/webtest/epaper_i.php?lang=en&ID=645 SHINI PLASTICS TECHNOLOGIES, INC.

Special Reports

2012 Quarter 3 Issue 12

Get the Most from Your Granulator – Six Tips for Proper Maintenance & Operation

Share to:

As we all know, waste utilization can help injection molding and extrusion business saving the cost. This is a benefit of granulator in plastics industry. Before better recovery plants coming out, granulator has been the preferred recovery tool for injection molding and extrusion businesses. However, any brand of granulator will have a certain life, in order to make better use of the granulator and save material cost, it is necessary to plan your own preventative maintenance schedule to ensure a long, productive life for your unit. When you bought your granulator, your supplier probably provided comprehensive instructions on when and how critical maintenance should be performed. All you have to do is go through the instructions carefully, get a better understanding of the machine and thereafter keep the machine in good maintenance and repair. In this article, the author gives some quick guidelines for you to follow so you can avoid major granulator problems.

Keep your blades sharp

Your blades will go dull if you use your granulator long enough—guaranteed. The question is how to judge whether the blades are dull. If you’re wondering why your regrind contains more dust than normal, why throughputs are down and noise-levels are up, chances are your blades are dull. This is, by far, the most common granulator problem. Check your blades regularly. By observation, you can find out whether there is metal fall into the feed hopper and if yes, how to avoid such problems from happening? Moreover, remember your granulator has not only rotor blades, but one or more bed knives as well. If one is dull, as is the other.

1. Check before starting-up

When you got a new granulator, there are two points for you to take care of. First, before starting the granulator, check whether the rotor blades work normally by rotate them manually. Second, check whether there is metal debris in the feed hopper. That’s probably all the checking operations before starting, easy but hard to persevere with. After starting, make sure the direction of rotation of the rotor stays the same with the arrow mark on the machine. Keep the machine in idling condition for 2 to 3 minutes and began to feed if no anomalies happen.

2. Check your blades regularly

A visual inspection on sharpness of blades should be put into practice. This practice should be built into your regular preventive maintenance schedule, including daily check, weekly check and monthly check. If they are dull, you have two choices: replace or re-sharpen. Most suppliers provide either sharpening or replacement programs, or both, and this should be clearly outlined in your manual.

3. Don’t forget the screen

If your blades are dull, especially if they’ve gone unattended for long periods of time, your screen and screen cradle may have suffered as well. For most of the regrind are produced by impact force rather than blade load, and the regrind obtained are in big size and with certain compact velocity. So take a look at the screen holes—if they are beginning to appear pear-shaped, it’s probably time for a replacement, again from your granulator supplier. Shini has listed all the blades and screens in the spare parts list and you can get whatever you want from Shini for your granulator.

Mind the pitch

The pitch is pre-set before the granulator leaves the factory but a lot of things can happen on the road. That’s why it’s so important to check the pitch as soon as your granulator arrives, after every blade repair or exchange, and on regularly scheduled intervals. Shini granulators have special technical requirements in this area, low-speed granulators.

Tolerance between rotating blades and fixed blades of Shini’s low-speed granulators SG-16, SG-20 series and sound-proof central granulators SG-23, SG-30, SG-36, SG-43, SG-50 and SG-70 series is normally between 0.2mm and 0.3mm, and for Shini’s roll-feed granulator SGF-26E series, the gap is between 0.1mm and .15mm. Using the presetting knife jig , feeler gauge, and a pair of gloves, adjusting the gap is a relatively simple process. Remembering to do it is not. Put gap adjustment in your maintenance schedule and increase the life and effectiveness of your granulator.

Always empty your storage bin

Your granulator has a bin to collect the regrind after it is ground and falls through the screen. This bin is often— and inaccurately—referred to as a storage bin. You should never, ever store regrind in this bin. Regrind is just held there temporarily so it doesn’t spill all over your floor. If the granulate stays too long in this bin, it backs up. And when it backs up, it increases wear in the blades, wear in the screens, and of course, throughput decreases dramatically.

The obvious answer to this problem is to either slide out the bin and empty it at regular intervals or use an evacuation tube fixed to a feeding blower to automatically remove the granulate from the bin. When using a blower, make sure it works normally and the regrind is conveyed smoothly.

Proper feeding for the granulator

Eat slowly helps digestion while gobble does harm to it, even causes choking pain. Granulator is somehow more like people eat. Over-feeding your granulator will, obviously, back it up, reducing productivity and, in some cases, the granulator will simply cease working. Just as it’s better to automatically remove regrind from your granulator, it’s also better to automatically feed your granulator—either with a robot or a conveyor. That way, there is no chance of over-feeding your unit, causing inefficiency and downtime. So, under your careful maintenance, granulator will perform better and pay you back.

Proper feeding is important. If your granulator sits idle and the rotor spins without parts, the energy efficiency ratio is greatly decreased. You can and should expect a certain throughput rate from your granulator but if your scrap is sitting next to your machine in a drum, box or storage area, you are definitely not getting the most from your unit.

Don’t forget belt tension

Particularly with a new unit, it is exceedingly important to check and readjust the belt tension. Why? After a few hours of operation the belt will give way, almost to the point of its maximum dimension. So, after about five hours of operation, shut down your granulator, remove the belt guard, and tighten the belt per the instructions in your manual.

However, what about an older granulator? Perhaps you’ve owned it for years and have regularly checked knives, screens, gaps, feeding and discharge, but your granulator has started to jam, stall, or even seems to vibrate excessively. Check the belt tension. Over time, a belt may need to be replaced as well. Bottom line: don’t forget to include this important area in your regularly scheduled maintenance check.

Don’t lose your bearings

This probably goes without saying, but don’t forget to grease your bearings. Bearing lubrication can directly affect your entire granulator. If you hear your granulator rattling, grinding and otherwise making noise, it’s too late and the damage has been done. Bearing lubrication failure will lead to bearing life shortened or cause the whole machine cease-working and cause economic loss. In view of this, you had better regularly grease your bearings. Bearings that are properly lubricated will extend the life of your granulator.

All in all, if all safety and operation procedures are followed carefully, your granulator will function properly for a long, long time. The most important point is to make sure the good preventative maintenance schedule have been carried out regularly. As a result, the granulator will work at its best to pay you back.

Special Reports

If you want to read other articles, back to2012 Quarter 3 Issue 12.