Author: Larry

The soft sheet-metal feed table on AB Dick’s direct feed presses is prone to ‘self-damage’ if allowed to jam into Micro Lateral Guide.

When this happens, the ‘forward edge’ of feed table is bent down at its’ center, reducing support to the forward ends of paper support rails.

A bent feed table does not suffeciently support the pile load, allowing the downward force of ‘paper-height-regulators’ to force/pull the front-edge of pile down too low.

This unstable condition causes the feed table raise to become inconsistent.

This condition does not present to much of an problem with a full lift, but when the pile is low (light), the false table raise signal from an unstable feed table causes table to raise too high, causing press to feed doubles and paper jams when feeding at the bottom of pile.

There are two solutions to this problem;

1: Shim-up/support front ends of paper rails with a folded thickness of taped chip-board spacer. See Photo attached.

2: Remove feed table and have metalsmith straighten lead-edge and weld 1/8″ thick angle iron support to inside edge of feed table.

In any event, fix it! Its’ costing you down time and money.

If you want to print a uniform screen or solid accross the varying layers of an envelope, stick a layer (or 2 ) of Duct Tape on the impression cylinder and create a Back-Packer.

A layer of compressable Duct Tape behind the image area conforms to the thicknesses of the back-side of the envelope producing uniform back cylinder pressure against the blanket.

To position Duct Tape accurrately, trip impression cylinder and create an image on back cylinder, then stick Duct Tape over the image area.

Before printing, back-off impression cylinder and run an envelope to evaluate print image quality.

If printed image is incomplete, adjust impression pressure to higher setting until you get that perfect image.

Time is money.

Why waste valuable press time unloading/re-handling freshly printed sheets to reuse a single paper dolly?

If you do you are losing money!

Extra press delivery dollies save press time and reduce risk of ‘causing’ offset.

If you use multiple presses of same model, having extra paper dollies is a no-brainer.

 

Applying spray adhesive onto backs of Polyester plates is an effective way to reduce plate stretch but is also messy.

I have seen some pretty sticky/messy presses where operators coat plate back-edges by lifting plate tail-ends and spraying adhesive on the press.

An innovative Pressman from Sacramento, California uses a small ‘Spray Booth’ constructed from a cardboard box that is both clean and effective.

He took a cardboard box several inches longer and wider than plates and fixed/taped it on a base that presented the boxs’ opening from a table top at a 45 degree angle.

To use, he placed the plates face down on angled inside surface to sprayed it.

This improvised spray booth helped contained ‘overspray’ and concentrated more of the adhesive on the plate rather than shop.

A cost effective adhesive spray for this use is Elmer’s Spray Adhesive which is available at most Ace Hardware stores for about $5.00 a can.

The Kompac KwikVac System utilizes the suction developed by a strong hand-operated Suction Bulb with one-way valves.

Suction from KwikVac sucks up waste solutions directly from Kompac nip thru tubes in TimeSaver Seals, automatically transfering liquid waste into waste container at backside of press.

As you print, wetting solution used is automatically replaced as needed by dispenser valve located at the center of Kompac.

As fresh solution dispenses at Kompac center, fresh solution pushes contaminated solution away from center of Kompac where it concentrates at edges near seals.

Give Kompac KwikVac a squeeze or two when you notice discoloration or a lumpiness in wetting solution near seals and you automatically remove contamination, on-the-fly.

This simple step removes paper fiber, sizing and chemical contamination allowing you to print and hold consistent color at high production speeds.

Depending on sheet length, type, and quality, a squeeze or two at 5,000 to 10,000 impressions keeps fountain solution PH and clarity within ideal operating range.

Note: Stock cut with a dull knife leaves more edge-fibers exposed at edges, keep your cutter blade sharp.

You can also use a blanket that is narrower than sheet which eliminates 80% of paper fiber contamination in both Kompac and inking system.

Keep a close eye on the amount of solution sucked-up at ‘both sides’ of Kompac as you release squeeze bulb.

The amount of contaminated solution removed will indicate if one of seal suction hole is plugged with clumps of long paper fibers.

When plugging occurs, use your long neck suction syringe to suck out paper fiber from TimeSaver Seal holes at next press stop.

When cleaning Kompac, squeeze suction bulb and release squeeze-grip slowly to reduce air sucking.

