Dealing with fabrication shops
Dealing with fabrication shops
(OP)
Hi,
I'm having a fairly complex lifting cart fabbed and assembled by a local fabrication shop and so far have had 9 made. The cost is around $3k ea.
To take cost out of the design I really need to see exactly how the shop is coming up with the price and where the most money is being spent but they are being a little cagey. I don't know if they're overpricing the components or if I'm wasting tens or hundreds in unnecessary machining, weldment complexity or material cost.
Is it usual for a fab shop to supply a complete breakdown of costs if asked, or do they usually keep this info to themselves?
Thanks,
Mong.
I'm having a fairly complex lifting cart fabbed and assembled by a local fabrication shop and so far have had 9 made. The cost is around $3k ea.
To take cost out of the design I really need to see exactly how the shop is coming up with the price and where the most money is being spent but they are being a little cagey. I don't know if they're overpricing the components or if I'm wasting tens or hundreds in unnecessary machining, weldment complexity or material cost.
Is it usual for a fab shop to supply a complete breakdown of costs if asked, or do they usually keep this info to themselves?
Thanks,
Mong.





RE: Dealing with fabrication shops
Where the conversation turns from precise detail to generalities or avoidance, that is the area to start with.
RE: Dealing with fabrication shops
RE: Dealing with fabrication shops
If you could try to discuss with them methods of making cost saving you might get somewhere.
If you have no luck go somewhere else. Nothing like competition to get attention
RE: Dealing with fabrication shops
Almost everything I know about fabrication comes from talking to our fabricators. This includes cost and drafting practise.
Remind them that you will sell more lifting carts if they are cheaper.
A good book to read on this stuff in general is Product Design for Manufacture and Assembly by Boothroyd, Dewhurst and Knight. Unfortunately, it does not have a section on welding, so it does not solve your present problem. It is still very useful.
Look for some welding textbooks. My college book was Modern Welding Technology by Howard B. Cary, which contains a lot of design advice. It has a photo of the SS Schenactady. All books on welding design should have one. I went to school rather a long time ago. Perhaps someone can recommend something more recent!
Lincoln Electric has all sorts of welding articles on their website.
RE: Dealing with fabrication shops
Then, make up your own operation sheets for all the pieces and the assembly. It's probably best to put it all in a spreadsheet, using typical values for metal removal rate and metal deposition rate, and figuring scrap loss from stock lengths and such. Beat on that for a while, and you'll better understand what the fabricators said.
Mike Halloran
Pembroke Pines, FL, USA
RE: Dealing with fabrication shops
RE: Dealing with fabrication shops
As the source of the design, you should have a clear idea of what processes are likely to be necessary and their relative cost. If you can provide the suupliers with enough detail of assembly and parts, they are less likely to give you what you do not need.
RE: Dealing with fabrication shops
Tobalcane
"If you avoid failure, you also avoid success."
RE: Dealing with fabrication shops
Attitude goes a long way.
To me it sounds as if you might be saying "I think you're screwing me and I want to see where."
It's not surprising that an approach like that isn't getting you far.
I've never had any difficulties with any type of shop when asking "I'd like to get your input on how to make this design more manufacturable" - after establishing a contract. Too many people try to use fab shop quotes as free design reviews.
RE: Dealing with fabrication shops
A design note...
I do not believe in machining weldments. Design your weldment to work with ±1/16" (±1.5mm) tolerances. Add slots and make things adjustable.
If something requires machining tolerances, make it a separate component, and get it fabricated in a machine shop.
Composite fabrication methods can get very expensive, very fast. Hand your fabricator work they are good at.
RE: Dealing with fabrication shops
It would be tough to fit the various bearings in a recent Toyota RWD axle without at least a bit of machining.
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RE: Dealing with fabrication shops
However, if I asked them what the cost drivers were/where I could make their lives easier I'd hope to get some feedback.
To get really good feedback you might need to guarantee some minimum level of orders or something if you don't already have a long history with them.
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: Dealing with fabrication shops
Know the total weight of steel including wastages ,know the ball park pricing for general fabrication cost / kilo (includes,cutting,bending, rolling welding etc). add to this the inspection cost,fixturing price any machining like drilled bolt holes ,stress relieving,metal finishing cost any 3rd party inspection or approvals .
The simple way would be get China prices/unit, add 40% and you may be perhaps close to US price
RE: Dealing with fabrication shops
1. Standard Estimate
a. receive a set of drawings
b. Are they complete or a design concept
c. Are DXF's and Flat patterns available – has the correct allowances been used
d. Are Model files available in IGES or Step format for CNC Machining
e. Have cutting list been produced – are they accurate for welding
f. How much effort will the CNC programmers & fabricators have to put in to decipher the drawings
g. Are materials specified exactly or are alternatives available
h. Are proprietary fixtures and fitting specified correctly, do we have to source obscure items.
i. Tolerances
j. Finishing required
k. Lead-time
All fabrication engineering shops are ego driven; they love to be central to the design. Fabricators find it irresistible to be able to sit down with Mechanical engineers and show them where they have gone wrong and how to simplify. When a fabricator owns a project, the quality is good and the cost will then reflect.
If you are dogmatic in your approach this too will reflect in the cost.
With advent of 3D software, everyone and their uncle believes that they're Designers, I forget how many times I've heard, "Well my Cad package was able to.........
With the above in mind, we estimate materials at cost, base CNC machine time and Base labour. This is the break even cost.
With this base figure mark-ups are added to material (20% to 40%) and labour (10% to 100%)
A contingency sum based on intuition (say10%) maybe added, this is for negotiation.
2. The *&^% Off price
a. No effort just think of a figure and add 100%
RE: Dealing with fabrication shops
I am sure like many others when I started out I would provide detailed quotes and processes and suggest possible changes in order to reduce these. Often potential customers armed with this information would then go elsewhere; you soon learn this is not a good use of your time.
On the other had if you have a regular customer who you trust you will provide this information and always look at ways to reduce costs, at the end of the day that is how you will both stay in business.
RE: Dealing with fabrication shops
Norbert www.linked in.com/pro file?viewP rofile=&am p;key=2315 1971&t rk=tab_pro
www.gdt-llc.com
http://
RE: Dealing with fabrication shops
Selling price = Cost * Markup.
Markup depends on how much you really want this job.
That's market forces I'm afraid.