• Project : - Newsprint Reel mileage.

• Target : Prepare best method to calculate web-offset Newsprint (NP) reel mileage 

• Time line : 2016-2018

• Project posted in WAN-IFRA World Printers Forum Dated - 26-04-2017

How Newsprint paper mileage expressed ?

Paper mileage is calculated as - Pages / Kg (250 pg/kg) or Square meter / Kg (23 m²/kg) .  When number of pages / kg increase we said mileage gained.
For example :
42 GSM = 250.6 pages / kg (w.r.t size 0.190008 m²) in case we get more than 250.6 >  pages/kg then,  we say it is gain in paper mileage. If one NP reel Net weight = 1220 kg  gives 38,500 copies (8 pages/copy) then, What will be the grammage calculation ? 

(38500 copies * 8 page) / 1220 kg = 252.45 Pages/Kg  = 41.70 g/m²
[ Standard 42 GSM - gives 250.6 Pages/Kg ]

From this figure, we say net reel weight (collected) is below the standard GSM 41.7 g/m² (42 GSM) - here we got more pages (252.45 pages/kg) and that is gain from the reel.

Comparative study on Reel mileage :

Choosing the correct method for calculating Newsprint paper mileage can be challenging, as each method has its own advantages and disadvantages, and the accuracy of the result depends on the reliability of the data collected. Here's a comparison of the three methods :

Method 1: Net weight collected:

Advantages:

• Simple and straightforward calculation.

• Requires only the net weight of paper used and the number of pages produced.

• Suitable for situations where accurate data on individual reels is available.

Disadvantages:

• Ignores paper waste and variations in paper thickness.

• Can be inaccurate if data collection is not rigorous.

• Not considering balance reel weight.

Method 2: Mean/basis GSM:

Advantages:

• Takes into account approximate paper thickness based on GSM.

• Can be more accurate than the net weight method, especially if paper waste is significant.

• Easier to implement for large production volumes.

Disadvantages:

• Requires accurate basis grammage data, which may not be readily available.

• Can be subject to errors if the basis grammage data is not representative of the actual paper used.

Method 3: Paper thickness:

Advantages:

• Provides a direct measure of paper thickness (actual) in usage.

• Can be very accurate, especially if combined with data on reel diameter and length.

• Suitable for situations where precise control of paper consumption is critical.

Disadvantages:

• Requires specialized equipment or methods for measuring paper thickness.

• Can be time-consuming and expensive to implement.

Choosing the right method:

The best method for calculating paper mileage depends on several factors, including:

• The level of accuracy required.

• The availability of reliable data.

• The resources available for data collection and analysis.

• The specific needs of the application.

Here are some general recommendations:

• If you are looking for a simple and quick estimate, the net weight method may be sufficient.

• If you need a more accurate result, the mean/basis grammage method or the paper thickness method may be more suitable, depending on the availability of data and resources.

• In situations where precise control of paper consumption is critical, the paper thickness method is likely to be the most accurate, although it requires specialized equipment and may be more expensive to implement.

Ultimately, the best way to choose the right method for calculating paper mileage is to consider the specific needs of your application and the resources available to you.

• Our question is - Whether we can collect exact net reel weight every - time / production/ day / month ?

• Only trusted weight gives you trusted result.

• Consolidating data give only approximate result and we can't find on what day problem start ? and when it ends?.

How do I check my NP mileage at lost?

• If I fix my GSM as per mill, then we can get close to actual mileage and calculate net weight and paper caliper based on GSM.

• If My Net reel weight collected is accurate, then we get GSM , paper caliper base on Net weight collected.

• If I move with paper caliper measured and trust, then we get GSM and net weight based on it, personally I feel exact Newsprint mileage calculation based on paper thickness is best method. Because paper caliper is measured accurately by real time data from RPM of reel and we get length of web by formula, so we can trust paper thickness based reel mileage. 

It is important that we have to fix or trust one variant, then we can calculate other data related to paper mileage.