A slow release of suction bulb allows time for solution to flow from center of Kompac towards suction orfices without sucking air.

When you are satisfied that Kompac is clean and free of ink and solvent, re-insert fountain bottle to allow clean wetting solution to enter Kompac nip.

When Kompac Nip is full, squeeze and release Kwikvac slowly twice to purge residual ink and solvent from TimeSavers Seals and suction lines and you are ready to re-ink and print.

Over the past 15 years North American Paper Manufacturers have changed from an acid to an alkaline process for making printing papers.

First with copier papers where paper’s PH mattered little, but when exposed to fountain chemistry of the printing process, calcium carbonate, styrenated starches leaches away from the paper and into the process from blanket, to plate, to dampener and inking system causing much grief.

Larger press and graphic supply manufacturers addressed this issue with calcium cleaners, PH neutralizers, and fountain re-circulators, but there are still improtant steps that need to be taken by offset pressman.

The primary problems/symptoms of alkaline poisoning are;

• Dry toning on the plate.
• Calcium build-up on blanket that produces ink framing around sheet contact area.
• Blanket looses affinity to pick-up complete image/ink from plate.
• Ink tinting on printed sheet.
• Fountain PH shifts from acid 4.5 – 5.0 to a more alkaline 5.5 – 6.0 and even a 7.0 PH.
• Ink rollers strip, and will not carry ink properly causing an increase in ink feed, resulting in an over-inked condition and eventually emulsification and plugging.

The solution is not to use a stronger roller wash, it simply is to use a good water misible roller wash (Like Varn V-120) followed periodically by a good calcium deglazer (Like Varn Revitol) to remove calcium glaze, followed by a rinse of 15% white kitchen vinegar and water to neutralize and condition roller to accept ink properly.

In addition to using a good graphic supplied calcium remover (not CLR!), you should use an approved fountain solution designed to handle calcium.

Keeping calcium from accumulating in the fountain eliminates a major portion of this problem.

Purge old solution and replentish fountain solution frequently.

This simple step can keep plates, blanket, dampener, and rollers from developing a calcium build-up.

If you use the Kompac dampener, the problem of calcium build-up in the dampener is more noticable and can develope within only a few thousand sheets when printing on high alkaline stocks.

If you experience a calcium build-up with your Kompac, using a ‘Slim’ or ‘Spot’ Blanket with a Kompac KwikVac and TimeSaver Seals will make a dramatic difference in reducing calcium build-up in Kompac, as well as your ink system, and blanket.

Stick a 2″ pad of adhesive backed Velcro onto your paper stop plate at impact area of delivery to reduce lead-edge impact with coated stock. This will improve sheet delivery/stacking at high production speeds and eliminate lead-edge denting/marking.

Velcro pads are available at most all Fabric and Sewing Material Stores.

Over time soft ink rollers become sensitized from chemical and physical contaminations of the printing process.

Soft roller pores collect contaminates such as ink pigment, dye, clays, calcium carbonates and other paper bi-products which creates a ‘barrier’ to ink, causing rollers to reject ink once water is introduced into the inking system.

Roller surface sensitization is a gradual process that developes over time to where it negatively effects the inking system’s ability to supply adequate ink supply to the plate.

Sensitized rollers is more of a problem with presses with ‘intregrated’ dampeners that carry more/excess wetting solution within inker.

The most vexing symptom of having sensitized rollers is having to ‘over-ink’ the plate in order to hold color.

This condition evenutally leads to the development of tone bands accross plate that appear to be caused by excess pressure or worn ink oscillator roll/cylinder gears.

I know of Printers who have re-geared presses at recommendations of Field Engineers hoping to solve this problem.

The solution is simple. First you must recognize the problem and its cause. Then institute a procedure of proper preventive roller maintenance.

A good water misiable roller wash is ‘necessary’ to cut through paper a bi-product roller glaze. Pure petroleum solvents alone won’t do, you ‘need’ the strong detergent properties of a good water misiable roller wash to cut/disolve paper bi-products.

A weekly application of Varn Revitol helps to cut the deep contamination cuased by dyes that actually become absorbed in soft roller surfacces. At first use you will emmediately notice a blue/purple color leaching out of your soft rolls which is the blue paste tone that makes carbon black look blacker.

Follow up each application of revitol with a water misiable wash deluted with water until the revitol does not change color. Then as a final wash, follow up last application of water misiable wash with a neutralizing rinse of 15% white kitchen vinegar and water to make roller surfaces more ink receptive.

