Case Study: Rosewood Furniture Co. Quality Issues

Case Study: Rosewood Furniture Co. Quality Issues

 

Instructions

 

Your report must use a range of reference material (academic journals and books) and show clear evidence of your thinking through detailed critical evaluation.   Your report can include case study evidence. Any sources you have used to compile your reports such as journal articles, reference books, web pages, etc. must be properly referenced in the Harvard style.

 

Your submission for this assignment should be in the form of one report, approximately 3000 words. Supplementary diagrams may be included if necessary providing they are correctly cross referenced.

 

 

 

 

 

Assignment:

 

Quality managers and professionals in industry are often asked to evaluate their current approach to quality management and assurance by investigating what other tools, techniques and technologies are available to support the development of the quality function.  Modern measurement practices such as scanning; co-ordinate measurement machines are common choices along with new approaches to quality assurance such as Poke-Yoke, Robust Design, SPC/Six Sigma, QMS software.

 

In addition, Industry 4.0 is regarded as the next-generation of modern tools and techniques to support manufacturing, including quality assurance, utilising the internet of things and cloud infrastructure, big data and sensor technology for predictive process control.

 

For your assignment please address the following questions.

 

Q1 Write a review on the development of modern quality practices from the 1950’s to the present day, including the benefits and the problems of each strategy. In particular you will need to discuss:

 

  • The way that the adoption of quality standards and models has supported the adoption of modern quality practices [25 marks]

 

  • The way in which modern measurement technologies and QMS software have enabled quality departments to support manufacturing [15 marks]

 

  • The key organisational enablers and barriers to the adoption of modern quality management                                                                         [10 marks]

 

 

Q2. Write a detailed overview of Industry 4.0 with respect to data management and sharing from a quality management point of view. Your answer should include key sub-components such as sensor and in process measurement data, inspection records, process control and feedback, 3D virtual data, QMS software, ERP and communications through the supply chain.

 

  • Overview of I4.0 and impact upon quality [20 Marks]
  • Utilisation of CAD, QMS and ERP software in managing requirements of

Quality Standards                                                 [15 Marks]

  • Integration of sensor and in process measurement data within process control and correction [15 Marks]

 

 

 

 

 

          

Submission Details and Dates

 

What and how you are required to submit

 

Each individual is required to submit one report/portfolio which must contain all of the above sections.

 

All submissions are to be made electronically via Canvas and Turnitin.

 

Avoiding Plagiarism Accusations

 

Please note that whilst some notes and materials will be provided to support this task it is expected that you will carry out your own research and use a variety of information sources to complete the task. However, all of your work must be presented in your own words and not taken directly from any other source. All sources you have used in your search must be clearly and appropriately referenced using the Harvard referencing system and a list of references included in the back of each submission. Using sources which have not been appropriately referenced or taking any data directly from any source which you include in your work will be regarded as plagiarism and may result in you failing this part of the report or even the whole module. It is acceptable to use quotes, photographs and/or diagrams from other sources, where appropriate, but these must be properly referenced. Any quotations you wish to use from external sources must be less than 200 words in total for any submission of your report and again must be cited and referenced correctly. All quotations must be shown within quotation marks.

Case Study: Rosewood Furniture Co. Quality Issues

The basic flow for furniture production is shown in Figure 1.  All of the parts and/or raw materials are kitted together and issued according to the MRP date. The materials then wait to be processed on a pallet identified with a Works Order label. Production volumes vary but are 100 tables per week on average. The factory works five days per week, giving a cycle time of approx. 24 minutes, and a month can be assumed to be four weeks.

Figure 1: the basic production flow

The sub assembly process carries out some basic machining of legs and side panels on Routers, Lathes and drills.  No formal checks are carried out on parts entering the system as it is assumed that the pallets will have no shortages.  The leading hand points out they do not always get a parts list anyway but when issues are found they feed this back to the stores informally. The wooden parts are then finish sanded before the various pieces of hardware such as captive nuts, brackets, etc. are inserted into the semi-finished parts and then all of the parts are collected together with any parts unused in this operation and sent onto the final assembly and finishing operation.

