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Long Tooling Stick Out for HDPE

Mavigogun

Plastic
Joined
Aug 22, 2022
I have a project to sculpt large HDPE blocks, and am looking for feedback from folks who have employed long tooling (~7") on foam, plastics, composites, or wood. My spindle will support a 3/4"/20 mm diameter shank, and will be operating around 6 HP. I don't intend to make cuts of any great depth- so a cut length of more than 1"/25 mm isn't necessary. I'd like 7" of stick out to allow for cutting through pockets and completely facing sides, but will have need for ball nose, tapered, and flat end tools.

Are these tool parameters realistic? I have a tool maker reading to cut carbide, but would first appreciate feed back from those with real world experience employing long tooling into comparative materials. Thanks for your consideration.
 
I just finished a similar sounding HDPE job on my Haas VF2. Used 1/2" and 3/4" tools, both with about 6" reach.

These were stub flute, relieved shank, solid carbide cutters. 3F, corner rad, uncoated. Used the shortest projection holders I had.
I ended up at something like 5k rpm, .004" fpt, 1xD axial and 10-20% radial for the 1/2". 10k, .006" fpt, 1xD axial and 20-30% radial for the 3/4".

Those are conservative numbers, I didn't want to risk pushing it. Also was concerned with tool whip on the 1/2".

HDPE cuts like butter. I used air blast to avoid melting or recutting chips but that was probably optional at my speeds.
 
+1 on the air blast, I used spray mist successfully when I had it. Watch for the anything wrapping around the shank as this will weld and melt the job in no time. If cutting into corners make sure that your tool rad is smaller than the radius you are cutting as you don't want to stop in corners.
 
Those are conservative numbers, I didn't want to risk pushing it. Also was concerned with tool whip on the 1/2".
Much appreciated. Do you reckon 7" with 3/4" diameter is manageable? (part of me wants to hear "yes"- but the part that isn't keen on $700 for a custom tool would be happy with "no"!)
 
I remember seeing a video where someone was machining styrofoam with an absolutley ridiculously long cutter maybe 12" long or even more. When the cutting forces are really low, you can get away with geometry that could never work on metal.
 
I just finished a similar sounding HDPE job on my Haas VF2. Used 1/2" and 3/4" tools, both with about 6" reach.

These were stub flute, relieved shank, solid carbide cutters. 3F, corner rad, uncoated. Used the shortest projection holders I had.
I ended up at something like 5k rpm, .004" fpt, 1xD axial and 10-20% radial for the 1/2". 10k, .006" fpt, 1xD axial and 20-30% radial for the 3/4".

Those are conservative numbers, I didn't want to risk pushing it. Also was concerned with tool whip on the 1/2".

HDPE cuts like butter. I used air blast to avoid melting or recutting chips but that was probably optional at my speeds.

Thanks much for the invaluable insight. How powerful was the spindle driving that operation? (kW/horse power)
 
Spindle HP is not as important as chip evacuation. And a CL of 1" needs width of cut for an answer. Multiple passes is better that trying 1" deep x .75 wide. Chips will wrap if they cannot clear and things go south quickly after that.
 
Spindle HP is not as important as chip evacuation
While I appreciate the reflection, the spindle power very much informs what is required for what seems to me an aggressive cut; achieving such in my roughing would save considerable amount of time- if there is sufficient power to drive the tool. Just now I'm trying to decide between several spindles and cost points; if 3 hp is sufficient for what was described (which I doubt), I have an opportunity to have an ATC system at a good price. If this will require 7-8 hp, I may opt for manual tool change.
 
Re-reading, I see the machine in question was a Haas VF2- so likely a 30 hp/22.4kW spindle. Yikes.
 
So you don't have the job and don't have a machine to do it with? And do not have the experience to do it? Wish you good look. I know a bit about machining HDPE, but I'm just a little guy. Sometimes fill an 8 yard recycle container every 2 weeks with swarf, sometimes not. Sometimes more.
 
I remember seeing a video where someone was machining styrofoam with an absolutley ridiculously long cutter maybe 12" long or even more. When the cutting forces are really low, you can get away with geometry that could never work on metal.
I used to run this back in a previous life. Thats a 13" long tool, either 1" or .75", in a bt30 spindle. Would routinely run 2" deep (all the flute length the tool had. Could absolutely go deeper with a different tool) full width at basically max machine speed. The world of styrofoam is so much fun :D
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So you don't have the job and don't have a machine to do it with? And do not have the experience to do it? Wish you good look. I know a bit about machining HDPE, but I'm just a little guy. Sometimes fill an 8 yard recycle container every 2 weeks with swarf, sometimes not. Sometimes more.
You seem to have gotten your ego wrapped around your tool.
 
Nah, he's just reacting politely to being told a bunch of shit by a guy who's never done anything. Me, I tend to be more outspoken :)

Characterizing asking about spindle power as "being told a bunch of shit", we clearly don't share the same values. Yes, chip evacuation is an important consideration. So is heat. Work holding. Distortion. No, that doesn't preclude relatively deep, rapid cuts, managed correctly- as I have witnessed, and others have attested to.
 
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Yeah I've ran 20xD-30xD with .125"-.062" cutters in Aluminium.

cutting some polymer with a .75"-1" with only 10-12xD, that's child's play.

easy peezy, letter rip :D
 
Characterizing asking about spindle power as "being told a bunch of shit", we clearly don't share the same values. Yes, chip evacuation is an important consideration. So is heat. Work holding. Distortion. No, that doesn't preclude relatively deep, rapid cuts, managed correctly- as I have witnessed, and others have attested to.
You're welcome. Please show yourself out. Lots of things are big words are important. But if you had the answers you would not have asked.
ID ten T problem.
 
You're welcome. Please show yourself out. Lots of things are big words are important. But if you had the answers you would not have asked.
ID ten T problem.
Like a drunk wondering into someone else's house, telling the residents to leave.

I asked about the spindle power in an operation. It wasn't your operation. You were not equipped to judge why I wanted to know, got bent out of shape when the invitation to digress was rejected after polite acknowledgment, became abusive.

You don't have to share my interest or concerns- in which case, this thread isn't for you. If you have topical contributions to make, have at it, they will be appreciated.
 
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