly, the error is not scaled proportionally between the support space and the coordinate space. The length error of one micrometer on the strut, converted to the coordinate error in a certain direction of the platform, depends on the current position of the platform and the geometry of the hinge point, with different magnification factors near different areas. This explains why in parallel structures, the diagnostic language for serial structures such as’ one axis inaccurate ‘often fails.

Thirdly, the absolute geometry of the entire machine can be zeroed out by comparing standard components. The positioning of Equator is not “geometrically absolutely accurate”, but “offset measurable and retrievable”. The conversion model of the three poles remains unchanged, but the actual zero point of the machine is re established using standard components, which is the basis for comparative measurement.

1.7 Official component diagram: Explain 15 items one by one

The official installation and controller guide (ID 132816300 and 500 share the same set of part numbers) provides a complete set of component diagrams. The following table explains the structural roles and maintenance significance of each of the 15 items.

Serial number	Official name	Structural role	Maintenance relevance
1	Base casting	The entire machine foundation supports the support arm, drive housing, and parallel constraint mechanism, transmitting the platform and workpiece load to the installation surface	determines the reference rigidity; The deformation of the casting body is a structural problem and cannot be covered up by parameter tuning
2	SP25 probe assembly	Installed under the motion platform, the three-axis analog scanning probe outputs continuous deflection	probe deflection criteria, and the forefront of probe replacement; Fault characterization is often confused with structural problems
3	Floating/moving platform	A moving component supported by three driving rods, with a probe mounted underneath and capable of three-dimensional movement and rotation with the platform	The platform’s posture is determined by the three rods; Loose platform attachments will manifest as global errors
4	Support strut	A set of passive support struts that are different from the driving strut and participate in platform support and attitude constraints	The name is often confused with the driving strut; The two have different functions and cannot be processed on the same rod
5	Top casting	Forming upper and lower frames with the base casting, the upper hinge point and the upper end of the counterweight mechanism rely on this	The upper and lower frames together form a fixed base of a parallel structure, which belongs to the scope of “structural deformation” judgment
6	Drive strut	Three linear drive struts, namely the P/Q/R axis body, on which the linear encoder scale is mounted	Core measuring component; The damage to the grating body is not within the scope of board level maintenance
7	Counterbalance mechanism	Offset the weight of the motion platform and probe components, reducing the continuous load on the drive strut	The internal structure is not officially disclosed; When it manifests as weak/overloaded movements, it must be handled according to official procedures
8	Upper pivot/Hooke’s joint	The two degree of freedom hinge point at the upper end of the strut ensures that the strut does not transmit bending moments; At the same time, it is the geometric reference for pose conversion, and the clearance between hinge points and position accuracy affect the global conversion; Belongs to assembly level rather than component level issues
9	Support arm	Extend upwards from the base to provide a fixed support position for the upper hinge point	Determine the stability of the upper hinge point position; Deformation directly pollutes geometric models
10	– (This item is not listed in the official image)	–	–
11	Drive housing	accommodates the drive part and guide of the strut, and connects the fixed end of the strut to the frame	contains the drive unit inside, which is within the scope of board level evaluation, but needs to be evaluated before making a decision
12	Parallel constraint mechanism	Constraints the platform’s degrees of freedom together with three struts to suppress unnecessary attitude drift	Constraint anomalies will manifest as decreased repeatability rather than single axis deviation
13	Fixture plate	Carrying workpieces and fixtures, 300 is a 305 × 305 mm aluminum plate (41 holes M6/M8/¼ “, optional 441 holes), 500 is a 510 × 510 mm (M8 insert, optional M6/¼”)	Removable parts; Flatness and installation surface cleanliness directly affect the measurement benchmark
14	– (This item is not listed in the official image)	–	–
15	Stop button	Safety stop, part number 300 is A-5504-0255, and part number 500 is A-6078-0259 (distinguished by model, not interchangeable)	Electrical components, replaceable; Belongs to a safety circuit rather than a metering circuit
–	Workpiece and fixture	Installed on the fixture plate, the weight is pressed towards the platform and base by the fixture plate, with a maximum weight of 25 kg for 300 and 100 kg for 500 (including the fixture plate)	Load changes will change the direction of structural deformation; The clamping position relative to the standard part should be ≤ 1 mm

The 10th and 14th items in the table are missing numbers in the official component diagram’s numbering sequence. This table is left blank and will not be filled in for speculation. This is the most easily filled in place when quoting official images – missing numbers are missing numbers.

