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Thread: Hsm rules!!!
02-17-2012, 05:53 PM #21
02-17-2012, 06:42 PM #22
02-18-2012, 07:10 PM #23
Here is the one that shows what I am trying to accomplish. If we are to take back our #1 spot in manufacturing, this is how we will have to run. I look at machining like a race car driver I know, "you never go fast enough" . This however is not at the expense of quality. I truly enjoy tool grinding, but the real reward is when a shop "sees the light", when it comes to alternate machining styles. I have seen owners faces lite up like a kid in a candy store. As an afterthought, I will post a video of steel castings (full of sand pockets) being machined with an uncoated carbide endmill. I am sure many shops have to deal with this problem.
Production milling - YouTube
02-19-2012, 09:09 AM #24
I have been wanting to try the HSM type of slot cutting when the need arises. I'm wondering if there is a "rule of thumb" about the best/maximum tool diameter for a given slot width.
02-19-2012, 09:59 AM #25
Thanks for posting this James!
02-19-2012, 10:05 AM #26
02-19-2012, 10:18 AM #27
02-19-2012, 10:26 AM #28
02-19-2012, 02:52 PM #29
Smaller diameter tool means you get to spin it faster.
Since you have 4 teeth either way higher RPM gives higher feedrates.
At some point the smaller tools flexes and you have to back off chipload.
Average chipload is best calculated here in a CAD or software designed for light engagements as the standard formulas don't work.
Spend two or three days slogging though the parameters and I find when doing high DOC low radial engagment milling like this a 5/8 gives the highest MRR rates up to about 1.25-1.5 DOC. Deeper than this and a 3/4 is better because you need the thicker core for stiffness.
A good CAM system will program the correct feedrate when you are on the material and speed up to 1000+ IPM when you are in the air.
If you have never done it I'll warn you it is scary as heck when you first run an endmill 1 inch deep at 450 IPM.
Everything just looks wrong when the slides start moving and you will never get to the stop button in time if there is one small programming error.
You know you are getting somewhere when you start calculating your MRR in cubic inches per second on 4140.
02-19-2012, 06:41 PM #30
One other thing to consider is wear on the ballscrew. When cutting a slot one axis does nothing but move back and forth. If the distance the axis moves is too small the lubrication can be pushed out of the area and ballscrew wear can take place. The larger the radius used when trochoidal milling a slot thats in line with x or y axis the better.
02-20-2012, 04:55 AM #31
False brinelling is what Ed is talking about - there was a thread on emastercam last year somewhen about it. Quite interesting.
Apparantly by memory first 'discovered' by Ford when transporting cars on the railways - the cars would rock back and forth ever so slightly and when they got to their detination, wheel bearings were fooked.
02-20-2012, 10:26 AM #32
I used 12mm coated carbide 3 flute in Robodrill and after slight tweaking we managed to cut trochoidal 15mm wide 20mm deep slot 1mm per second in low carbon construction steel. 4000 rpm, 800mm/min feed.
No vibrations, superior surface and chip evacuation was absolutely perfect.
I like HSM a lot. No way could I make this slot in conventional way in such a time in 30 taper mill in reasonable time and wear !
Table motions look so smooth and gentle, no sharp turns and accelerations.. like mother swinging a cradle..
Also - trochoidal will wear tool evenly. With conventional slotting, especially with 30 taper machine, you'll wear only 2mm end and also you get rid of corners very fast. Especially in steel.
02-21-2012, 06:27 AM #33
IPT = desired inch/tooth
D = tool diameter
RDOC = radial depth of cut
A 1/4" end mill at .010" RDOC and a desired IPT of .001", would need .00287 inch/tooth to achieve that.
I've found that many cutters --especially larger diameter-- can withstand a very large inch/tooth at which point you can throttle the tool for life, part output and/or finish. A little cost analysis is useful for determining which direction to go.