Proper roller maintenance is critical to keeping your alcohol dampener in good condition and operating at its optimum.

Metal rollers must be kept clean, smooth and free of oxidation, and soft rolls must stay soft and sensitized to remain hydrophobic and ink free.

Metal rollers can be cleaned with most good quality plates cleaners, then wiped clean with water and coated with a 50/50 solution of gum and water.

Rubber rollers require special care since they have open surface pores that can accumulate/collect contaminates from the printing process. Ink pigments, paper sizing, and traces of some alcohol substutites accumulate in the roller surface causing the roller to loose its’ hydrophobic affinity to where it carries less and less water and eventually picks up ink.

When this happens you must deglaze and recondition the soft rollers to re-develope and sensitize it’s surface to reject ink and attract water.

First you must remove all contaminates with a good cleaning. A product called ‘Mati-clean’ works well as the first step in removing roller contaminates. It cuts ink pigment and paper sizing well. A 50/50 mix of a good water misible roller wash also works well as the step #1 wash to remove surface contamination.

Once you have performed a complete step #1 wash, step #2 is to rinse and lightly scrubb the rollers with a liberal application of isopropl alcohol to remove any hint of a petroleum film/residue from the rolls.

Then step #3 is an application of a 50/50 mix of gum and water will coat the roller to where it will accept fountain solution without rejection.

When not using your press, always coat your ‘clean’ fountain rollers with an application of 50/50 gum and water to seal the surface until next use.

A quick test to tell if your rubber rollers are becoming contaminated is to wipe them briskly with a cotton pad saturated with isopropl alcohol. If you wipe off a purple stain its an indication that your rollers are absorbing blue paste toner and other dyes used in ink.

If you find that you are increasing your water setting, chances are your rollers need to be cleaned and re-conditioned.

Note: If this cleaning procedure does not bring your soft rollers back into a usable state, check durometer to determine if rubber has hardened beyond specifiactions.

In an emergency situation, you can hand scrub soft rolls with a fast dry deglazer to remove a deep glaze condition, but always follow up with alcohol and then 50/50 gum solution before use.

If durometer it too hard (beyond specs) replace all soft rolls as a set.

Rubber rollers are manufactured with a texured surface which is produced by a spinning grinder wheel.

The the hills and valleys of the textured surface is what provides the grip/surface that allows ink to adhere to and flow from roll to roll thoughout the ink train.

When the roller’s ‘valleys’ become plugged, the rollers surface becomes smooth to where ink does not adhere properly.

To check rollers condition, use your sense of sight and touch.

Soft rollers should have a dull, satin surface appearance, and exhibit a marked resistance to the drag of your fingers as you drag them accross the rollers’ suface.

If rollers have a smooth slick feel to the drag of your fingers and look glassy, they are glazed.

When rollers glaze, the textured ground surface does not hold and transfer ink effectively, forcing you to run more (thicker ink films) ink and water to achive required ink densities.

Thicker ink films result in dot gain, hickies, mottled solids, ink drying problems, and most likely increased spoilage and waste.

There are several types of glaze that effect roller performance.

Paper lint, gum, ink vehicle and pigment residue, and calcium carbonate, and each requires cleaning to effectively remove them.

If you use a good quality water misible roller wash (one that mixes well in ‘warm’ water and stays in suspension) you will remove most all paper, ink, and chemical glaze. In addition, if you use a good deglazer/desensitizer (like Varn Revitol) at least weekly, you will keep your rollers in clean and in good operating condition.

Roller cleaning sequence should go like this;

* Remove ink with a good waster misible roller wash followed up with a water/15%Vinegar-rinse that is warm or at room temperature.

*weekly, follow up water misible wash with applications of Varn Revitol.

Re-apply until revitol does not change color, then follow up Revitol with application of water/15%Vinegar-rinse to all remove traces and neutralize alkali PH of Revitol and condition ink rollers to become ‘more’ ink receptive.

The liquid holding capacity of the Kompac causes wetting solution to contaminate faster than dampeners with greater fountain capacity.

On long runs, fountain contamination caused by paper surface sizing, spray powder, and chemical neutrizers collect and concentrate in Kompac wetting solution.

