CNC dedicated mill or CNC converted mill?

[Ian Johnson 1Participant @ianjohnson1]

Posted

the clock gauge is a 1 micron Mitutoyo.

**LINK**

Regards

Barrie

That's an impressive test Barrie, might try it on my KX1 although my dial gauges are 0.001" and are plenty accurate enough for me. If I got a one micron dial gauge I think I'd end up in the loony bin searching for the mythical lost micron!

IanJ

[Anonymous]

The only tolerance that matters is the tightest. If the machine needs to hit 0.01mm tolerance then everything has to be set up to do that. The fact that 0.03mm tolerance might be acceptable for some parts is irrelevant. In order to hit 0.01mm everything needs to be considered. For instance how about the following:

Even premium grade cutters are ground to a tolerance, may be 0.01 or 0.02mm depending upon size

Spindle runout of 0.01mm would be good on a hobby level machine, never mind the addition of a collet system

A 150mm length of aluminium will grow by 0.01mm for a 3°C change of temperature

Andrew

[Former MemberParticipant @formermember32069]

[This posting has been removed]

[SpurryParticipant @spurry]

Barrie

What sort of electricity supply does your Wabeco mill use? Voltage and Amps?

Pete

Posted by Barrie Lever on 13/07/2020 19:03:51:

However with great care you will be able to do what you require on a hobby type machine, if you check the video link below you can see a positioning test on my Wabeco mill, however this is just positioning, everything no matter what machine goes down hill from a free running position test, the clock gauge is a 1 micron Mitutoyo.

[Duff MachinistParticipant @duffmachinist36701]

Posted by Barrie Lever on 13/07/2020 19:03:51:

Duff

Well it is a tall order but do able… [clipped]

Regards

Barrie

 

Thanks Barrie.

…and thanks for your link. As you (and Andrew) suggest, it's only when they get to work do you find out the real world accuracy of the machine and set-up.

The Wabeco is on my radar albeit beyond my price range (at the moment).

I also had a look at the Sieg KX1 which Mick and Ian suggested (thanks Mick and Ian) but had to exclude that model because of the limited y axis (110mm or 115mm depending who's spec' blurb you believe). There is the iKX1 with has a larger table (again, specs vary) , but availability seems to be the problem and I have no idea of price for that one. Sieg CNC catalogue thingy. The KX3 is beyond my price range.

I note what you say about routers and will take heed. Thanks.

I'll spend the next few evenings researching CNC machines like the Wabeco, Sieg, and Denford and see how far I get. I think it's fairly clear that to satisfy the tolerances I need, I'm going to have to spend a bit more.

Thanks everyone for your help.

Duff

Edited By Duff Machinist on 13/07/2020 21:26:54

Edited By Duff Machinist on 13/07/2020 21:28:55

[Former MemberParticipant @formermember32069]

[This posting has been removed]

[Former MemberParticipant @formermember32069]

[This posting has been removed]

[Anonymous]

Posted by Barrie Lever on 13/07/2020 20:20:05:

Andrew is correct about the build up of errors but that can be dialled out to a degree……………..

Quite so, but even measuring a cutter diameter is non-trivial. In theory an even number of flutes can be measured with a standard micrometer. But it's not easy to determine if the flutes being measured are precisely in line with the measurement axis. An odd number of flutes is more of a problem. Of course one can buy flute micrometers for 3 and 5-flute cutters. A quick search found a Mitutoyo 3-flute micrometer on sale at the bargain price of £224, plus VAT of course!

Andrew

[Duff MachinistParticipant @duffmachinist36701]

Duff

Not so much spend more money but spend very wisely and understand the level of the small mountain that you are about to climb.

Are you able to say what you plan on making?

Barrie

Will do Barrie. Thanks. It usually takes me about a year on average to decide before spending any money. During that time, I usually go around in circles covering all the bases. I never make a rash decision and, so far, I have never regret a purchase. I'm a few months into that process

Can't say too much about the projects but one, the precision one, does involve photometry. Precision needs to be way better than 10 microns but the prototype instrument is designed so that extreme accuracy can be dialled in. Nonetheless, some parts require a tight tolerance.

Cheers,

Duff.

[EmgeeParticipant @emgee]

Anyone had a Malware TROJAN  Warning when using the Sieg CNC Catalogue thingy link an earlier reply ?

Emgee

 

Edited By Emgee on 13/07/2020 23:05:23

[Former MemberParticipant @formermember32069]

[This posting has been removed]

[EmgeeParticipant @emgee]

Malwarebytes screenshot when using the Sieg link in the above posts. Emgee

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Emgee on 13/07/2020 23:04:13:

Anyone had a Malware TROJAN Warning when using the Sieg CNC Catalogue thingy link an earlier reply ?

Emgee

.

Not I

MichaelG.

[ iPadOS/Safari ]

[JasonBModerator @jasonb]

One other thing to consider when doing what Barrie suggests and testing each cutter then adjusting the software to compensate is that this needs to be done prior to a job starting and then the cutter should not be removed from the holder. So this means you will need multiple tool holders and reasonable quality ones at that and as you may double up on the same shank size then multiple collets which again will need to be better than "standard" quality.

So you could be looking at spending say £100 per tool and would need to have them all set up ready to go which would likely be a need for 10 commonly used tools so that is another £1000 to come out of your budget.You also need to consider the spindle once you get into swapping preset tooling so you need a system where the tool holder goes back in the same position each time.

Also now that you have the tools cutting accurately you are going to want to holed the work accurately particularly if the work will need repositioning for completing eg turning upside down to remove the holding allowance. So a good quality vice will be needed say £500

Andrews mention of heat making your part expand will also need to be considered, Flood coolant will need a pump and suitable enclosure, tanks, etc so that will have to come out of the budget. The other option is air preferably with some form of fog buster lubrication so you want a decent compressor that can supply a constant volume of air for long run times. This is also likely to make the most noise so think about neighbours. Again an enclosure is best if doing a lot of CNC work.

