Number of views: 5067 Author: Aili Industry Release time: 2027-04-21 Source: Ai Li Industrial
The difference between customized EFU and standard models is most directly reflected in the mounting hole positions. The hole position of the standard EFU follows the universal module, and the equipment factory can open corresponding holes in the sheet metal to install it; the hole position of the customized EFU must follow the structure of the equipment mounting surface, and the position, hole diameter, and hole spacing of the fixing ears may be non-standard. If the hole positions on the confirmation diagram are only marked with coordinate values and no reference or tolerance, the EFU processed from the sheet metal may not be installed on site - if it is 1 mm different, the bolts will not be able to pass through. To confirm the mounting hole position of the customized EFU, what needs to be done is to align the datum plane, hole spacing tolerance, fixing method and sealing surface on the same confirmation drawing, instead of just giving the supplier a sheet metal drawing of the equipment and waiting for the goods.
The most common problem with the hole position marking of customized EFU is that the datum is not uniform. The hole positions on the equipment factory's sheet metal drawing may be based on the lower left corner of the mounting surface. If the EFU supplier's confirmation drawing is based on the center line of the box, the coordinate values on both sides will be different. The first step to confirm the hole location is to on the confirmation drawing clearly mark the reference plane or line , and let the equipment manufacturer and EFU supplier use the same reference.
For device-side EFU, it is usually recommended to use the mounting surface as the benchmark. The mounting surface is the surface that fits the sheet metal of the device. The coordinates of the hole positions are derived from the two adjacent sides of the mounting surface, which is most intuitive. If the EFU box has folded edges or flanges, the benchmark should be the plane inside the folded edge, not the outside of the folded edge - the outside of the folded edge is affected by sheet metal bending rebound, and the dimensional consistency is not as good as the inner plane. In the customized EFU project, Aili Industrial organizes the confirmation drawing according to the equipment drawing. The datum plane, datum edge and coordinate direction of the installation hole position are marked on the drawing one by one to avoid misalignment between processing and assembly.
The length and width of the customized EFU can be given a tolerance of ±1-2mm, but the mounting hole spacing is a matching dimension, and the tolerance must be tightened. The result of the hole spacing being out of tolerance is very direct: the holes do not match up, and either the holes are expanded or the box is forcibly installed, causing the box to deform and the sealing surface to fail.
should be listed in a separate category on the confirmation drawing The hole spacing, hole diameter, and hole position coordinates , and tolerances tighter than the outer dimensions should be marked. The hole diameter is usually 0.5-1mm larger than the bolt diameter as an assembly allowance, but the tolerance of the hole spacing should be controlled within ±0.5mm. The specific value depends on the processing accuracy of the equipment mounting surface and the bolt specifications. If the holes on the sheet metal of the equipment factory are laser cut or punched out by CNC, and the hole spacing has good consistency, the hole spacing tolerance on the EFU side can be ±0.5mm. If the equipment mounting surface itself is a welded structure with large thermal deformation, more margin needs to be left for the EFU hole position, or waist-shaped hole compensation can be used instead.
An easily overlooked detail is the way the mounting ears are connected to the cabinet . If the fixed ears of the customized EFU are welded to the box, the post-weld deformation will cause the hole position to shift; if it is punched after bending and forming, the hole position accuracy depends on the stability of the bending size. When confirming, the supplier should be asked to explain the molding process of the fixing ears. The welded parts need to be processed with holes after welding, rather than punching holes first and then welding.
Mounting holes do not exist in isolation. When the EFU is fixed on the equipment mounting surface, the pretightening force of the bolts will press the box against the sealing strip or gasket. If the hole distribution is unreasonable - for example, the distance between the fixed points is too large, or the fixed points fall outside the sealing path - the box will be partially warped after being fixed, the sealing surface will not be pressed tightly, and the airflow will leak from the bypass.
When confirming the hole position, you should look at three things at the same time: whether the fixed point falls on the rigid structure of the box (near the structural ribs and folded edges, not in the middle of the thin plate), the relative position of the fixed point and the sealing path (the fixed point should be close to the sealing path, so that the pressing force acts directly on the sealing surface), and whether the fixing sequence affects the sealing (when fixing multiple bolts, tighten them symmetrically from the middle to both ends to avoid one side of the box being pulled and deformed first). Aili Industrial's ultra-thin EFU uses a customized brushless DC motor and a dynamically balanced impeller. When customizing the box structure, the internal stiffener arrangement can be adjusted according to the fixed point position of the equipment installation surface, so that the fixing force is transmitted to the rigid parts of the box instead of allowing the sealing surface to bear deformation.
