As the geometric reference origin of the whole inspection system, ultra-precision granite inspection bases have completed nanometer-level surface grinding and full metrology verification before leaving the factory. Many on-site commissioning personnel simplify installation and leveling as “leveling and locking support points”. They finish delivery once the horizontal reading meets the standard. However, after a period of operation, problems such as micro-deformation of the reference surface, plane deviation and unstable repeated positioning accuracy of equipment occur. Most of these issues are not caused by product quality defects, but because hidden and easily overlooked details during installation and leveling are not properly handled. Based on abundant on-site service experience in semiconductor, optical inspection and CMM projects, ZHHIMG Group (ZHHIMG®) sorts out the core points that are most likely to be neglected in the installation and leveling of granite bases.
Verification of the underlying foundation condition is a pre-inspection item often skipped. Most on-site installers only check whether the ground at the placement position is flat, ignoring hidden risks brought by long-term foundation settlement and uneven hardness of ground layers. Although the surface of ordinary workshop floor looks solid, the lower structure has insufficient bearing capacity and will undergo slow uneven settlement under the dead weight of granite bases. Such settlement will not appear immediately, but gradually expand after the equipment runs for months, directly damaging the horizontal state and reference surface of the base. ZHHIMG’s on-site specification requires that before the base is in place, in addition to visual inspection, engineers need to evaluate foundation pouring thickness, underground pipeline distribution and foundation creep caused by start and stop of large surrounding equipment. For heavy granite bases, foundation bearing capacity tests shall be carried out when necessary. Areas with backfill and expansion joints should be avoided to prevent later foundation deformation from transferring to the stone.
The force uniformity of support arrangement is prone to the misunderstanding that “qualified horizontal reading equals balanced force”. During on-site leveling, operators tend to adjust support screws according to spirit level readings and consider installation finished once horizontal values are acceptable. In fact, overload on single support points will introduce additional stress inside granite. When superimposed with residual stress released before factory delivery, it will lead to slow arching deformation of the plate surface. Granite inspection bases adopt statically determinate multi-point support logic. Support positions cannot be arbitrarily added, removed or shifted. Gaskets with different materials or thicknesses cannot be mixed. Skewed shims or undersea pads will form stress concentration points. ZHHIMG technical team will verify the bearing status of each support point one by one on site to ensure uniform load distribution and avoid excessive local compressive stress, preventing external load from forcibly acting on the granite base.
Thermal soaking for thermal balance of the base is a step frequently cut short to save construction time. Many projects rush the schedule and start leveling immediately after the granite base arrives on site. Although granite has a low thermal expansion coefficient, there is temperature difference between the factory constant-temperature workshop, long-distance transportation, outdoor storage and customer site. Temperature gradient forms inside the stone and causes temporary micron-level warping. The horizontal data obtained under such condition is only a false steady state. After the stone temperature gradually matches the on-site environment, the base shape rebounds and the horizontal reference drifts. ZHHIMG requires that after the base is positioned, it must stand still on site for sufficient time to achieve overall thermal equilibrium. Leveling can only start after the temperature difference across the plate surface is controlled to a tiny range. Leveling shall be suspended if ambient temperature and humidity fluctuate sharply in a short time.
Evaluation of surrounding vibration sources is rarely checked synchronously during leveling. People focus on the horizontal condition of the base itself, ignoring that surrounding vibration will interfere with the authenticity of leveling readings. Low-frequency vibration generated by workshop air compressors, conveyor lines, fans, gantry equipment and adjacent machine tools will transfer to the base through the ground. Electronic level readings keep fluctuating, so commissioning staff can only adjust repeatedly and obtain unstable leveling results. The impact of vibration will not disappear after leveling. Continuous micro-disturbance during subsequent equipment operation will reduce the repeat accuracy of inspection equipment. During on-site service, ZHHIMG will survey vibration sources around the base in advance. Vibration isolation measures will be added if needed. Leveling work will be arranged at time slots with minimum environmental disturbance to guarantee reliable and valid horizontal data.
Recheck sequence and full-area reference verification after leveling are often simplified as single-point horizontal inspection. Traditional inspection only reads horizontal data at the center of the base plate, ignoring the correlation between different areas of the base. The value of granite inspection bases lies in the geometric benchmark of the whole plate. Qualified horizontal data at the center alone cannot guarantee stable geometric status of the full surface. After fastening the supporting structure upon leveling, acceptance cannot be done immediately. Tightening support screws will bring minor force changes. Recheck of plate horizontal condition and flatness at multiple points shall be conducted after standing for a period. The data will be compared with original factory metrology files to confirm no new deformation is introduced. ZHHIMG guides customers to complete multi-point cross verification and record full reference data after leveling, establishing on-site reference files for regular comparison and timely detection of tiny reference changes. 
Tightening method and anti-loosening treatment of supporting fasteners are easily overlooked details. Many commissioning personnel tighten all support bolts at one time with high torque. Excessive force pushes up the base and causes local bending of the stone. Granite is brittle. Excessive concentrated jacking force may not only induce deformation, but also create hidden cracks in severe cases. Support adjustment screws shall be tightened in a stepwise, diagonal and low-torque cycle way instead of applying large jacking force at once. Meanwhile, vibration in workshop will gradually loosen screws. ZHHIMG recommends reliable anti-loosening solutions and regular inspection of fastener status to prevent support point loosening and force redistribution.
Surface protection and surrounding environmental control are often neglected after leveling is finished. During leveling, metal debris, oil stains and coolant can easily fall onto the granite reference surface and penetrate tiny pores of the stone, leading to local hygroscopic expansion and damaging plate flatness. Many teams do not protect the benchmark plate during leveling. They clean the reference surface after equipment assembly. At that time, contaminants have permeated into the stone and can hardly be removed completely. ZHHIMG suggests covering protective plates during the whole leveling and equipment assembly process and removing them only after completion. The installation area should be kept clean and dry.
In summary, installation and leveling of granite inspection bases is far more than simple horizontal calibration. Horizontal reading is merely a superficial indicator. Easily overlooked factors including foundation condition, support force balance, thermal equilibrium, vibration interference, recheck logic, fastener operation and surface protection jointly determine the long-term reference stability of the base. With rich experience in ultra-precision project implementation, ZHHIMG Group keeps controlling every detail in installation and leveling workflow, avoiding reference drift caused by improper on-site installation, and supplying long-term stable granite reference bases for semiconductor inspection, AOI, CMM and laser measurement equipment.
Post time: Oct-13-2026