Some papers which are ‘too neutral’ ( high alkaline) can raise fountain PH from desired 4.5-5.5 to 6.5-7.0 within 1,000 sheets causing dry-tone.

If solution contamination is not removed, image fidelity and ink density can go down hill fast with each succeeding impression.

The solution has been to stop, suck-out the contaminated solution that collects near seals, allow dispenser bottle to replentish fountain, re-wet plate, re-start press and print.

When making a color wash, the routine process of stopping, sucking out ink-solvent waste, disposing of waste, re-applying ink solvent, restarting press wastes valuable press time.

Daily non-productive time required to refresh and clean your Kompac represents many lost hours every month.

*Using TimeSaver Seals in your Kompac II is the solution to this delima!

PressSaver’s Kompac TimeSaver Seals have suction holes cut inline with Kompac nip connected to a Squeeze Bulb connected to remoted waste container.

When fountain solution becomes contaminated, just one quick squeeze sucks-out fountain contamination near seals and dispenser bottle automatically replentish solution.

Waste solution passes thru Squeeze Bulb and goes directly into one-gallon waste collection jug behind press, and the press never stops!

When cleaning your ink system, waste ink/solvent automatically sucks-out just as contaminated fountain solution, with just a few quick squeezes of the Kompac SqueezeVac.

When using an ink clean-up blade, TimeSaver Seals allows you to clean press and Kompac at same time without stopping press.

Note: Seal latching springs must be ‘slightly’ re-formed 1/8″ offering clearance for Seal’s hose connector.

See/enlarge attached photo to observe spring shape and required hose clearance.

‘Kompac TimeSaver Seals’ is the trade name of PressSavers, Inc’s Patent Pending TimeSaver Seals.

Go to Kompac Vac Category and follow Kompac SqueezeVac to learn about complete Kompac SqueezeVac System.

Plate lead edge ink build up is caused by excessive form roll pressure due to too heavy of a form roll to plate setting or a loose Kompac.

The Kompac II form roll ink stripe to a dry plate should be no less that 1/8″ and no greater that 3/16″. A setting greater than 3/16″ will cause the form roll to hit the plate lead edge too hard causing a lead edge ink build up.

The Kompac III form roll ink stripe to a dry plate should be no less that 1/8″ and no greater than 5/32″. A greater setting than 5/32″ will also cause a lead edge ink build up.

A loose Kompac will also cause a lead edge ink build up on the plate.

If your Kompac ‘bounces’ as it rolls accross the plate cylinders’ opening, chances are the mounting brackets are loose or the interface between the Kompac and its’ brackets, or brackets to press are worn.

This condition allows the Kompac form roll to fall ‘into’ the plate cylinder opening where the form roller hits the lead edge of plate cylinder too hard causing a lead edge ink build up. Replace worn parts or tighten bracketry to resolve any loose condition and re-adjust form to plate setting.