The finishing stage paints and lacquers the furniture parts in three different colours.  These are then assembled together to ensure that the threads are not blocked before disassembly.  All parts are then packed including any loose hardware such as nuts, studs, washers, etc.  Each piece of furniture has a basic spanner and instruction leaflet printed in the appropriate language included in the packaging.

Some problems found at finishing

This operation complains that semi-finishing often send parts that have missing inserts, holes out of position or missed, parts that have not been sanded, dust on parts, missing hardware or scratched parts.  When they spot issues they correct these and feedback informally.

Inspection and despatch

A percentage of boxes are opened and audited prior to despatch.  A number of issues have been found of late.  The details of these have been included in a report circulated to the factory managers on a monthly basis.

Some of the problems found at final inspection

This month the following are typical issues:

  • Legs a different colour to top
  • Missing screws in assembly
  • Missing parts oHardware x 3 oLeg x 1 oBrass foot x 2
  • Missing tools
  • Scratches
  • Incorrect paperwork (instructions)

Bill of Materials for Table

Part Description Number Required Source
Table top 1 In house
Leg 4 In house
Captive nut (two per leg) 8 Purchased part
M8 Stud x 60mmm (two per leg) 8 Purchased part
M8 Nut (two per leg) 8 Purchased part
M8 Plain Washer (two per leg) 8 Purchased part
Angled Bracket (one in each corner of table top) 4 Purchased part
Brass Feet (One per leg) 4 Purchased part
Spanner 1 Purchased part
Instruction Leaflet 1 In house

Table 1: Rosewood Furniture Co. Table BOM

Non-conformance procedures

When problems are found in despatch, the whole consignment is quarantined and inspected.  This inevitably takes time and on average delays despatch by one day.  Costs for re-packing are £0.50 per carton but customers are becoming increasingly concerned by delayed deliveries as most of the furniture is bought online and despatched against a promise date.  Thus customers arrange to be off work to meet the delivery which then fails to arrive.

Other problems

Customers are reporting that the tables have uneven legs and “wobble”.  After several customer visits it has become apparent that the problem is not caused by faulty assembly by the customer.  It appears to be due to:

  1. The leg lengths varying excessively
  2. The positions of the captive nuts varying by +/- 1mm
  3. The angled brackets that hold the legs to the table tops being out of position by +/- 2mm. This in turn means the holes through which the leg studs go are out of position by a similar amount.
  4. The hole positions in the angled bracket vary by +/-1mm

The use of brass feet, which have felt pads, is supposed to mitigate these process issues but clearly does not.  Some “wobbly” tables have been reported at final assembly but little formal investigation has been carried out.

The design manager has insisted that the problem lies in manufacturing and has responded by tightening the dimensional tolerances for the table as follows:

Table legs are cut on a band saw.  The new tolerance for the length of these is +/- 1mm

There are two holes that are drilled into the tops of each leg to take the captive nuts. The position of these holes is dimensioned from to bottom of the leg.  The new tolerance for these holes is +/-

0.8mm.  The legs are 1200mm in length

The angled brackets are pushed into slots located in the underside of the table top. These are cut by routers during the semi finishing process. If the slots are not cut deep enough the bracket will sit higher than desired.  If they are cut too deep then the bracket will be pushed too far towards the table top.  In both cases this will lead to the vertical position of the holes that are designed to take the M8 studs to attach the legs varying.  In extreme cases the leg will appear too short on one corner and too long on another. The revised tolerance for these slot depths has been set at +/- 0.5mm.

The holes in the angled brackets are dimensioned from two datum edges to ensure that they are central and equally spaced in the bracket. The positions both horizontally and vertically have a tolerance of +/- 0.5mm.  Inspection studies carried out at Rosewood Furniture has shown that the position of these holes varies and some are out of tolerance.  The supplier disputes this finding saying that their measurements show the holes are consistently within tolerance.

An exploded diagram of the partial assembly is shown in figure 2.

