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Non cumulative Material Leveling

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daniel morais
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Hi my friends,

I would like to discuss some cases that I faced today. I'm leveling material from Spider but, I think that algorithm always considers that if you do not use the material in each period the same material goes to another period for use. The cumulative concept that's right for materials like bricks, gravel, cement and others but, for leveling composite materials like concrete and asphalt, that do not consider stock in real life the way is different. Spider have some key for not considering this? According picture bellow the leveling works very well because Spider consider that quantity not consumed (8units) in 11/30/21 will be cumulate and will consumed 12/01/21 together other, even resource Truck do not capacity (992units consumed) faced (1000units income (produced)). In systems where the material is produced and this product must be 100% used the stock concept is right? Have some way to consider this situation?

8010
truck_consumption.jpg

Follow file link,

https://we.tl/t-cK8c6F8ewd

Best Regards,

Daniel Morais

 

Replies

daniel morais
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Yes, well understand, is because strict links just work well with one predecessor and one successor, for this reason your use is too restrict, only in some cases.

Best Regards,

Daniel

Rafael Davila
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Exactly, this is the point.  There are many reasons an activity might be delayed, in this model it was a date constraint the easiest way to force the delay. But it might be resource leveling or a delay in a predecessor, a delay that at initial schedule does not happens but as the schedule moves will happen.

Using strict links is error prone and unreliable. If strict links were so reliable everyone would be into it but no one suggested their use, everyone knows strict links are unreliable. Even Spider Project knows and the best t can do is to issue a warning when it happens.

Strict links happen when minimal lag constraint equals maximal lag constraint; maximal lag is a functionality not available in current scheduling software.

Sixty years of project planning: history and future

  • 2.3.1 Maximal relations: Maximal relations were included in the original MPM; however, they were not adopted into the widespread commercial software used by the majority of planning professionals.
daniel morais
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Hi Rafael,

But in real life, with materials don't stockable (this is our issue), this situation never will happen, I mean, the consumption in different days with production, so i understand that this restriction on activity 201 don't happen no?

Best Regards,

Daniel

Rafael Davila
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Daniel,

... if we could modeling like real life, material producing by one activity and be consumming by others activities all leveling by materials restrictions

The issue is with the need for reliable strict links, so unreliable I never use them; they might hold at initial run but a delay to successor may create problems.

ssd01  

https://www.mediafire.com/file/95z3nlo8zuzpg8k/Trucks_Asphalt.060.sprj/file


ssd02

https://www.mediafire.com/file/pvt8ozjm66fkuhl/Trucks_Asphalt.061.sprj/file

Best Regards, Rafael

Rafael Davila
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In my experience sizing the construction crew is rarely a continuous function but a step function.  Usually increasing crew size means different equipment.  The production rate is not always linear with the crew size.  The asphalt placing is no exception; similar to earthwork the operation must be balanced.

Planning the asphalt paving and compaction process

Planning for earthwork operations is somewhat similar.

In practice we usually have several crew options, each with a different composition and different production rates but with the skill to perform the same work. Sometimes the crew selection goes to a specific crew; sometimes several crew options can be considered as multi-resources sharing the same skill. The use of multi-resources and skills is useful when you have several crew options and want to keep the options open; as the schedule moves the crew selection might be different to accommodate for re-distribution of resources.

Marcus Possi
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PART 2 / 2 – stockable materials – sand & water & orange_juice - pdf here

 

 

 

Rafael Davila, Bogdan Leonte, Vladimir Liberzon, and Daniel Morais

 

Thanks to Spider Project algorithms and engines … it is easy to Spider Project model and take care of it since I was young.

“It is necessary to adjust material consumption to make ends meet with the stock, otherwise there will be a fake schedule.”

