Automated Line Bender

Arduino-controlled Automated Line Bender for Acrylic

Originally presented by Chris Lehenbauer from Phase Dock Inc. at the 2019 Bay Area Maker Faire, California, this series will help guide you through the design and execution of a controller for automating different processes, including light industrial automation.

<<Access MORE DETAIL as an Instructable>>

Submitted: March 2021. The additional details will (hopefully) make it easier to build the Line Bender of your Dreams!

Use the Phase Dock User Group to bring your questions and comments to me and to our community.

PART 1: INTRODUCTION TO LINEBENDING

Part 1 of a 5-part series on automating a Plexiglas/acrylic linebender with a simple Arduino-based controller.

This video introduces you to the process of linebending acrylic sheet (Plexiglas), and describes the components of a manual linebender.

PART 2: ARDUINO CONTROLLER COMPONENTS

This video discusses readily-available, low-cost components that can be used to build an effective automation control based on an Arduino microcontroller.

PART 3: BUILDING THE CONTROLLER

In this video we assemble an Arduino-based automation control for a Plexiglas linebender in real time.

PART 4: UNDERSTANDING THE CODE

In this video we take a look at the concepts and logic used in the controller’s code.

Understand the Code

Download the code to control a Line Bender

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PART 5: TIPS FOR BUILDING THE LINE BENDER

I’m happy to share some photos and some tips about the design and construction of a line bender. It really isn’t that complicated, and I put it together after scouring the web and YouTube, of course….

I slapped my first version together in a couple of hours. Just treat it as an iterative exercise and you will be able to decide the size and angles that will best fit your purposes.

Two-sided linebender lets you set-up for different angles This is handy, but make sure your power supply can support the longer/double length nichrome wire.

Some pointers:
I use good multi-ply “blondewood” plywood from Lowe’s/Home Depot for the main construction. In addition, I used two layers for the main body, because you want it to be both strong and stiff.

I used 2x4s as legs so I have clearance to use ViseGrip welding clamps to hold my workpieces. I also use drill press clamps a lot.

The hinges are from Lowe’s, but you can find similar hardware at most building supply stores:

I use their 4″ strap hinges, but I recommend that they are the heavy-duty, tight-pin hinges like these.
I find that the plastic spacers keep the hinge from being sloppy, so the hinge stays consistent on the bend.
I hacksaw off the straps because the straps only need to be about an inch long past the pin, not the full length. That still leaves you two screws in each leaf of each hinge.

I use the Lowe’s aluminum channel to shield the nichrome wire. I think this is 5/8″ wide stuff. That gives you a nice radius on the acrylic bend.

I’m using magnetic catches on these angle stops. Be sure they always seat at the same place. These have some give, and they weren’t designed to be precision instruments, but they work pretty well.

IMPORTANT:

Get all your nichrome wire from the same source. I recommend Jacobs Online, mostly because they can give you all the gauges you want, in order, without skipping them.

Make sure to install a spring on one end of each nichrome wire. The nichrome expands so much when it heats that you need the spring to keep it tight. You don’t want it to droop or touch your workpiece.

Shoot for 6 to 6.5 watts/linear inch of nichrome. It should take about 2 to 3 minutes to heat up a bend in 1/8″ acrylic sheet. This is a good power level to let the heat soak through the sheet without boiling it on one side.

TIP:

Think of it like cooking on a grill: too hot and the outside of your meat gets black, while the inside might still be “frozen.”

What you want is a slow, even heating that gets the acrylic soft enough to make a good bend, avoids carrying material stresses into the bend (by forcing a bend in material that is not fully softened), but you also want a process that isn’t so hot that the acrylic starts to bubble/boil. It’s a fine line to walk…and it may take a number of test runs before you get the magic combination for your application and the thickness and color of the acrylic you are working with.

I would definitely recommend a 24V DC power supply; 12V pushes too many amps for those little relay boards to take.