You don't say how many items you want to make but I get the feeling this is not a couple of uses per month hobby project. If so you will also want as solid a machine as you can afford which will be able to remove metal at a reasonable rate rather than a less rigid router that although it will do the job will only be able to nibble away at the workpiece and take several times as long to do what the heavier machine could.

The other question is what are your CAD skills like as you will need to be able to 3D (2D may suffice for some items) model the parts you want to make and then run them through CAM to get the code for the machine. This then brings us onto how much you know about feeds, speeds, chip loads etc as you will need to tell the CAD what cutting parameters you want for the tool and the type of cut it is taking.

Edited By JasonB on 14/07/2020 07:38:07

[JasonBModerator @jasonb]

There are some gantry routers that will take a good cut but may well be beyond your budget. I've had a few of this guys videos pop up as suggested viewing on Youtube and mostly watched the ones of his home built "mill" but he had a router before and has now got this one that comes as a kit or assembled frame and you add spindle, motors etc. Not sure what accuracy it gives.

Worth watching a couple of the mill videos to which will give you an idea of how multiple tool holders speed up the work.

PS, if you watch in youtube the subtitles work reasonably well.

 

Edited By JasonB on 14/07/2020 07:56:20

[Neil LickfoldParticipant @neillickfold44316]

Making parts consistently to 10um is actually a tall order. Barrie is far from a beginner machinist and buying a machine and replicating what he has done is not an easy achievement. A Fanuc robodrill come to mind. **LINK** or the small Hass mills etc. But these are well over the hobby budget but are the lower end of dedicated mills. What you really want is a second hand DMG that is 10 years old or so. Is another option.

There are many others. Some of the machines I saw a few years ago were not capable of making parts to 0.01mm .

You will need to invest in good cutters and good holders. Currently the better ones are the holders that seat on the taper and the face of the spindle. The new series of hydraulic collets are actually out performing the shrink collet chucks.

[Andrew EvansParticipant @andrewevans67134]

Is it a possibility to 'rough out' with a hobby CNC mill and then finish the crucial dimensions with say a surface grinder or in a manual way? Based on what others are saying it sounds like producing parts to that spec purely with a CNC mill might be beyond your budget

Edited By Andrew Evans on 14/07/2020 09:41:12

[BazParticipant @baz89810]

Why don’t you sub contract the work out to those with the 1/4 million pound machines and the small fortunes worth of tooling not forgetting the temperature controlled environment who can actually do the job, save you an awful lot of s**t, grief and aggravation.

[John PParticipant @johnp77052]

Posted by Andrew Johnston 13/07/2020 22:13:49

Quite so, but even measuring a cutter diameter is non-trivial. In theory
an even number of flutes can be measured with a standard micrometer.
But it's not easy to determine if the flutes being measured are precisely
in line with the measurement axis. An odd number of flutes is more
of a problem. Of course one can buy flute micrometers for 3
and 5-flute cutters. A quick search found a Mitutoyo 3-flute
micrometer on sale at the bargain price of £224, plus VAT of course!

Hi Andrew

I use much simpler methods for doing this as seen here in the photo.
With the cutter mounted in a vee block the relative height of the shank
and the highest point of any cutting edge enables the cutter diameter
to be calculated.

I would normally do this at the time the cutter is sharpened as the
cutter can be rotated on the machine about its center and measured in
this way , if a specific size is required since the diameter is known it
is a simple matter to regrind to the required size.

The real fun starts if a tapered cutter is ground since there is no reference
diameter, a small test piece is cut to work out the relative center distance
at the full cutter depth.This pair of 6 mm cutters were reground at approx
3 deg taper and 1 mm radius edge to cut the vanes on this turbine
compressor wheel.

John

[Former MemberParticipant @formermember32069]

[This posting has been removed]

[JasonBModerator @jasonb]

If error were the same in X&Y it would be easy enough to do it with the CAM too, just entering a larger or smaller cutter dia eg if your test was coming out 0.02mm too large with a nominal 6mm cutter you could just enter cutter dia as 5.98mm and the path would then run 0.01mm closer and remove the oversize.

[Former MemberParticipant @formermember32069]

[This posting has been removed]

[geoff adamsParticipant @geoffadams14047]

Barrie

g41 g42 are cutter comp on dia of the cutter program the profile of your part in cam or by hand enter the cutter dia in the machine control if part comes out oversize alter the dia on the machine not in the cam

back in the day with no cam this was very powerful tool to hold tight tolerances on profiles.

i have mach 3 on two of my mills and is not always happy with these g codes fusion 360 has an option to use g41 g42 that i do use

back to the original thread on holding tolerances on cnc machines we had a job that was about 3" 3" steel gear plate the tolerances were.0005 on pitch of holes we did this on a big Matchmaker bed mill had to warm mill up for about 3 hours run job 3 hours what was happening as the machine warmed up the colum moved stable for about 3 hours then moved again to hold these tolerances everything needs to be temp controlled room including inspection all our jig borers were in temp controlled rooms this was in the aerospace industry

Geoff

[Former MemberParticipant @formermember32069]

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[geoff adamsParticipant @geoffadams14047]

Barrie

back in my day we did not have cam or a computer everything done with calculator and log tables never came across a cnc machine that did not have g41 g42 must b be a nightmare without cam

no i have never seen a temp controller machine shop point being if you do need to hold these tols.these need to be considered if the tolerances are are needed or is a draughtsman being over the top for example job on 4 axis one hole +- .002 on pos and on dia on assembley turns out to be a hole for a screwdrive ??

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