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 CNC Router Build 
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Joined: Wed Feb 15, 2012 3:36 pm
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Post Re: CNC Router Build
I think it's expensive for what it is but probably worth having for a year, when you are getting to know your machine under different tools, etc.

I will probably renew it for another year when the time comes...but reluctantly.

1mm depth with a 6mm cutter should be nothing, but make sure to ease in slowly, i.e. sloping the entry, once you are 1mm deep, you should be fine, the trick is at the beginning, gentle does it:).

When I am not sure, I tend to listen to the noise of the cutter, if it starts to sound a bit rough, I have my finger on the PAUSE button.


Fri Dec 15, 2017 7:39 am
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Post Re: CNC Router Build
Well, as promised, here is a video with the new toroidal psu and my controller combo.

Watch the three stepper speeds in the video: normal jog, fast jog and then fast GO command at 3000rpm. It can go much faster, but you have to stop somewhere!

All with a microstep of 1600




Fri Dec 15, 2017 10:24 am
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Post Re: CNC Router Build
D1,
That's a very smart looking machine you linked to on Thursday. With all the sexy close-ups and the choice of music I think the guy has invented 'router-porn';-)

Edward,
Nice, simple power supply. What difference in motor performance are you getting compared with whatever-it-was-you-were-using-before?

Kit


Fri Dec 15, 2017 9:50 pm
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Post Re: CNC Router Build
Hi Kit,

No difference, as I also use a toroidal psu on my milling machine, albeit a commercial psu made by Leadshine in China. Unfortunately they don't make it anymore and I can't find a ready-made one with the same specs, so I simply bought the necessary elements to make my own. The commercial one was actually a bit cheaper than making your own.

Edward


Sat Dec 16, 2017 1:16 am
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Post Re: CNC Router Build
Morning all yes shame you cant get commercial toroidal psu i had a look on Zap and as you say discontinued. Makes you wonder why their isn't a demanded for them ?
Thats a impressive speed Edward but you really do need to put a load on it. As we all know thats steppers weak point faster they go less torque they have :-) . Thats why i am going for the 2.1 ration to stay safely within the power band .
Cutters still not turned up.


Sat Dec 16, 2017 2:55 am
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Post Re: CNC Router Build
Yes, the Zapp one is the commercial one I have, they are heavy so they are normally sent by ship to make it economical. But Leadshine themselves don't seem to have them. All the fanatical CNC guys like to make their own, it's so easy. It always costs more than you think because you need to do it properly with spade connectors, fuses and covered block terminals for safety.

This morning I tried two motors Master/Slave, each with their own driver, the same signal goes to each driver direct from the controller. It works really well, all I had to do is change a couple of lines in the C code. When you home, the C code has to be written so that it momentarily disables the slave thus allowing each motor to run independently from each other and travel to each of the home sensors independently. Once all is squared up, the slave is enabled again.

I am toying with the idea of having the X Home sensors placed around the middle of the cutting area, so you don't have to move the axis all the way to the end to set Home. It would save some time. However, there is a problem with that, the machine doesn't know where it is when you first turn it on, so unless I find a clever way, it will have to be Home at one end, in which case I will use the same sensors for both Home and Limits.

It looks like you are getting the same Alu cutters as me, I find them very good, I hope you don't break too many. I thought you had the mister system up and running.


Sat Dec 16, 2017 4:08 am
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Post Re: CNC Router Build
Look forward to seeing this all set up do you think the proximity sensors are accurate enough to ensure gantry is always aligned correctly . I will put a gauge on mine and see if it goes back to exact position every time . In Mach first thing you do is ref all which sets the machine coordinates so the machine knows ware it is . I wouldn't worry about the time it takes to get from your ref points if you can get your stepper to run as quick when its connected to a ballscrew .I do find theirs another issue with my ball screw mounts they have rubber seals which are very tight which makes it difficult to turn the ballscrew i am hopping they slacken of in time .
This is for you Kit a bit of the making of the advert https://www.blinkink.co.uk/a/9809 .It was shot at Clapham Road studios the only people i know who have a Volo.
D1


Sat Dec 16, 2017 4:54 am
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Post Re: CNC Router Build
I read somewhere that these proximity sensors have an accuracy of around 0.05mm. So you will be fine. For real accuracy 0.01 would be ideal. I will investigate.


Sat Dec 16, 2017 11:33 am
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Post Re: CNC Router Build
Thanks for that link D1. I love watching the process of making a film, so much effort from so many capable people. It's interesting to see the convergence of stop-motion and CGI in animation, just as in mainstream cinema.