 

Spider Project has a specific productivity type, that when modelled with skills, under the CPM added to Liquid Scheduling or - A.I., made passible to Paulo Cabral and I produce the following compliment:

 

Here are our assumptions:

ü  The asphalt production and consumption are under the same calendar to make it easy to understand;

ü  The asphalt production is a “contract” with a fixed duration – greater than the “calculated longest path” spam;

ü  We have not sequenced in rigid way (modern vicious CPM) – instead, we let the activities free allow spider to decide what is the best result obeying the priority applied (old CPM + A.I., we call liquid scheduling);

ü  We considered asphalt as sand or water, or even orange_juice, as stockable materials / not perishable materials;

ü  We did not assign the maximum number of trucks – 22 in a Team; but 22 different Teams, with a 100% workload “truck” skill resource type. The skill truck has 22 different trucks;

ü  We made a graphic to analyse the sand/water/orange_juice losses – we cannot use “stocked asphalt;”

ü  We started using all trucks – 22 units

 

8025
bxx1.png

 

watch the video to understand how we did it.

File here

Pic here

 

 

The losses of materials (“asphalt” not used and stocked at supplier) are related to the number of trucks used in each activity.

 

The pic above has:

1 – intersection – yes, it is possible and profitable to make two activities at the same time

2 – number of trucks used simultaneously;

3 – asphalt balance – asphalt plant production x asphalt consumption

4 - 1000 tons/day – 100 tons/h in Asphalt plant

5 – “asphalt” consumed every day;

6 – first, second, and third activity (from the highest to the lowest priority) running according to the amount of produced material;

7 – the over quantity material produced but not used for the former activity, is passed to the next activity in advance, with the possible quantity available;

 

Although we applied all the trucks – 22, the algorithm decided for 18 trucks.

Note: why 18 trucks?

(1)    100 tons/h in asphalt plant with each truck with 5.4 tons/h ~ 18.5 units;

(2)    More than 18 trucks wont suit plant capacity.

  

8026
bxx2.png

Pic here

 

Adjusting manually the maximum trucks quantity from 22 to 18 – manually we got:

 

8027
bxx3.png

Pic here

 

A dim increasing in material losses. … 1158/1013

 

 

Adjusting manually the maximum trucks quantity from 22 to 8 – manually we got:

 

8028
bxx4.png

 

An increasing in material losses. … 5249/1029

And an increasing in project time from 6/03/2022 to 16/03/2022

Let Spider Project does the arduous work for you.

watch the video to understand how we did it.

Pic here

 

 

Marcus Possi
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PART 1 / 2 – not stock material – asphalt & concrete & tomatoes - pdf here

 

 

 

Rafael Davila, Bogdan Leonte, Vladimir Liberzon, and Daniel Morais

 

According to Mr Liberzon this task is not trivial and today Spider Project does not model this case, yet.

“It is necessary to adjust material production to consumption if maximal consumption is less that maximal production capacity and adjust the number and workloads of assigned resources if maximal consumption exceeds the production capacity.”

 

Spider Project has more than 4 methods of assignments opportunities: direct assignment, Teams, Multi-resources, skills, and their mixings, so we tried a lot, and the best natural results will be described here – as far as we (Paulo Cabral and myself), could reach it.

 

Here are our assumptions:

  • The asphalt production and consumption are under the same calendar to make it easy to understand;
  • The asphalt production is a “contract” with a fixed duration – greater than the “calculated longest path” spam;
  • We have not sequenced in rigid way (modern CPM vicious) – instead, we let the activities free allow spider to decide what is the best result obeying the priority applied (old CPM + A.I., we call liquid scheduling);
  • We called asphalt or concrete, or even tomatoes, as not stock materials /perishable materials;
  • We made a graphic to analysis the asphalt losses – we cannot use “stocked asphalt;”
  • We started using all trucks – 30 units

 

8018
a1.png

watch the video to understand how we did it.

File here

Pic here

 

 

The losses of materials (asphalt not used and storage at supplier) are related to the number of trucks used in each activity.

