Metal Shop Blueprints

One of the core skills of any process in manufacturing is called “print literacy”. Meaning that the person carrying out an operation is capable of reading a blueprint or “drawing” to satisfy the requirements of the part.

Depending on the level of involvement per department in a shop, employees will need to have a more in-depth understanding of blueprints (particularly in a metalworking shop).

The following departments only need to know a portion of print reading.

Laser Operator/Punch Operator

This applies to all CNC (Computer Numerically Controlled) punch and laser machines.

The operator needs to know the following print literacy skills:

  • How to find the material in the notes or material block of the customer provided print/drawing.

This is important because the laser or punch operator much match the proper type and thickness of material with the program provided to them for a particular job. Once they have verified the need to the material, and satisfied that need with the appropriate sheet of metal, they can successfully do their job.

Grinding/Deburring Department

The department is responsible for cleaning up any sharp areas, and putting a preliminary finish on parts that require further process (such as bending).

People in this department will need to know a few things about a blueprint to carry out their position satisfactorily:

  • Did the laser/punch operator use the proper material?
    • The type of material may be difficult to determine, such as 304 stainless steel, versus 316 Stainless Steel; or 6061 Aluminum versus 5052. But, the thickness and basic material differences can be easily determined.
  • Are all features in the cut piece?
    • Surely this could be determined by the laser operator; however, when “feeding the shop”, the laser operator is seldom given time to check over a programmer’s accuracy.
    • Sometimes holes are overlooked by programming and never make it to the laser or the parts. A good employee could quickly glance over the blueprint and check the flat part for any obvious missing elements.
  • Checking the finish block or notes for surface finish requirements.
    • This could vary from a “32 micro” all the way to a #4 grain finish.
  • Do all welds have to be ground flush and burn marks removed? [This will be noted on the drawing in most cases].
  • Were any welds missed?
    • Is the weld pattern appropriate for what is called out on the drawing?
  • What is the next process?
    • While it can be obvious sometimes where a flat part should move to (if the blueprint shows the finished part as a box, then bending in the next stop). Some parts remain flat, others require more attention in areas like milling, welding, pre-finish inspection or paint.

Though the department is often seen as a low-skilled area of many shops, expectations seem to be set higher than you’d think; it’s always good to know more than required.

Press Brake/Bending

A lot of though processing goes into running a press brake, and wrapping your mind (figuratively) around how to make a flat part into a complicated box, bracket or abstract shape that the customer is asking for.

Things on a blueprint that help press brake operators are:

  • Which tooling they should use
    • Some shops will provide tooling suggestions or requirements right on their drawings (this information is typically written in by hand from the programming office, along with bend tolerance and bend allowance).
  • Minimum/Maximum bend radius
    • Many customers add the information onto their blueprints for the acceptable radius on a bend for tolerance purposes.
  • Dimensions of the finished part
    • A press brake operator must be able to determine the overall dimensions, and smaller measurements to satisfy the need of the drawing. Adjustments must be made to get the appropriate dimension in order for the part(s) to be any good.

Apart from the information on the blueprint, the brake operator must also know his/her machine. Sometimes programmers do not think about “tonnage” on a machine. Tonnage makes a difference if a part is long and made of thick material (the machine will not bend it properly and it is dangerous to try and bend without “relief cuts” on thick material that would exceed the tonnage rate of the machine).

Welding

The welding department has their very own requirements for a drawing. The programmer breaks down the parts to be constructed, then has them cut out and bent… But the welder must fit all of the bits and pieces together to bring the part to life.

These fabricators need to fit everything up and hold a tolerance (sometimes an unrealistic tolerance at that!)

The more information they can pull from a blueprint, the better.

  • Overall dimension
    • It’s a NECESSITY. When fitting up parts to be welded together, knowing the final dimensions is important. Parts can be tacked together, then measured before clamping down, and eventually the final weld process.
  • Method of weld
    • Blueprints should call out specific methods of welding (not the type of welder). Methods such as spot weld, plug weld, fillet, etc.
  • Length of weld
    • Yes! Blueprints most certainly should let a welder know if their stitch weld should be three-quarters of an inch every inch, or one inch every five inches.
  • Final use of product
    • Is the product going to be used in the food industry? If so, the welds have to be food grade to limit bacteria. If the product needs to have water tight welds, this information should be on the blueprint as well.

Sure, there are a lot of different variables in the welding department, but they’re simplified with a good blueprint.

The ANSI (American National Standards Institute) and the AWS (American Welding Society) have a complete set of welding symbols published which are used as a standard for draft people creating drawings.

Shipping Department/Quality Control

I’ve lumped these two departments together to save you some time while reading. Since these two departments are held equally accountable for incorrect parts going out the door, it’s only fitting that they know the same information.

They’ll need to know EVERYTHING a blueprint has to offer.

  • Material type and thickness
  • Finish specification
  • Welding requirements
  • Overall dimensions
  • Milling done correctly
    • All holes are tapped to the appropriate thread size and pitch
    • All PEMS are installed
    • Counter bore or countersink processes have been done properly
  • All other processes have been completed satisfactorily including finish

There is a lot of information included in a blueprint, and knowing how to understand the information provided is just as important as the information contained.

It’s my belief that all members of the shop should double check the department before them for accuracy on a part before proceeding with their process.

Checking each other eliminates time and material wasted. Such as bending 300 parts that were the right material, but were sanded instead of grained. Once bent, these parts will be garbage, since applying an even grain to a bent part can very problematic.

Some blueprints are open for interpretation, while others are very black and white, with no grey area whatsoever.

In order to have a properly run shop, all staff should be trained in blueprint reading as it applies to the business. Doing so aids in the ability to cross-train others in multiple departments.

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