Let's talk scrap

[Dead Money]

How do you guys plan potential scrap when quoting, processing and executing jobs?

 

Picture this:

Contract job shop environment

100 pc order

Inexpensive material .5"x1"x2" 6061

Cycle time 10 minutes per part

Manually load 4 stations to complete part

A couple tight tolerances

Outside service - Anodize

 

How much extra material do you order?

Do you consider a couple parts lost in setup normal?

Do you consider lost parts in production a failure in the process?

 

I'm curious how the rest of the world handles this

[gcode]

I moved your post to the Machining forum

You'll get some replys there.

This forum is for comments and feed back on eMastercam

[Dave.L]

How do you guys plan potential scrap when quoting, processing and executing jobs?

 

Picture this:

Contract job shop environment

100 pc order

Inexpensive material .5"x1"x2" 6061

Cycle time 10 minutes per part

Manually load 4 stations to complete part

A couple tight tolerances

Outside service - Anodize

 

How much extra material do you order?

Do you consider a couple parts lost in setup normal?

Do you consider lost parts in production a failure in the process?

 

I'm curious how the rest of the world handles this

 

The material size you list is pretty small so at 100 pcs you won't have much scrap so I would not calculate the scrap value as part of the order.

 

The amount of extra material is a loaded question. If you have run the part before and don't need to prove a program than the amount will be low. If the tolerances are tight and you don't have a good method, well then you need more. If your anodizer will lose or destroy some then you need more.

 

10 minute cycle time for the part size you mention seems very high but it's hard to say without seeing it. I would guess that you are going way too slow on the feeds.

[chris m]

Four stations might explain the cycle time; probably more load and unload time that spindle run time.

 

We run [1] for [1] here; doesn't matter what it is. Considering the stock amount you're looking at I'd have [5] extras in the lot just to make sure.

 

C

[spade117]

Considering the stock amount you're looking at I'd have [5] extras in the lot just to make sure.

 

What do you mean by stock amount? The amount of pieces or the size? What determines that you get 5 extra pieces?

[chris m]

At $3 or so per pound you're looking at less than half a buck worth of material per piece. If it is a new job with [4] stations you're talking about at least a couple of hours worth of setup time in a typical job shop environment; call that $130 - $160 worth of time. If you run one-for-one and bone a piece it'll cost you another $130 or $160 to set it up again when you get more stock, so it seems reasonable to invest $2.50 in more stock to avoid this.

 

As I said, our policy here is to run one-for-one with no extras, the theory being that we'll control our process better if we know how painful it'll be to suffer a non-conforming part, BUT from a pragmatic point of view it sometimes makes sense to have a little insurance.

[Dave.L]

At $3 or so per pound you're looking at less than half a buck worth of material per piece. If it is a new job with [4] stations you're talking about at least a couple of hours worth of setup time in a typical job shop environment; call that $130 - $160 worth of time. If you run one-for-one and bone a piece it'll cost you another $130 or $160 to set it up again when you get more stock, so it seems reasonable to invest $2.50 in more stock to avoid this.

 

As I said, our policy here is to run one-for-one with no extras, the theory being that we'll control our process better if we know how painful it'll be to suffer a non-conforming part, BUT from a pragmatic point of view it sometimes makes sense to have a little insurance.

 

 

Running 1 for 1 is just not practical. Mistakes happen. To expect people to be perfect is just not rational. (or maybe you don't have tight tolerances)

[spade117]

I understand all that you are saying...just trying to figure if there is a *set in stone* method that is used. I know in theory that using your best judgement every time you process a job is probably the best route to take. I'm just trying to understand if there are other ways for it to be done.

[Dave.L]

I understand all that you are saying...just trying to figure if there is a *set in stone* method that is used. I know in theory that using your best judgement every time you process a job is probably the best route to take. I'm just trying to understand if there are other ways for it to be done.

 

 

Spade, it's pretty tough to have a rule of thumb. Our terms our that we can ship +/- 10% of an order (most orders). So, for repeat jobs that run well, we purchase 10% more stock so we know we can ship all good parts. If we know we will have some scrap, we buy 15% extra assuming 5% will be scrap. But on a job of 100 pcs, that's only 10 pcs.

 

Material cost, part tolerances, repeat job or not...these are all factors needed in the process.

[chris m]

Dave, that's old-school thinking brother, the Six Sigma police have been notified and will be around to speak with you directly. Truthfully, we bone a lot fewer parts now that the guys know they don't have a couple to "waste" but sometimes it can be a real hassle. As far as tolerances go, we are turning parts with .0005 total tolerance all day long, but we're set up to do it; cutting tools, gaging, machine tools are all top-dollar because of the work we do.

 

C

[Dave.L]

Dave, that's old-school thinking brother, the Six Sigma police have been notified and will be around to speak with you directly. Truthfully, we bone a lot fewer parts now that the guys know they don't have a couple to "waste" but sometimes it can be a real hassle. As far as tolerances go, we are turning parts with .0005 total tolerance all day long, but we're set up to do it; cutting tools, gaging, machine tools are all top-dollar because of the work we do.

 

C

 

 

Chris,

 

I expect replies like this from the people that have never done this work - I would not expect it from you.

 

I hear it all day long "we sneak up on our parts" which is such a BS statement since removing a few tenths will cut toally different than a few thou. We run some very expensive Bu copper parts and the customer sends us the material, the exact quantity they want (60 pcs lots). We do a damm good job but we are all human and we do scrap one every other lot or so and that's with keeping the machine setup (at least the critical tools). It's heat treated material (and hardness varies lot to lot) with very tight tolernaces and the parts change when they come out of the machine (and we plan for it). We even rough these then do a finish OP.

 

I can tell you, not one person on this planet could make these parts the first time will ZERO scrap.

 

People who care will make little scrap regardless of extra material or not.

[Guest CNC Apps Guy 1]

If it were my shop, 1 extra piece for us, and depending on the annodizer's track record, a couple for him,.

[McLaren]

I'm with Dave on this one. And I just wanted to add that sometimes it is cheaper to hurry up and scrap a part then spend an hour creeping up on dimensions so you don't waste $0.50 in material and 10 minutes in cycle time.

[Newbeeee™]

Yep - for cheap mtl bish bash bosh out the part, measure and adjust then you're good to go!

Saves pu(another word for cat but it won't let me write it damn political correctness)ssy footing about.

[htm01]

we run at least one extra, can put it in the showcase at the end of the job.

[chris m]

sometimes it is cheaper to hurry up and scrap a part then spend an hour creeping up on dimensions

 

AMEN brother; our shop rate is $170/hr so this makes even more sense for us, but we don't do it that way, welcome to Lean TPS machining! The only place we can get away with this type of thing is on bar-fed work because I always pad the calculations; if 48" makes 77 pieces, the paperwork says it makes 75 so the guy can just let it rip, offset, and hopefully make the second piece correct.

 

C

[RandleXX]

In the world of machining titanium castings there is no such thing as scrap. Some of the casting cost more to replace than we would make for the whole job. Its a long slow process.. machine material safe, CMM, adjust to machine net, lots of on machine probing and every cut is watched very closely. Scrap is not an option..

[Guest CNC Apps Guy 1]

^^^ in that case, I worked at a place where we dealt with the same stuff, expensive, long lead time for customer supplied material, difficult, etc... We ended up making a steel "forging" for a couple reasons, we needed it for fit check on the machining fixtures and CMM fixtures as we were not scheduled to recieve the material in enough time to wait for them. It also helped out when the castings came in heavy, we already had the appropriate toolpaths to clean up the forging to net in the affected areas.