There is nothing in the structural list of this machine at 1.8

The three negations are equally important because they determine what not to look for when taking action.

**There is no granite base. The official names are Base casting and Top casting, which refer to castings. Granite is the official term used to describe the traditional Cartesian structural features, not the material used for this machine.

No screw, no belt drive. The three struts are linearly driven, and the grating is directly mounted on the struts. Anyone who looks for the “screw nut pair” and “synchronous pulley” in the disassembly diagram is looking in the wrong direction from the beginning.

There is no Z-axis pillar. The Z-axis displacement is synthesized by the coordinated expansion and contraction of three struts. The 205 mm height of the raised type is the height of the working volume from the base, and the Z-direction working volume is still 150 mm – what has been changed here is the installation height, not the stroke.

2. Criterion layer: Translate ‘normal structure’ into measurable criteria

2.1 Characterization of structural faults: first distinguish what it looks like

There is a fundamental difference between the fault characterization of parallel structures and serial structures: if one axis is damaged in a serial structure, the phenomenon is often limited to that direction; Any change in any loop in a parallel structure will affect all directions through the coupling of the three struts. Therefore, the key to the criterion is not ‘which direction is off track’, but ‘whether the way of off track is like a structural problem’.

Characterization	Common Explanation of Serial Structure	Priority Doubt Direction in Parallel Structure	First Step Action
Simultaneous deviation in three directions, decreased repeatability	Rare (except for benchmark issues)	Joint clearance, parallel constraint mechanism, platform attachments	Check repeatability instead of single point deviation
Single point local out of tolerance, other points normal	Local error on this axis	More likely to be probe/needle, fixture or workpiece surface	Prior probe and fixture, then discuss structure
Inconsistent reverse scanning results	Reverse clearance	Friction and small clearance of hinge, improper balance of counterweight	Conduct forward and reverse comparative tests
Repeatability varies with workpiece weight	pre tensioning of guide rail or foundation	elastic deformation of structure varies with load	variable load test
Platform movement is rough and there is abnormal noise	Screw/guide rail lubrication	Drive strut guidance, hinge point lubrication status, counterweight mechanism	Shutdown inspection, do not forcefully operate
Overall increase in comparison uncertainty, decrease after recalibration	Machine drift	Temperature and preheating, structural stress release	Retest according to temperature control and preheating specifications

The core purpose of this table is to correct errors: On Equator, using the diagnostic habit of serial structure for troubleshooting makes it easy to mistake false impressions for conclusions.

2.2 Official publicly available quantitative criteria

There are not many criteria that can be directly referenced in official documents, but each one is a hard line. The table below lists them one by one.

Criteria	Official caliber	Explanation and measurement method
Comparison uncertainty	± 0.002 mm (300/500)	The premise is to measure immediately after recalibration, clamp the position relative to the standard part ≤ 1 mm, and use certified standard parts; This is not an absolute measurement accuracy
Head deflection	≤ 4 μ m	Criteria in the common error table of the usage guide; View path: UCCServer Equator → Advanced → Equator Server → Coordinate Measuring Machine Controller → General → Probe Deflection
Consistency of clamping position	Parts relative to standard parts ≤ 1 mm	Exceeding the limit of position difference will make the calibrated offset unusable
Grating resolution	0.0002 mm (data table aperture)	500 model usage guide has an additional 0.00001 mm aperture, which is inconsistent with the official document; External statements shall be based on random files
Trigger probe trigger speed	Recommended 10 mm/s	Used for TP20 configuration; The force triggered by the measuring point is related to velocity, and excessive velocity can amplify dynamic errors
Maintainability of internal components in the structure	There are no user repairable parts inside the host and controller	The official constraint is that users can repair themselves, not professional repairers; Refer to Chapter 4 Boundary
Only self maintenance items are allowed	Cleaning kit A-5504-9055 (including backup dust filter, prohibited cleaning agent), controller fan filter A-5696-0120 (12 piece set, replaced in high pollution environment for 6 months), and probe inspection	In addition to these three items, the manual permission needs to be clearly defined first

2.3 Establishment of Structural Baseline: Three Required Records

The most difficult part of structural problems is that ‘how much has changed’ cannot be answered because there is never a baseline. It is recommended to collect three records when the machine is in good condition, and use them as a reference for all subsequent judgments.