There's still a magic to stop-motion that purely computer generated images cannot quite capture but that will change over time, not just because of the software developments but also as the users learn how to synthesise whatever that last bit of magic actually is.

Hey, I've just invented a new way to make movies! Use Andy Serkis style motion capture to move a real, robotic cored plasticine Gromit puppet through a virtual set... OK, maybe not.

Edward,
We one-off constructors will never be able to compete with the bulk-purchasing power of the major manufacturers. Not while they can get plentiful labour to work for the kind of money you and I wouldn't get out of bed for.


Sat Dec 16, 2017 8:41 pm
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Post Re: CNC Router Build
On the subject of toroidals.... they are also the traditional way to power audio amplifiers - so that would be a good place to look if using recycled parts... Xformers are very reliable but more fancy designs will have short circuit and over-voltage protection... I just made sure it had a fuse on the output - in fact it should also have one on the mains input...

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This is a 36vdc supply with 300w transformer.

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Ammeter is handy for keeping an eye on actual current - as opposed to what you might think it is...


Mon Dec 18, 2017 5:34 pm
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Post Re: CNC Router Build
A nice power supply, though it's a pity you could only get an American 'ON/OFF' bezel ;)

The analogue meter is nice too, but they're getting as rare as hens teeth these days, and a lot more expensive. I was after a source of one (a milliameter in fact) for a possible precision level project recently and the meter was going to cost about 3 times as much as the rest of the instrument put together.

Kit


Mon Dec 18, 2017 9:42 pm
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Post Re: CNC Router Build
Hi Kit

The ammeter is $17.50 at Altronics or $14 if you are a member. They have a 1 amp full deflection model.

But yes - it's annoying the switch surround is US - like they think the rest of the world should also be upside down!


Mon Dec 18, 2017 10:21 pm
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Post Re: CNC Router Build
Gerald, in future you should order your switches from China. Not only are they cheaper, but they also have "Australian only" versions in all kinds of fancy colours.

My Chinese ammeter, "English only" version cost me £5 from ebay. It measures up to 20A, handy for the four motors. It came with not so clear instructions of how to use it in Oz: "Turn device in sun direction but stop when sunset arrives"

Image


Tue Dec 19, 2017 1:03 am
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Post Re: CNC Router Build
I'm happy with the quality and support of the local product which is likely also from China, and the price is not so bad once you convert.

Re your example - did they ship you the wrong version by mistake - hence it being upside down??? Or maybe you didn't face it the right way at dawn?

BTW 20 amp is a lot of amps - I'm going to bet the needle hardly moves most of the time!

Given that if your transformer is maybe 500 watt and the rectified voltage is 70vdc - then max current will be ~ 8.36 amps. But even a 3 amp rated motor, flat out, is not using 3 amps constant rms. Hope you correct me if I'm wrong.... :)


Tue Dec 19, 2017 2:55 am
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Post Re: CNC Router Build
My transformer is 625VA x 0.8 (PF)=~500W. I think with 4 motors running a 5A ammeter may just be a little borderline at times, so ideally I'd like a 10A one, but not easy to find analogue ones with a 10A scale. There are lots of 10A digital ones on ebay that also read volts, I wonder if they are any good...


Tue Dec 19, 2017 3:47 am
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Post Re: CNC Router Build
Ed. I just checked a 3.8 amp nema 34 motor on my analogue power supply with a Leadshine DM856. At about 500rpm the ammeter read 0.6 amps. So with your 4 motors flat out, you probably won't use much more than 3 amps. So use the 5 amp version - at worst if you do pull more amps, the needle will go hard against the stop, but it probably won't bend... :) And at the Chinese prices it won't matter if it did bend...


Tue Dec 19, 2017 4:46 pm
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Post Re: CNC Router Build
What I forgot to mention was that I wanted a centre-zero milliamter. All of a sudden the field narrows!

As it turns out I'm reliably expecting Santa to deliver the glass-with-bubble-in version of the very sensitive level I had planned to build, so I'm not in the market at the moment.

The current draw of a stepper is, as you all know, in rapid pulses. A natural concern with switch-mode supplies is their ability to provide the required peak current at short notice which a linear supply can do without difficulty. I've recently ordered some sub-ohm resistors to use as a metering shunt so I can put my oscilloscope onto a stepper and look at the real current and voltage waveforms, something I've wanted to do for a long time. Obviously you will all be first to see the results.

Gerald's measurements of average current will be very useful for working out just what power rating of transformer is REALLY needed for a linear power supply in this application, though it's the stationary condition that will draw the most ironically. Anybody want to design a 'constant torque' driver that ramps up the peak current with step frequency? Gerald, what current limit is that DM856 set to?


