[houdini]

Hello, I am brand new to this site and new to cnc machining.
I just got a job at a local CNC shop and they seem to be having problems with milling a block. I wondered if I might get some input.
The block is A2 14"*16"*6".(x-y-z)
They are using a approx 1" maybe up to 1.5" index end mill, that has 2 index
pieces in it.
The machines is a Milltronics VM24 I believe.

they are making a mold for a stamp for a shovel head, It is taking forever, they have tried multiple different end mills and broke them usually with in a hour trying to get a good fast speed.

The mill is running loud and isnt removing a lot of material when trying to get it optimum.
last I heard the program was set to 12hrs and was only going to remove .5" in a area as big as a flat tip dirt shovel.(say 9*10")

Any tips or suggestions for this block with this machine.
ie different tooling, feeds speeds, you know what I mean.

We do 95% Aluminum, so Im assuming thats why they aren't figuring it out quickly.

Heck I dont even know, does A2 come annealed?, I would hope so.

Thanks
CHEERS!

[AMCjeepCJ]

Well I have a milltronics and cut prehardened D2 at 61 Rockwell at about 50 cubic inches per hour! I have an entire write up with pictures on this site. I dunno but I bet you are spinning your endmill waaaay too fast but you didn't give any real info...

I wonder if A2 work hardens? I'm at home but maybe you could find the info on crucible steels website but if not, contact one of their salesmen and ask for one of their spec sheets on A2... It will give you all the info you need. Otherwise call tech support at a tool company like ingersoll and pick their brains...

[garnetram]

I have several years of expierience on VM24 as well as VM15 and a VM20. Some of the best results I have found in tool steel, 304 and 316 ss as well as 400 series and others has been a cobalt rougher, such as a Hanita. But I have used Niagra and others with good results......Try a DOC of 50% of dia for slotting and a 100% DOC of dia for profiling with a 50-75% stepover. I dont have the exact SFPM or CPT but as I recall on a 3/4 EM try 500-600 RPM at 5-6 IPM. I know it sounds slow but the DOC and stepover make up for the slow IPM. Cutter life is excellent, stress and heat are not driven into the part and it is much easier on your machine than an indexable EM, keep full flood coolant and possibly an air blast for slotting. With a CAT40 I did not like going over a 1" dia EM.

Hope this helps!

[moldcore]

Hey guys, he also posted this in the “moldmaking” forum and I believe found some answers there. In any case he needs to give us a lot more information. It sounds like he is using a ball end mill (he probably doesn’t know the difference) with one or two inserts (he gives different answers). His profile says he is in Salt Lake City, not surprising from what I’ve experienced here.

[houdini]

Actually I do know the difference, but like I said I am new to machining.
Hence why I am asking the questions.
I am not the machinist though, the machinist has worked for this company for 14 years they told me, but like I said they are 95% Aluminum, I assume thats why there having a hard time.

They were using a .75"*8"or so, rougher but they chewed it up squaring 2 ends.
I dont know if this is the best way, but they used the entire 5-6" of the flutes for entire coverage passes on the material.

They are currently using a Mitsubishi Carbide AQXUR202SA20L 1-1/4 DIa., 2 inserts, short edge type, Long. (http://www.mitsubishicarbide.com/mmu...eads200503.pdf

The end mill is like 9" long but they cut 1 off of it.
This is the 5th day and they have gone through 5 pair of inserts both sides.

I asked the type of A2 , they said it was standard annealed. Like 28-32 hardness he said( I dont know if thats correct for standard)

Current parameters.
Currently it is set to .025 doc, cutting at radius except for first cut is 100% obviously. speed is 800, feed is 7in. per min.

With the end mill I mention hear what would you suggest, I think they said they paid like $300 for it so I dont think they will want to buy something else, they already broke so many before buying this one, and they just ordered 20 more inserts, there the other half of the mold still to do.

They do have some type of ball nose endmill also, but there not that far yet, still roughing. Well like I said its been say with troubleshooting 4 days and they have a flat head shovel cut only 2.5" into the material, that sounds wrong to me, even with my little knowledge.

The machinist says it is because the tool is 8" long(fastcam states a 8.5" or so tool length on the screen while running, if that tells you anything) and the machine is not rigid enough?

[AMCjeepCJ]

oh

[houdini]

***************
Dude,

If I understood you correctly you said the tool was 3/4" with 6 inches
of flute and 8 inches long?!!!! The machine is probably not your
problem, lol, your tool has way too much overhang and 800 rpm is way too
fast for your feedrate... Go smack the programmer, look him in the eye
and say, "This is-are-was steel you nimrod!"

Good luck but I don't think your problem is the A2 nor the Milltronics
machining center, lol...

Picture this, I'm thinking of an example where a a guy is trying to dig
a hole with a Bobcat skid steer and when it's not digging right he
gets all worried about the engine rpm's when in reality he ought to take
the forks off of it, put the digging bucket on and then go hire an
operator who knows how to run the thing...

Why in the hell are they using so much flute anyway?? I must be
missing something because it sounds like your company is used to cutting foam
board not metal... I really wish I could help but nothing you say
they are doing makes ANY sense at all to me~ Sorry bro...
***************

I dont know why this didnt show up here, so Ill put in the quote.

Anyway they wanted to use the 6" of flutes to square the block sides, he was trying to do shallow passes with the flutes covering the entire area in one pass instead of doing a shallow cut and working your way down in steps, he just used the long a$$ flutes in 1 swipe.

[AMCjeepCJ]

yep, I realized that AFTER I wrote that so I erased it. I personally wouldn't have squared it up that way because of cutter deflection but whatever. Either way, I probably shouldn't have written what I wrote even though I still think they're going about building this the wrong way... Good luck