**First copy: Record of original reading consistency for the three poles. At the same set of calibration points, return to zero multiple times and record the degree of dispersion of the readings in the strut space. This record reflects the consistency between driving and feedback, rather than coordinate accuracy.

**Second copy: Record of positive and negative comparison. Perform approximate measurements in both positive and negative directions at the same batch of points and compare the results. This record best exposes the contribution of hinge friction and clearance, as it is a blind spot in unidirectional scanning.

Third copy: Repetitive record of variable load. Measure the same set of points using two types of loads with significant differences in quality (such as no-load and load close to the upper limit), and compare the repeatability. High load sensitivity indicates that the elastic deformation of the structure is involved in the outcome.

All three records were taken when the machine was operating normally and did not involve any disassembly. Their function is to turn ‘the machine is not working now’ into ‘how much has changed in which link’, which is a prerequisite for whether maintenance can be verified.

3. Disposal layer: force flow analysis and step-by-step disposal

3.1 Force Flow: What is the responsibility of each link from the motor to the workpiece

Understanding power flow is the core methodology of this structural maintenance. The force starts from the motor and is transmitted along the strut, hinge point, platform, fixture plate, and workpiece. Each link has a clear stiffness function and clear failure consequences. Draw the force flow as a line, and there will be a corresponding relationship between which ring is broken and what phenomenon will occur.

Flow process	Bearing form	Stiffness contribution	Failure consequences (sequence of phenomena)
Drive unit (inside the drive strut)	Linear thrust, along the axial direction of the strut	Provides drive stiffness, does not directly determine the measured stiffness	Insufficient thrust or uneven action → Inaccurate positioning, servo error, rough action
Drive strut body	Pure axial tension compression	Main bearing stiffness: shortest load path, highest material utilization	Abnormal rod body/grating → Consistent collapse of omnidirectional accuracy, unable to be restored by parameter tuning
Hooke hinge (both ends)	Two directional rotational degrees of freedom, no bending moment transmission	Ensure the premise of a two force bar; The hinge point position is a geometric reference	clearance or wear → reverse inconsistency, decreased repeatability, attitude drift
Motion platform	Bearing the load transmitted between the probe and the workpiece	Consolidating the axial force of the three struts into the platform pose	Loose platform accessories → Systematic deviation of more than three points, changing with position
Fixture board and fixture	Surface contact force transmission	Determining the stiffness of the connection interface between the workpiece and the machine	Unclean installation surface or uneven clamping → Local out of tolerance, disappearing with reinstallation
Workpiece and installation surface	Tested object and contact interface	Directly affects measurement results, independent of machine structure	Surface roughness or deformation → Single point out of tolerance, repeatability is still acceptable

The most memorable point in this force flow is that the segment with the highest stiffness contribution is also the segment with the highest error amplification factor. The strut and hinge point are located upstream of the force flow, and their changes will be coupled in all directions along the three struts; The fixture board and workpiece are downstream, and the problem is usually limited to specific locations. The order of maintenance and inspection should therefore be from downstream to upstream: first confirm the workpiece, fixture, and stylus, then discuss the platform and hinge point, and finally the strut.

3.2 Step by step disposal process (numbering steps)

The following process does not involve internal disassembly of the aircraft body and is designed in layers based on the official allowed scope and third-party professional judgment capabilities.

Level 1: External confirmation (required after each shutdown)

Power off, gas source does not need to be processed (this machine does not require gas source), confirm that the stop button and safety circuit are normal.
Use cleaning kit A-5504-9055 to clean the work area and dust filter without using any cleaning agents throughout the process.
Check the stylus: whether the ball head is damaged, whether the thread is tightened, and whether the length is consistent with the programming.
Check whether there are chips, burrs, and stains on the installation surface of the fixture board; When reinstalling the fixture board, tighten it in diagonal order.
Record the ambient temperature and continuous operation time to determine whether the preheating and temperature gradient requirements are met.

