I have been a regular to this forum and used a lot of information I found here for my own personal projects. I finally decided to become a member and share my experiences with everyone. I, like many of you, have spent countless hours researching the process, design, and build of a hydraulic tubing bender. It seemed cumbersome at first but it all started to come together. I'm good with CAD and have and engineering/design background which has helped. This thread is different in that it isn’t progressive. The bender is complete and in action. Ill add photos and answer questions as I have time.
Why did I choose to design a vertical tubing bender over a horizontal? The answer is simple... space savings. The likely hood of bending something that would hit a shop ceiling of 10' or even 8' was unlikely. Also the ability to go vertical would allow me to use a digital degree finder rather than a degree wheel.
I started the process by trying to learn about hydraulics. There are lots of sporadic sources for information on hydraulics but I found none specifically directed towards tube bending. I searched for different formulas that would enable me to design my bender to the following specs:
1. 2" OD x .250" wall 4130 chromoly steel
2. Bend 180°
3. Use as small of an electric motor that would meet my needs
Capacities / Calculations
It was complicated to find all the formulas for the job so I made my own excel calculator spreadsheet to help those who want to build a hydraulic tubing bender out. The intent is a one stop shop to choose the parameters to design your own bender and make inputs giving you an idea of what tubing size and thickness does to hydraulic pressure and horsepower based on hydraulic cylinder size and stroke. PM me and Ill email it to you.
Pump
Through my research I discovered that a 2 stage hydraulic pump commonly used in log splitter applications would be a perfect match for a tube bending application. The 2 stage pump allows for a smaller capacity horsepower motor to get the job done. The one I chose was a 2 stage 11gpm capacity. It is capable of 3000 psi but I didn’t want to operate anywhere close to those pressures. At a pre-set 780 psi, the pump goes from 11gpm flow to 2gpm. This allows for rapid speed up to 780psi and steps to the 2nd stage for larger capacity steel tubing using a smaller HP electric motor. To give you an idea, the bender I designed can bend 1.625" x .083" chromoly 90° in 6 sec at 290psi at 2.0HP. The same 1.625" x .083" chromoly bent 90° now takes 30 sec at 290psi but only 0.37HP.
AC Electric Motor
With my tube capacity requirements defined and the use of a 2 stage pump, a 2 HP motor was the choice. I chose to get a 220v motor over a 110v for lower amperage and longer life. The motor needed to be 3600 rpm to match the designed specs of the hydraulic pump.
Cylinder / Control Valve
I needed to be able to bend greater than 90° in a single stroke of the ram to account for tube spring back. With the swing arm having a center pivot (center of where die mounts) to the cylinder ram pivot point being 15.75", I used a series of arcs in CAD to determine the cylinder retracted and extended lengths. A 3.5" cylinder exceeded my max tubing capacity requirement with the stroke needing to be 24". I needed to be able to extend the ram and retract it therefore a dual action cylinder was my choice. With the pump constantly pumping while the motor is running, the hydraulic fluid needed to be an open flow system to keep the pump cool. This is where the valve selection became important.
The valve is a 4 way, 3 position directional control valve, lever actuated, tandem center (pressure open to tank with ports A & B blocked in the center position). The tandem center spool is primarily used with double acting cylinders. Spring centered (spool will return to neutral when the handle is released). The valve needed to meet or exceed the 11gpm and 3000psi requirements of the pump. I chose a valve that flows 12 gpm and has a max 4600 PSI operating pressure.
Reservoir
The reservoir was an area that needed to be closely researched. The hydraulic pump is kept cool by the fluid. I need to have a capacity that would allow for full extension of the cylinder, fluid in the lines and pump, and an excess to keep the system cool. I went with a 5 gallon capacity. I converted gallons to cubic inches and needed a particular width to be able to mount on the mainframe in front of the uprights. Knowing the length and width, I figured the height to meet the 5 gallon capacity.
Mainframe / Uprights / Swing Arm
I looked at the different brands/designs of benders and it quickly became obvious that the pro-tools style 105 was the most common. The die selection is the most comprehensive offered by any company at a price that I could afford. Now that I had a die design to fit my needs and budget, I had to figure out what the spacing was on the holes and what made the bender mainframe and swing arm hole spacing capable of using a wide variety of dies with different centerline radius's. I found a drawing that had the straight line spacing for each hole spaced off the center of the pivot pin. I went to work drawing up the swing arm and mainframe uprights in CAD. I worked out the math on the stresses that would be applied to the swing arm and main frame at my max capacity and chose to go over the minimum requirement for a long life. The mainframe is 3/4" steel plate and the swing arms are 1/2" plate. I added 1/8" doublers for added strength around the pin holes. I wanted to be able to use the bender sitting on a short roller shop stool. This allows me to sit and work at an eye level and keep the bender closer to the ground rather than the ceiling (the whole point in going vertical rather than horizontal). The uprights are 36" tall. The mainframe needed to house an electric motor, hydraulic pump, reservoir, cylinder, valve and filter. It also needed to be portable to move around the shop. I used steel swiveling caster wheels for ease of movement. Also I installed leveling feet for precise rotary bends. I mounted the reservoir on the front. The length of the mainframe was tailored to the hydraulic cylinder retracted length at an angle that allowed full extension of the 24" ram to pivot the 15.75" swing arm greater than 90°. I wanted the bender to look clean. I bent the support legs 90° to give clean lines. The enclosure is 16ga aluminum.