Kit


Tue Dec 19, 2017 10:31 pm
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Post Re: CNC Router Build
Interesting Kit. You quite right that an oscilloscope should give a more real picture. But knowing the average current tells you if the supply is working within specs.. and gives an indication of how many watts you really need. Most linear supplies are way bigger than necessary because people take the motor current settings too literally...

The test I did was with the Leadshine set to 3.7 amp peak limit. When the motor stops the current drops quite noticeably, since I have 1/2 power standby enabled.

Re your idea for a "constant torque" supply. Easy Servos (closed loop stepper drives) are the closest thing to this. :)

For the plus/minus ammeter - you seem to know a bit more about it already, but sounds like any low value center meter could be used with an appropriate shunt.


Wed Dec 20, 2017 5:25 pm
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Post Re: CNC Router Build
Dont know much about power supply's so will leave that to the experts .Must say i have always noticed the current demand is a lot less then you would imagine . I always put one of those cheap voltage ammeters on the stuff i build
Image2017-12-20 12.29.24 by D 1, on Flickr
They ok and you can calibrate them if they are reading out i just use them for a quick indication if something is going wrong . It also indicates current draw and i think in the pic thats with four 4amp motors . So yes current draw is never as much as it should be never understood this so sort of ignored it .
Hi Edward did a test on my proximity sensors . At sub 100mm/m gantry moves they seem spot on .
[flickr]Image2017-12-20 17.11.06 by D 1, on Flickr[/flickr]
When run at normal jogging speed not so good but that might be down to gauge moving not sure .
Hi kit lots of vintage dials out their .
[flickr]Image2017-12-20 19.33.02 by D 1, on Flickr[/flickr]
My little collection props for film never got round to :( .
Having break from router job needs doing .
D1


Thu Dec 21, 2017 2:38 am
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Post Re: CNC Router Build
I'll try with a 5A ammeter and see how close it gets to total destruction! I also like the digital ones like you have in D1's box. I'll order one from Ebay.

There is a little shop in Lincoln that specialises in vintage instruments, old radio valves and the like as well as reclaimed stuff from old aircraft, good for props I should think.

Good to hear the prox sensors are accurate as I have quite a few.


Thu Dec 21, 2017 6:11 am
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Post Re: CNC Router Build
Yes. Dials look so much better than digits and give a more immediate relative indication....

Is there any rule for power supply ratings with steppers? Based on evidence, it looks like the actual current use is about 1/4 the drive setting.

Very short peaks may be much higher, but only an oscilloscope will see that. In any case, transformers can handle peaks well above their constant rating. So - maybe a rating like 1/3 of the combined motor currents will be pretty safe...

I'd also add not to under-rate the rectifier diodes - they are usually the first thing to die in a linear supply, and are inexpensive. So use one with voltage and current well above the transformer ac output rating - like double at least..


Fri Dec 22, 2017 6:04 pm
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Post Re: CNC Router Build
There are some guidelines on power supply rating on the GekoDrive website at http://www.geckodrive.com/support.html/

They're a little confusing as it talks about ratings for 8 wire motors in either series or parallel, but I recon their 'series' rating of 1/3 the specified motor current fits their diagrams, my knowledge of current in series circuits and the measurements mentioned above.

Regarding rectifiers, the peak diode current will be much higher than the output current but rectifiers are dirt cheap anyway and can be well over-rated without breaking the bank.

Merry Christmas one and all!

Kit


Sun Dec 24, 2017 4:30 am
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Post Re: CNC Router Build
Hi Kit this is the wiring PDF for the motors i use https://cnc4you.co.uk/resources/Stepper ... %204Nm.pdf it states the different current draw for the different wiring methods . But in reality they draw nothing like that. But when i set my drivers up i use the current settings in the PDF . 4 Amps in my case and that seems to be best setting . Anymore and the motors get hot any less they dont run smooth . As say dont understand any of this but i always try and get a transformer with the highest ampage just to be on safe side . I dont think having to many amps is a problem ?
On another note was rummaging through my wood box the other day and found some examples of good ply and bad ply .
[flickr] Image2017-12-21 17.02.52 by D 1, on Flickr[/flickr]
The top one is the good one and i have seen some with even more layers . Needless to say its not cheap but its a lot tougher than MDF .
D1


Sun Dec 24, 2017 5:06 am
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Post Re: CNC Router Build
i notice the name sieg has come up a few times in this off topic post, mostly about milling just wondering what you guys think of the little lathes like the c2 or c3, i have been tempted to buy one. been waiting to ask you guys your opinions might have got one before xmas except i haven't been able to log in for some reason for the last couple of weeks and then after one failed log in i get that caption thing to do, but it doesn't do anything for me anyway.but i sorted it out now i hope.