Level 2: Externally measurable and quantifiable (establishing evidence of phenomena)

Perform repetitive testing: Test the same workpiece multiple times using the same program, record the degree of dispersion, rather than looking at the difference in a single test.
Conduct forward and reverse comparative experiments: perform forward and backward approximations on key features and compare the differences in results.
Perform variable load test: Repeat step 6 with workpieces of different qualities and observe whether the repeatability changes with the load.
Check the deflection of the probe to confirm if it is within the criterion of ≤ 4 μ m, and follow the path listed in Chapter 2.
Organize three records and compare them with the baseline established in Chapter 2 to identify the “stage of change”.

Level 3: Disposal requiring professional judgment

If the phenomenon points to the hinge point/platform/constraint mechanism, first conduct a visual and tactile inspection (for any abnormal noise or obvious clearance), and do not adjust the assembly relationship of the hinge point or constraint mechanism by yourself – such adjustments will change the geometric model and the benchmark must be re established.
If the phenomenon points to the driving strut or grating, stop using and record the phenomenon without disassembling the strut body. The linear encoder scale body belongs to precision measuring components and is not within the scope of board level repair after damage.
If the phenomenon points to the controller side (error, communication, servo abnormality), record the two-stage content of the error message (error type+detection failure item), and evaluate the replaceable parts of the power module, driver board, interface board, connector, fan, storage medium, cable, etc. according to the board level thinking.
After any third level disposal is completed, it must be rechecked: repeatability testing, uncertainty verification, and confirmation of license and software status. Only when all three are passed can it be delivered.

Level 4: Identified as a structural problem

If both the variable load test and the forward and reverse tests indicate structural deformation, first exclude temperature factors (preheating, temperature drift, sudden environmental changes), and then exclude installation and foundation factors.
16. In cases of structural deformation, issues with the upper and lower castings, or the need for original factory calibration or encrypted upgrade packages/license migration, decisions shall be made in the direction of returning to the factory or being handled by official business representatives.

3.3 Safety Tips (Four Not to Skip)

Do not inspect the drive part while it is live.The strut drive part has servo power, and in case of misoperation, the platform will move quickly, with both the probe and hand within the range of travel.

Do not use cleaning agents to wipe the surface of the grating or strut.Officially, cleaning kits are explicitly prohibited from using cleaning agents; Grating is a precision measuring element, and solvent residue can contaminate the reading window.

Do not make any attempts to adjust without recording the baseline.Each adjustment of the parallel structure will affect all directions through coupling, and without a baseline, it is impossible to determine whether the adjustment has been fixed or replaced with a faulty method.

Do not disassemble the counterweight balancing mechanism by yourself.The official listed it as an independent component but did not disclose its internal structure. After disassembly, it lacks assembly basis and may also change the force balance of the platform.

4. Boundary layer: under what circumstances do you not do it yourself

4.1 Accurate Meaning of Official Caliber

The official document states that there are no user repairable parts inside the controller and the host. The original text inside the controller reads’ There are no user serviceable parts inside the controller. ‘The official process is to replace the parts as a whole, and the replacement will be carried out by the business representative.

The object of this sentence is’ user ‘. It constrains the user’s hands-on permissions and defines the boundaries of warranty and liability, rather than describing whether the technology is repairable. Reading it as’ This machine is technically impossible to repair, no one can repair it, and can only be sent back to the original factory ‘is an out of bounds interpretation of the original text.

4.2 What can third-party professional maintenance do

At the component and board levels, the scope of professional maintenance work is clear: power modules, driver boards, interface boards, connectors, fans and filters, storage media, and cables. These are standardized electronic and electromechanical components with traceable specifications, measurable electrical parameters, and replaceable parts of the same specifications.

Three boundaries need to be clarified simultaneously:

Firstly, the warranty status will change.Non original factory repairs will render the corresponding original factory warranty for the component invalid. This must be explained to the user before use, and it is up to the user to decide whether to accept it.

Secondly, repair does not equate to deliverable.After any repair, the machine must be recalibrated – accuracy (repeatability and comparison uncertainty), safety (stopping circuit and limit), and license availability (software license and version verification). If any of these three criteria are not met, the machine cannot be delivered for use.

