Bending steel tubes correctly is hard enterprise. Ensure you’ve requested all the best questions earlier than you set materials in your bending machine. Lincoln Brunner
Can we make this? It’s a query we get virtually each day. A tube fabricator is requested to cite a component and doesn’t know if it ought to.
What looks like a easy query is definitely very difficult. And the reply requires a number of items of data.
The Half
What materials is being bent? We have a tendency to consider supplies in broad classes: carbon metal, stainless, titanium, nickel-based alloys, aluminum, bronze, brass—even some plastics. However inside every materials are dozens of various grades and requirements.
Typically a request for quote will include very generic materials necessities equivalent to carbon metal, leaving it as much as the bending store to find out the grade. Different instances, the RFQ will include very particular materials necessities, equivalent to ASTM A500 sequence or 409 aluminized stainless tubing.
Some supplies are a lot simpler to bend than others. If in case you have not labored with a specified grade earlier than, greatest do some investigation.
What form is the tubing? Tubing is available in all types of shapes. Is it spherical? Sq.? Rectangular? One thing else?
CNC tubing benders have a most tube diameter they’ll settle for, a quantity based mostly on a spherical tube. If the form is nonround, the store should decide if instruments will be designed for it and if the tube will be loaded within the bender.
Suppose you have got a machine with a most spherical OD of two.0 in. May this machine settle for a 2- by 2-in. sq. tube? The diagonal measurement on that sq. tube is 2.83 in., so that you possible couldn’t bend that half on that machine.
How thick is the fabric? Because the wall thickness of the fabric decreases, the required machine energy additionally usually decreases. Nonetheless, due to the better susceptibility to deformation, the half turns into tougher to bend.
What’s the required centerline radius? Centerline radius (CLR) is the space from the middle of the “circle” being shaped within the act of bending to the middle of the tube being shaped. It’s usually accepted that with most supplies, a CLR of 1x tube OD is the minimal radius a component will be shaped round. So, for a 2-in.-OD tube, the minimal CLR is 2.0 in. As CLR will get bigger, the quantity of energy required to make the half decreases.
FIGURE 1. A tube bender’s specification sheet sometimes reveals the machine’s energy capability.
The Machine
What’s the bender’s energy capability? Sadly, there isn’t a actual business customary that clearly communicates the facility capability of a CNC tubing bender. Often, the specification sheet on a machine will record tube sizes and supplies at sure wall thickness as the utmost. For instance, a 75-mm machine could have a chart as proven in Determine 1.
A chart like this defines the supplies the machine can bend, nevertheless it doesn’t inform the total story.
As famous beforehand, the CLR of the tube being bent will have an effect on the machine’s skill to tug the tube round, however the chart doesn’t outline what CLR was used to find out the tube sizes. Some producers calculate tube sizes utilizing a CLR of 1x tube OD, whereas others use 2x, however most use 1.5x tube OD. So, the capacities within the chart could be based mostly on 3-in.-OD tubing being bent on a 4.5-in.-CLR bend die. Additionally, not all supplies are created equally. There are high-tensile delicate steels, many alternative grades of stainless, and many others.
Keep in mind that the true measure of a machine’s energy is within the quantity of bending torque the machine can produce, and that’s in comparison with the quantity of torque required to kind the bend.
What’s the bender’s attain capability? We regularly concentrate on a bender’s energy, however one other limiting issue will be how far the instruments, particularly the clamp and strain dies, can journey to shut the clamps on a tube.
If the CLR is simply too giant, the clamps could not be capable of open far sufficient to permit load/unload or manipulation of the tube between bends. If the CLR is simply too small, the clamps could not be capable of attain far sufficient to shut in opposition to the tube.
Is there sufficient clearance? This query may go in both the half or machine class, however I consider it as a machine query as a result of many alternative machine types might help handle clearance points.
Multistack machines can transfer the pinnacle up or down vertically to permit bending farther away from the pinnacle. Machines which have very small bend heads that reach distant from the machine physique enable a tube to swing beneath it.
As well as, there are machines that may bend in each instructions. These make bends that will in any other case swing the half towards the machine physique swing away from the machine physique.
Different Concerns
Elongation. Because the tube is being shaped, it can stretch. It’s useful to know if the fabric can elongate as a lot as required. There are a few formulation that may give an estimated proportion of elongation required to make the bend, and that determine will be in comparison with the anticipated elongation proportion of the fabric (e-mail me on the handle offered on the finish for formulation).
Sq./Rectangle. It’s imperfect, however a fast approach to decide in case your machine can bend a sq. or rectangular half is to check the cross part of the utmost spherical tube materials to the cross part of the sq. or rectangular materials. If the sq. cross part is bigger than the spherical cross part, it’s possible above the machine’s capability.
Required Torque. Happily, on-line instruments can be found to find out required torque for you. I desire app.unisonltd.com. If I do know the utmost capability of the machine based mostly on tube measurement (as listed in Determine 1), I’ll enter these values into the app and decide the facility required to make that half. Then I’ll enter the specs for the half I have to bend and examine the facility required for it. If the required energy for my proposed half is lower than the facility required for the utmost listed dimension, I will be fairly certain the machine has sufficient energy.
Use the 80/20 Rule. Simply because a machine can bend a component doesn’t imply you essentially ought to. Generally, lower than 20% of the components you make needs to be above 80% of the capability of the machine you’re utilizing.
Why? Think about two an identical pickup vehicles that may tow 15,000 lbs. Over a 12 months, they each are pushed 100,000 miles in the identical situations on the identical days. One tows 15,000 lbs. for each a kind of miles, and the opposite tows 5,000 lbs. for each a kind of miles. On the finish of the 12 months, which truck can be in higher form? If you’re constantly bending components at 80% or extra of your machine’s energy capability, it’s time to begin searching for a bigger machine.