1. Take the Kompac off the machine and separate the rollers. Place the Kompac on a sheet of white bond paper on a light table. Bring the rollers slowly together until they just touch.- make a complete revolution of the rollers. No light should show through. Light would show only through depressed spots in the rollers (Low spots.) Operators putting excess pressure between rollers to compensate for low spots often cause ink burst marks (tracks) in the printed copy, sometimes confused with gear streaks or toning at the outer edges of the plate.
2. Calibrate the unit: Separate the rollers with the numbered calibrating knobs, disregarding the numbers. Use two strips of paper to set a slight drag equally on each side of the roller. It is important to the operation of the Kompac that the rollers are as parallel as possible.
3. Remove the small outer slotted screw from the calibration knobs and use a 3/32 hex wrench to loosen and reset the knobs to corresponding numbers.
4. Replace and retighten screws with both knobs set at the number “1”. “0” should separate the rollers, “2-2’/2” should be the operating position.
5. The numbers on the calibrating knob should always correspond when the rollers are exactly parallel. Never operate the unit with the knobs out of calibration after they have been set correctly.
6. With a plate on the machine, set the Kompac in the brackets on the machine without the spring. Let the Kompac fall down on the plate cylinder to assume a parallel position on the plate cylinder. Tighten the Kompac to a slight drag in the slotted brackets to hold the unit in place.
7. Hand operate the machine to ink up the Kompac and take an ink stripe. There should be an exact parallel stripe across the plate. (Do not Operate the machine under power without the springs attached.)
8. If the stripe is not parallel tap the slightly tightened Kompac up or down in the slot until it makes a perfectly parallel stripe.
9. Tighten the Kompac in the brackets and attach the springs.
10. With the plate still attached, operate the Press in the water position and adjust the unit to a very slight bounce evenly on both sides. Do not operate the machine with excessive bounce.
11. Add ink to the press and ink up the plate to a dense black. Stripe the Kompac form to be certain the roll is parallel. If not, make a slight adjustment.
12. Allow the form and fountain rolls to make contact for 10-15 seconds, place the single lever in the water position, use the hand wheel to make a rapid 1/4 inch turn opposite the nip. The ink burst strip should be approximately 1/8 and parallel. This will show the rollers are correctly calibrated.
13. Check the PH of the fountain solution. Use the manufactures minimum recommendation usually 4.0 – 4.5 acid and 5.5 – 6.0 alkaline.
14. Add fountain solution to the Kompac and with the press operating at a slow speed drop the form on the inked plate.
15. After dropping the Kompac rollers on the inked plate, the rollers should begin removing the ink evenly across the plate within 4-5 revolutions and clean the plate completely and evenly across in 20-25 revolutions. 
16. With the press off and the Kompac lifted off the plate, the plate should immediately begin drying evenly. Patches of water or excess water at the bottom of leading edges indicate more pressure is needed between rollers.
17. Excessive revolutions or inability of Kompac to remove ink from the plate indicate more water – or less pressure between the roller nip.
18. An area left inked in the middle of the plate can mean a slight low spot in the rollers of the unit. 
19. An uneven cleanup across the plate means the rollers are not parallel.
20. Water droplets or a complete instant removal of ink along the edge of the plate indicate leaking seals, or a weak pressure – plate ‘against the seal.
21. If rollers leave a residue or spots of balled-up ink segments, check chemicals or PH.
22. Kompac should remove all ink leaving a shiny, clean plate.
23. If the plate is clean at the front edge, but tones at the trailing edge, more pressure is needed form to plate. 24. Ink piling at lead edge bend of plate indicate too much roller pressure, glazed rollers, or chemicals causing excessive need of pressure.
24. A small amount of buildup in the plate edge over long runs is common. Stop the press and clean leading edge when needed.
25. Kompac will not operate properly with:
    1. Low spots in the rollers
    2. Glazed rollers
    3. Long or excessively soft ink or ink mixed with certain dryers
    4. Unbalanced PH in water fountain solution
    5. Rollers not parallel across plate
    6. Kompac tilted or binding in mounting frames
    7. Certain fountain solutions and inks are not compatible with the Kompac
    8. Paper plates made by certain manufacturers without their recommended 

NOTE: Kompac has discontinued manufacturing the 92260 seal. If you are still using these old style seals, you will need to buy the 92280 upgrade kit to use new style seals.

V-Belts, like other moving parts on the press, are subject to wear.  While they are manufactured with a combination of rubber and cord for extra strength and durability, they will eventually stretch, become frayed. loose their resilience, and become ineffective by losing their gripping ability.  Damage is also caused by the belts coming into contact with lubricants.

It is important for the press operator to realize that V-belts are made to standards and specifications. You cannot just pick a belt from the rack and install it on your machine.  Not only is the V-Belt’s width and diameter tapered, but it uses a pitch that must correspond to the sheave and pulley that it is driving.

Regardless of the manufacturer, most belts can be cross referenced by the numbers appearing on the belt.  Undoubtedly, some manufacturers produce a better belt than others.  However, belts are also classified for job ratings by the quality of the manufacturing.  The important thing is that you use a quality belt intended for your machine.

When belts need replacing, always replace them in sets to assure uniform performance from each belt.  When installing the new belts, use the adjustments provided to relieve and apply pressure.  Don’t damage the belt by stretching it over the sheave.  It should be adjusted and reseated in the sheave.  Belt tension should be checked carefully, as over tightening will cause serious stress on the drive motor from overheating.  Bearings are used in the side frames of the press to help provide lubrication and the shafts run true.  On small presses, shafts used to support and rotate using pulleys can be flexed and cause a bind by over tightening belts.  This is a common occurrence.