Thirdly, it is not recommended to handle certain situations externally.Structural deformation, situations that require original factory calibration, scratches on the linear encoder scale body, and controller issues that require encryption upgrade packages or license migration, all lack external feasible means and basis. It is more prudent to make decisions based on the direction of returning to the factory or handling by official business representatives.

Why can’t we apply the experience of lathe and coordinate system to the maintenance of this machine

This is the most important judgment that this article wants to leave for readers.

Experience failure point one: Errors are no longer divided into axes.The maintenance language for lathes is “X-axis reverse clearance” and “Z-axis screw movement”, and the CMM is “indication error of a certain axis”. In a parallel structure, errors in three directions are generated by nonlinear conversion coupling of the same set of struts, and the concept of single axis does not exist physically. Using a split axis approach for troubleshooting can take up a lot of time in the wrong direction.

Experience failure point two: Accuracy does not rely on geometric absolute accuracy.The idea of serial structure is to “adjust the geometry to the most accurate” and use a laser interferometer to point and compensate axis by axis. The accuracy of Equator is based on a comparison mechanism: the machine allows for offset, as long as the offset can be captured and deducted by the standard part. This means that ‘machine absolute accuracy’ is not a necessary condition for its validity, and measuring it using the idea of absolute geometry will lead to incorrect conclusions.

Experience failure point three: The diagnostic language for the transmission link is not applicable.Screw pre tightening, guide rail crawling, reverse clearance, coupling alignment – these words have no corresponding terms on this machine. Instead, there are hinge point clearances, axial states of struts, weight balance, and platform constraints.

Experience failure point four: The coupling relationship between clamping and structure is different.On the CMM, the weight of the workpiece is mainly borne by the worktable, and the relationship between structural deformation and workpiece weight is relatively weak. The workpiece of Equator is pressed against the platform and base by the fixture plate, and the change in load will affect the direction of structural deformation. Therefore, the diagnostic value of the variable load test on it is much higher than on the CMM.

Experience failure point five: The intuition of ‘hard support for large items’ needs to be reversed.When encountering insufficient stiffness, the intuition for serial structures is to “thicken, intensify, and reinforce”. The design logic of this structure is opposite: it relies on the load path and force form rather than the size of the components. Strengthening it often disrupts the balance and counterweight relationship, creating new problems.

5. Verification layer: How to prove the effectiveness of the repair

5.1 Three layer verification: from phenomenon to criterion

Completion of repairs does not mean delivery, delivery requires evidence. The evidence is divided into three layers, passing through each layer.

The first layer: the phenomenon layer.Has the previously reported phenomenon disappeared. This layer is the easiest to pass through, but also the least reliable – the disappearance of phenomena may be covered up rather than resolved.

Second layer: criterion layer.Whether to return to the quantification range provided by the official or baseline. This layer is a hard line and cannot be replaced by subjective judgment.

Third layer: Stable layer.Does it still hold after a period of running time. This layer is the most necessary for parallel structures, as coupling will amplify residual problems in subsequent use.

5.2 Delivery Acceptance Form

Acceptance criteria	Criteria	Collection methods	Record requirements
Repeatability	Compared with the baseline before maintenance, the degree of dispersion has decreased	The same program tests the same workpiece multiple times	Record the mean, range, and number of measurements
Uncertainty comparison	Same measurement level as the official ± 0.002 mm caliber	Immediately measure after recalibration, clamping position relative to the standard part ≤ 1 mm, using certified standard parts	Record the certificate number and date of the standard part
Positive and negative consistency	The difference between positive and negative results returns to the baseline range	Approaching key features in both directions	Recording in different directions without taking the average
Load sensitivity	Repeatability difference between two loads within baseline range	Variable load test	Record the mass of two loads
Head deflection	≤ 4 μ m	View according to official path	Record the original value when viewed
Safety circuit	Stop button action effective	Actual trigger once	Record trigger result
Software and License	Normal Startup, Version Verification Passed	Confirm after Cold Startup	Record Version Number
Environmental conditions	Temperature and gradient meet requirements	Record environmental temperature and continuous operation time	Indicate whether preheating requirements are met

The usage of this table is to fill in once before and after maintenance, and look at the two columns side by side. Only filling in the column after repair is equivalent to no verification.

