Prolean’s Machining Standard

We follow the GB/T19001-2016/1S09001:2015 Standard in our machining process, you can check our certification below, for more information, you can check the CNCA official website.

GENERAL TOLERANCE

For manufacturing, we provide two types of tolerance standards: “General tolerance” and “Tight tolerance.” We use the general tolerance if no tolerances are specified on the drawing. If you want tighter tolerance for your parts, ensure that you have specified the position and features where you need tighter tolerance in the technical drawing.

Thread tolerances

We provide four different standards for thread: UNC, UNF, Metric, & NPT.

UNC: UNC is the standard thread defined by the Unified Thread Standard (UTS). It is suitable when your project needs liberal tolerance for the assembly. UNC threads are commonly used in general applications.

UNF: It is also a Unified Thread Standard (UTS) defined standard. – This standard is known as the designation for Unified Fine Thread standard.

Metric: Metric standards for threads are defined according to ISO 261 and 262 & tolerances are based on ISO 965

NPT: NPT refers to National Pipe standards, and threads under these standards follow ANSI/ASME B1.20.1

We do not accept ACME or Thor-labs thread standards, but we still consider NPS, NPTS, STI, and BSP according to our client’s requirements. Therefore, we suggest specifying the standard thread specification while submitting the drawing for a quote request.

Metric Tolerances

If the tolerance of threads is not mentioned on the drawing you sent us, we maintain tolerance according to ISO 965-1 for your parts. This standard thread tolerance is for both internal and external threads (6H for internal threads & 6g for external).

Under ISO 965-1, there are three thread tolerance class designations: high, medium, and low if you’re drawing or requirement doesn’t provide such information. As a default, we’ll utilize medium class.

UNC & UNT

Without a tolerance specification, we adhere to the thread tolerance ASME B1.1-2003 standard for UNC & UNT threads, 2A for external threads, and 2B for internal threads.

Visual Inspection and Protection

Consistent visual Inspections are carried out to ensure the parts match the models, have the required Surface quality, contain all the features, and are defect-free. Quality control personnel perform a visual inspection for each item.

We provide two different surface finish standards and guarantee them through visual examination. We evaluate the finish to see whether it meets your requirements or not.

Cosmetic: A cosmetic finish is a consistent surface finish without aesthetic flaws on the primary side of parts. It Guarantees the uniform visual of parts.

Non-Cosmetic: This term relates primarily to aesthetic appeal. However, minor visual flaws and surface blemishes may be present.

Constant visual inspection conditions

The quality of surface finish (Cosmetic & non-cosmetic) will be ensured by visual inspection under the following conditions.

Quantification of cosmetic surface quality

We check the surface to ensure that there are no scratches, scuffs, staining, blemishes, hanging marks, or other minor imperfections on the surface. After that, we examine the following factors to verify that parts from each batch are aesthetically consistent.

•  There is no difference in surface colour among the identical parts.
•  For surface polishing (sanding or brushing), we use the same grit and ensure the brush marks go in the same direction.
• Gloss units are uniform across the batch.

Process requirement

• The same manufacturing procedure, setup, and instructions are used for the whole batch. However, it might merely be changed to raise the quality.
•  Raw material from the same batch will be used to maintain uniform properties.
• The pieces won’t ever contact each other after they’ve been cleaned and de-greased.
• The same grit of sandpaper will be used in the same direction for the primary surface polish. In the case of bead blasting, all parameters will be the same.
• All batch parts will undergo secondary surface finishing simultaneously within the factory.
• Workers will wear gloves to prevent fingerprints and other markings on the surface. In addition, we believe pieces should be packaged one by one.

Parts cleaning & protection

Primary cleaning

We follow the same process for primary cleaning of parts from corrosive and non-corrosive material that involves removing dust, oil, chips, burrs, and sharp edges of parts.

• Sharp edges will be chamfered with a size of 0.25 ±0.125 mm, maintaining a uniform appearance.
• Hand tools will be used if we find chamfer the small edges difficult with a machine tool.
• Deburring will apply to internal threads, bores, and blind holes with the help of deburring tools.

As we offer the deburring standard of 0.25 ±0.125 mm, please specify if your parts need to be deburred beside this during the quote request. Our engineers will consult you before proceeding with the manufacturing. We have two options;

•  Deburring + Sharp edges
•  Deburring + Rounded Edges

Protection

Non-Corrosive Materials

Parts from non-corrosive materials such as plastic and fibres get de-greased after machining, so go with a simple cleaning process with alcohol. While proceeding with cleaning, if the inspection team found chips, burrs, and cutting fluid marks on the surface, they reject those parts and send them to the primary finishing stage.

Corrosive Materials

Parts will be cleaned by dipping them in corrosion inhibitors such as WD 40 and ITW RP 631oil to prevent corrosion. These forms of inhibitory oils will create a thick surface covering.

Parts will then go through multiple layers of packing to protect them. We won’t use multilayer packing immediately; the first parts will be vacuum-dried.

Our standard defect comparison books have guidelines that specify the Level of the defect (AQL: Cr 0 M 2.5 m 4: Acceptable quality level is 2.5%, which means up to among the samples, 2.5% defective pieces are acceptable)

We considered a discrepancy according to the customer’s requirements and technical standards.

• Minor defects: Negligible effects on the aesthetic appeal but no effect on the functionality of parts
• Major Defects: Can cause disturbance for parts during assembly or in end-applications
• Critical defects: These not only affect the functionality of parts but can cause harmful or hazardous situations during end-use applications.

We will communicate the outcome to the customer for possible disposal if the parts do not satisfy the customer specification or Prolean standards.

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