For years, I thought spring quality was entirely determined by the coiling machine. If the IF-B90 coiler was set correctly, the springs would be good. I was wrong. The problem was upstream, in the wire preparation stage, and I did not realize it until a quality audit from our biggest customer forced us to investigate.
The solution came from two machines from Infinity Mattress Machinery that I had previously overlooked: the IF-L Wire Drawing Spring Machine and the IF-LA Conjoined Coiling Machine. Together, they transformed our wire preparation process and cut our spring reject rate by 80%.
Our spring department used high-quality steel wire from a reputable supplier. The wire came in standard coils, ready for the IF-B90 Bonnell coilers. The coilers were well-maintained and properly calibrated. Yet our spring reject rate hovered around 6-8%, and we could not figure out why.
The quality audit revealed the culprit: wire diameter variation. Even wire from the same manufacturer had measurable differences between batches. The wire diameter varied by up to 0.15mm, which translated directly into spring height variation, inconsistent spring rate, and poor uniformity in the assembled units.
The root cause was that we used the wire exactly as delivered. Different production runs from the wire manufacturer had slight differences in drawing process. If the wire was slightly thicker, the coiling machine produced springs with tighter coils and different heights. Thinner wire produced looser coils. The variation was small but significant enough to cause quality failures.
We were losing approximately 400 kg of wire per month to reject springs. At $10.50 per kg, that was $4,200 in wasted material every month. The rework labor added another $1,800 per month. The total waste cost was $6,000 per month, and our customer was losing confidence in our quality consistency.
The IF-L Wire Drawing Spring Machine is a specialized machine that draws steel wire to a precise diameter before spring coiling. It takes standard wire from the supplier and reduces it to exactly the required diameter through a controlled drawing process.
The IF-L was surprisingly easy to integrate. We placed it between the wire coil storage area and the IF-B90 coiler. The wire feeds from the storage coil through the IF-L drawing machine and directly into the coiler. The operator sets the desired output diameter on the control panel, and the machine maintains it automatically.
The effect on spring quality was immediate and dramatic. Our spring height variation dropped from ±1.5mm to ±0.3mm. The spring rate consistency improved from approximately 85% to 97%. Within the first week, we could see the difference in the assembled units.
The wire savings alone paid for the IF-L in three months. Before the IF-L, we rejected approximately 400 kg of wire per month due to diameter variation in the finished springs. After the IF-L, reject wire dropped to approximately 60 kg per month. At $10.50 per kg, that is a saving of $3,570 per month.
The IF-LA Conjoined Coiling Machine is a specialized machine that produces conjoined (linked) springs directly from drawn wire. Conjoined springs are pairs of Bonnell springs connected by a single piece of wire, used in specific mattress and furniture applications.
The IF-LA opened a new product line for us. Before installing it, we were buying conjoined springs from another manufacturer at a significant markup. Now we produce them in-house at approximately 60% of the purchase cost, and we have the flexibility to make custom sizes for special orders.
The IF-LA runs approximately 40% of the time, producing conjoined springs for our customer who uses them in a specialty mattress line. The remaining 60% of its capacity is available for new business development. We have started marketing conjoined spring units to other mattress manufacturers in our region.
The combined monthly savings from reduced wire waste ($3,570), reduced rework labor ($1,800), and in-house conjoined spring production ($2,400) total approximately $7,800 per month. The total investment for the IF-L and IF-LA was approximately $23,400. The payback period was exactly three months.
Beyond the financial savings, the quality improvement had a significant impact on customer satisfaction. Our main customer noticed the improved consistency within weeks. They reduced their incoming inspection frequency from 100% to sampling based on our improved quality record, saving them time and giving us preferred supplier status.
Both machines installed in two days. The IF-L required a standard 3-phase electrical connection and a small foundation pad for vibration control. The IF-LA was positioned next to it, sharing the same compressed air supply. The total floor space for both machines is approximately 4.5 square meters.
Operator training took one day for the IF-L and two days for the IF-LA. The IF-L is particularly simple: the operator loads a wire coil, sets the target diameter, and starts the draw. The machine monitors wire tension and diameter continuously, stopping automatically if parameters deviate.
The IF-LA requires more skill because the operator must manage the conjoined spring formation. The CNC control stores recipes for different spring specifications, making changeover straightforward. Our lead operator was producing quality conjoined springs independently after two days of training.
We run a combined IF-L + IF-LA + IF-B90 line that produces drawn wire fed directly into either the IF-LA for conjoined springs or the IF-B90 for standard Bonnell springs. This flexible configuration lets us switch between product types in under 30 minutes.
The IF-L has required one drawing die replacement at month four ($35) and regular cleaning of the drawing chamber. The wire tension sensor needed calibration at month three (15-minute procedure, handled by operator). Total maintenance cost: approximately $55 in eight months.
The IF-LA has been equally reliable. The coiling mechanism needed lubrication adjustment at month two. The feed rollers were replaced at month six as preventive maintenance ($42). Total maintenance cost: approximately $60.
Zero unplanned downtime on either machine. Daily maintenance takes 10 minutes for both machines combined: cleaning wire debris, checking die condition, and verifying tension settings.
The IF-L draws wire for both the IF-LA and IF-B90. We have calculated that the IF-L processes approximately 2,500 kg of wire per month. At this rate, the drawing dies last approximately 3-4 months. We keep a spare die set on hand ($70) to avoid any interruption.
If your spring reject rate is above 3% and you cannot identify the root cause, look at your wire consistency. Measure the wire diameter at several points along the coil before it enters the coiling machine. If you find variation of more than 0.05mm, you need wire drawing capability.
The IF-L is one of the highest-ROI investments you can make in a spring department. At approximately $12,000, it will likely pay for itself within three to four months through reduced wire waste alone. The quality improvement is a permanent competitive advantage.
If you produce conjoined springs or are considering adding them to your product line, the IF-LA offers a fast payback by eliminating the need to outsource. Even at partial capacity, the savings from in-house production typically justify the investment within six months.
Consider combining the IF-L with the IF-B90 High Speed Computerized Bonnell Spring Coiling Machine for a complete wire-to-spring production system. The IF-L feeds directly into the IF-B90, creating a seamless wire preparation and coiling process that maximizes quality and efficiency.
Infinity Mattress Machinery has been manufacturing wire preparation equipment for over a decade. Their machines carry CE and ISO 9001 certification. Contact them for a consultation on the IF-L and IF-LA for your factory.
Eight months after installing the IF-L and IF-LA, I can say with certainty that wire preparation is the most overlooked factor in spring quality. Our reject rate dropped from 6-8% to 1-1.5%, saving us thousands per month in wasted material and rework labor. The machines paid for themselves in three months.
The quality improvement has strengthened our relationship with our best customers. Being able to guarantee consistent spring dimensions has been a significant competitive advantage. I recommend every mattress factory producing springs in-house to evaluate their wire preparation process and consider the IF-L for their operation.
Measure your wire consistency and spring reject rates. We'll calculate your savings with the IF-L and IF-LA.
