Advice for setting feeds and speeds?

[haroldm]

hey guys, let me start my detailing my position and how things operate at my current place of employment.

In the past, well at least in the last eight years i have been here, i would program a part and then getting the feed and speeds in the ball park, the machinist would be responsible for the final set numbers used in the actual running of the part. Ok, fast forward to this week, now the boss wants the feeds and speeds set in the CAD room and these are not to be change, which i am actually ok with, to a degree, but i am running into an issue that i dont see an easy fix for. basically i have gotten feedback from all of my machinist and the numbers they end up using do not reflect in any way the formula driven numbers from the machinist's handbook. how can i attempt to compensate for feeds and speeds that they are using strictly from

experience? I can change my material parameters to reflect any speeds and feeds they want, but by using this "calculator" it is not going to match their numbers if they seem to change them on a "whim" or "gut feeling". Sorry for the long post if you managed to make it this far, maybe you might have some suggestions? Thanks.

[90rsgnuguy42]

Sounds like the "boss" needs a little educating. The only thing an operator should be able to change are feeds and/or speeds since these are going to vary depending on a number of conditions, fixturing, out of holder tools etc.. I used to work for a Fred Flintstone like that. Not usually too open to reality. Good luck.

[YoDoug®]

Could you use a variable feedrate like in the is thread? It would allow the operators to change the feedrate without having to edit the program.

 

 

feedrate variable multiplier in post

[Hardmill]

quote:

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now the boss wants the feeds and speeds set in the CAD room and these are not to be change,

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You can run the same job twice and not require the

same feeds and speeds. Tell yer boss to stay in the

office. He obviously doesnt know what hes talking

about, machinists almost always needs to tweak

something at the machine. Just the wa y it is.

 

 

PEACE

[haroldm]

thanks guys, i hear and know all you are saying, but my boss is more of the "this week we do it this way" kind of guy. Very frustrating i know. I told him i could get very good starting numbers using the handbook, it is there for a reason, and he has even gone so far as to have me call the tool manufactures to see what formula they use and i have to combine that with what he thinks when he is walking by and hears the machine run. Well i knew i could find any magic answers, basically i think i just need to vent. i hope he gets over this very quick because it is seriously affecting my work flow. And to make thinks more interesting, he has managers writing up machinists that touch the g-code..haha..anyways, thanks for the input guys.

[Philcott]

Harold,

 

First of all, I would be more inclined to use the tool manufacturer's speed and feed information than the "handbook's".

Second I would show the boss the range of speeds and feeds in the information and try to explain how there are many factors involved in fine tuning each setup. For example Kennametal's new KC9240 turning grade for 304 SS has a recommendation of 300 to 600 SFPM. If turning a .625" diameter part you can be between 1920 and 3840 RPM. Machining at either end of the range could make a huge difference on tool life and finish.

Write them up for screwing up not trying to make the job run better. Maybe have them consult with the programmer so everyone is on the same page but don't tie their hands.

 

Phil

[ReDEyZZ]

quote:

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now the boss wants the feeds and speeds set in the CAD room and these are not to be change

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Impossible.

[haroldm]

Thanks Phil, and that is kinda what i am running into as far as covering all of the different variables that go into determining speed and feed. For example, Iscar might suggest 400 to 600 SFM for cutting 2024T3 and mastercam will use 400 SFM which in comparison is on the low end, now i can adjust that accordingly but another manufacturer will suggest 600 to 800..which is correct? They all are to some degree, it just depends on so many factor, condition of tool, length of cut, ect. I know what your saying and i agree, but it is just hard to tell that to someone that does not want to listen. whew! felt good to get that out.

thanks.

[Programinator]

quote:

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now the boss wants the feeds and speeds set in the CAD room and these are not to be change

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What prompted your boss to try to implement this. What was wrong with the way it was being done?

 

At the machine tweeks must be done. Thats just the way it is.

 

I'd leave if i was forced to try and do that. Its just going to waste time.

[Justin Beebe at Folsom Tool]

Wow,

 

I program, set up, and run my own jobs and I always optimize the program at the machine. Most of the time my numbers are close right out of the gate but I can't imagine not being able to change the feed/speed at the machine. What ever changes I make at the machine I just go back and change the mastercam file to match that way if I ever have to repost the program it will be optimzed. This is the reason the machines have overrides so you can optimze. Numbers can look good on paper and in Cad/Cam systems but it's hard to know for sure until you watch it cut.

