[MBViklund]

I am cutting some big steel parts and I am having problems with chatter, especially when milling in x+ and x- direction. I can find combinations of feed, speed, DOC and WOC that cuts perfect in Y direction but will not work when cutting in x direction. Anybody else experienced this?
I have adjusted the gibs with no result, I have a little more backlash in the Y ballscrew than the X screw. Is the difference in rigidity in different directions that big or am I having some other issues causing this?

[AUSTINMACHINING]

Funny you should bring this up. I've had the exact same issue I've been trying to track down. I've only been able to look into it briefly between making parts. I recently spent a lot of time adjusting gibs which improved my back lash a little (still above .002" both X and Y), but still got chatter in X+/-. Like you, My Y axis moves are silent. The last time I milled, I really cranked down on the x axis thrust bearing. Probably way more than spec (Whatever that is, I don't know). It seemed to help reduce the chatter a good degree. I don't have the required spanner wrench to tighten the thrust bearing, but I was able to get it tight enough to "feel" it have more resistance when turning the screw manually. I suspect the bearing is toast. I need to get the bearing spec from Novakon to replace. I'm happy to buy from Novakon, but if there is a higher price/quality one from another vendor, I'm happy to pay more if it means longer life between replacement. Nice big chunk of metal BTW.

[RCaffin]

That looks like resonance, not chatter, to me. If so, the problem is that you may be using a cutter which is too large for your machine at the DoC and spin you are running. ie, the forces are a bit too high.

You could try reducing (or increasing maybe) the spin, reducing the DoC or reducing the cutter size.
In one case I was able to damp out the resonance by clamping a rather large block of steel to the table.

Cheers
Roger

[LeeWay]

This is where a variable helix end mill can be helpful.

[AUSTINMACHINING]

Still doesn't explain why it's only in X axis though.

Sent from my SM-G900T using Tapatalk

[LeeWay]

There may be very slight variables to each axis. The Y axis has more weight on it. The tram may be just a bit different between X and Y. There may be very slight head play left to right and none or less front to back. Different backlash on each axis.
Different amounts of gib contact on each axis. Feed rate may need to be raised a little or the RPM's, but I suspect the RPM's may already be at max.

[Novakon]

I was thinking about this last night while semi watching a TV program. It dawned on me the chatter might be coming from the head from the Z axis linear ways. The harder the material you are cutting, the more effect we could see from deflection in the X-axis direction. This makes sense because of the large Y-axis work envelope. It may not be related to the X or Y axis at all.

Regards,
John

[RCaffin]

It dawned on me the chatter might be coming from the head from the Z axis linear ways.

I agree. That's what I was trying to say. (My emphasis)

Cheers
Roger

[MBViklund]

Hello everyone

Making lighter cuts removes the chatter. But then it would take for ever to machine parts like this. I am already using 4 fl variable helix mills, 3/8" and 1/2" carbide ones.

I have been experiemented a little bit with a indexable 16mm 2 fl mill wich actually cuts nice. In the video I am cutting at 2900rpms, 500ish mm/min feed, WOC 8mm and DOC 3mm. https://www.youtube.com/watch?v=D_HhUJehptc

I also think the sorce of the vibrations might be the Spindle or collumn. But there is no adjustments there. All screws are tight and I can't do anything to the linear ways?

[RCaffin]

That's a pretty aggresive cut for a little Tormach. I would hesitate to cut that hard.

Cheers
Roger

[AUSTINMACHINING]

Hello everyone

Making lighter cuts removes the chatter. But then it would take for ever to machine parts like this. I am already using 4 fl variable helix mills, 3/8" and 1/2" carbide ones.

I have been experiemented a little bit with a indexable 16mm 2 fl mill wich actually cuts nice. In the video I am cutting at 2900rpms, 500ish mm/min feed, WOC 8mm and DOC 3mm. https://www.youtube.com/watch?v=D_HhUJehptc

I also think the sorce of the vibrations might be the Spindle or collumn. But there is no adjustments there. All screws are tight and I can't do anything to the linear ways?

That looks pretty good to me although I've only cut a small amount of 304SS. I was using a Melin 5 flute nACRo coated end mill which allowed me to double my SFM over un-coated carbide. Machining 304 is painfully slow, so anything to speed it up helped.
What grade of steel are you cutting ?.

[MBViklund]

That looks pretty good to me although I've only cut a small amount of 304SS. I was using a Melin 5 flute nACRo coated end mill which allowed me to double my SFM over un-coated carbide. Machining 304 is painfully slow, so anything to speed it up helped.
What grade of steel are you cutting ?.

It is s355j2 or ss2142. I can cut a lot more aggressive with the indexable mill than with all other cutters I have tried. The resonance/chatter problem does not appear very often with the indexable mill. But with all other mills I have tried.

