aluminium troubles

This topic has 25 replies, 13 voices, and was last updated 25 November 2019 at 16:41 by old mart.

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24 November 2019 at 12:51 #438557
john routley
Participant
@johnroutley14843
hello all, im looking for some help,

i just got a cnc lathe, but having trouble with turning aluminium, we did have some troubles with the machine and had to have a company come out and regrind the bed because there was some problems with it, but still cant get the ali looking any good
anyone know what is going wrong?
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24 November 2019 at 12:51 #9951
john routley
Participant
@johnroutley14843
Poor finish on ali….help
24 November 2019 at 13:27 #438563
JasonB
Moderator
@jasonb
Looks like a cutting issue can you give some more info:

Type of tool and type of insert if not HSS

Speed

Feed

DOC

Dry or what type of lubricant and how is it applied

Grade of aluminium

Edited By JasonB on 24/11/2019 13:31:13
24 November 2019 at 13:27 #438564
Nick Hulme
Participant
@nickhulme30114
Provide cutting and cutter data to save people guessing what you may or may not be doing.
24 November 2019 at 14:41 #438581
Ian P
Participant
@ianp
and the grade of aluminium

Edit, Oops as its already been asked

Edited By Ian P on 24/11/2019 14:42:09
24 November 2019 at 14:45 #438583
old mart
Participant
@oldmart
Are you using inserts designed for aluminium? Grooving inserts seem to be elusive in the sharp grades. Some type of lubricant is required for aluminium, or it tends to stick to the cutters. Some alloys machine much better than others, pure soft aluminium is terrible to work with.

This is the sort of question which might be better on the Practical Machinist forum, they would be able to suggest the most suitable grooving tooling.

Edited By old mart on 24/11/2019 14:49:03
24 November 2019 at 15:16 #438587
john routley
Participant
@johnroutley14843
thank you for the reply's guys, i cant get hold of my machinist today
the ali is 6082 and we always use coolant,

i cant get the rest of the info you need until tomorrow, but i'll get a full list of tip feed speeds etc
its a brand new cnc, but it did come with issues we have had to address, its far better than it was but we are still getting a finish thats no good for what we need the items for.

kind regards john
24 November 2019 at 16:20 #438601
Neil Wyatt
Moderator
@neilwyatt
It's clearly tearing, suggests build up on the tool tip. Are you using suds or neat cutting oil?

I'm used to getting a near mirror finish on 6082 with inserts and just hand applied neat oil.

I have struggled to find ground and polished grooving/parting inserts but I would guess they would help.

Neil
24 November 2019 at 16:38 #438606
JasonB
Moderator
@jasonb
Neil and Old Mart the MGGN style grooving and parting inserts are easy enough to find for Ali and non ferrous, stick em in one of Uncle Ketan's holders. I'd suggest the 200 size (2mm) for benchtop machines
24 November 2019 at 18:10 #438632
john routley
Participant
@johnroutley14843
Posted by Neil Wyatt on 24/11/2019 16:20:09:

It's clearly tearing, suggests build up on the tool tip. Are you using suds or neat cutting oil?

I'm used to getting a near mirror finish on 6082 with inserts and just hand applied neat oil.

I have struggled to find ground and polished grooving/parting inserts but I would guess they would help.

Neil

Posted by Neil Wyatt on 24/11/2019 16:20:09:

It's clearly tearing, suggests build up on the tool tip. Are you using suds or neat cutting oil?

I'm used to getting a near mirror finish on 6082 with inserts and just hand applied neat oil.

I have struggled to find ground and polished grooving/parting inserts but I would guess they would help.

Neil

hello Neil, we are using suds rather than oil, for the general parts we make out of derin oil is not needed but we are really struggling with this ali, i know part of the issue was machine alignment but i think its now something we are doing wrong
24 November 2019 at 19:18 #438645
Baz
Participant
@baz89810
John, you say it’s a brand new machine and yet someone has had to come out and regained the bed, that is appalling on a new machine, can you supply details of size of machine, it’s not just the grooving that’s rubbish, the turning of the radius is pretty dire as well, soluble oil should be fine on that grade of ally.
24 November 2019 at 19:32 #438646
not done it yet
Participant
@notdoneityet
Baz,

I think he said the CNC was ‘brand new’, not necessarily the lathe…
24 November 2019 at 19:46 #438649
john routley
Participant
@johnroutley14843
Hello baz your very right its a bit shocking, i brought this large lathe and a 4 axis mill, + and load of other machines at the same time, for the most part im very happy but this finish on the lathe is way off what i would expect….is it machinist or machine is the thing or just the tooling.
my guy has been machining for 30- years but not this material.
24 November 2019 at 19:54 #438652
JasonB
Moderator
@jasonb
Posted by john routley on 24/11/2019 19:46:59:

is it machinist or machine is the thing or just the tooling.

