Blank Spring Setup and Tool Alignment on a CNC Coiler

1. Why the blank spring is the master setup condition

The blank spring is the neutral mechanical state from which later features are developed. It should coil smoothly, remain horizontal, achieve the smallest stable diameter available from the chosen tooling, cut cleanly and leave the forming zone without excessive swarf or wire damage. If the blank spring is wrong, adding pretension or hook motions only makes diagnosis more difficult.

The source setup therefore progresses from tooling selection and wire alignment to controlled hand feeding, gradual coiling-point engagement, cutter alignment and finally fine diameter adjustment. The order is important: each step establishes the geometry needed by the next.

2. Select the forming-tool set

The source identifies four tools for initial setup: the arbor, block wire guide, coiling point tool and pitch tool. The arbor establishes coil diameter and provides the cutting edge; the block guide supports the incoming wire; the coiling point forces the wire around the arbor; and the pitch tool is aligned in preparation for hook operations and to support the wire where required.

3. Use the correct jog-speed strategy

The source machine allows a relatively fast manual jog when tools are clear and a slow jog for close work. Source example: the manual uses a dial value of 4 for fast manual movement and approximately 1 for fine adjustment. The principle is to reduce jog speed before bringing carbide tools close to the arbor or cutter. The cost of a few extra seconds is far lower than a chipped coiling point or broken arbor.

4. Establish the incoming wire centreline

1. Loosen the tool-holder binding mechanism. The tool holder must be able to slide laterally while the block guide is aligned.
2. Install the pitch tool and arbor. Secure the pitch tool in its internal clamp but leave the arbor available for final rotational and axial setting.
3. Hand-feed the wire through the guides and feed rolls. Back off feed-roll pressure so the wire can move freely by hand.
4. Install the block wire guide and spacer. Slide the holder until the guide groove lines up with the incoming wire centreline.
5. Lightly secure the holder. Prevent lateral movement while still allowing the arbor to be set accurately.

Misalignment here is a major source of friction and swarf. The source’s later troubleshooting notes describe a locally made tool whose groove position differed slightly from the previous tooling; the resulting wire misalignment created heavy swarf until the arbor position was corrected.

5. Set arbor protrusion and cutting geometry

The arbor must extend far enough beyond the block guide to support at least one spring coil and provide a usable cutting edge. It must not extend so far that it interferes with hook forming. The source also rotates the arbor so its cutting surface matches the cutter face and maintains a small but safe clearance between the two.

Source example: the source cutter face is described as having approximately a 17° angle that is aligned to the arbor cutting edge. Too little clearance can chip the arbor during the cutting stroke; too much clearance can leave the spring incompletely cut. These details are specific to the source tool geometry, but the general principle is universal: the cutter must pass the wire with sufficient support and minimal lost motion without striking the arbor.

6. Establish cutoff home and stroke

The source moves the cutter to its maximum stroke position, sets a reference, then establishes a separate home position used for the start and finish of the cutoff cycle. Later, the cutter is brought close to the wire and adjusted laterally so the cutting edge strikes the wire centre. The cutter is then moved through the wire once to prove the alignment before the machine is returned to home.

Do not use repeated production cuts to “find” the correct lateral position. The setup goal is to align the cutter mechanically first, then use the servo stroke for repeatable cycling.

7. Align the pitch tool

The source aligns the pitch-tool end approximately flush with the face of the block guide and keeps the top surface of the pitch tool parallel with the bottom of the block guide. The pitch tool is commonly associated with compression-spring pitch, but in this process it also supports hook formation and can help prevent thinner wire from being pushed out of the side of the block guide. If it is too far forward, however, it can act on the spring during normal coiling and reduce pretension.

8. Set block-guide clearance by feel

This is one of the most important manual setup steps. The wire should be a controlled but loose fit between the arbor and the block wire guide. The source recommends checking this by pushing and pulling the wire by hand with feed-roll pressure removed. If the wire is too loose, it may escape from the guide during coiling. If it is too tight, the machine must overcome unnecessary friction; the source links excessive tightness to spring heating, excessive swarf, tool wear, distortion and difficulty developing pretension.

9. Apply feed-roll pressure conservatively

Once the hand-pull test is satisfactory, restore feed-roll pressure. The source uses independent entry and exit adjustments and makes the exit side slightly higher than entry so the wire remains positively controlled through the feed train. Source range: approximately 300 lbf on smaller 0.91 mm wire up to around 600 lbf on 1.4 mm wire, with the exit setting often about 50 lbf higher. The manual repeatedly says to use only the minimum pressure required to avoid slippage because excess feed pressure can bend the wire and produce a curved spring.

10. Align the coiling-point groove

Using the diameter and coiling-point axes, align the tool groove with the incoming wire. Then use the torsion axis to align the bottom of the coiling-point tool with the bottom of the arbor. This places the groove at the correct height and lateral position so the wire enters the coiling point without being forced up or down.

The tool should engage the wire sufficiently to start the helix but must remain clear of the arbor itself. Physical contact between carbide and arbor is not a forming method; it is a crash.

11. Start the first coil safely

1. Bend the wire around the arbor. The initial hand bend gives the wire a path toward the coiling-point groove.
2. Move the coiling point toward the arbor. Make contact with the wire, not the arbor.
3. Feed very slowly. Use the low manual jog/feed setting and observe the wire start to coil.
4. Guide the first turn with a tool. As the wire end returns toward the block guide it can catch on the guide edge; the source uses a screwdriver to steer the first turn safely.
5. Increase feed only after the wire passes the guide. Once the helix is established, generate a longer blank spring.

12. Find the minimum stable blank diameter

After a blank spring is being generated, the source zeros the diameter position and then reduces the diameter axis in very small negative increments. Source example: when close to the optimum, changes of roughly 0.01–0.02 mm are used. The goal is the smallest achievable blank diameter, because this keeps the spring wire firmly on the arbor cutting edge.

There is a turning point. If further inward movement causes the spring diameter to increase rather than decrease, the process has passed the stable forming condition and is beginning to distort. The correct response is to move back toward the previous position rather than continuing to force the tool inward.

13. Keep the blank spring horizontal

The spring should emerge from the arbor in a horizontal plane. If it points upward, the source corrects the coiling-point axis in the negative direction; if it points downward, the correction is in the positive direction. The exact sign convention is machine-specific, but the diagnostic principle is valuable: vertical spring drift indicates that the coiling point is not correctly positioned relative to the arbor, and the smallest stable diameter generally occurs when the spring leaves horizontally.

14. Source-specific tooling matrix

The manual includes a tool-selection chart that links wire size, arbor, guide groove, coiling-point groove and approximate spring diameter. To remove product-specific identities, the table below retains only the technical ranges.

These dimensions are source examples, not design equations or generic spring standards. They are useful because they show how a single arbor can cover several wire sizes while groove tooling remains more closely matched to wire diameter.

15. Blank-spring acceptance before moving on