 

The pic above has:

1 – 1000 tons/day – 100 tons/h in Asphalt plant

2 – asphalt balance – asphalt plant production x asphalt consumption

3 – first activity (highest priority) waits the necessary amount to start and finish its job

4 – second activity waits the necessary amount to start and finish its job

5 – third activity (lowest priority) waits the necessary amount to start and finish its job

6 – asphalt plant time to produce first volumes

 

Adjusting trucks from 30 to 18 – manually we got:

8022
a2xx.png

 

watch the video to understand how we did it.

Pic here

 

 

1 – the maximum calculated asphalt losses

2 - no spam between activities – the shortest duration

 

Note: why 18 trucks?

  1. 100 tons/h in asphalt plant with each truck with 5.4 tons/h ~ 18.5 units
  2. More than 18 trucks wont suit plant capacity – less than 18, parallel paths will be set to optimize asphalt balance working with rotten asphalt (STOCKED ASLPHAT)
  3. The operator – spider operator, must change trucks units by himself.
  4. In this specific case the asphalt losses are on 2750 tons, what seems to be ~3% - refer to pic below

8024
a3xx.png

Pic here

daniel morais
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Thank you Rafael,

The solution works like your first approach by hammock but, I think how conceptual question would be better if we could modeling like real life, material producing by one activity and be consumming by others activities all leveling by materials restrictions with improve with concepts "material not stockable" like Vladimir said, "It is necessary to adjust material production to consumption if maximal consumption is less that maximal production capacity and adjust the number and workloads of assigned resources if maximal consumption exceeds the production capacity", where reads "adjust the number and workloads of assigned resources if maximal consumption exceeds the production capacity" I would include "automatically" until finds the better condition, because in this case (asphalt, concrete and others like this) must be considered how "non stockable material", in other words, the difference between produced material and consumed material is lost, he can be calculated for the scheduler know how much is your lost but shouldn't go to next period, because the material is perishable.

Best Regards,

Daniel Morais

Rafael Davila
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Leveling the Prodution Capacity as a Spatial Resource is another way.

SRZ01  the asphalt application activities are not linked among each other.

https://www.mediafire.com/file/2kt1ou2zt87zsku/Trucks_Asphalt04.001.sprj/file

SRZ02  <== if we increase the production capacity enough say to 200 then 2 of the activities can be scheduled at the same time.

Because "materials"/"consumable resources" can be set to be fractional in this model we have no issue with loss of granularity.

daniel morais
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Hi Bogdan,

I did understand, thank you so much for your help.

Best Regards,

Daniel Morais

Bogdan Leonte
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Daniel,

the formula is ment to fine tune the resource allocation, not calculate them.

You can use another formula to get with aproximation the number of resouces:

Number = if (Code = 'B', RoundTo(100/Prod+0.5, 0), Number)

 

So first us:

Number = if (Code = 'B', RoundTo(100/Prod+0.5, 0), Number)

Reschedule

then use:

Number = if (Code = 'B', if ( Prod * Number * MeanWorkDay [ Code , ?Calen , Calendar ] <1000, Number+1, if ( Prod * (Number-1) * MeanWorkDay [ Code , ?Calen , Calendar ] <1000, Number, Number-1)), Number)

Reschedule and repeat the second formula if necessray.

Best regards,

Bogdan

daniel morais
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Hi Bogdan,

 

It works very well now, but one observation, if I will start with 1 resource on each activity with truck, the calculus stop before the maximum ideal and after this, I must to leveling again and again until he finds the ideal model with productivity 100ton/h, the concept of the formula is this?

Best Regards,

Daniel Morais

Bogdan Leonte
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Daniel,

when I made the formula the code for the calendar of the trucks and the code of the trucks were both B. When I tested it it worked properly becase of this coincedence. Here is the corrected formula that takes into account any situation:

Number = if (Code = 'B', if ( Prod * Number * MeanWorkDay [ Code , ?Calen , Calendar ] <1000, Number+1, if ( Prod * (Number-1) * MeanWorkDay [ Code , ?Calen , Calendar ] <1000, Number, Number-1)), Number)

Best regards,

Bogdan

daniel morais
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Hi Bogdan,

Thanks for the formula, but don't work very well for one detail, on formula we need to consider too the resource Asphalt Usine because she always must be 1 unit. When load the formula the quantity of the Usine is change too, observe bellow. I changed the concept divinding in it into smaller sections, but i think that the calculus is the same.