Analysis to find accuracy of GSM mentioned by paper mill ;

We tested more than 40 sample of NP Reel labels and found reels with higher accuracy rate of GSM in particular mills and rest with more deviations. Using below calculator we can get grammage accuracy rate, actual grammage, amount of unaccounted weight and paper thickness . Mostly there will be variation in mean grammage (Basis weight mentioned by mill)  data, which as to be measured or check for cross verification.

To the printer, variations in grammage are a cause for concern both as regards the performance of the paper in the press and as a cost factor relating the number of copies printed to the price metric ton for a given nominal grammage (Actual measured or calculated value with decimal fraction). From a production performance point of view, the consistency of the grammage is important; wide grammage variation about the mean value and the corresponding variations in material properties, may be a cause of poor or inconsistent press performance even though the mean grammage of a consignment is exactly as specified. 

The tolerance limits on the mean grammage of a consignment are of major importance from a cost point of view. Help of worksheet as shown in picture, we can compute average grammage from the list of data per consignment or per 100 ton. As per tolerance accuracy rate between ± 2 is considerable, that we have to measure or check grammage frequently. 

Calculator to find accuracy of grammage :

From following calculator, we can try our own data for checking accuracy of grammage and paper thickness of Newsprint; 

Note : For result hit Submit button after editing your own value in the above calculator. 

• Positive deviation in GSM (basis GSM < actual GSM) leads to a loss in mileage, meaning you pay more for less paper. This occurs because the length of the paper is shorter than expected for the given weight. (Example 42.1 g/m² is loss against basis GSM 42 g/m²

• Negative deviation in GSM (basis GSM > actual GSM) results in a profit, as you get more paper for the same weight and payment. This means the length of the paper is longer than expected. (Example 41.8 g/m² is profit against basis GSM 42 g/m²)

By frequently monitoring the grammage difference and taking corrective actions, you can ensure you are getting the value you pay for and avoid potential losses. Additionally, being cautious while procuring consignments by considering the mill's reputation and quality control measures can further minimize the risk of receiving paper with inconsistent grammage. 

Overall, your approach to managing grammage variation seems well-structured and effective. By combining monitoring, proactive procurement practices, and potentially negotiating with paper mills for consistent quality, you can ensure your business operates efficiently and avoids unnecessary costs.

For example from our calculator result as said above, if we purchase NP @ cost INR.67000.00 per ton then, un accounted weight is multiplied with this to find additional payment that we made surplus per reel  ; Jeonju 20.18 * 67 = INR 1352.06 and Jamsankoski -4.85 * 67 = INR - 324.95
[Note: negative implies profit as we saved  money on un-accounted kgs of NP].

Apart from this, we provided / included diameter data of reel  from label to above calculator. So it also compute  paper thickness based on GSM and length of web, this can be verified either by physical measure or from machine real time data (our machine give paper caliper while production). 

We have recently tested one NP reel - Papier masson WB # ***93131 for GSM accuracy, and paper thickness using above calculator. Test result was satisfactory with 100% efficiency, as our caliper data result that matched completely with our web offset machine Mitsubishi DS calculation - 65.89 ɥm picture is taken as proof and posted here. Also this program compute actual grammage as 40.135 g/m² (three decimal fractional integer), Net weight of reel as 858.10 kg, and with difference 2.9 kg of weight w.r.t grammage.

Paper thickness as 65.99  ɥm based on length and 65.77 ɥm based on weight was calculated, this give maximum and minimum range of thickness possibility of the NP reel for cross verification. We got 65.89 ɥm real time data from MHI-DS machine for this Papier masson reel and our calculator also computed an average paper thickness as 65.88 ɥm.

We continue our testing with program calculator above for accuracy test and our result were satisfactory with the performance. Grammage accuracy  between ± 0.5 match quickly with machine caliper calculation and mostly fit between caliper range calculated by our above program. Newsprint like Papier masson WB, Langer are more accurate in grammage that is between ± 0.5 . 

For more on paper caliper or thickness click here ; Paper thickness