How to Make Concentric Reducer Flat Pattern Using Free Download Plugin in Autocad + Reducer Flat Pattern Calculator

Guide and Tutorial Video of How to Make Concentric Reducer Flat Pattern

Tutorial Video

You can watch how to use this plugin in our YouTube channel. Do not forget to like and subscribe :).

Have you ever felt confused fabricating concentric reducer? Do not know how to start?

Now, you can start from drawing the reducer flat pattern less than 1 minute, as long as you have an autocad program. Because we provide you a free download plugin to automatically draw your flat pattern reducer.

Magic Free Download Plugin for Drawing Reducer Flat Pattern

What is a Reducer and Its Flat Pattern?

The reducer which is stretch to a flat pattern is a 2D image of the surface of a 3D reducer. This stretch pattern will be used as the base for fabricating the reducer.

Autocad Guidence:

Free download and activate the magic plugin:

1. Click the DOWNLOAD REDUCER FLAT PATTERN PLUGIN (file will be in ZIP format).
2. Extract the ZIP file and use the FAS file.
3. Upload the FAS file into AutoCAD with the APPLOAD command or you can also drag & drop the file into your autocad worksheet.
4. Tip: If the folder window does not appear, type FILEDIA, and then enter the number 1.

Drawing reducer flat pattern using plugin

• Type CR in any place and then press enter.
• Enter the larger diameter of the reducer, and then enter.
• Enter the smaller diameter of the reducer, and then enter.
• Enter the height of the reducer, and then enter.
• Click to define the midpoint.
• Reducer flat pattern drawn automatically just less than one minute. That is how the magic works.

Reducer Flat Pattern Material Calculator

Calculates material requirements based on the height and width of the reducer flat pattern layout. It provides high accuracy for estimating and purchasing departments. This will be the real needs of the material requirement, based on my experience

Is the Concentric Reducer is the Most Popular Fitting?

In the world of piping and ductwork, the concentric reducer reigns supreme compared to its sibling, the eccentric reducer. The reason is simple, symmetry.

The concentric reducer features a single straight centerline running from the large end to the small end. This perfectly truncated conical shape allows fluid or air to flow more stably with minimal turbulence—especially in vertical piping runs.

This inherent advantage is what makes it superior to the eccentric reducer. Just imagine, for instance, any reader of this post who works in purchasing or procurement, or frequently sources fittings—you’ll rarely find suppliers stocking large quantities of eccentric reducers, whether in iron, PVC, PPR, or stainless steel.

If some of you, EngPocket users, are working on a piping project involving pump discharge, mastering how to fabricate this type of reducer is essential.

An error in determining the taper angle of a concentric reducer can lead to excessive back pressure that may damage downstream equipment.

With the CR (Concentric Reducer) plugin we invented above, we can ensure that the transition from the larger to the smaller diameter is geometrically precise. Manual calculations are no longer necessary, we’ve simplified the entire process for you.

The Challenge of Manual Reducer Fabrication Without a Plugin

Before the advent of advanced software or plugins like engPocket’s, reducer fabrication relied on manual layout methods drawn directly onto the workshop floor using chalk and a large trammel or compass. We had to calculate the slant height of the conical frustum (S) using the Pythagorean theorem:

To calculate the value of s, use the formula: s equals the square root of t squared plus the square of half the difference between D and d. Mathematically, this is expressed as:
$s=\sqrt{t^2+{\left(\frac{D-d}{2}\right)}^2}$s=t2+(2D−d​)2​

After that, you must calculate the development angle (θ) using the formula: θ equals 360 multiplied by D divided by 2, then divided by s. In other words:
$\theta =\frac{360\times (D\mathrm{/}2)}{s}$θ=s360×(D/2)​

Imagine how time-consuming this would be if we had to perform these calculations for many of different sizes in a single day.

A single miscalculation of the angle could result in a wrong cut metal plate that fails to meet its edges when rolled into shape. This plugin reduces that complex mathematical workflow to mere seconds.

Fabrication Tips After the Development Pattern Are Ready

Even though the plugin delivers an accurate flat pattern layout, several technical fabrication considerations must be observed to ensure a perfect concentric reducer:

• Plate grain direction: When cutting steel plate (such as BJLS or carbon steel), align the rolling direction perpendicular to the plate’s grain direction. This helps achieve a smooth, uniform curvature without kinks or distortions.
  
  
• Weld seam allowance: Plugins typically provide net dimensions.
  
  
• Always remember to add a seam allowance—approximately 10–20 mm—along both straight edges of the flat pattern to accommodate welding joints or lock-seam forming.
  
  
• Rolling process: A concentric reducer cannot be formed using a standard rolling machine in a straight pass. Due to its fan-shaped curvature, one side of the plate must be restrained during rolling so the material bends progressively as pressure is applied.
  
  
• This technique demands a skilled operator with considerable experience.

By understanding the theory behind concentric reducers and leveraging this plugin tool, you—as EngPocket users—can effectively bridge the gap between the engineering team responsible for design and the fabrication team executing the work on the shop floor.