8015
usingformula.jpg

Look bellow, how do not uses Resource Usine Spider consider that activities 4 and 13 works together is this not be happen, if i just put 1 resource on activitie's phase Asphalt Production the calculus increase this quantity I don't no why.

8016
using_formula_without_resource_usine.jpg

 

https://we.tl/t-Fd1fsG90I7

Best Regards and again thanks for your help,

Daniel

 

Marcus Possi
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Hi Daniel and folks.

 

The concempt applied ... after talking directly ith you, I think I definitely understood the problem. There are some not stock material, like asphalt or concrete in use, so it is not possible to store such material before starting activity.  

The sum of 3 bars (activities) must be exactly the same production bar above (production), and it must be a continuous work, in order to avoid losing time or keeping rotten storages.  Everything that is produced must be consumed.

 

After taking some time simulating and testing modules, with and because Paulo Cabral, I think we were able to solve with just one button press,  schedule resource calculation, without formulas or Scripps.

 

We are testing a solution with teams and with skills. We are only waiting some help from developers to complete the idea.

 

Only spider project can provide search elegance and simple answers.

 

Please give us a couple  of  days. ;)

Rafael Davila
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  • The following model does not use complicated formulas and while "productivity resource" quantity is calculated manually the software selects the best crew size among the difined multi-resource skills.
  • The activities are not linked one to another.
  • "productivity resource" quantity is a function of the selected quantity therefore partial workload models can be problematic.

Activity-Gantt-Trucks-Asphalt03-2-Trucks-Asphalt-model-by-Rafael-Davilapng-Page1

https://www.mediafire.com/file/jcqwwwrgnuno1mu/Trucks_Asphalt03.002.sprj/file

about Productivity Resource Quantity

Productivity-Resource

Rafael Davila
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Daniel the number 12x8.26x100=9912 is equal to the crew production rate 12 resources x 8.26 productivity of one resource = 99.12  but because quantity must be a whole number I multiply it by 100 to get 9912 which gives me more granularity as the last 2 digits are not truncated, also resource availability is adjusted multipling by 100.

Bogdan Leonte
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Daniel,

1. Partial workload and quantity works only for resource leveling. Here is a youtube link with a quick example:

https://youtu.be/39DD9iRhh-g

2. Regarding formula, I would do the following: 

Number = if (Code = 'B', if ( Prod * Number * MeanWorkDay [ Code , ?Code , Calendar ] <1000, Number+1, if ( Prod * (Number-1) * MeanWorkDay [ Code , ?Code , Calendar ] <1000, Number, Number-1)), '')

Some explanations:

If ( Code = 'B' ...) - Code of the resource Truck

MeanWorkDay [ Code , ?Code , Calendar ] - This is a modifier, basically it gets the average workhour/day from the Calendar table so you do not have to get change the value in the formula

1000 - is the quantity of asphalt/day (10 hours x 100 tones/hour). I could have created another modifier and if (Code = 'A'...) but I did not want to complicate the formula to much

if ( Prod * (Number-1) * MeanWorkDay [ Code , ?Code , Calendar ] <1000, Number ... - This avoids cycling calculations. It checks if by subtracting 1 from the resource number you get a volume of asphalt/day less than 1000.

The formula reads as follows:

For every resource that is Truck check if Productivity x Number of Resource Assigned x MeanWorkday Hours is less than 1000 tones it incremets the number of resources of that assignment by 1. Then it it checks that by subtracting 1 unit resource the number of tones of layed ashpalt/day will not go below 1000. If the second check is below 1000 then it does not decrement the number, else it decrements by 1.