[RCaffin]

Thinking out aloud ...
A 1/2" end mill has a lot of edge in contact with the metal. That creates a lot of drag or force. I find that can cause problems.
Is it possible that the indexable endmill you are using has small radius tips and the tips are all that is in contact with the metal? If so, it is possible that the design of the cutter means that the machining forces may be LESS.
Specs on insert?

Coated carbide may also create less drag, if it is the right sort of coating.

Cheers
Roger

[MBViklund]

Thinking out aloud ...
A 1/2" end mill has a lot of edge in contact with the metal. That creates a lot of drag or force. I find that can cause problems.
Is it possible that the indexable endmill you are using has small radius tips and the tips are all that is in contact with the metal? If so, it is possible that the design of the cutter means that the machining forces may be LESS.
Specs on insert?

Coated carbide may also create less drag, if it is the right sort of coating.

Cheers
Roger

The inserts are Mitsubishi APMT1135PDER-M

[RCaffin]

OK, about right. That insert has a very short wiper near the tip, but the actual length of the cutting edge is shorter than for an end mill.

All the same, I still say you have to make the trade-off for your machine: push it too hard (to get the short cycle time) and you may get chatter. Me, I would be more concerned about the chatter than the cycle time.
And a chattering machine is going to wear out a lot faster too.

Cheers
Roger

[MBViklund]

OK, about right. That insert has a very short wiper near the tip, but the actual length of the cutting edge is shorter than for an end mill.

All the same, I still say you have to make the trade-off for your machine: push it too hard (to get the short cycle time) and you may get chatter. Me, I would be more concerned about the chatter than the cycle time.
And a chattering machine is going to wear out a lot faster too.

Cheers
Roger

I agree with you. But my problem with the regular endmills i have tried. I won't get anywhere near the material removal as with the indexable. I have tried low DOC and wide WOC, up to 10mm DOC with low WOC, but it seems to chatter no matter what I do. I always run HSM toolpaths. In fact it wants to chatter even for the finish pass. I can't leave more than 0.1 mm 7mm DOC finish or else I get chatter. Anyone having recomendations for steelcutting endmills that works good with the Torus?

[AUSTINMACHINING]

I agree with you. But my problem with the regular endmills i have tried. I won't get anywhere near the material removal as with the indexable. I have tried low DOC and wide WOC, up to 10mm DOC with low WOC, but it seems to chatter no matter what I do. I always run HSM toolpaths. In fact it wants to chatter even for the finish pass. I can't leave more than 0.1 mm 7mm DOC finish or else I get chatter. Anyone having recomendations for steelcutting endmills that works good with the Torus?

I would try is using the shortest end mill possible for your required depth of cut, installed directly in an R8 shank to get as much rigidity as possible at the tool. That indexable looks to have a lot of stick out. I usually leave 3% of the tool diameter for a finish pass which has always worked well for me. From what I can find, that looks to be steel used for molds ?. I cant find it in the list for HSMadvisor. Your chips look to have a blue tint, so it looks like your SFM is correct.

[MBViklund]

I would try is using the shortest end mill possible for your required depth of cut, installed directly in an R8 shank to get as much rigidity as possible at the tool. That indexable looks to have a lot of stick out. I usually leave 3% of the tool diameter for a finish pass which has always worked well for me. From what I can find, that looks to be steel used for molds ?. I cant find it in the list for HSMadvisor. Your chips look to have a blue tint, so it looks like your SFM is correct.

Thats probably a good idea. I will order some r8 collets to try mounting the tooling directly in the spindle. Actually the tool stick out is less than what I need. I need 35mm since that is the material thickness, It is 32mm.


The material is a common construction steel around 150-190 HB.

Equal to:
S355J2G3 / S355J2G3+N
EN 10025-2 : 2004
ASTM E290-97a
NACE MR-0175 / ISO 15156
AISI A 350 LF2

[AUSTINMACHINING]

Thats probably a good idea. I will order some r8 collets to try mounting the tooling directly in the spindle. Actually the tool stick out is less than what I need. I need 35mm since that is the material thickness, It is 32mm.


The material is a common construction steel around 150-190 HB.

Equal to:
S355J2G3 / S355J2G3+N
EN 10025-2 : 2004
ASTM E290-97a
NACE MR-0175 / ISO 15156
AISI A 350 LF2

Here's some numbers from HSM advisor for a 156HB material. This is probably pushing the ragged edge of Horse power. With 5 flute and fancy coatings, the feed rate goes up over 100 IPM. I would use these SFM numbers, start slow on the feed and work my way up. Carbide comes apart when things start to vibrate. I've read Cobalt tools are tough and don't chip as easily as carbide when things get tough, but I've never tried any.

Attachment 297896

[mklotz70]

MBViklund Did you have any luck with finding a cure? I've been get chatter in the X, but I was cutting aluminum at the time.