DESIGN FOR MANUFACTURABILITY GUIDELINES

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DESIGN FOR MANUFACTURABILITY GUIDELINES
for Sheetmetal 

Bends

• Bends should be tolerance plus or minus one-half degree at a location adjacent to the bends.
• For the ease of manufacturing, multiple bends on the same plane should occur in the same direction.
• Avoid large sheet metal parts with small bent flanges.
• In low carbon steel sheet metal, the minimum radius of a bend should be one-half the material thickness or 0.80 mm (0.03 inch), whichever is larger.

Counterbores

• The minimum distance between two counterbores is eight times the material thickness.
• The minimum distance from a counterbore to an edge is four times the material thickness.
• The minimum distance from a counterbore to a bend is four times the material thickness plus the bend radius.

Countersinks

• The maximum depth is 3.5 times the material thickness at an angle of the hardware.
• A minimum of 50% contact between the hardware and the countersink is required.
• The minimum distance between two countersinks is eight times the material thickness.
• The minimum distance from one countersink and an edge is four times the material thickness.
• The minimum distance from a countersink and a bend is four times the material thickness plus the bend radius.

Curls

• The minimum radius is two times the material thickness with an opening to a minimum of one material thickness.
• The minimum distance between a curl and the edge of a hole is the radius of the curl plus the material thickness.
• The minimum distance a curl should be from an internal bend is six times the material thickness plus the radius of the curl.
• The minimum distance a curl should be from an external bend is nine times the material thickness plus the radius of the curl.

Dimples

• The maximum diameter should be six times the material thickness, and a maximum depth of one-half the inside diameter.
• The minimum distance that a dimple should be from a hole is three times the material thickness plus the radius of the dimple.
• The minimum distance that a dimple should be from the edge is four times the material thickness plus the inside radius of the dimple.
• The minimum distance that a dimple should be from a bend is two times the material thickness plus the inside radius of the dimple plus the radius of the bend.
• The minimum distance between one dimple and another is four times the material thickness plus the inside radius of each dimple.

Embossments

• The maximum depth is proportional to the internal radius or material thickness.
• The maximum depth for a flat embossment is equal to the internal radius plus the external radius.
• The maximum depth for a V embossment is equal to three times the material thickness.

Extruded Holes

• The minimum distance between two extruded holes is six times the material thickness.
• The minimum distance from an extruded hole to an edge is three times the material thickness.
• The minimum distance from an extruded hole to a bend is three times the material thickness plus the bend radius.

Flanges

• The minimum height of a bent flange is directly related to the material thickness, bend radius, and length of bend.
• The minimum width of a bend relief is one material thickness or 1.50 mm (0.06 inch), whichever is greater.

Gussets

• The width and depth, recommended at an angle of 45 degrees, is directly proportional to the radius and material thickness.
• The minimum distance that a gusset should be from the edge of a hole in a parallel plane is eight times the material thickness plus the radius of the gusset.

Hems

• The minimum diameter of a teardrop hem is equal to the material thickness, with a return flange height equal to or greater than four times the material thickness, and a minimum opening of 1/4 of the material thickness.
• The minimum diameter of an open hem is equal to the material thickness with a return flange height equal to or greater than four times the material thickness.
• The minimum return flange height of a closed hem is equal to or greater than four times the material thickness (the diameter is zero). NOTE: Closed hems tend to fracture at the bend and cause entrapment of solutions during the finishing process.
• The minimum distance from a hole to a hem is two times the material thickness plus the radius of the hem.
• The minimum distance a hem should be from an internal bend is five times the material thickness.
• The minimum distance a hem should be from an external bend is eight times the material thickness.