Again the formula can be modified to get you the exact value of resources to get more than 1000 or not to go below 1000 but I think some iterations and rescheduling may be better for the user to see what is going on with each iteration.

Hope this helps.

Best regards,

Bogdan

daniel morais
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Hi Bogdan,

1. This is true, leveling material and resource do not interact. I would use the function Variable Workload and Number but i can't adjust for Spider decreases/increases resource number (quantity) if you have some ideia please can you give me?

2. I'll input the average. 

3. ok

4. ok.

Since Spider can't do 3 and 4, the best solution until now is from Rafael.

Thank you 

Best Regards,

Daniel

Bogdan Leonte
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Daniel,

1. There is also another problem with the model, material leveling and resource leveling do not interact. Spider levels materials and levels resources but it does not level one depending on another. There is a function called Variable Workload and Number, using this Spider decreases/increases from minimum to maximum resource number and workload however this is taken into account only for resource leveling.

2. Since you have a workweek with different number of whours per day (see Saturday) you cannot adjust the number and workload for each day (manually) all you can do is calculate an average. Also if the consumption of asphalt is greater than the production then Spider will delay the activity wich consumes the material until there is enough.

3. In order to get an optimal solution for your model Spider would have to adjust number of resources and workload (especially workload) in order to get Consumption=Production (Income).

4. Also when using Variable Workload and Number you would have to manually (or formula) increase the number of resources in order to get a Consumption higher than Production (Income) and only after this Spider would reduce workload to mach the Consumption to the Income.

Numbers 3 and 4 cannot be done in Spider as it is now. Try using what Rafael suggested.

Best regards,

Bogdan

daniel morais
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Hi Bogdan,

"I looked over your model and I have a very simple question: Why does the asphalt usine have more work hours/day than the trucks? Also why does the start of work day of the truck = the start of the asphalt usine?" Yes you're right i will check and fix it. I tried input the conditin of real life but i do a mistake of a concept and do not saw this detail, thanks.

"I don't know the exact process but if the asphalt usine works 2 hours/day than the truck what happens to the asphalt that is produced after the truck day ends? Even if there are some technological times to start/stop the asphalt usine these should not be included in the schedule because Spider will consider them production times for the asphalt." Yes, you're right.

It would make more scence to have the asphalt usine work more than the trucks but the start day of the truck would have to start afther the asphalt usine. Yes, you're right i will fix it, thanks.

Best Regards,

Daniel

daniel morais
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Hi Rafael, 

I understood and works fine but a little doubt, the number 12x8.26x100=9912 on resource "productivity" must some function? or you put only for explain better?

Best Regards,

Daniel Morais

Bogdan Leonte
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Daniel,

what Rafael is proposing is very good.

I looked over your model and I have a very simple question: Why does the asphalt usine have more work hours/day than the trucks? Also why does the start of work day of the truck = the start of the asphalt usine?

I don't know the exact process but if the asphalt usine works 2 hours/day than the truck what happens to the asphalt that is produced after the truck day ends? Even if there are some technological times to start/stop the asphalt usine these should not be included in the schedule because Spider will consider them production times for the asphalt.

It would make more scence to have the asphalt usine work more than the trucks but the start day of the truck would have to start afther the asphalt usine.

Best regards,

Bogdan

Rafael Davila
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With some cell specific formulas and a script Spider can adjust the production resource quantity (#trucks x truck_productivity x 100) and instead of fixing the number of trucks you migh use variable quantities for Spider to figure it out.

2021-12-01-13-03-10

12x8.26x100=9912

I usually find it easier and a better fit to use multi-resources and skills with no need for complicated formulas, just use a few crews with increments in size.

daniel morais
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Hi Rafael,

This is true, but I would like to test and guarantee that the material produced is well consumed according trucks dimensioned. If Spider can calculate too the quantity of trucks will be amazing (considering that material like asphalt and concrete are not stockable).

