% Wastage from milling Sawlogs

[arboriculturist]

I am trying to determine approx. how much waste there is on average, when milling a mixed diameter load of SOFTWOOD sawlogs from 400mm up to the larger sizes.

 

We get 20 tonne loads at a time.

 

Whoever I ask seem to give wildly varying replies, with lots of 'ifs' and 'buts'.

 

I am just looking for an estimated average % of waste.

 

Thankyou for any replies in advance.

[se7enthdevil]

well if you go by the way timber is measured and use the hoppus foot guide then that will give you some idea. a hoppus foot is almost exactly 1 1/4ft3 so in theory the waste from sawing would be about 20%. there is room for an argument that with modern machinery it could be as low as 10-15% but i expect it relies on what you are producing.

[agrimog]

depends on what you are producing, can go from sawdust to as high as 40-50%,

[treequip]

I am trying to determine approx. how much waste there is on average, when milling a mixed diameter load of SOFTWOOD sawlogs from 400mm up to the larger sizes.

 

We get 20 tonne loads at a time.

 

Whoever I ask seem to give wildly varying replies, with lots of 'ifs' and 'buts'.

 

I am just looking for an estimated average % of waste.

 

Thankyou for any replies in advance.

 

What's the finished product?

 

More cutting = smaller product and QED more waste

[renewablejohn]

I only get sawdust and planks as waste as I oversize the outer cuts so that the offcuts can be turned into reasonable size split logs. Used to cut the offcuts thinner and use them for woodchip but it makes very poor quality chip due to the high quantity of bark.

[Big J]

Pretty high really. Depends on taper, dimensions of boards being cut and overall diameter of logs. We produced 92 cubic metres of cedar for one job, which came from 130 tonnes of roundlog material. Mixture of larger and smaller diameter timber too. I'd guess it would have been around 150 cubic metres of stock to start with, so recovery was only just over 61%. I'd not a wasteful miller either.

[agg221]

Wastage or co-product?

 

If you assume square edge, parallel sided boards of maximum possible width is the premium product then tell me the thickness and saw kerf and I can tell you the yield with a standard allowance for straightness and taper.

 

If you have a secondary market such as pallets for edge boards your yield goes up. If you have markets for sawdust and shredded bark and sidings it goes higher. If your kerf, board thickness go up, or your range of products goes down then your yield goes down.

 

A big mill will laser scan each log as it enters the line, auto-customising the cutting pattern to maximise yield. A small mill with an eye to profit can't do this time efficiently. Someone cutting for themself with limited supply can work to a cutting list and minimise waste.

 

Alec

[arboriculturist]

Thanks for the range of replies - Referring back to my question:

 

 

" I am just looking for an estimated average % of waste."

 

Is 25% 'the answer' most of you would given the hundreds of variables?

 

I would be using a mill costing 30K new - if bought in the UK.

[arboriculturist]

well if you go by the way timber is measured and use the hoppus foot guide then that will give you some idea. a hoppus foot is almost exactly 1 1/4ft3 so in theory the waste from sawing would be about 20%. there is room for an argument that with modern machinery it could be as low as 10-15% but i expect it relies on what you are producing.

 

That is possibly the best guide out there - 20% average. I don't suppose the team of experts who drafted the 'hoppus foot guide' did their calculations on the back of a fag packet.

[Big J]

That is possibly the best guide out there - 20% average. I don't suppose the team of experts who drafted the 'hoppus foot guide' did their calculations on the back of a fag packet.

 

The hoppus measure is a long way out on dimensioned softwood though. Instead of 20% wastage, it's more like 40%