Holes

• The minimum diameter of a hole should be equal to the materials thickness or 1.00 mm (0.04 inch), whichever is greater.
• The minimum distance between holes is directly proportional to the size and shape for the hole feature and the material thickness
• The minimum distance the edge of a hole should be from a form is three times the material thickness plus the form radius.
• The minimum distance the edge of a hole should be from a bend is two times the material thickness plus the bend radius.
• The minimum distance between a hole and the edge of the material is directly proportional to the size and shape of the hole and the material thickness.
• The minimum distance between the leading edge of a hole through a bend should be equal to the thickness of material plus the bend radius or two times the material thickness, whichever is greater.

Lances

• The minimum width of an open lance is two times the material thickness or 3.00 mm (0.125 inch), whichever is greater, with a maximum length of five times the width.
• The minimum width of a closed lance is two times the material thickness or 1.60 mm (0.06 inch), whichever is greater, and a maximum height of five times the material thickness at a 45-degree angle.
• The minimum distance from a lance to a bend in a parallel plane is eight times the material thickness plus the radius of the bend.
• The minimum distance from a lance to a bend in a perpendicular plane is ten times the material thickness plus the radius of the bend.
• The minimum distance from a lance to a hole is three times the material thickness.

Notches

• The minimum width is equal to the material thickness or 1.00 mm (0.04 inch), whichever is greater.
• The maximum length for a straight/radius end notch is equal to five times the width.
• The maximum length for a V notch is equal to two times the width.
• The minimum distance between a hole and the edge of a notch is directly proportional to the size/shape of the hole and the material thickness.
• The minimum distance from a notch to a bend in a parallel plane is eight times the material thickness plus the radius of the bend.
• The minimum distance from a notch to a bend in a perpendicular plane is three times the material thickness plus the radius of the bend.
• The minimum distance beyond the bend on the side edge is equal to the thickness of the material plus the bend radius, or two times the material thickness, whichever is greater.
• The minimum distance between two notches is two times the material thickness or 3.200 mm (0.125 inch), whichever is greater.

Ribs

• The maximum inside radius is equal to three times the material thickness, with a maximum depth of the inside radius.
• The minimum distance from a center line of a rib to the edge of a hole is three times the material thickness plus the radius of the rib.
• The minimum distance a rib should be from an edge in a perpendicular plane is four times the material thickness plus the radius of the rib.
• The minimum distance a rib should be from an edge in a parallel plane is eight times the material thickness plus the radius of the rib.
• The minimum distance a rib should be from a bend perpendicular to the rib is two times the material thickness, plus the radius of the rib, plus the radius of the bend.
• The minimum distance between two parallel ribs is ten times the material thickness plus the radii of the ribs.

Semi-Pierced Hole

• The minimum distance from a semi-pierced hole and a form is three times the material thickness plus the form radius.
• The minimum distance from a semi-pierced hole and a bend is two times the material thickness plus the bend radius.
• The minimum distance between semi-pierced holes is eight times the material thickness.

Slots

• The minimum width of a slot is equal to the material thickness or 1.00 mm (0.04 inch), whichever is greater.
• The minimum distance from the inside surface of a bend to the edge of a slot is directly proportional to the length of the slot, material thickness, and radius of the bend.
• When using slots and tabs the maximum width of the slot must be greater than the thickness of the tab and the tab length should equal the material thickness.

Tabs

• The minimum width is equal to two times the material thickness or 3.200 mm, whichever is greater, while the maximum length is five times the width.
• The minimum distance between tabs is equal to the material thickness or 1.00 mm (0.04 inch), whichever is greater.

Welding

• Spot welding should be restricted to joining coplanar surfaces.
• The minimum distance between welds is 10 times the material thickness. Using 20 times the material thickness is ideal.
• The minimum distance between a weld and the edge is two times the diameter of the spot weld.
• The minimum distance from a weld to a form is the spot diameter plus the bend radius.
• Use PEMs instead of threaded inserts.