Other than creating a bind, proper tension is needed on V belts to correctly contact the sheave.  Unlike the round belt, or flat belt, all torque is directed against the side of the sheave.  The taper of the belt must seat firmly against the taper of the sheave.  The belt is not intended to contact the bottom of the sheave.  The contact would lessen the effective action by relieving pressure on the sides, lessening the gripping action.  (Stretched or worn belts).  The seating of the belt in the sheave should allow the belt to ride just slightly above the pulley.

Before making the final adjustment, rotate the handwheel of the machine to allow the belts to seat evenly in both the driving and driven sheaves.  At the same time, check to be certain both sheaves are in perfect alignment.  Misalignment alignment of pulleys create problems for any belt driven system, but even more for v belts and sheaves.

Checking Belt Tension

Mechanics all have their own method for checking belt tension.  Some use a fist to hit the belt, using the reflex to determine the tension.  Others use a 1/2 inch give in the belt tension from both sides of the belt when squeezed together to adjust the belts.  The important thing is V-Belts need a tension that will eliminate slack in the belt.  Over tensioning will cause problems.

Care and maintenance of V belts other that adjusting is almost non existent as previously stated.  The largest problem is contact with lubricants.  There are no special cleaners, other than wiping clean with a dry rag.  To our knowledge, no belt cleaners are formulated and sold, and belt dressing is not recommended.  Wear and replacement of V belts on printing presses is largely overlooked by press owners and operators.  They do make a difference in a smooth operating drive train.

Speed Control

Many newer small offset machines are now using speed controllers which are tied into the electrical system though a electronic board, and controlled from a central panel.  But, many still use the basic variable speed pulley.

The variable speed is a universally used, un-complicated system of raising and lowering the speed by driving a turning shaft with different diameter pulleys.  The pulleys used are tapered sheaves driven by V-belts to control the position with respect to the depth the belts will ride.

As with other sheave type pulleys, the V-belts are tapered to correspond to the pulley using the torque created by the side of the belt rather than the bottom.  Instead of one piece, it is manufactured as two separate side plates.  The halves are joined by a shaft and held tightly together by a compression spring.  By raising and lowering the motor mounting plate with either a lever or a crank, the tapered belt will lower into the pulley and separate the plates as tension is put on the belts.  The spring pressure between the two pulley halves will take up the slack in the belt and force the belts to ride higher as the tension is relieved from the belts.

Normally the variable speed pulley is fastened directly to the shaft of the motor, directly driving another pulley. When the belts are riding high it takes on the characteristics of a larger pulley, changing the drive ratio between the pulleys –  under most circumstances, increasing the speed.   As the belts drop lower, it  becomes a smaller circumference and lessens the speed.  Obviously, the speed is changed in increments by the crank or lever.  however, the increment posted on the press does not necessarily reflect the speed.

The variable speed is universally used on all types of machinery.  It is economical for manufacturers to install on machinery.  It is simplistic and works well, but when used under stressful conditions such as a printing press, it needs maintenance.

Most pulley halves use a key and key way slot to mount the pulley halves in alignment on the shaft.  The halves need to slide on the shaft as the belt raises and lowers into the pulley.  If a bind develops because of lack of lubrication, the belt forces the pulley apart – causing vibration and strain on the motor plate and belts.  It also becomes noisy.  The belts produce heat, causing the un-lubricated pulley to form rust, which will wear away the key and enlarge the key way.  When this damage is allowed to go unchecked, the pulley will become ineffective and need to be changed.

The binding pulley halves will also pinch the belt causing premature wear.  Changing the speed of the press – when not in operation, forces the belt into the pulley rather than using a turning motion to allow the belts to seat into the halves.  Improper adjustments of the motor plate when attempting to regulate the speed is another source of problems.  The belt should never bottom out to the point that it supports the weight of the motor.  This causes vibration and noise.  A belt riding too high on the pulley will cause loss of torque.  Always use the manufactures speed recommendations.

Certain pulleys are equipped with grease fitting, but are usually hard to access.  Belts should not be exposed to grease.  The most common way used to lubricate the pulley is to separate the halves with a screwdriver.  Spray the shaft with a lubricating oil, the work the halves several times to be certain they are sliding freely on the shaft.  If you decide to remove the pulley from the motor and disassemble it, to inspect for wear, care needs to be taken.  The coil spring is usually compressed on the shaft tightly.  When the clip or fastener is removed, the spring can fly.

When replacing the pulley on the motor, tighten it securely on the flat of the shaft to prevent slipping.