I'm not sure if the modelate how hammock and MH (Man Hour) resource if will won't lost the condition IN/OUT = zero (ideal condition), I think that with material is more sense. Because this way the flow would be "Consume to production" or activity type "productivity" to activity type "hammock" when the correct flow shoud be "Production to Consume".

Best Regards,

Daniel

Rafael Davila
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As asphalt is consumed as soon as it is produced it is not a constrained as a consumable resource. The constraint is on the production rate ant it can be modeled as a renewable resource whose available quantity is the maximum production rate.

Activity-Gantt-Trucks-Asphalt03-1-Trucks-Asphalt-model-by-Rafael-Davilajpg-Page1   click on thumbnail.

To get more granularities with the production rate I am multiplying the quantity for resource "rate" by 100.

https://www.mediafire.com/file/vs66ht2k26vklkw/Trucks_Asphalt03.001.sprj/file

daniel morais
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Hi Bogdan,

Follow my answers: 

A. No, the production of asphalt usine are according with the real cenario in construction, 100ton/h into of calendar real. This production don't need be increase or decrease it's already adjusted. 

B. Not only increase but decrease too, depending on the production. Should be interesting if we could calculate the quantity of trucks, (according with the produtivity, workload and volume sets) for use all asphalt produced.

C. This would not be the main idea and desire, but I understand that it would be a consequence of after all the leveling calculations.Best regards,

Best Regards,

Daniel

Bogdan Leonte
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Hello Daniel,

I read all the posts and I have a couple of questions, regarding the purpose of the model related to material leveling?

Here are some scenarios I though after reading the posts:

A. You want to adjust the prodction of the asphalt usine in order to produce less than the maximum capacity?

B. You want to be able to increase number of trucks in order to lay all the asphalt  produced considering the maximum capacity of the usine?

C. You want to leave the model as it is but calculate the monetary loss for each day based on asphalt that has not been layed?

Best regards,

Bogdan

daniel morais
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Hi Marcus,

The concempt applied is wrong because the sum of 3 bar bellow (activities) must be exactly the same time to bar above (production) because everything that is produced must be consumed, remember this material don't consider stock.

You Second schedule show that happen cumulative stock of material for after be consumed, don't can this way, everything produced on day must be consumed on the same day, if happen some sold, the must be considered how lost.

Best Regards,

Daniel

Marcus Possi
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Hi Daniel and Vladimir,

 

I made a short video, trying to understand what you presented as an obstacle. here

 

 

Imagining some a limited supplier (asphalt) and limited resource quantity (trunk), considering the SPRJ sent, I made some simulations.

I considered a regular common calendar 7 days a week, 10 hours, and a limit of 100tons asphalt production, 3 road construction activities consuming asphalt according to its length.

Take into consideration that an activity will only begin if there will be enough material to support it.

Please take a look and inform any mistake / misunderstood in the model I made. by CPM calculation ...

 

I recorded it in Portuguese :)

by CPM calculation ...

8012
c2.png

 

by Resource Leveling + LSM

8011
c1.png

 

file SPRJ is here: https://www.dropbox.com/s/m1nkhu3b3ttwtui/Trucks_Asphalt.001.sprj?dl=0

daniel morais
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Ok Mr. Liberzon, thank you for answer. I think this is important feature because for example Eolic Farms (concrete trucks) and Roads (dump trucks) the material leveling is excellent way for balacing the best quantity of resources according the material production (consumption). The Spider algorithm can be an excellent support for the best decisions where many times this resources can be expensive if bad dimensioning.

Best Regards,

Daniel Morais

Hi Daniel,

this task is not trivial and today Spider Project does not model this case.

It is necessary to adjust material production to consumption if maximal consumption is less that maximal production capacity and adjust the number and workloads of assigned resources if maximal consumption exceeds the production capacity.

We will think about the best way to model this task but today this can be done only manually.