Plating

• Outside sharp corners receive twice as much plating as flat surfaces.
• Allow for pitch diameters for screw threads, which can increase four times the plating thickness.
• Tapped holes may need to be re-tapped after plating to ensure accuracy.
• Projections accumulate more plating than other areas.
• Recessed areas may be difficult to plate, resulting in little or no coverage.
• Lap-welded joints trap plating solutions. One solution is to raise welds on embossed areas by 0.015 in. (0.3 mm) to allow for flushing and blow drying between the surfaces.
• Masking of stampings and fabrications to anodize certain areas is not recommended.
• Design drain holes/vent holes for plating solutions and rinsing.
• Design tabs/holes for attachment to part racks.
  
  
  - Uday Mahajan

Design for Assembly and Design for Manufacturing

DFA AND DFM

"Design For Assembly and Design For Manufacturing"

Design for Assembly (DFA) techniques aim to reduce the cost and time of assembly by simplifying the product and process through such means as reducing the number of parts, combining two or more parts into one, reducing or eliminating adjustments, simplifying assembly operations, designing for parts handling and presentation, selecting fasteners for ease of assembly, minimizing parts tangling, and ensuring that products are easy to test. For example, tabs and notches in mating parts make assembly easier, and also reduce the need for assembly and testing documentation. Simple z-axis assembly can minimize handling and insertion times.

The impact of DFA will be found throughout the overall design and manufacturing process. Use of DFA to reduce the number of parts will help reduce inventory, and so will help reduce inventory management effort. As a result, it will support activities such as Just In Time (JIT) aimed at improving shop-floor performance. Use of DFA to develop modular products making use of common parts will allow the variety desired by Marketing while limiting the workload on the Manufacturing function. Modular sub-assemblies can be built and tested independently. Model variations can be created at the subsystem level.

A variety of DFA checklists and guidelines is available. They provide statements of good practice, and prompt the designer to check, for example, that the number of parts in a sub-assembly is below a certain limit, that no unwieldy assembly operations are required, and that the number of different types of screws has been minimized. DFA is also supported by computer programs that assign scores to products as a function of their ease of assembly, and estimated assembly cost and time.

Companies using DFA techniques have reported reducing the number of parts, the number of assembly tools, the number of assembly operations, the assembly space, the number of suppliers, and the assembly time by up to 85 %.

Design for Manufacture (DFM) techniques are closely linked to Design for Assembly techniques, but are oriented primarily to individual parts and components rather than to DFA's sub-assemblies, assemblies, and products. DFM aims to eliminate the often expensive and unnecessary features of a part that make it difficult to manufacture. It helps prevent the unnecessarily smooth surface, the radius that is unnecessarily small, and the tolerances that are unnecessarily high.

The DFA objective of reducing the number of parts may lead to highly integrated, complicated, multi-functional parts. DFM aims to keep individual parts simple, because overly complicated parts can have hidden costs that are not initially apparent.

DFA and DFM are closely linked to EDM/PDM and concurrent engineering. Designers should be able, through the EDM/PDM system, to access information that will help them improve the design of the part they are working with. They will be able to call up computer programs that can analyze the current state of their design, point out where the design is too complicated, and indicate possible areas of improvement. DFA and DFM are best carried out at the conceptual design stage, before major decisions about product and process characteristics have been finalized. At this early stage of the design, there may not be a lot of information to work with, but the EDM/PDM system will make sure that whatever information exists can be made available to the product team. 

So in conlusion I can say following are the steps/point to be taken care for DFA and DFM:

• Simplify the design and reduce the number of parts.
• Standardize and use common parts and materials.
• Design for ease of fabrication.
• Design within process capabilities and avoid unneeded surface finish requirements.
• Mistake-proof product design and assembly.
• Design for parts orientation and handling.
• Minimize flexible parts and interconnections.
• Design for ease of assembly.
• Design for efficient joining and fastening.
• Design modular products.
• Design for automated production.
• Design printed circuit boards for assembly.     

