I would say that generating and maintaining a consistent and efficient in-feed is probably the most important factor in increasing packing speed, accuracy and efficiency.
A good in-feed will increase productivity, reduce give away and ensure smooth running of the machine and equipment.
Without a good in-feed, waste will increase, you will lose £££ in product give away and deadlines will be missed due to slow downs and faults.
A good in-feed saves you money!
Table of contents:
- What is an in-feed?
- Why do I need an in-feed?
- How do in-feeds work?
- Matching product transfer speed
- Ideal in-feed equipment and machinery
- How does an in-feed save me money?
- Facts and figures (Calculations of costs and labour)
|Without an in-feed:
||With a good in-feed
What is an in-feed?
An in-feed is the process that transfers your product to be packaged to your weighing machine.
This can be done in a variety of methods, with the most common and most effective solutions utilising a large hopper to hold your product and an elevator to lift it to your weighing machine.
Many systems also utilise a vibratory feeder above the weighing machine to trickle the right amount of product on to the weigher in a consistent and uniform fashion.
Why do I need an in-feed?
In-feeds ensure that a constant and uniform flow of product is fed to your weighing machine. This is important as weighing machines generally use vibratory feeders to fill weigh hoppers with product. These vibratory feeders are controlled by the weighing machine and are set to a constant amplitude and speed.
If they contain too much product, they will over fill the weigh hoppers, if they contain too little product, the weighing machine will become drastically slow in calculating and depositing weighments.
A constant and uniform flow of product ensures that the settings for the vibratory feeders are optimized and accurate so that the weigher will transfer and weigh the correct amount of product, quickly and efficiency for as long as it is running.
If you do not have an in-feed and are manually filling the weighing machine, your target weights will be inconsistent and inaccurate during the beginning and end section every time the weigher is re-filled or topped up.
When the product is re-filled, there will be too much product on the weigher which will result in over-scaling and product give away. It may also over stress the weighing machine leading to faults which require parts, servicing or repair. When the product is running out, the weigher will become incredibly slow and inefficient which will affect your packing machine and out-feed. Your paid labour will also be standing about idle waiting for the weighing machine to get back up to speed.
How do in-feeds work?
Generally, in-feeds are, or at least can be controlled by your weighing or filling machine, which could be a multihead weigher or a linear weigher or even an auger or volumetric filler.
With a multihead weigher, the in-feed is controlled by either a centre load cell that measures how much product weight is sat on top of the multihead weigher, or with eyes, infra-red sensors that can determine how much product is on top of your weighing machine or in your weighing machine’s hopper.
The first type (load cell) is a far more accurate way of controlling your in-feed as the multihead weigher will only call for more product when it is running low, ensuring that a uniform amount of product is available to weigh at all times.
The second (infra-red sensor) is a less consistent albeit, more common method that works by “over loading” the amount of product on your weighing machine by calling for product until the sensor goes out of range. The sensor’s range is generally an unreliable and unmeasurable amount which can be affected by light, shiny surfaces, construction of the machinery and the angle of the sensor. These types of sensors often need “tweaking” by repositioning and angling or calibrating to ensure that the product feed is consistent.
Both types work by detecting how much product is on your weighing machine and calling for more product (sending a signal) if there isn’t enough product. The feed signal needs to be connected to the in-feed machinery to start and stop the in-feed flow as required.
If you have a multitude of elevators, conveyors, vibratory feeders and other machinery that provide product to your weighing machine, it is important that these are all controlled by the same system to ensure that once your weighing machine is full, the product is not still being produced at the other end. If this isn’t done, you will not only end up with product all over the floor, but potentially too much product traveling up an elevator that could either over stress the motor and cause it to burn out or over fill your weighing machine which could cause over-scaling and potentially exploding bags due to over-filling.
If your product is fed by an elevator that moves too quickly or if it has large flights that carries too much product per flight, then you will end up with a lot more product on top of your weigher than you would with a slower elevator with smaller flights. This will be amplified if you have not set-up your load-cell or eye sensor properly.
That isn’t to say that slow elevators with small flights are better! It is imperative that your elevator speed and construction matches what you actually require.