5.3 A desensitized reconstruction condition

A certain 3C precision structural component factory (anonymous due to customer confidentiality requirements) experienced batch out of tolerance after model replacement. The phenomenon is very typical: three directions deviate simultaneously, and the repeatability also decreases, but the single point deviation is not significant. At first, the on-site investigation was carried out according to the idea of dividing the axis, suspecting the drive in a certain direction, and repeated parameter adjustments were unsuccessful.

Following the process outlined in this article, it was discovered during the first level of external confirmation that there were residual chips on the installation surface of the fixture board, and the clamping sequence was not diagonal. After cleaning and re clamping in the prescribed order, the repeatability significantly decreased, and systematic deviations in all three directions disappeared simultaneously.

The value of this case lies not in the conclusion, but in the sequence: The coupling characteristics of the parallel structure will make a downstream contact problem look like an upstream structural problem. Perform downstream confirmation first, with the lowest cost and highest benefit.

The working condition in another direction is that a certain automotive parts supplier (anonymous due to customer confidentiality requirements) reported poor consistency in reverse scanning. After the first two stages of testing are completed, the positive and negative differences remain stable and are unrelated to clamping, pointing towards hinge friction and balance of weight, and ultimately being professionally handled as needed. This type of problem will not disappear due to recalibration, recalibration can only mask it.

5.4 The Three Most Common Mistakes in the Verification Phase

Replace repeatability with a single difference.The single difference contains too many variables, and the repeatability reflects the inherent state of the machine.

Only test standard parts, not actual workpieces.The standard parts are light and have a regular shape, and the influence of load and clamping cannot be seen. Validation must include workpieces that are close to actual working conditions.

Immediately load and use after repair.Parallel structures require a period of stable state after maintenance, starting with moderate load and conventional point positions, and gradually returning to full load.

Frequently Asked Questions (FAQ)

Q1: Are the three struts of Equator equivalent to the X, Y, and Z axes of the CMM?

No. The three axes of the CMM are perpendicular to each other in space, and their actions do not interfere with each other; The three struts of Equator converge diagonally from the fixed end onto the platform, with P/Q/R being the expansion and contraction amounts of the three diagonal directions. Any movement is the result of the three rods simultaneously changing length and working together to complete it. X/Y/Z are platform coordinates calculated by the control system based on the lengths of three struts, not the three independent directions that actually exist on the machine. This difference determines that the two cannot be applied to each other in terms of error models, diagnostic languages, and maintenance methods.

Q2: Why is it emphasized that the strut is only subjected to tension and compression? Is the bending moment that severe?

Serious. Once the bending moment is transmitted by the strut, the force form changes from pure axial to axial bending, and the stiffness will significantly decrease. The deformation is no longer simply a repeatable elastic elongation, but will introduce hysteresis related to the loading direction. So Hooke hinges must be used at both ends to provide rotational freedom, so that the struts are not forced to bend when the platform tilts. The shape of the rod determines its suitability for tension and compression, and the degree of freedom of the hinge ensures that it is indeed only subjected to tension and compression. Both conditions are indispensable.

Q3: What is the difference between installing a grating on a strut and on a workbench?

The grating on the workbench represents the displacement of the workbench, with the driving point located further upstream and separated by a transmission link; The grating quantity on the strut is the same component as the driving point, and the driving point and feedback point are the same source. This brings two benefits: the Abbe offset is minimized, and the transmission source of return error (the gap between the rotation and the straight line) does not exist at all. At the same time, it also comes with a cost: the elastic deformation of the structure itself will be read by the same ruler, so the structural state must be managed through a comparison mechanism, rather than relying on the ruler to filter out structural errors.

Why are there no items 10 and 14 in the official component diagram?

These two items are missing in the official part number sequence. This article is left blank truthfully and no speculation is made. It is a common mistake to “fill in missing numbers” when referencing official component diagrams – filling in may seem to make the table more complete, but in reality introduces entries that do not exist in the official document. The correct approach in such situations is to retain the numbering and clearly indicate the missing information, so that readers know the original appearance of the original data.

Q5: What is the difference between a strut and a drive rod, and can they be treated as the same?