Tips for Running Project Meetings

Tips for Running Project Meetings

Everyone dislikes meetings that drag on. So your job is to make it focused, highly driven and to add a sense of purpose. If you do this, then you’ll boost team motivation and morale. Here are 5 tips to help you...

Tip 1: Plan wisely

To make sure you get the most out of your meetings, you need to plan them wisely. Prior to each meeting, write down 3 goals that you want from the meeting. Here are some examples:

• "I want the team to know we're on track"
• "I want any issues or risks to be raised"
• "I want them to feel valued and motivated"

Then you need to work out how you're going to achieve your goals. The next few tips will help you with this...

Tip 2: Open and close carefully

Like in theatre, people most remember the opening and the closure the most. So open and close your meetings carefully. When you open the meeting, tell them what the purpose of the meeting is, what you want to get out of it and why it's important. This gets their attention and sets the scene. When you close the meeting, tell them what has been agreed / achieved in the meeting and the next steps going forward.

Tip 3: Control the conversation

You need to be in complete control of the meeting at all times, to ensure that:

• The meeting follows the agenda
• You never get stuck on a single issue
• One person doesn't dominate it
• Everyone has their say

Start by standing or sitting in a prominent place in the room. Raise your voice a little to add presence. Jump in frequently when people talk too long. Be polite but strong. Control the meeting as a coach would control a football team - by constantly watching, listening and directing the team. If possible, ask someone else to record the minutes. This gives you the time needed to control the conversation so that the agenda and your 3 goals are met.

Tip 4: Park it and move on

Often in meetings, a single issue can consume the majority of the meeting time. If the issue is not related to your specific meeting goals, then tell the team to "park it and move on". Record the issue on a whiteboard or paper and address it with the relevant team members separately after the meeting. This keeps your meetings short and focused.

Tip 5: Keep it action orientated

Projects are all about "getting things done". So make sure that where possible, every discussion results in an action to be completed. Focusing on the actions that are needed, is a great way of reducing the length of meetings.

- Uday Mahajan

Deliver your Projects Faster

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Deliver your Projects Faster

Here are 5 tips for delivering projects faster...

Tip 1: Find Shortcuts in your Plan
Project Managers usually spend 80% of their time executing and 20% planning. The reason is that the Execution phase is where the excitement is, so they roll their sleeves up and get started executing as quickly as possible.

But if you spend extra time in the Planning phase, then you can usually identify shortcuts which enable you to produce the same project outcome in less time.

So when you think your project plan is complete, take extra time to re-look at your plan from the point of view of delivering it faster. By doing this, you'll find that you can schedule things to be done in a way that takes less time, with less effort.

Tip 2: Automate Manual Tasks
You need to automate your manual daily tasks to help you do things faster. Here are some of the manual tasks that many Project Managers do each week that could be automated using project software:

• Summarizing data for your Weekly Status Reports
• Collating Timesheets and Expense Forms
• Updating your Project Plan with timesheet data
• Working out whether the project is on track
• Reporting on risks, changes and issues.

You don't need to perform these tasks manually. You can invest in project software to do all this for you. Your team will enter the data you need and the software will group and summarize it all for you. All you need to do is run reports and view the current status of your plan to ensure it remains on track.

Tips 3: Manage Execution Carefully
When your project gets underway, manage your project against the plan vigilantly. It’s easy for the plan to sit on the shelf, and for the team to go in their own direction. Instead, you need to lead the team by making sure they complete only those tasks which have been planned, and not other tasks which have cropped up along the way. So manage the project execution carefully. You can also save time in the Execution phase by:

• Working your suppliers and contractors hard
• Mitigating risks and issues before they affect the timeframe
• Saving all non-critical tasks until after the project is complete
• Not allowing unplanned tasks to be completed, unless critical
• Not implementing change requests, unless they are critical.

Tip 4: Double up on Resources
Usually, the easiest way to shorten the length of the project is to assign more resources to it. However, this isn’t possible for many projects because they have a limited budget and a limited pool of resource.

