Important factors for rough price estimate in milling.

[filiptheking]

Hello!

If you work at a company that mills different parts for other companys. How do you give the customer an estimate price?
Do you use your CAM-program to estimate the time and the price or do you just look at some important features on the part to make a really fast estimate?

How can you estimate the price without spending lots of time in a CAM-program? Which factors is important?

(I'm mostly intressted in parts made with 5-axis mills)

 

[JNieman]

We mostly use two things: Experience and a little math.

Sometimes we'll make a quick rough program but certainly don't spend "lots of time". More of a "get back to me by lunch with some rough numbers" and also if we need any special tooling and other consumables.

Factors depend on the part. Geometry, # of setups, will it require passivation / heat treat or special "gingerly" approaches for precise surfaces, etc.

"Parts made with 5-axis mills" is a pretty broad brush. Does this mean extremely tight tolerance 'organic' surfacing with ultra-small scallop size and no hand-finishing allowed? That's a big factor. Is it just blocky parts with odd-angled holes? No big deal there.

Without seeing parts there really is no advice I can give. Quoting and Estimating is a bit of an art, sometimes. Especially if you're really under the gun to get a quote turned around.

_________________________________________
NX8.0, Solidworks 2014, AutoCAD, Enovia V5

 

[filiptheking]

Thank for you answer!

What are your thoughts when you look at these parts? We assume that we will use some high end machine of your choosing, one that is common in the industry.
What would you approximate the machine time to for each part?


Part 1:

http://www.3dvieweronline.com/share/xbZmFmN1eSaWQrp/xbZmFmN1eSaWQrp

part 2:

http://www.3dvieweronline.com/share/MUNE3gGfJG01MLw/MUNE3gGfJG01MLw

Lets say that the surface roughness can be 50 μm on all surfaces and that we just compare the time that it takes to machine those geometries. The stock is 100x70x40 mm and the volume of the finished part is 120 000 mm^3 for both parts.


What in the parts geometry contributes most to the machine time? Small radii, non-developable surfaces etc?
I know that these parts would be possible to machine in a 3 axis mill without repositioning the stock. But if you had to reposition the stock, would that contribute much to the price?

 

[MikeHalloran]

My browser doesn't support WebGL, so I can't view your parts. I don't care.

For parts you are already making, you can measure and calculate the Metal Removal Rate, which is typical for a given material and finish and some other things.

For a putative part, you calculate how the process would work, including selecting a machine and a cutter, feeds and speeds, etc., and how much volume of material you will remove.

You can use the feeds and speeds or the representative MRR and volume to be removed to estimate machining time. Best to do it both ways for a while, until you develop a feel.

Note that cutter selection may be determined by allowable radius on inside corners and stuff like that.

Doing a large part in two setups requires extra time to move the workpiece and to re-align it to the machine. It may be a lot of extra time if tolerances are tight and/or the job doesn't justify some kind of indexing fixture.



Mike Halloran
Pembroke Pines, FL, USA

 

[filiptheking]

If you choosed an average MRR for the roughing and average MRR for the finishing, would that give you a good rough estimate on the machine
time?

I'm thinking like this:

Average MRR for roughing mulitplied by the volume removed by the roughing process + the average MMR for finishing multiplied by the volume removed by the finishing process = machining time.

An other question is what average MRR I should choose. Is it possible to take an average of the MRRs for many roughing processes on many different geometries and get a standard value that works? And the same for finishing of course. Do the average MRRs for roughing differ much between different geometries? And for finishing?

Could you give me a guess on a good MRR for roughing and a good MRR for finishing, that could work as a standard value for many different parts? We assume that we have the optimal machine with the optiaml tools, feeds and speeds for minimal tool wear.

Maybe I need to add the "lenght" of the smallest radius or something to get an better esitmate?