Packaging product item automatically put in cart

Hi,

Looking for some ideas on how best to automatically add a packaging product item to the cart so that the item has a weight (but no price), so that the correct shipping option will be chosen. I'm thinking this should be a genuine "product".
I dont want to "mark up" my product wieghts or prices, as this would unfairly penalise clients with more products and push them into a higher shipping option bracket.

Cart example:=
1 x product1 £10.00, 98 grams

Upon checkout, this then chooses a shipping rate for 0-100grams, say royal mail international

so shipping then is say £10.00

I then box up or jiffy bag up the product and go to the post office and it weighs 145 grams because of the packaging, and costs me say £14, as its over 100g.

What I'm looking for is a way that automatically adds a "single" packaging product in tiers. Trigerred at the point of a product being added to the cart.

so if my cart weight is 0-1000grams, it adds a packingproductId that weighs say 75g for a small jiffy bag.
if my cart weight is 1000-2000grams, it adds a packingproductId that weighs say 200g for a large jiffy bag.
if my cart weight is 2000-4000grams, it adds a packingproductId that weighs say 500g for a small cardboard box.

There would always just be one of these products in the cart, and it would be removed should the cart be emptied.

anyone done anything like this?

Thanks,
Craig.
nop 3.8

I thought I'd add that I use the ShippingByWeight plugin to store all my shipping options.

First, I should mention that if you think Royal Mail rates are based on weight alone, then you might be able to instead use Fixed or By Weight Plugin, and then set up from/to weight ranges with "Additional fixed cost" compensating for your packing material weight.

If you want to use Royal Mail, then Shipping Director’s “Packing” would allow you to add weight for the box/packing material using variable $PackageBoxWeight:

Decimal         $PackageBoxWeight    [$TotalWeight] <= 1000 ? 75 : [$TotalWeight] <= 2000 ? 200 : [$TotalWeight] <= 4000 ? 500 : 700
Packing         Pack                 true         Packing.FirstFitSingleBox
OptionExit      Shipping             true         Shipping.RoyalMail


Alternately, you could use the Surcharge Expression to add a calculated amount to the normal Royal Mail rate.

I can't add surcharge to shipping options as I don't want to give advantage or disadvantage customers with higher or lower quantities in the the cart.
Happy with my complex set up of royalmail, parcel force , variations for every conceivable destination country and weight segment.
The big letdown is that nop can't give me packing weight to match the cart weight.
So, are you saying that I could have say 4 packs set up in SD, small envelope, large envelope, small box, large box, and SD could select the packing based on total cart weight, then it would add that packing weight to the cart weight to give a shipment weight. Only after that it could then select from my shipping records in the offline byweight plugins records, and present to customer for choice(could be STD or recocorded dlvy for ex)?
Also, would it add the packing weight to the shipping record in nop, so the packing slip shows total weight, And the admin panel for the shipping record shows this total weight?

Look forward to you reply !

The example above just calculates an additional weight for each box packed.  SD packing is "single box" size, yet you can calculate which size to use based on 'total cart weight' (are any other conditions ;).   Also, it is possible to have multiple box sizes with multiple Packing records and constrain which items get packed in each size box (with Packing's Exclude expression), but set up is a bit more complex. Most carrier's rates are weight-based, so the complexity is not really needed unless you have "large" (yet light) products that would incur "dimensional weight".

RE: "packing slip shows total weight"
SD creates 'virtual' items so that it can pack them.  The Shipments will not show/include the additional weights, because nopC uses the actual products.