Dealing with fabrication shops 2

[mingmongmang]

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.

 

[ornerynorsk]

A reputable shop should be willing to work with you to help modify the design for improved manufacturability. An unwillingness usually indicates that you are their "gravy job", and you are being charged an unreasonable amount.

Where the conversation turns from precise detail to generalities or avoidance, that is the area to start with.

 

[btrueblood]

The latter. If you want to learn how to bid steel fabrication, join their company and learn the trade. If you want competitive pricing, let the bid to several companies. If you want to just get the cost down, go sit down with the shop and a stack of your drawings, and maybe a beverage or two, and ask them how you could take some money out of the design.

 

[alansimpson]

Fabricators generally won't give breakdown of their costing. It is considered their business, not for outsiders.
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

 

[drawoh]

mingmongmang,

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.

JHG

 

[MikeHalloran]

By all means, talk to the fabricators.

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

 

[abboberg]

If you can find a supplier with an onboard manufacturing engineer, then you will have a lot more latitude in knocking down the cost. I have dealt with one fabricator who consistently priced at 20-30% of (yes, that's "of") their lowest-bidding competitor because the manufacturing engineer worked from a baseline of what was sustainable for them, then put significant time into producing the parts as cheaply as possible. This process also involved negotiation on our end (read: design changes) to simplify their processes even more. Without a manufacturing engineer or someone similiarly-skilled on their end, you are left with micro-managing from your end. In our case, multiple-competetive bids did not even come close to getting the cost reduction we needed - it came down to one extremely clever manufacturing engineer at one supplier.

 

[TheTick]

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

When it comes down to it, it's none of your business how much their processes cost. They should, however, be willing to show you the processes they use.

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.

 

[Twoballcane]

Did you get at least three or four other bids to do the same job? It will shake out the houses that might take you for a ride. With us in our contract, before awarding the job, we demand a cost break down and their process of how they plan to make the product. And we do this with three or four other shops so we get a fair estimate of what the job may cost.

Tobalcane
"If you avoid failure, you also avoid success."

 

[MintJulep]

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.

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.

 

[drawoh]

mingmongmang,

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.

JHG

 

[Tmoose]

"I do not believe in machining weldments. "

It would be tough to fit the various bearings in a recent Toyota RWD axle without at least a bit of machining.

http://image.fourwheeler.com/f/1833...toyota_fj40_land_cruiser+toyota_rear_axle.jpg

 

[KENAT]

Yeah, as with most others I wouldn't generally expect a breakdown in the detail you're asking.

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.

Posting guidelines faq731-376

http://eng-tips.com/market.cfm?

(probably not aimed specifically at you)
What is Engineering anyway: faq1088-1484​

 

[arunmrao]

I too encounter such situations,where I am asked to provide cost breakdown , honestly I do not like giving it .

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

 

[karmoh]

In my world there are 2 methods of pricing, each broken down as follows

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%

 

[ajack1]

Well speaking as someone who does a lot of quoting, it will depend on your relationship with the customer.

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.

 

[ProEDesigner00]

I used o run a software called Costimator

http://www,mti.com

made it. We would evaluate our own designs once this program was set-up properly. What this did was to provide a time study of our designs and the cost of that design. This program was so detailed that it would measure the amount of time to strap band something to a pallet to ship back to us. We would then go to our suppliers and negotiate with them the true cost of doing something. Now I know alot of you are going o hit on me because the cost of R&D is different than production. This program took that into account. What it showed us was how costly our designs were. I did not like the job because this BIG company was always trying to squeeze the last penny from the small MOM POP shops we dealt with. In the end it gave us a better look at what our designs were actually costing and we were able to adjust for that.

Norbert

http://www.gdt-llc.com

http://www.linkedin.com/profile?viewProfile=&key=23151971&trk=tab_pro

 

[PeterCharles]

Cost = material + labour.
Selling price = Cost * Markup.

Markup depends on how much you really want this job.

That's market forces I'm afraid.