Issues with revising the tolerances

Operators have pointed out that the router depth is set manually using a “fence” or rule.  The angle fixture has not been calibrated.

The sawing operation is carried out by pushing the uncut leg against a stop and cutting by eye using a band saw.

Drilling is carried out using a drill jig that sets to hole positions from the opposite end to the drawing datum, i.e. the top of the leg instead of the bottom.  This would be fine if the leg length could be guaranteed.

The Angled Brackets are made from strip mild steel material that the supplier sources but does not cut. There is only a nominal tolerance to the width of the strip of +/- 0.5mm.  As they are expected to be symmetrical attention has not been paid to the orientation of them as they are inserted. See figure 3.

Figure 3: Drawing of the Angled Plate

 

Data from these operations

Tables 3 and 4 contain the data from the leg sawing operation and the overall width dimension of the angled brackets.

Leg Cut Length
Sample Number Average Range
Sub Group 1 2 3 4 5
1 1201 1202 1199 1198 1202 1200.4 4
2 1201 1202 1200 1199 1198 1200.0 4
3 1201 1201 1202 1199 1202 1201.0 5
4 1200 1200 1202 1202 1199 1200.6 3
5 1199 1199 1199 1200 1201 1199.6 2
6 1198 1200 1202 1201 1199 1200.0 4
7 1199 1200 1200 1201 1202 1200.4 3
8 1200 1201 1201 1202 1200 1200.8 2
9 1198 1199 1199 1200 1201 1199.4 3
10 1199 1199 1200 1200 1201 1199.8 2
11 1201 1202 1202 1200 1201 1201.2 2
12 1199 1199 1198 1198 1199 1198.6 1
13 1199 1200 1201 1200 1202 1200.4 3
14 1198 1200 1200 1201 1201 1200.0 3
15 1200 1201 1201 1202 1200 1200.8 2
16 1199 1199 1198 1200 1201 1199.4 3
17 1199 1200 1200 1201 1202 1200.4 3
18 1198 1197 1200 1201 1201 1199.4 4
19 1200 1199 1200 1201 1198 1199.6 3
20 1201 1201 1199 1200 1199 1200.0 2
X Bar-Bar R Bar Sigma hat
1200.1 2.9 1.25
Cp 0.27
Cpk 0.24

Table 3: Leg Length Capability Study

 

Angled Bracket Strip Width
Sample Number Average Range
Sub Group 1 2 3 4 5
1 70.0 70.0 70.1 70.3 70.3 70.14 0.3
2 70.1 70.5 70.2 70.0 70.2 70.2 0.5
3 70.5 70.5 70.4 70.3 70.2 70.38 0.3
4 70.1 70.2 70.2 70.4 70.1 70.2 0.3
5 70.5 70.4 70.3 70.1 70.1 70.28 0.4
6 69.8 69.6 69.7 69.9 69.5 69.7 0.4
7 70.1 69.6 69.9 70.0 70.3 69.98 0.7
8 70.1 70.2 70.3 70.0 70.1 70.14 0.3
9 69.8 69.9 69.5 69.6 69.8 69.72 0.4
10 70.3 70.5 69.9 70.1 69.9 70.14 0.6
11 69.6 69.7 70.0 70.0 69.9 69.84 0.4
12 69.9 70.0 70.1 69.9 70.3 70.04 0.4
13 69.8 69.8 69.9 70.1 70.1 69.94 0.3
14 69.7 69.7 69.9 69.8 69.8 69.78 0.2
15 70.2 70.3 70.4 70.0 70.1 70.2 0.4
16 69.6 69.8 70.3 70.2 70.0 69.98 0.7
17 69.8 69.6 69.8 70.1 70.2 69.9 0.6
18 70.2 70.3 69.9 69.7 70.1 70.04 0.6
19 70.4 70.2 70.3 70.1 70.0 70.2 0.4
20 69.6 69.7 69.7 69.9 69.8 69.74 0.3
X Bar-Bar R Bar Sigma hat
70.0 0.425 0.19
Cp = 0.88
Cpk = 0.88

Table 4: Angled Bracket Capability Study

 

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