After the customized EFU arrives, the order of inspection of the installation holes should be the holes first and then the sealing surface . If the hole position is wrong, the device cannot be installed, and the inspection of the sealing surface is meaningless.
Specific actions: Use a tape measure or caliper to check the hole spacing and hole diameter, and compare it item by item with the confirmation drawing; place the EFU loosely on the equipment mounting surface, and check whether all bolts can pass through the holes freely without reaming or tapping; if there is a hole that does not match up, check whether it is a hole spacing problem or a deformation of the equipment mounting surface itself. After the hole position is confirmed, check the sealing surface: with the sealing strip or gasket installed in place, use a flashlight to shine from one side and observe whether there is a light-transmitting gap from the other side; or use a feeler gauge to check the gap between the sealing surfaces. If the gap exceeds the allowable range of the sealing strip compression, it needs to be adjusted.
For customized EFU, the confirmation drawing is the only basis for hole location acceptance. The hole position table of the standard model cannot be used for acceptance comparison of customized projects. In the supply of customized EFU, Aili Industry organizes the complete machine configuration according to the confirmation drawing. The mounting hole positions, fixed lug positions and sealing surface structure are marked one by one in the confirmation drawing. The measured hole positions during prototype or first unit verification are compared with the confirmation drawing, and the batch execution is based on the same benchmark.
It should be avoided to only give coordinate values without marking the reference plane on the confirmation drawing. It should be avoided to mix the hole distance tolerance and the external dimension tolerance. It should be avoided to punch the fixing lug first and then weld, which will cause the hole position to shift after welding. It should be avoided to only look at the hole position without checking the sealing surface compression status. It should be avoided to use the standard machine hole table to accept the customized EFU. The core of custom EFU mounting hole position confirmation is not 'holes are drawn on the drawing', but the datum, tolerance, fixing and sealing surface form a closed loop on the confirmation drawing that can be processed, assembled and accepted.
What is the general hole spacing tolerance for customized EFU?
The hole distance is recommended to be within ±0.5mm, and the hole diameter is 0.5-1mm larger than the bolt diameter. If the equipment mounting surface itself is greatly deformed, waist-shaped holes can be used for compensation, but the adjustment direction of the waist-shaped holes must be indicated on the confirmation diagram. The appearance length and width tolerance can be relaxed to ±1-2mm, but it cannot be mixed with the hole spacing tolerance in the same mark.
What should I do if the equipment factory sheet metal drawing and the EFU confirmation drawing are inconsistent with each other?
Use the actual mating edge of the equipment mounting surface as a unified reference, and mark the coordinate conversion relationship between the equipment side and the EFU side on the confirmation drawing. The safest approach is to ask the EFU supplier to redraw the hole layout of the equipment mounting surface on the confirmation drawing and mark the datum and tolerances instead of directly citing the coordinates of the equipment sheet metal drawing.
The hole positions don’t match up but they’re not much different. Can the holes be enlarged?
Not recommended. Hole expansion will destroy the anti-corrosion coating or plating around the hole, and may also produce metal shavings contamination on the equipment end. If the deviation is within 0.5mm, you can check whether the bolt specification is too large; if it exceeds 1mm, it should be returned to the supplier for correction or redoing according to the confirmation drawing. The condition of the sealing surface cannot be guaranteed after forced expansion and assembly.
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Check items |
Confirm key points |
|---|---|
datum |
The installation surface is used as the reference, the inside of the fold is not the outside, and both sides are unified. |
Hole spacing tolerance |
Within ±0.5mm, marked separately from the appearance tolerance |
Fixed ear technology |
Process the holes after welding instead of punching first and then welding |
Fixed and sealed linkage |
The fixed point is close to the sealing path and falls on the rigid structure of the box |
Arrival inspection sequence |
First, make free holes to check the hole position, and then check the sealing surface for light transmission or feeler gauge. |
Aili Industrial's 70mm ultra-thin EFU supports customization of non-standard sizes and installation hole positions. The position of the fixing lugs and the box reinforcement structure can be adjusted according to the actual hole layout of the equipment mounting surface. The installation hole positions, fixing lug technology and sealing surface structure are marked one by one in the confirmation drawing. For customized EFU projects, Aili Industries organizes prototype verification according to the confirmation drawing, the measured hole position data is archived together with the confirmation drawing, and batch execution is based on the same benchmark.
Learn about Aili Industrial EFU products and customized configurations. Check out the compact models.70mm ultra-thin EFU , the entire machine structure can be viewedEFU equipment fan filter unit , non-standard interfaces and hole positions can be viewedCustomized EFU , control scheme can be viewedDC speed regulating EFU equipment fan filter unit . Please submit the equipment installation hole location map, sealing method and estimated quantity to facilitate confirmation of hole location benchmarks and fixing plans.
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