[Mr. Dayshift]

We program a little modestly, try to standardize tooling for speedy set-up, consistent results.

 

Crib notes for cutter sweet spots might help you out. I kept a notebook of them when I was an operator.

 

Those catalogue values are 'melt speed' because they have to sell the productivity of the tool.

 

Lastly, it's funny how most guys will slow a noisy machine down, but never wind it up when things are good.

[Dan@clover]

We have a problem close to yours, Management wants us to run at what a seller tells them the tool can run at. Not understanding that it won't last as long and some if the smaller, older VMC's can't handle it.

 

So the only solution I found was to program the speed and feed to the sellers numbers, Call over management and let them watch the tool be dissolved. Now they don't question the operators twinking or expect the job to be done in have the time because that's what the guy selling the tool told them.

 

Besides proving them wrong feels great!!!

[Robert Critelli]

quote:

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Sounds like the "boss" needs a little educating

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I am one of the lucky ones, I am the plant operations manager, and when we decided to go with a cnc machine I volunteered myself to get the training for the machine and programs, That way I could train my machine operator myself. I do have one boss who happens to be the owner and also knows nothing about what we do, every once in a while he will tell me somthing that makes no sense and i just say ok and ignore him, as for feeds and speeds I se them high and put an M48 code at the begining of my programs which allows the operator to manually adjust the run feeds at the machine. The operator is the one who really knows what is going on so I would never take control from him

[Michael Sullivan]

quote:

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Impossible.

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+1

 

your boss is a Maroon.

[cobra95kev]

quote:

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Those catalogue values are 'melt speed' because they have to sell the productivity of the tool.

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I hear you on that one. Our Iscar rep told us most of the book values are based on a 15 minute tool life run time.

[Matthew Hajicek - Singularity]

Our lathe guys are telling me that they need to adjust feeds and speeds depending on what material lot their Titanium came from, even though it's the same alloy and heat treatment. Some of it is just more gummy than the rest. Also, no formula will tell you how rigid your setup is.

[SydwazShawn]

Does he still make you block your material square, or can you use a carrier? Just kidding, but good luck with all that nonsense.

[jnicely]

There is a reason for the manual speed and feed over-rides on the control...

If there was a magical formula, there would be a machine shop on every block.

I'd suggest sidetracking the bossman, get him into researching the ever-rising material costs...

works every time!

[Dracbus]

I had a boss that was the same way. everytime things got a little slow he would have me mess with the speeds and feeds like one day i was magically going to figure out a system for any possible situation. Lucky for me he also programs. So one day i sat him down and showed him all the things we would need to change. We came to a mutual agreement and made dafualt and common tool files for our most used tools and saved them. Same with the materials lists. We managed to set it up so it came out fairly close to what we wanted and the machinists can just adjust using the button on the damn control cuz thats what its there for. We are a mold shop so its not very comoon to make the same part over again. We also have 10 different machines. which changes everything. It took a long time and alot of ajusting and there a couple of other areas that we set up to do this that i dont really feel like going into detail about. Such as machine definition stuff so your endmills will calculate right for which ever machine your on. Cuz we all know a 30 year old lablonde dosnt run the same speeds and feeds with the same endmill as a brand new okuma.

 

Now the tricky part is explaining that to your boss in a way that dosnt xxxx him off.

[Santa Fe]

Harold, you know I always try to make my programs the way the operators don't have to move anything. This based on SFM, chipload, LOC, #of flutes, etc. but mostly on machinist experience.

 

I would say give the operators a good starting point and luckly they will not have to move anything but most times there will be something to improve.

 

As cncjb said, I like to run my programs and if I tweek anything on the machine then I go back to my file in mastercam and update it to what I did on the machine.

 

This will be more of a long process for you guys. Get with the operators and ask them to write down what they change in the program and in a few weeks you will be able to identify what works and what does not.

 

Good luck

[Kelly Burns]

Theres always the alternative of going to the floor and actually running the job you programmed. Crazy thought I know, but if you want to find out how your cutters perform go use them. You should know anyway if your responsible for setting the initial parameters for a new or old job. Yes we all optimize after the initial part, but you should be able to ballpark without to much thought either going by experience with material, or using the cutter catalogs to get close. Go find out for yourself at the machine is always the best way, if your not sure . I wouldnt leave it up to the operator to set the feeds and speeds, your cut depth affects all of this and this is something that has to be determined before it ever hits the floor. Learn your tools either by experience or having someone get you a basic chart of what there capable of cutting at.