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Peripheral cooling through tool holder at high rpm

Stefano Prato

Plastic
Joined
Apr 17, 2021
Greetings,
I have to do a slot milling operation where I would like to have a better chip evacuation. I was considering toolholders or reduction sleeves with peripheral cooling supply.
I was afraid that at 15.000 rpm (the slot is 2mm so I need high RPM) coolant might not reach the tool cutting edge due to centrifugal force. I bought a Schunk sleeve for the tendo e hydraulic holder and at very low rpm the coolant is far from the cutting edge.

Do you think that a toolholder with embedded coolant channel might perform better than a sleeve? Do you think that 15000 rpm might be too much anyway? Could my problem depend also on low through spindle coolant pressure (1.5 MPa - Okuma Genos M560)?
 
Could my problem depend also on low through spindle coolant pressure (1.5 MPa - Okuma Genos M560)?
That's not helping. You need at least 500psi, preferably 1000psi.
I don't have much experience with tools with coolant grooves so I can't help you there.
Are there any tool holders that have coolant holes that are angled toward the center of rotation instead of straight?
 
Are there any tool holders that have coolant holes that are angled toward the center of rotation instead of straight?
Yes.

download (2).jpeg

I thought that reduction sleeves also have collant channels and holes oriented but I'm not sure; maybe they are just straight.
 
I'd get a tool that has the coolant holes going through the shank.
I got one of those ready for quote. Price was a little high. I would prefer to use standard endmills because for my application I will need at least 2 endmill per part and I hope to run it at night so time shouldn't be a concern. I also fear that at high RPM coolant might not reach the cutting zone. I will update with the results.

Guhring also make a similar endmill https://www.guhring.com/ProductsServices/SizeDetails?EDP=9068080020000 . I'm waiting for a quote.

Emuge has an endmill with coolant directly to the cutting zone but it's much more expensive than alternatives https://www.emuge-franken-group.com...-cil-frontale-in-md-jet-/p/000000000010704565
They also make a model without coolant but with chipbreaker which might be an even better option; still too expensive.

I would really like to find a solution with standard inexpensive endmills
 
Rego Fix Powrgrip "CF" collets are the very best I've found for high RPM external coolant coverage. I run them up to 16,000 RPM and am very happy with the way the coolant doesn't fan out. However, I have 450psi (3.1mpa). Your through coolant pressure is very low.
 
Rego Fix Powrgrip "CF" collets are the very best I've found for high RPM external coolant coverage. I run them up to 16,000 RPM and am very happy with the way the coolant doesn't fan out. However, I have 450psi (3.1mpa). Your through coolant pressure is very low.

Agreed. The RegoFix CF collets aren't like any of the other, similar, solutions to this I've experimented with. I don't know how they pull it off, but every other coolant slot collet design instantly fans out - CF is like a solid column of coolant going exactly where you want it to, regardless of RPM, and even with some of the more advanced straight cutting oils designed for TSC use.

Literally the only problem with RegoFix is the price. Everything else about the PG system is exceptional.
 
Agreed. The RegoFix CF collets aren't like any of the other, similar, solutions to this I've experimented with. I don't know how they pull it off, but every other coolant slot collet design instantly fans out - CF is like a solid column of coolant going exactly where you want it to, regardless of RPM, and even with some of the more advanced straight cutting oils designed for TSC use.

Literally the only problem with RegoFix is the price. Everything else about the PG system is exceptional.
I agree totally, I only run RegoFix PG holders when I can and the CF collets are a no brainer but if the OP is eyewatering at a couple "expensive" endmills he's certainly going to cry when he sees how much just a single PG holder plus collet (especially cf collet) plus press costs.
 
I got one of those ready for quote. Price was a little high. I would prefer to use standard endmills because for my application I will need at least 2 endmill per part and I hope to run it at night so time shouldn't be a concern. I also fear that at high RPM coolant might not reach the cutting zone. I will update with the results.

Guhring also make a similar endmill https://www.guhring.com/ProductsServices/SizeDetails?EDP=9068080020000 . I'm waiting for a quote.

Emuge has an endmill with coolant directly to the cutting zone but it's much more expensive than alternatives https://www.emuge-franken-group.com...-cil-frontale-in-md-jet-/p/000000000010704565
They also make a model without coolant but with chipbreaker which might be an even better option; still too expensive.

