topic Optimizing The Feeds and Speeds For Specific Roughness in Fusion Manufacture Forum

Optimizing The Feeds and Speeds For Specific Roughness

sai_tejaRT58C — Tue, 15 Oct 2024 12:44:29 GMT

Hi

I am currently working on achieving the optimal speeds and feeds to meet a specific surface roughness requirement as outlined in a detailed drawing. Could anyone suggest how manufacturers generally calculate the specific speeds and feeds for different materials to achieve this? Additionally, I would appreciate any resources, articles, or recommendations on how manufacturers approach this process. Any insights or references would be helpful

For Example, For a Facing operation, the surface roughness range is Ra 6.3 - Ra12.5, and also in the different pockets the roughness specified is Ra 25 so how can I change the feeds and speeds accordingly using the same 20 mm Flat end mill, The material I am machining is Grey Cast Iron

Re: Optimizing The Feeds and Speeds For Specific Roughness

programming2C78B — Tue, 15 Oct 2024 15:16:09 GMT

Do you have a profilemeter or do you need it right the first time?

Re: Optimizing The Feeds and Speeds For Specific Roughness

sai_tejaRT58C — Tue, 15 Oct 2024 15:34:41 GMT

No I don't have a Profilometer as iam trying to do the CAM simulation and to create NC code using Fusion Manufacturing

So how can I ensure to get the roughness using a CNC mechaning as those feeds and speeds will help us to calculate the time estimation of the complete mechaning

Re: Optimizing The Feeds and Speeds For Specific Roughness

DarthBane55 — Tue, 15 Oct 2024 16:05:50 GMT

Way too many variables involved. Experience is key for this. If you don't have it, you will have to test and test and test. Start with manufacturer of your tool's specs, and adjust as needed. With time, you will know what you need, but right off the bat, your setup, tool, and machine rigidity will all play a big part in what you are asking for, which we don't have. There is no magic number that anyone here can give you to ensure you achieve exactly what you need.

Re: Optimizing The Feeds and Speeds For Specific Roughness

programming2C78B — Tue, 15 Oct 2024 17:39:43 GMT

Feed at .0007" cpt with a 66% tool stepover, coolant enabled, .005 axial finish pass. It'll get you extremely close.

Re: Optimizing The Feeds and Speeds For Specific Roughness

DarthBane55 — Tue, 15 Oct 2024 17:43:50 GMT

I'd say that is pretty impressive, without even knowing the type of machine, actual tool, insert grade and corner radius, I don't know how you can come up with a number!

Re: Optimizing The Feeds and Speeds For Specific Roughness

sai_tejaRT58C — Wed, 16 Oct 2024 04:34:37 GMT

Hi @DarthBane55 ,

Is there really no way to predict the achievable surface roughness based on specific parameters like speeds, feeds, depth of cut, and the tool being used? Does this mean that a newcomer to machining would have to experiment with different settings and tools for each material to find the optimal combination?

I came across the Taguchi method, which seems to suggest conducting a series of controlled experiments on the material to derive a mathematical relationship between these factors. Is this approach even valid in practical machining environments, and how commonly is it applied?

https://www.sv-jme.eu/?ns_articles_pdf=/ns_articles/files/ojs3/1505/submission/1505-1-1990-1-2-20171103.pdf&id=5951

Re: Optimizing The Feeds and Speeds For Specific Roughness

DarthBane55 — Wed, 16 Oct 2024 12:35:01 GMT

You can predict to a certain degree, but it depends on rigidity a lot, and the tool insert grade, geometry, corner radius etc. Usually, you start programming a CNC machine after you have a few years of hands on experience using the machine, so you already have a pretty good idea about your tools and machine behavior in various materials. But like I said, the tool manufacturer will give you good start points, which you will play with to get exactly what you need. It's not too hard, just start with manuf. specs, make a part but leave material on the face so you can take multiple cuts without needed to redo a new part for each test. You can still get the 1st part to your liking if you have enough material to face off. Usually a facemill with give a very flat face, if you need it rough, you can use it with only 1 insert so that it leaves a rougher surface, but generally, if you go with manuf. specs, you'll get a very nice below 20 finish most likely. But then again, you said you don't have the surface finish measuring tool, so how would you actually know what you got? If you need to respect a certain surface finish as per part drawing, you will absolutely need that measuring tool, otherwise you won't know exactly what you got. You'll be close, but not exact.

Re: Optimizing The Feeds and Speeds For Specific Roughness

sai_tejaRT58C — Wed, 16 Oct 2024 17:46:50 GMT

@DarthBane55
I would like to know how a CAM engineer determines the appropriate speeds and feeds based on surface roughness requirements. Since it's not feasible to use trial and error for different materials, tools, and jobs every time, how does a CAM engineer predict the surface roughness and program the CNC machine accordingly? What methods, formulas, or guidelines are typically used to make these predictions efficiently during the CAM programming process?

Re: Optimizing The Feeds and Speeds For Specific Roughness

leo.castellon — Wed, 16 Oct 2024 20:02:02 GMT

As Darth has already said, it is impossible to calculate this exactly and hit that magic number on the first try, there are too many variables. A popular Youtuber, Titans of CNC, runs a massive Heller F6000 machine and if I ran the same numbers as he does on my 1999 vintage HaasVF2, there would not be any comparison on the finish with what they could get on their machine and mine. I have been in the business for 30 years, and the speed and feed calculators are just that, calculators, it is up to the user to verify those numbers with their work holding, machine rigidity, tooling quality and programming, it can even vary between different batches of material.

Part of what you are asking for is determined by the amount of experience of the programmer.

LeoC

Re: Optimizing The Feeds and Speeds For Specific Roughness

jeffescott — Thu, 17 Oct 2024 04:24:38 GMT

You are aware of the cusp height prediction in fusion?

also run the passes with an offset so it doesnt cut the same groove everytime