Spring Manufacturing Process
The spring manufacturing process starts with you, the customer. Once a Request for Quote (RFQ) is received, along with a print or sample, we promptly work to provide a quote back to you the same day, within a few hours in most cases. RFQs are first checked to see if we can provide a part straight from our Stock Catalog. Upon submitting a quote, we would point out any deviation at this point, examples being wire size or finish. We may also make any design recommendations, to ensure a reliable spring, as well. Once you submit a PO, the CAD drawing and Specs are reviewed to ensure a good design. All required tolerances, such as zinc plating are listed for manufacturing and then any POs for outside processing are written up.
The order is then entered into our computer, an acknowledgement is generated back to the customer, the internal order is then posted to stock raw material, we place an order for material if needed. If material is available the order is sent to the shop to either go to the coiling, handwork, or secondary department.
This is the area where the automatic CNC coiling machinery operates. Automatic coilers can handle wire from .008" to .625".
This is where small quantities of springs are made by hand. If a customer wants less than 15 springs, the job is given to the Hand Work department, since the setup time is minimal, the springs can be produced more economically.
The secondary department is where small quantities of wire are bent by hand. Once the spring is coiled, this is where the ends of torsion springs are formed, where loops are put onto the ends of extension springs, and where wire forms are made.
This is the department where the ends of compression springs are ground. A lot of the work is done with automatic machines, which pass the springs between two large grinding wheels so that both sides of the spring can be ground at once.
Compression Springs are by far the most common type of spring. However Extension and Torsion are also coiled via production machinery.
When dealing with large batch quantities, both mechanical and CNC machines are used to coil the springs. The picture shows a view from the front of a mechanical coiler. The link takes you to video of CNC machines.
The four large rollers on the front of the machine work in pairs and force the wire through the wire guide towards the coiling point as shown in the picture on the right.
There are two grooved coiling points, one vertical and one horizontal from the right hand side of the machine which are positioned round a half round mandrel. The four large wire feeders force the wire through the coiling points which in turn force the wire round the mandrel thus giving you the required spring coils.
The number of coils can be adjusted by the amount of wire feed. The pitch spacing and the free length of the spring is governed by the spacing tool just visible on the right hand picture at the twenty past position. When the spring coiling is completed, it is cut off by the cutting tool.
Before this process can begin, tooling maybe required, mandrels may need ground, or created to ensure proper bend radius.
For the smaller batch sizes and particularly when using thicker wire sizes, we use semi-automatic CNC or a lathe.
A variety of springs can be coiled off a machine:
Conical springs: You may need a compression spring that's smaller at one end than the other. This is called a conical, or tapered, spring. These are basically made just like any other compression spring.
Variable-pitch springs: Sometimes you'll want a compression spring that starts out light and after a certain load is placed on it, becomes stronger. This is called a variable-pitch spring and you can see springs like this in race cars or motorcycle shock absorbers.
The key is to have some way to remember TWO coil counts: one for the first section, and one for the second. Once you can do this, then you can change where you switch from one speed to another and come out with the exact spring that you want.
Snap-rings: Snap rings are easy. Just coil an extension spring with the right diameter and cut off single rings, one at a time.
Nested compression springs: Sometimes, you'll need a compression spring that's stronger than any single spring can be. In that case, you can make nested compression springs — one spring inside the other — that will be a lot stronger than a single spring. Some automobile valve spring assemblies are actually nested springs, so are the suspension springs on railroad cars. Nested compression springs are easily designed: just remember two things:
Nested compression springs must be different-handed. If the outer spring is right-handed, then the inner spring must be left-handed, or vice-versa.
The outside diameter of the inside spring CANNOT be larger than the inside diameter of the outside spring. If it is, the springs will not nest.
Very heavy wire: What's the heaviest wire that can be made into a spring? Well, coiling cold, the heaviest is about 5/8".
Springs made from larger material start as straight bars of steel with the ends tapered down. The bars are heated red-hot and then coiled on special machinery. Some railroad suspension springs are made from 2-1/2" bars, and there have been 6" bars being made into compression springs that are used as shock absorbers for underground military command sites.
Very light wire: Common commercial coiling machines typically handle wire as fine as .008", but Diamond Wire Stocks springs made with wire as fine as .003". These micro springs are often used in medical or nano technology devices.