No. The driving strut is a P/Q/R three-axis body with linear drive, and the grating is mounted on it, which is the core measuring component; The strut is a passive support component that participates in platform support and attitude constraint, and does not undertake driving functions. The official component diagram lists them as item 6 and item 4 respectively. The consequence of confusing these two is that the direction of investigation deviates directly – using the method of driving components to check a passive support component, nothing can be found.

Q6: Since it is a parallel structure, can’t the precision be adjusted according to a single axis?

Yes, it’s not possible. By changing the length of a strut in a parallel structure, the platform not only moves in that direction, but also simultaneously adds rotation and translation, and the constraints of the three struts are coupled with each other in space. Therefore, there is no linear relationship where adjusting a certain element improves a certain coordinate. The correct approach is to treat the machine geometry as a whole, maintained by a set of models based on hinge points and strut lengths, and zeroed by comparing standard parts, rather than compensating by point by axis.

Q7: Can the internal structure of the counterweight balancing mechanism be found?

Officially listed as an independent component, but the internal structure has not been disclosed. This must be truthfully stated: the only thing that can be confirmed is its function – to counteract the self weight of the motion platform and probe components, so that the driving strut does not have to continuously resist gravity; The internal structure shall be based on official data sheets and manuals. Therefore, in terms of maintenance judgment, it belongs to the component that should be handled according to official procedures when the phenomenon points to it, and it is not recommended to disassemble it by oneself.

Q8: What can be used and what cannot be used based on the maintenance experience of this structure and coordinate system?

The usable parts are limited: cleaning and maintenance standards, needle inspection, temperature control and preheating awareness, repeatability and basic ideas for comparative measurement, which are the universal functions of measuring equipment. The parts that cannot be used are all related to the “transmission chain” and “split axis geometry” – screw pre tightening, guide rail crawling, reverse clearance, coupling centering, and axis by axis laser compensation, which do not have corresponding components on this machine. More importantly, the diagnostic sequence should be reversed: the coupling of parallel structures will make downstream contact problems look like upstream structural problems. Checking the fixture and clamping first is often more efficient than checking the structure first.

Data source explanation

The technical parameters and structural description of this article are quoted from the following official documents: Equator 300 data sheet H-5504-8251-06-A (2026-02), Equator 300 specification manual H-5504-8252-04-A, Equator 500 data sheet H-6078-8310-01 (ID 107491), Equator comparator usage guide H-5504-8500 (ID 145539), Equator controller technical specification H-5504-4000-01-A (2011-01), Equator installation and controller guide ID 132816/107657.

The component name and number sequence are taken from the official complete machine component diagram (ID 132816), and 300 and 500 share the same set of numbers; The 10th and 14th items are missing numbers in the official sequence. This article truthfully marks them and does not make any supplements.

There are differences in aperture between official documents, which are explained in parallel in this article. The best option is to choose one: the 500 grating resolution data table is 0.0002 mm, and the usage guide is 0.00001 mm. For external statements, the random file shall prevail; The English document for 300 working temperature is+5~+50 ° C, and the old Chinese version is+10~+40 ° C. The following single version shall prevail.

The two working conditions in the article were reconstructed based on the actual fault types and desensitized. The customer name was requested to be anonymous and did not include any traceable part numbers; Any empirical thresholds involved that are not found in official documents are marked as industry practices and are not referenced as official specifications. The maintainability boundaries of internal components of the machine, as well as changes in the original factory warranty status after repair, shall be subject to official documents and business agreements.

Need a specific repair plan?

Every Equator fault eventually comes down to a specific machine type, duty cycle and batch. The criteria and procedures in this article can be used as a shop-floor checklist; when something does not add up, talk to us directly:

Item	Detail
Company	NINGBO JCE INDUSTRIAL TECHNOLOGY CO., LTD. (JCETech)
Address	Room 12B17, Building 2, Zone A, Ningbo R&D Park, Juxian Subdistrict, Hi-Tech Zone, Ningbo, Zhejiang 315048, P.R. China
Contact	Mr. Li / Mr. Zhang
Phone	+86 157-5780-7400 (Mr. Li), +86 132-2194-1413 (Mr. Zhang)
Online booking	jcetech.cn/contact

Repair intake and on-site service are handled at the same address. Please call before shipping a unit so transport and scheduling do not have to be repeated.