Centring Multiple Blow Pins at Same Station

When more than one pin is used on the same station, they must be set precisely at the same height or all the tops may not trim. The best way to set the height begins again by inverting the strikers and closing the moulds.

With the spanner nut snug, slowly and carefully lower the pins until the one of them contacts the piece of bar stock. Tighten this pin in place, loosen the spanner nuts and lower each remaining pin until it contacts the bar stock. Then tighten the spanners, check the centring and adjust if necessary. Finally, turn the strikers back over.

When More Than One Pin is Used, They must be Set Precisely at the Same Height
Use a similar method and bar stock to check a pin’s straightness. Place matched thicknesses of bar stock, in turn, under either side and then under the fronts and backs of the cutters on each pin.
Carefully apply pressure until the cutter contacts the piece. If the pin is straight, you will not easily remove one of the two pieces. If the pin is bent, you can readily pull out a piece. A bent pin may cause cutting problems and needs to be replaced.

Let’s review these two procedures we’ve just covered. Set all the pins at the same height and carefully lower them until the first one contacts the piece. Tighten it in place, lower the others until they too contact the pieces – tighten them as well. Check and adjust centring and turn the strikers over.

To check straightness, place the pieces under the cutter at points opposite each other. Try to remove one piece, if one can slip out easily, the pin may be bent. Bent pins can cause cutting problems.

Mounting Blocks
The mounting blocks secure the blow pins to the moving plate. The method differs from machine to machine. This machine uses a ‘T’ slot arrangement. By loosening the mounting bolts, the blocks can be slid into different centre distances to match the spacing of the mould cavities.

Mounting Blocks
Other machines have several tapped hole patterns which will accommodate the mounting blocks at different centre distances. On these particular machines, the moving plate usually acts as a blow air distribution manifold too. The air passes from one central connection through the plat and down into the blow pins.

Machines with Tapped Hole Patterns Which Accommodate the Mounting Blocks
When repositioning the mounting blocks on plates like these, it is necessary to ‘unplug’ the air ports at the correct centre distances and to block the ones that aren’t. After setting the blocks in the right positions, the mounting bolts are snugged down, and the centring is checked.

Repositioning the blocks is mostly done to change centre distances. It may be necessary though, if the pin can not be centred side to side suing the fine adjustment on the mounting block. If this is the case, loosen the mounting blocks and move the blocks until it can be centred within the range of the fine adjustment.

Repositioning the Blocks is done to Change Centre Distances
As stated previously, depending on the type of machine, the mounting blocks may be secured with a ‘T’ nut system – or they may bolt directly to the moving plate. By loosening the mounting bolts these may be repositioned over the correct hole pattern.
Before securing these, air ports must be opened, and the other plugged. The blocks are usually moved to match a different centre distance. They may also be moved if a centring adjustment is out of the range of the adjusting screws. At the base of the station is a fixed bottom plate. The plate itself or the attached stripper plates are designed to strip the top flash and the containers flow the blow pins.
When centre distances change it is required by some designs that the entire bottom plate be changed as well. These strippers are repositioned by loosening the bolts holding them onto the plate.

Lower the blow pins, centre the strippers, and tighten the bolts as you hold each plate in its new position. Depending on the design of the strippers and the tolerance between them and the blow pins, they may have to be loosened during the blow pins centring procedure. Be sure to retighten them afterwards.

Hydraulic Cylinders
The moving plate travels up and down as pressurized oil or air is directed to one or the other side of the calibration cylinder’s piston. Hydraulic cylinders have become the standard on calibration stations because oil power can be controlled better than air power.
Control of the cylinder’s movement is critical to the efficient production of quality containers. It is important to control the speed at which the cylinder travels. It is most important to control the distance that allows the blow pins to travel downwards. As the machine control directs pressurized air or oil to one side of the cylinder, what leaves the other can be throttled by adjusting a flow control valve.
Downward speeds should be set so that pins are inserted quickly but not so fast that they damage the mould. The upward motion should also be quick so that cycle time is saved. Some machines are equipped with proportional hydraulic controls that allow speed to be varied during different segments of the cylinder’s movement.
Rather than adjusting manual flow controls, dials are adjusted for the desired speed during each part of the station’s movement. In most cases the controls should be set so the beginning and the end of the stroke is slow and the middle part of the stroke is fast. This combination produces quality containers, maximizes the machine’s cycle time, and minimizes wear on the machine.
Whether manual valves or proportional controls are used, the cylinder’s speed should always be set so that minimizing wear on the machine is the first consideration.
The most important adjustment on the calibration cylinder is the ‘stop nut’. The ‘stop nut’ limits the downward travel of the blow pins. It must always be adjusted so that the cutting sleeves just barely contact the striker plates.

To set the stop nut, carefully jog the cylinder until the cutters first contact the mould. Loosen the lockdown and spin the nut clockwise until it bottoms out on the cylinder housing. Next, retract the cylinder rod slightly; lower the stop nut another half turn. Lastly, retighten the lockdown.
Once in production, readjust the nut until all the nuts are being cut.

The cycling may have to be stopped to make this adjustment safely. Always use extreme caution when adjusting the stop nut. Protect your personal safety and be careful never to raise the nut so much that cutters can travel beyond the strikers and in to damage the mould.

The stop nut adjustment should always be checked after cutters are changed. They will always have to be readjusted whenever moulds are changed as part of a new setup. If all the flash on the same side can’t readily be cut with a stop nut adjustment, check that all pins are adjusted to the same height using the pieces of bar stock.