Author Topic: Brainstorming  (Read 136 times)

pep

Brainstorming
« on: July 14, 2019, 08:05:28 AM »
As a boot, this will go against, best practices, history and formulas. I am starting to question the tool speed of a mill and turning speed of a chuck, as it relates to quality of the finish.

Watching CNC equipment run and the finishes produced, what is common, they all use high rpms. That in mind, I have begun to up the tool and chuck speeds of my runs lately. Not extreme but starting at twice what is normally thought to be proper.

Knowing this adds heat and stress, I reduce the feed speed, and keep the cuts light. I am seeking a better finish as an end result.

So what are some the thoughts form the seasoned machinist that are here? 

Pep

4GSR

Re: Brainstorming
« Reply #1 on: July 14, 2019, 10:22:35 AM »
You're learning!  May not work good on some things, but on most.  Don't be afraid to increase your feeds a bit too at higher RPMS/SFM.  On newer boxes of inserts, they generally give you a what I call a "Ball park" range of speeds and feeds to work in.  In the home shops where you don't have 15,000 RPM spindles, generally cut those in half if not thirds for a start.
« Last Edit: July 14, 2019, 12:01:59 PM by 4GSR »
Ken

Terrywerm

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Re: Brainstorming
« Reply #2 on: July 14, 2019, 11:10:15 AM »
I experiment with speeds all the time, and sometimes I get burnt, literally!  My general rule of thumb is to run close to recommended speeds and feeds for the heavier cuts, but I usually increase the speed and reduce the feed for a light finish cut. Doing it that way usually works well for me. How much to increase the speed?  It varies, and it's mostly guess work, but you develop a feel for it after a while.

Rigidity of your machinery is what makes the difference. The modern CNC machines are VERY rigid compared to some of the machinery we have in our shops. This increased rigidity is what allows those newer machines to produce the finishes they do at the speeds and feeds that they are capable of. One has to remember that as speed, feed, or DOC increase, the stresses on the machine rise significantly. If the machine is not rigid enough to withstand those stresses, you get chatter and increased roughness in general. Rake angles are also super important. Rake angles that work beautifully for one metal leave a horrid mess on another.

It's really a big learning process, but if your memory is like mine, where you don't remember every detail that passes in front of you, start writing things down. If you find a combination that leaves a beautiful finish on a part, write down the material, speed, feed, DOC, and what kind of tooling you used along with other notes that you feel are pertinent. Keep that log available and add to it often. Maybe even give each entry a star rating to make it easier to find the best ones later. You might even split it all up by type of metal or other details, anything to help you find the piece of information later when you need it. After a while you'll get to where you will remember the details for the materials you work with most often.
Terry

Making chips with old machines!

Bill Gruby

Re: Brainstorming
« Reply #3 on: July 14, 2019, 03:00:13 PM »
 As time moves on during the machine learning process you will find that a given set of numbers, speeds etc., are only a place to start. Sometimes they are right, other times they need to be changed. It's up to you to decide what is right and what is wrong. Yes, as Terry said you will make mistakes and other times you will be dead on. It's all part of the learning process and your ability to adapt to the situation at hand. I for one do not use the numbers any more, I use what works for me.  Nothing wrong with a little brainstorming.

 "Billy G"
« Last Edit: July 15, 2019, 08:09:17 AM by Bill Gruby »
Don't sweat getting old, you'll still do dumb shit, just slower.

An Optimist will tell you the glass is half full, the pessimist half empty, the engineer will say the glass is twice as big as it needs to be.

savarin

Re: Brainstorming
« Reply #4 on: July 14, 2019, 08:10:16 PM »
As I dont know any better I Have to play with speeds and feeds to find what works well.
Too fast and I find the tool tip wears away virtually straight away. Instant lesson.
This also applies to tool stickout, sometimes I go way over what seems to be the "correct" method and so far have got away with it.
I believe all rules are for guidance only and not for following blindly

pep

Re: Brainstorming
« Reply #5 on: July 15, 2019, 07:28:54 AM »
As I dont know any better I Have to play with speeds and feeds to find what works well.
Too fast and I find the tool tip wears away virtually straight away. Instant lesson.
This also applies to tool stickout, sometimes I go way over what seems to be the "correct" method and so far have got away with it.
I believe all rules are for guidance only and not for following blindly

I've not seen much regarding tool stick out. Do consider if to much breakage, chatter or flexing is possible.

Using the lathe and end mills, run the largest  tool or mill. Lathe 1/2 toolbits, end mills limited by the machining required. General facing 3/4, for now, but looking at  fly or face mill  type for a future addition.

"tool tip wears away" would it be safe to say Carbide Tipped or inserts provide some resistance there, and that the inserts are the better option of the 2 types?

CNC machines are like Top Fuel, and my Pro stock machines will never produce the quality for many reasons . But can be tweaked to preform better if the right adjustments are made, and cutting hardware used.

My thinking anyway and could be all wet also.

Pep


4GSR

Re: Brainstorming
« Reply #6 on: July 15, 2019, 08:13:45 AM »
One thing to remember about braised carbide tipped tools.  There are two common grades out there, C-2 and C-6.  In the old Carboloy system, it was C-2 was 883 and C-6 was 370.  Still see a few of them around today.  Getting back to those two grades, C-2 is good for mainly cast iron and some stainless steels.  They don't do too good on steels even though they will work.  C-6 grade is for most steels and do not work good for cast iron or stainless steels.  Maybe that will help maybe not.

If you want to venture into insert tooling, go for it!  The same grades above follow the same parameters with many variations and I'm not even going to go into that.  There's lots of information out there that will make your head spind.  But you can basically be safe staying with the "gold" color inserts for steel and they usually tell you that.  Cast iron and stainless steels will have a slightly different coating.  But remember, doesn't always follow this basic rule of thumbs.  And then you have your really basic insert grades that have no coatings.  Also have to pay attention to edge geometry on an insert.  How much honed edge do you want?  This has an affect on how carbide edge will hold up. 

I can go on and on.  I hopes this helps. if you find a particular insert you want to try, pass it by us and we'll advise if it will work or not.

Ken

savarin

Re: Brainstorming
« Reply #7 on: July 15, 2019, 09:12:52 PM »


I've not seen much regarding tool stick out. Do consider if to much breakage, chatter or flexing is possible.

Pep
Heres the most stickout I've used Pep.
https://www.youtube.com/watch?v=IC-o4z_ZMp8
I did this a few rimes to get a large end radius on some brackets that had to fit snug to a tube.
In this instance it was bolted on to fit round an 80mm dia steel tube

Carpenter84

Re: Brainstorming
« Reply #8 on: July 15, 2019, 09:31:49 PM »
Well, now you have to post more videos, Charles. And make sure you speak in them! I'd love to hear your accent and dialect.
Shawn

First 9x42 column mill,
Enterprise 10x28 lathe,
Ko Lee 6x12 surface grinder,
Airco dip/stick 160 welder,
Fully stocked wood shop.

savarin

Re: Brainstorming
« Reply #9 on: July 15, 2019, 11:57:29 PM »
Ha Ha, not much chance of that Shawn, videos require planning, you dont think I plan stuff do you?  ??? :))

Carpenter84

Re: Brainstorming
« Reply #10 on: July 16, 2019, 06:34:22 AM »
Nahh. Just press record and start machining.
Shawn

First 9x42 column mill,
Enterprise 10x28 lathe,
Ko Lee 6x12 surface grinder,
Airco dip/stick 160 welder,
Fully stocked wood shop.