This isn’t much detail but enough to give a guy the thought process and level of detail required to design and build his own bender. The machine weighs just over 300lbs. It is a hoss that will last forever. I'm in the process of building another with a few upgrades and modifications to include a rotary indexer, a redesigned reservoir and going electronic with the valve and use a HMI display to control the ram movement using micro switches. Also in the works are 2 different endmill notchers and a full electronic rotary bender.
Why did I choose to design a vertical tubing bender over a horizontal? The answer is simple... space savings. The likely hood of bending something that would hit a shop ceiling of 10' or even 8' was unlikely. Also the ability to go vertical would allow me to use a digital degree finder rather than a degree wheel.
I started the process by trying to learn about hydraulics. There are lots of sporadic sources for information on hydraulics but I found none specifically directed towards tube bending. I searched for different formulas that would enable me to design my bender to the following specs:
1. 2" OD x .250" wall 4130 chromoly steel
2. Bend 180°
3. Use as small of an electric motor that would meet my needs
Capacities / Calculations
It was complicated to find all the formulas for the job so I made my own excel calculator spreadsheet to help those who want to build a hydraulic tubing bender out. The intent is a one stop shop to choose the parameters to design your own bender and make inputs giving you an idea of what tubing size and thickness does to hydraulic pressure and horsepower based on hydraulic cylinder size and stroke. PM me and Ill email it to you.
Pump
Through my research I discovered that a 2 stage hydraulic pump commonly used in log splitter applications would be a perfect match for a tube bending application. The 2 stage pump allows for a smaller capacity horsepower motor to get the job done. The one I chose was a 2 stage 11gpm capacity. It is capable of 3000 psi but I didn’t want to operate anywhere close to those pressures. At a pre-set 780 psi, the pump goes from 11gpm flow to 2gpm. This allows for rapid speed up to 780psi and steps to the 2nd stage for larger capacity steel tubing using a smaller HP electric motor. To give you an idea, the bender I designed can bend 1.625" x .083" chromoly 90° in 6 sec at 290psi at 2.0HP. The same 1.625" x .083" chromoly bent 90° now takes 30 sec at 290psi but only 0.37HP.
AC Electric Motor
With my tube capacity requirements defined and the use of a 2 stage pump, a 2 HP motor was the choice. I chose to get a 220v motor over a 110v for lower amperage and longer life. The motor needed to be 3600 rpm to match the designed specs of the hydraulic pump.
Cylinder / Control Valve
I needed to be able to bend greater than 90° in a single stroke of the ram to account for tube spring back. With the swing arm having a center pivot (center of where die mounts) to the cylinder ram pivot point being 15.75", I used a series of arcs in CAD to determine the cylinder retracted and extended lengths. A 3.5" cylinder exceeded my max tubing capacity requirement with the stroke needing to be 24". I needed to be able to extend the ram and retract it therefore a dual action cylinder was my choice. With the pump constantly pumping while the motor is running, the hydraulic fluid needed to be an open flow system to keep the pump cool. This is where the valve selection became important.
The valve is a 4 way, 3 position directional control valve, lever actuated, tandem center (pressure open to tank with ports A & B blocked in the center position). The tandem center spool is primarily used with double acting cylinders. Spring centered (spool will return to neutral when the handle is released). The valve needed to meet or exceed the 11gpm and 3000psi requirements of the pump. I chose a valve that flows 12 gpm and has a max 4600 PSI operating pressure.
Reservoir
The reservoir was an area that needed to be closely researched. The hydraulic pump is kept cool by the fluid. I need to have a capacity that would allow for full extension of the cylinder, fluid in the lines and pump, and an excess to keep the system cool. I went with a 5 gallon capacity. I converted gallons to cubic inches and needed a particular width to be able to mount on the mainframe in front of the uprights. Knowing the length and width, I figured the height to meet the 5 gallon capacity.
Mainframe / Uprights / Swing Arm
I looked at the different brands/designs of benders and it quickly became obvious that the pro-tools style 105 was the most common. The die selection is the most comprehensive offered by any company at a price that I could afford. Now that I had a die design to fit my needs and budget, I had to figure out what the spacing was on the holes and what made the bender mainframe and swing arm hole spacing capable of using a wide variety of dies with different centerline radius's. I found a drawing that had the straight line spacing for each hole spaced off the center of the pivot pin. I went to work drawing up the swing arm and mainframe uprights in CAD. I worked out the math on the stresses that would be applied to the swing arm and main frame at my max capacity and chose to go over the minimum requirement for a long life. The mainframe is 3/4" steel plate and the swing arms are 1/2" plate. I added 1/8" doublers for added strength around the pin holes. I wanted to be able to use the bender sitting on a short roller shop stool. This allows me to sit and work at an eye level and keep the bender closer to the ground rather than the ceiling (the whole point in going vertical rather than horizontal). The uprights are 36" tall. The mainframe needed to house an electric motor, hydraulic pump, reservoir, cylinder, valve and filter. It also needed to be portable to move around the shop. I used steel swiveling caster wheels for ease of movement. Also I installed leveling feet for precise rotary bends. I mounted the reservoir on the front. The length of the mainframe was tailored to the hydraulic cylinder retracted length at an angle that allowed full extension of the 24" ram to pivot the 15.75" swing arm greater than 90°. I wanted the bender to look clean. I bent the support legs 90° to give clean lines. The enclosure is 16ga aluminum.
This isn’t much detail but enough to give a guy the thought process and level of detail required to design and build his own bender. The machine weighs just over 300lbs. It is a hoss that will last forever. I'm in the process of building another with a few upgrades and modifications to include a rotary indexer, a redesigned reservoir and going electronic with the valve and use a HMI display to control the ram movement using micro switches. Also in the works are 2 different endmill notchers and a full electronic rotary bender.
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