As we don't know what he programmed into the machine or the tooling it's still going to be speculation. Would also help to know the macine.
24 November 2019 at 19:55 #438653
john routley
Participant
@johnroutley14843
ill bring up all the specs tomorrow
24 November 2019 at 20:04 #438656
Neil Wyatt
Moderator
@neilwyatt
Posted by john routley on 24/11/2019 18:10:19:

hello Neil, we are using suds rather than oil

Check the tool tips closely for any build up of material. If it is sticking to the tip, try using brush applied neat cutting oil or even paraffin and see if it perks up.

How sharp are your tools?

Neil
24 November 2019 at 20:35 #438660
Anonymous
Hmmm, 6082 ought to be easy-peasy.

The finish is poor everywhere; looks like tearing, but could possibly be chatter? First are we really sure that the material is 6082? And where did it come from, commercial stockholder or other?

Insert tooling or HSS? You can turn 6082 with CCMT inserts, but CCGT insert are way better and give a better finish. I use aluminium specific inserts for parting off, although they're not polished in the same way as a CCGT insert. However, parting inserts need to have a continuous feed, preferably greater than 4 thou per rev, otherwise they can chatter quite badly. For accurate (manual lathe) grooving I use HSS tooling.

I generally turn 6082 dry, except for parting off, and still get a good finish. The biggest problem with 6082 is birdsnesting of the swarf, which then dulls the finish. Note it dulls the finish, it doesn't produce the results seen.

Summary: given the poor finish everywhere look for a common factor, which is likely to be the material or machine.

Andrew
25 November 2019 at 09:35 #438709
john routley
Participant
@johnroutley14843
hi guys,

I've contacted the material supplier, weve brought about 20m if it.

We have tried machining from 500rpm to 2500 rpm using css and also fixed spindle speeds

dia turning has been done at 0.25mm/rev with a 0.06 dia finishing cut at 0.05 feed

All the tools are 25×25 shank WNT tools ali tips and using CCGT120404 inserts

the "o" ring tool is a 2mm wide grooving insert firmly gripped in a grooving holder

the radius grooves (5mm) are machined with a 3mm rad tip. roughed out and then finished with a profile program

we have brought aluminium specific polished tips for all the tools

we flood the material with coolant while cutting

parting is terrible, material goes snotty very easily,
25 November 2019 at 09:47 #438710
Hollowpoint
Participant
@hollowpoint
I'm no cnc expert but it doesn't look like you are doing anything wrong to me.

I would try some material from a different supplier. That way you will know one way or another if its a bad batch of aluminium.
25 November 2019 at 10:50 #438714
mark smith 20
Participant
@marksmith20
My view is your depth of finishing cut off the diameter ( 0.06mm – 2.3 thou)is too small for a carbide cutter.

Edited By mark smith 20 on 25/11/2019 10:51:56
25 November 2019 at 11:01 #438717
JasonB
Moderator
@jasonb
Rpm does not really tell us much as diameter of work is unknown. M/min would give us a better chance. Your insert maker should have speeds in m/min and DOC data

Also what temper is your 6082. T6 is usual but if you have a lower number that is softer and not as nice to maching

Edited By JasonB on 25/11/2019 11:03:50
25 November 2019 at 11:10 #438718
Kettrinboy
Participant
@kettrinboy
6082/HE30 alloy should be easy to get a finish on but it can age harden over the years and then you can get problems with mottled looking finishes and tearing , as said I would try material from a different supplier and hope it's not been lying around the warehouse for too long. also generating the width of the grooves with a narrower tool rather than plunging in with a full width tool will usually give a better finish under most circumstances.
25 November 2019 at 11:14 #438720
john routley
Participant
@johnroutley14843
hi,

the diameter is 45mm 1 3/4" its supposed to be T6 grade

just machined a previous sample (machined outside) finish is completely different and quality is excellent,

so i'm now drawn to the material as being the issue

thanks for all your help.

thought I was going mad
25 November 2019 at 11:19 #438722
Anonymous
If the grooves are 5mm wide then the part is on the order of 70mm diameter. Speeds and feeds seem ok. What is the nose radius on the CCGT inserts? The CCGT inserts are much less sensitive to small DOC and fine feeds than CCMT inserts.

I'm with Hollowpoint, my bet is on the material, or rather less likely contaminated coolant.

Andrew

Much too slow yet again; that's what comes of checking facts and figures before posting.

Edited By Andrew Johnston on 25/11/2019 11:21:53
25 November 2019 at 12:07 #438725
Circlip
Participant
@circlip
I get a mirror finish on 6082 with no coolant and hand ground HSS tools.

Regards Ian.
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