I would really like to find a solution with standard inexpensive endmills
Why do you need two endmills per part? That mikron endmill I linked is specifically designed for slotting in SS/Ti/Inconel.
 
Why do you need two endmills per part?
Because the part has a lot of slots (2mm large and 3,3 mm deep). Right now the only option is to use small 2mm high feed endmills but it is too slow. A slitting saw can't be used.P_20231216_180758.jpg
Powrgrip is cool and I use Regofix for my ER toolholders assembly. The price of the toolholder itself is not a problem as the alternative is Big Kaiser hydraulic or high precision collet system; is the investment for the press that is too high at the moment. I just started the shop and I don't often need high performance solutions; still I like Powrgrip more than shrink fit.

Also the problem is that 2mm endmills have 6mm shank so maybe the coolant for a 6mm collet will be directed to the edge of an hypothetical 6mm tool.
It is strange that manufacturer do not supply data about the angle of this coolant channels and the behaviour of the flow in an RPM-Pressure curve or something like that; it should be something that you can simulate without too many problems
 
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You either spend cold hard cash or bleed machine time there is no cheap solution.

I would be running that with my Haas SMM2 or Kira neither of which has TSC at 10000 rpm and 800mm/min feed rate with a bog standard uncoated 3 flute end mill. I would go full depth and if I found I broke a cutter which costs me very little I would take 2 passes.
 
Are those through slots or just grooves? Why isn't flood coolant taking care of that?
The grooves are mostly through slots, on the other side of the plate there are other wider grooves with a 90 degree offset. It is basically a net. The pressure of flood coolant is also very weak but personally I think that chip are not formed properly. I get a lot of burr with standard endmills and burrs might obstruct chip evacuation.
10000 rpm and 800mm/min feed rate with a bog standard uncoated 3 flute end mill. I would go full depth and if I found I broke a cutter which costs me very little I would take 2 passes.

With high feed I'm doing 15000 rpm and 0.11 mm/z (3600 mm/min), but I'm limited to ap = 0.2 mm. The deeper I tested was ap = 2 mm with standard endmills and didn't go well. That seems to be a very aggressive cut.
 
High feed generally means light fast cuts. Either small step over or small step down.
 
Are you using uncoated cutters?
No, haven't tried. Usually endmills intended for steel have some coating on them. I might try your suggestion in January when I will start the next batch of parts. Right now I used Iscar (cheap), Garant (very cheap) and chinese stuff. I'm considering to try Fraisa (medium/high price), Mikron (high price) and maybe Ghuring (not quoted yet). Emuge is too expensive even if it might works (I got the Emuge price from a reseller not an agent).
 
No, haven't tried. Usually endmills intended for steel have some coating on them. I might try your suggestion in January when I will start the next batch of parts. Right now I used Iscar (cheap), Garant (very cheap) and chinese stuff. I'm considering to try Fraisa (medium/high price), Mikron (high price) and maybe Ghuring (not quoted yet). Emuge is too expensive even if it might works (I got the Emuge price from a reseller not an agent).
I buy all my cutters in quantity from a Chinese supplier I have been using for years. Carbide comes from Kennametal if I remember correctly and there machines are all Walter. I have never had any joy using coated in Alu. Any interruption in coolant and they get adhesion and boom new cutter and generally a new collet also. I used a lot of Garr in quite a few companies and some really high end stuff in toolrooms but I don't need to push the envelope anymore.
 
For toolholder I tried Regofix ER collets, both with double contact (BIG+) and without, and Schunk Tendo E also with and without dual contact.
I was considering to try Big Kaiser hydraulic holder on size (no reduction sleeve, according to the BIG guy no sleeve is the first choice) with side coolant holes and New Mega Baby Collet Chuck. According to one of the tool supplier of the brands I listed above I shouldn't use hydraulic holders for milling in general; another one said that I only should care about runout for this application (I agree with him). The Big Kaiser vendor told me to use Milling Chuck as the first choice (I don't really understand this but I guess they know what they say).
Now I would really like to use PowrGrip but it is a huge investment. Somehow as a recently started shop without much equipment investing in powerGrip seems both a terrible and awesome choice: I might maximize the value of the investment by building my library mostly based on PowrGrip but I might also waste money since I don't really need that level of performance.
 








 
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