It’s no good just purchasing any old elevator with an unknown angle of ascent, belt width, distance between the flights and height of the flights. In order to optimize your in-feed, you need to ensure that your elevator matches your packaging specification.
Matching product transfer speed
Most elevators can be controlled by an inverter which allows you to set a frequency that will determine the speed of the elevator. The motor on your elevator should have a plate with frequency ratings, amps, power specifications etc. which are important to know so that you install the correct inverter.
Once installed, the inverter should be setup to “ease” the elevators stopping and starting and run the elevator at the correct speed for your product.
This could take quite a bit of trial and error to get right, but it is essential to maintain an even and consistent flow.
The speed of the product being deposited from the elevator should match the speed that the weighing machine is weighing the product so that there is a constant and consistent flow of product being deposited onto the weigher and moving through the weigher. This will ensure that your weighing machine always has exactly the same amount of product on top of it which will make it easier to set up and optimize to get extremely fast, accurate and efficient weighments.
Ideal in-feed equipment and machinery
- Large hopper with vibratory feed
- Ensure that the hopper always has some level of product.
- Set the vibratory out-feed to move product steadily on to the elevator. The product transfer speed should match the speed of the product being weighing machine.
- Inclined flighted elevator
- Use an inverter to control the speed of the elevator. The product transfer speed should match the speed of the product being weighing machine.
- Ensure the flights are well spaced apart and do not carry too much or too little product per flight. Try to ensure product flow is consistent (uniform) at the top of the elevator, not dropped in large heaps.
- Vibratory feed hopper
- This is not required but has huge advantages in maintaining a consistent flow.
- A secondary hopper above the weighing machine will ensure that the in-feed remains completely consistent as it is fed onto the weighing machine.
- This will also allow for more error and inconsistencies of the elevator if it is going to fast or drops product in large heaps.
- This will need to be on a separate frame / gantry from the weighing machine however, as the vibration will affect target weights.
- Ensure that this always holds a good amount of product so that any shortages at the beginning of the in-feed or delays in filling the main hopper will be compensated.
How does an in-feed save me money?
Without an in-feed you will experience slowdowns, over-scaling errors (faults), down time due to over stressing the machinery and product give away from inaccurate weighing.
You will require at least one person to continually fill and top-up product onto the weighing machine, more if your product is contained in heavy bags, barrels or containers.
You will require at least one person to collect the finished bags and check their weights, again possibly more due to inaccurate weighing and over-scaling caused by over-filling the weighing machine.
Your packing speed will be drastically reduced over each working day meaning that more time and labour is required to fulfil your orders.
More time will be spent out of production waiting for repairs, spare-parts and maintenance due to over-stressing the machinery by over-filling.
More idle time will be spent waiting for the machinery to be reset each time there is an alarm or error from over-scaling or exploding bags due to over-filling.
Facts and figures (Calculations of costs and labour)
Based on the Multipak Standard Range packing line running dry, loose product (peanuts) at 250g per bag on laminate film for 8 hours per day with standard working breaks.
Line consisting of a multihead weigher, gantry or frame, bagging machine, off-take elevator and a rotary table.
Maximum speed of packing line: 60 bags / minute
Average speed of packing line with optimal in-feed: 45* bags / minute
Average speed of packing line with no in-feed: 30** bags / minute
*This assumes 2 hours break, changing film, hygeining before and after shifts. Total running time of 6 hours / working day.
**This assumes 2 hours break, changing film, hygeining before and after shifts plus slowdowns and down time of at least 2 hours. Total running time of 4 hours / working day.
Required to fulfil an order of 100,000 bags with an optimal in-feed:
- 5 days running
- 2x workers to top-up hopper, check and collect finished bags
- Total cost of labour: £520 (£6.50/hour, 8 hours / day for 2 people)
Required to fulfil and order of 100,000 bags without an in-feed
- 7 days packaging
- 2x workers to continually feed weighing machine, reset faults and clear dropped product
- 2x workers to check bag weights and collect finished bags.
- Additional packaging film from wasted/split/over-filled bags
- Additional product from over-filled/spilled bags
- Total cost of labour: £1456
- Cost of extra product & packaging film: £10 – £500
- Total additional cost compared to optimal in-feed calculations: £1000
- Total additional cost compared to optimal in-feed calculations / year: £50,000