Typical Process Flow

1. Initial Inspection    
The initial inspection evaluates the safety of the casing. A detailed inspection of the casing is the first and very important step in the process of retreading. This guarantees that the carcass is intact and in good condition. If so, it can be used as base for a new retread tire, which also means it can be used for another tire life. Therefore it must be ensured, there are no injuries which might reduce the safety or performance of the retreaded tire. 

To increase quality weusually do operate with three types of inspection:
Visual Inspection– Inspection Spreader KTJ

Inflation Testing Inspection – Pressure Testing Machine CQJ

Non-destructive Inspection - Shearography

Visual Inspection– Inspection Spreader KTJ	Non-destructive Inspection - Shearography

Tire inspection spreader is used to inspect the casing from inside to outside to evaluate the safety of the tire and make the decision whether the tire can be retreaded. Find and mark all visible and repairable defects on the acceptable tires.

Why we need to inspect before retreading?

Tires are collected from various areas and each tire’s condition is different. To ensure the retreading quality of each tire, we must check the collected tires.

Tires are not acceptable if the following conditions happen:

* Sidewall damage is beyond repair limits.

* Bulges caused by separated or broken part of wires on the sidewall.

* Wires of sidewall bruise breaks, contusion and blow outs, etc.

* Bent, distorted, torn, burnt, broken, deformed and excessively senile beads.

* Deep & rusty penetrated steel wire cuts which cause separation.

* Ply separation, excessive damage and extremely large orifice around crown area.

inspecting tire	inspection spreader for Michelin factory

Pressure Testing Machine CQJ is used to test the tire strength and check the tire of air leaks under the high pressure with computer monitor system.

 

Some defects (such as the damage caused by unsubstantial or broken wires) can only be found under high pressure. Inflating pressure into the fixed tire, monitor the surface images on the computer screen.

This machine can be used to inspect precisely the following three parts of tire.

Surface: covering the light damage and cracks.

Shoulder: covering the abruption and cracks.

Sidewalls: covering the invisible cracks, broken, bulges.

2. Buffing 
The primary objective of buffing is to remove the worn tread surface, true up the roundness, and prepare the surface for a new tread. The origin tread design and some of the undertread is removed to provide the casing with the required dimensions and surface texture.

Tire Buffer YLM Front View	Tire Buffer YLM Back View

 

Replaceable Profiling Template

This buffer is designed with profiling template to ensure buff precisely, which can buff the tread with different curvatures based on different needs by changing related template. The replaceable template decides the buffing radius and curvatures. The replaceability improves the performance and ensures the buffer can buff different size tires with different curvatures.

3. Skiving & Repair 
Check the buffed surface and remove all injures identified during initial inspection and replace the material with structurally sound materials that will return the casing to a useful life.

4. Building 
An uncured cushion gum that will develop the bonding between procured tread and casing is applied to the casing. Procured treads are cut to net length, applied and splice on the casing. And the pressing system promote a strong tread-to-casing bond.

Tire Builder YLT Front View	Tire Builder YLT Back View

The tread cutter is fixed on the frame, which consists of the articulated arm and jig saw. It is used to cut the extra flat tread to optimize length at the joint, which is convenient for operating.

5. Enveloping      
In the procured process the uncured cushion compound has to vulcanize while the procured tread has to be kept in position. Therefore the tire is put into an envelope which presses through a vacuum system, the procured tread uniformly on the cushion and the casing.

Horizontal Enveloper (suitable for simple factory layout)	Vertical Enveloper (suitable for whole factory  monorail system)

 

Envelope expander/spreader usually has two mainframes: vertical and horizontal based on clients’ specific needs and technical process. The vertical one usually works together with whole factory monorail system and turntable. The horizontal one works with steel rim loader without whole monorail system.

Turntable (for inside envelope loading)	Steel Rim Loader (for steel rim loading)

6. Curing      
Curing chamber is an autoclave-type device that applies specified heat and pressure, and over a period of time, causes the bonding layer in the built tire to cure, and permanently adheres the new pre-cured tread to the prepared casing.
 

Optional Heating System: With steam (heat conduction oil) or electricity.

 

Dual Control System:

Manual / PLC + manual. Touch screen available (optional).

 

The PLC-controlled curing chamber is with control and functions as follow:

Parameters recorder

Differentiated Pressure Control

Safety Interlocking System

Our curing chamber is completely insulated by multi-layer special aerospace insulation materials and covered with stainless steel, which ensures very low heat loss, high energy efficiency.

  
7. Final Inspection 
To ensure a quality tread each tire passes a thorough inside and outside visual inspection. It is mandatory that the tire meets all customer and government regulations. Some retreaders are also using instrumented inspection like shearography or high pressure testing machine. Unacceptable tires are rejected and scrapped.

hot retreading line

1. Initial Inspection
Initial inspection for regular tires is to do visual inspection, and press testing inspection to make a decision whether the tyres can be retreaded or not.    
Equipments involved:  Inspector KTJ, pressure testing machine CQJ.

2. Buffing 
Buffing is to remove the old, worn tread surface. Before buffing, put tire in YLM and inflate it. Tire will rotate with buffer and tread will be buffed away by YLM to the pre-set arc.     
Equipment involved : YLM buffing machine
  
3. Skiving 
Skiving means polishing the mendable broken parts and then repairing the small holes.
Equipments involved : skiving machine, pneumatic rubber extruder
  
4. Building 
Tire building means gluing cushion gum and suited tread to the polished tire under the help of tire builder.
Equipments involved: latex mixer, YLT builder

5. Curing
Vulcanization is the procedure that bonds the new casing and tread tightly. During the vulcanization the uncured rubber becomes tough and durable tread gradually. Put the prepared casing into the segment press, when the mould close and up to the certain pressure, the casing will be pressed on the mold with set pattern. Then over a period of time, the mold with pattern will be vulcanized.
Equipment involved: KGFL Segment Curing Press and KGL Frame Automatically Hydraulic Curing Press 
Equipment involved: HFL segment curing press, FL two-piece curing press

 6. Final Inspection 
Final Inspection is to inspect all the treated tires thoroughly to make sure high quality.
Equipments involved: Spreader KTJ, CQJ pressure testing machine