But that's not to say that you can't double up on resources for the right tasks. It just means that if you do this, then other tasks will be under-resourced. So why would you do this?

In most projects there are tasks on the “critical path” that must be completed to deliver the project. If you assign more resources to these tasks than are necessary, you can usually complete them earlier than expected. And it makes sense that if every critical path task is completed faster, then the entire project will be delivered quicker than expected.

Tips 5: Get the Critical Tasks done first
In many projects the last 20% of tasks, take 50% of the length of the project. This is because the team have left the difficult tasks until the end, which happens to be when they are tired and need a holiday!

Instead, identify the tasks in your plan which are the most complex and challenging to complete. And if possible, tackle those tasks at the start of the project, when people are fresh and enthusiastic. You’ll find that they can complete those tasks in less time and to a higher standard of quality than if they were left until the end of the project. And with those difficult tasks completed, the rest of the project should be easier to deliver.

- Uday Mahajan

5 Steps to Hiring the Right Staff

To ensure you hire the right staff for the right roles, take these steps:
1. Define the Role
Sounds easy, but defining the role properly is the most important step to take when recruiting new staff. You need to create a Job Description document that describes the:

• Purpose and responsibilities of the role;
• Reporting and communication relationships;
• Skills, experience and qualifications needed;
• Team fit and performance criteria;
• Salary, rate, commission and benefits; and
• Work environment and special conditions.

2. Find Top Candidates
Next, advertise the role both internally and externally. Make your advert as specific as possible by listing the key responsibilities. Explain the challenges that they will face. List any special requirements. Make it sound enticing, but don’t oversell it.
Then while the adverts are running identify your selection criteria for interviews, based on the characteristics in the Job Description.
When the adverts close, review your list of applicants against the selection criteria and choose between 3 and 5 applicants to interview.
3. Interview Candidates
Next, interview the selected candidates. Make sure you prepare fully for each interview, so don't just "wing it". For every interview, you should:

• Prepare a list of questions before you start.
• Cover all areas of the Job Description during the interview.
• Address any strengths and weaknesses from their CV.
• Consider the quality of the questions they’ve posed to you.
• Be specific, direct and to the point at all times.

Don't be afraid to take notes during the interview. You will find that if you're interviewing more than 3 candidates, you will need to rely on the interview notes heavily when progressing to the next stage.
4. Test Candidates
Depending on the type of role you're recruiting for, you may also want to formally test your candidates. Here are 10 ways that you can test candidates to determine their suitability against the Job Description:

1. Perform personality, competency and numerical testing.
2. Get them to send samples of work completed in the past.
3. Ask them to perform specific project tasks. For instance, if hiring a software developer, get them to write you an example program.
4. Perform a second interview with management.
5. Get them to meet the team and allow the team to ask questions.
6. Take them for lunch with your team and see how they socialize.
7. Get them to do a formal presentation to your team.
8. Seek 3 professional references, all from past employers.
9. Ask them for 2 personal references, for character checking.
10. Speak to their prior customers to confirm their competency.

5. Select Candidate
Based on the interview and test results, the next step is to select the right person for the job. If you have a number of people that you can't decide between, then here are your options:

• Hire neither and start again. It's difficult to do this as you've put in a lot of work to get to this point. But it may be better to start again than hire a candidate who will not meet your needs fully.
• Hire both and deliver earlier. In some cases you can split a Job Description in two and allocate the responsibilities to more than one person. It's challenging and risky doing this, but in some cases you can deliver the project earlier and at the same cost by hiring 2 gifted candidates at the same time.
• Select the best candidate. In most cases you're landed with this option. If both candidates are "on an even par", then don't pass the decision on to someone else, go with your gut feel. We could give you numerous statistical testing methods to choose the right person, but at the end of the day they have to be able to do the job and fit in with your team—and only you will know which candidate is best to do this.

- Uday Mahajan