Estimating workshop fabrication costs.

[Tristan.]

This is for a uni group design project. One of the last bits to do is the manufacturing costs section. Basically I'm trying to estimate the costs to produce this:
https://i54.tinypic.com/2v0oaxy.jpg
(all made from 40 x 40 mm box 3mm thick mild steel)
And I need one key value, for it all to come into place. how long it would take to weld together. The whole things made from 40mm box section, in 3 big bolt together sub assemblies. Theres essentially there's 457 welds on it, roughly halved between 40mm T joint fillet and 40mm butt joint welds. plus 8 1000mm lap joint fillets. Mig or arc would be suitable, and the choice will depend on comparing the costs of each. Though if I can only get data for one kind It doesn't matter.

Obviously with it being third year coursework I can hardly cite some bloke off BCF telling me they'd take x seconds each. (though that kind of approximation would be helpfull, so I can do some fag packet maths to get an idea) so what I really need to know is if there's some kind of industry standard or rule of thumb I can look up, or something along those lines. Even a theoretical capability stated on welders would be a better startpoint. Overheads, wages, costs of employment, time to mount and prep etc I'm all capable of sorting. I just need this one value, and an actual source to cite.

Cheers for any help

[fredsredhat]

couldnt even begin to guess how much work there is there! i'd say at least 2 full days cutting and welding. but dont take my word for it as i only manufacture roller shutters and only really have a bandsaw and mig welder rather than a full fabricating workshop. for you to get to a figure I'm on £8.67hr if that helps

EDIT though i could time welding a 40x40 box as we use this a lot

[Tristan.]

that would actually be excellent if you could do that. Though I initially said that I wouldn't be able to use empirical stuff like that, after having basically every lecturer involved and stumped in finding a usable value I've been told to use real lfe values/quotes. So thats exactly what I need. Either an estmate or an actual rough timing. If any other fabricators can then the more the better. Plus I get to cite BCF in an essay.

[ZRX61]

[ZRX61]

[Tristan.]

[ZRX61]

[Tristan.]

Plymouth.

[hmmmnz]

at a random stab in the dark i'd say there was about 25hrs in that
so 1000quid labour + materials,

is there no one in the college who can do the welding?? do they not have a welding/fabrication course running at the school??


i personally think your hub steering axles are up to the job looking at the pic
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[Blackwolf]

ZRX61, there wasnt really any need for that. Yes the "proper" names are SMAW, GMAW and GTAW.

But ask almost anyone in the industry and its MMA, MIG/MAG and TIG/TAG. As TIG is not hugly pratical for that job in hand. That leaves stick and MIG, which are both perfectly acceptable. if you actually do some research stick is still a vety popular welding mothod for large amount welding.

There was no need for that kind of reply.

Tristan, all I could reccomend is was a techntion at uni how long it would take to do one weld and multiply it out for all the welds. Do you have to take into account the costs?
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[ZRX61]

[kestrel]

Tristan.
It's difficult to estimate an accurate fabrication time on something like this without a bit more detail. A one off job like this takes a considerable amount of time, making large numbers on a production run would work out *MUCH* quicker per unit.

As a rough guide, we use circular TCT pull down saws, a square cut in 40x40x3 RHS takes about 10 seconds. The only practical welding process for this type of work is MIG, again as a guide, a 'Tee' joint, incorporating two fillets and two butts would take less than a minute.

Each member of this structure will require the saw to be set up for length and cut angles, so for a one off you must factor in the set up time plus the actual cut time, on a production run of 10 units the additional 9 pieces are cut time only.

One of the most time consuming aspects of any fabrication is setting up the various components relative to each other. This is where jigs are usefull. A jig removes this set up time, it doesn't need to be complicated but it does need to hold the components in their correct position and at the same time leave access to the weld joints. A quick glance at your structure suggests that you could actually fabricate it in sub assemblies using smaller jigs. Once you have made your various jigs you can cut and prep all of your material for however many units you require, assembly is then just a case of loading the various members into the jig and welding.

Charging out rates vary considerably, the fab shop I work in charges £30 per hour.

[Tristan.]

Very helpful thanks.

I left a key point out of the OP. It's theoretical costs for producing it in house, not contracting it out. (Though when the in house time is found then working out a contract price at £30/hour is easy enough to compare)

There is a fab lab in uni, but with it coming up to dissertation deadline there's no time to get the technicians to do a few runs. I got them to give me some 40mm box though, so I can cut clamp and weld it at home. I'm shit at welding so thats not much use, but I can take it with me round local fab shops to say "how long would it take you to do this?"

Kestral, thats very helpful. Couple of questions

I'm working on the assumption of about £12/hr for the welder. For the bloke who does the cutting, clamping, prepping etc, any idea what sor of wage he'd be on?

I've only welded rusty crap on a farm, or as a hobby. I've never welded any new metal. How much prep does metal fresh from the rollers take?

I've counted the cuts that it'll take. And I've treated right angled cuts different to other ones. How much longer do you reckon to dial in an angle on a saw? (though as you say with batch and queue that's several extra processes per assembly)

Also, I've just done the startup costs today, from memory I think I've considered a pull down saw, pillar drill, mig setup, grinder, welding mask, apron and gauntlets, bandsaw, extraction system, fire extinguisher , compressor, gun and respirator and some PPE, Anything else ubitquous to a shop floor?

[kestrel]

[ZRX61]

It's just occurred to me that I may know the lecturer, whats his name?
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[warped one]

With all the size's jotted down I reccon I could have all the pieces cut in about an hour.

Then jigging and welding it all up i'd say the rest of the day, with an hour the next morning to clean it up.

Your total length of weld is 26,280mm. The way I'd do it is get it all tacked and in place first then blast the lot together in a oner.

It's really not that difficult to make since most of the pieces are replicated, so your not changing the saw angle all the time, or the back stop.

And my workshop used to charge me out for between £25 and £100p/h depending on the job we were doing, or how much i'd wound my manager up that day.
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