Diamond Wire Spring can manufacture one of the largest ranges of springs in the industry.
SHORT ORDER DEPARTMENT
Making springs by hand basically consists of bending wire around a rod called an arbor or mandrel. The arbor is secured in the chuck of a lathe.
For the smaller batch sizes and particularly when using larger wire sizes we use a CNC lathe.
Square and rectangular wire: All types of coil springs can be made from either type. Using these materials gives you a stronger spring than if you use round wire for the same design. We make large quantity Square or rectangular wire springs at our Texas facility, where then have machines to coil the flat stock.
Spring wire that gets shaped has to have the bending stress relieved in the form of heat treating. Various wire materials require different lengths of time for stress relief.
The process of baking out the stress in the wire may change the dimensions of your spring. Stainless steel coils will generally expand slightly when heated: music wire coils will generally contract slightly.
Wire forms: Wire forms are any shape made out of wire — not just a coil. There are a jillion different kinds of wire forms.
Limited-travel extension springs: Sometimes you'll want to make an extension spring that only extends so far and then stops. You'll see these sometimes on screen doors, or farm fencing, these are called draw bar springs:
You may want to make an extension spring with extended hooks, like this:
The best way to do this is to coil the spring as if it were a torsion spring and then bend the ends over to form the extended hooks.
Loops and Hooks
Loops will work best for most extension springs. Sometimes, though, you'll want hooks — like when you'll want to slip the spring onto a pin, for instance.
Making hooks is very simple, once you've made loops: all you have to do is cut the end of the wire off so that it doesn't come all the way around to the body of the spring.
Extension springs are also sometimes made with hooks that are separate from the spring that swivel. The last few end coils would be a conical shape to hold the hook in place.
Torsion Spring Ends
Don't forget that torsion springs come left-handed and right-handed. Be sure to make you request the correct direction.
Torsion Springs start with straight arms. They quite often have one or more bends, to fit within a movement device, tooling, or to hit a stopping point in the final product.
Double torsion springs: You recall how torsion springs can be either left-handed or right-handed? Well, sometimes you'll want to make a torsion spring that's both. Such springs are sometimes found on clipboards, and they might look like this.
Making double torsion springs means making some pretty specialized tooling, Depending on the wire size, they can be formed on a CNC machine or a manual lathe.
A common requirment for compression springs is to grind the ends flat.
In the majority of cases this grinding flat of the ends is done on an automatic grinding machine. These machines consist of a round plate into which bushing are fitted. The bushing inside diameter is of a size so that the springs will fit leaving a small amount of spring protruding top and bottom. The plate then turns slowly round so that the bushing plus springs pass in between either one pair of grinding wheels or as in the illustrated photograph, two pairs of grinding wheels depending on what type of machine is used. The grinding wheels grind the ends of the springs flat and square and then they drop into a waiting box for inspection when they are thoroughly tested to make sure they comply both dimensionally and in their load requirements.
If you're looking at the end of the spring, the ground surface should look like the graphic, once ground.
The other thing to check is how square your ground ends are. You can do this by setting your spring down next to a carpenter's square, a machinist's square, a book, or anything else that stands up straight. Then, holding the bottom end of the spring next to your square, turn the spring around and watch the gap between the square and the top end.
If your spring is perfectly square, there will be no gap as you turn the spring around. A small gap is OK, since the ends of the spring will flatten out under load (Commercial squareness in spring shops is ±3 degrees). Generally 3/4 of the bearing surface is ground and 1/2 of the wire thickness is ground off.
Checks tolerance to ensure your springs were manufactured to your specifications. Tolerances generally held to S.M.I. commerical standards and not to a machinist block.
This section will tell you about a few of the finishing touches you can put on your springs. Some of these are necessary, while others may be called for by the design you have in mind.
We can paint your springs or add a color code stripe, in any color on our paint line.
eCoating, Powdercoating, Passivating, Plating, Electro polishing, or Magna flux are all examples of types of coatings added to springs, mostly as an environmental protection.
SHIPPING / RECEIVING
Before your springs are shipped we package them in bags, boxes, drums, or pallets all dependent upon the lot size. We can handle customer release schedules to incude JIT, Kanban, and Blanket orders.
We can custom label each package or each part. We will ship using which ever freight carrier the customer requests.