Tue Dec 26, 2017 10:11 pm
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Post Re: CNC Router Build
D1,
The current rating given for stepper motors is the maximum continuous current you can feed through all the windings at once without any pulsing. In other words, put a 2.8v battery across each winding of your motor and each will draw 2 amps. Good old Ohm's Law: divide the 2.8 volts by the 0.7 Ohms and you get 4.0 Amps.

Amps squared times Ohms (or volts x amps) gets you the heat produced: 4 x 0.7 = 2.8 Watts per winding. It's overheating that sets the limit so strictly speaking they should give an ambient air temperature at which these results are valid.

In parallel, the amps add to give you the 4 amps, in series the volts add to give you the 5.6v given but the power calculations stay the same as do the volts/amps on each winding.

In practice we don't ever sit the motors with constant current on all the windings (I suspect the controllers still pulse the current even when we're not actually stepping, another job for the oscilloscope to check) and if motors had thermocouples in them we could raise the peak current well above the rating and use internal temperature as the limiting factor.

Chardie,
The Sieg lathes are a version of the 7 x 14 inch Chinese 'mini lathe' available from many different sources. There are also 12 and 10 inch versions available which are not worth the saving of money. These are equivalent in size to the well loved Myford lathes which cost about 6 times the money and have been the mainstay of model engineers since WW2.

There are a number of options around with different accesories included in the very variable price so check what the added bits would cost to decide if it's a good deal. I bought a variant from within Australia for $660 inc delivery about 2 yeqrs ago which came with a 4" chuck rather than the usual 3" with the backplate to suit. This means it takes all the chucks, faceplates etc specified to fit the Sieg C4 rather than the C3 without the expense of adaptor plates. Well worth it in my view. There is a version of that lathe currently available in Australia which comes with 3 and 4 jaw chucks in 4" size. Worth a look

https://www.ebay.com.au/itm/new-mini-me ... Sw~AVYvSVz

Kit


Wed Dec 27, 2017 9:15 pm
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Post Re: CNC Router Build
Hi Kit well ya lost me their doesn't take much when it comes to all things maths . Does that explain how a 4 amp motor only really pulls less than a amp in reality then ?
No matter as i say it works so will go for that .
Been using router for day job just MDF and PLY but i am coming to conclusion a slower spindle would be nice ! . For domestic use when you have neighbors to think about the high speed cutting noise is horrible . I have always know CNC routers are noisy but when you are in a big hanger of a workshops surrounded by people making noise it doesn't seem a issue .
But when ya doing a bit of pottering over exmas period in a small shed on a quite housing estate its really noticeable . I can see why manufactures want high speed spindles it gets the job done quicker but for us hobbyist its not such a issue . I have found if i drop the spindle speed down to 6000 the noise is acceptable but you are then on the lower tolerance of your average spindle motor :(
Their are low rev spindle out their apparently

So if anybody is thinking of building a router in near future and slow turn around on jobs is not a issue but noise is i would seriously consider trying to find a low rev spindle.
D1


Thu Dec 28, 2017 3:30 am
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Post Re: CNC Router Build
Interesting, about the noise. Although I built my workshop with triple glazed windows, etc. to pre-empt this, I still worry about the prolonged noise inside affecting your hearing, as having to wear ear mufflers is a pain. So I will have to wait and see, but if necessary I will build an isolating box around it, maybe made out of polycarbonate sheet for the transparent side and other high density acoustic foam materials. A frame is easy to build with extrusion.

In your case, D1, you'd need a hell of a box, so I'm not sure if it's practical.


This is for Chardie, if I had to buy a small lathe, I would probably look at these, Swisstec. I have a Wabeco 3000 lathe, but I want to replace it with something a bit smaller, as I don't use the lathe too much. Something I can convert to CNC.

Image


Thu Dec 28, 2017 8:45 am
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Post Re: CNC Router Build
Nice looking lathe me still not happy with my SC4 but stuck with it now. So many things wrong with it as said before even the emergency stop doesn't work!.
Yeah box round router is essential next years job going to get some sealed glazing units for doors. Still dont think it will make much difference with that high pitch noise though .
Have found more details on that spindle its a GDK80-12Z/2.2 made by GDK http://www.hqd-china.com/products_detai ... Id=81.html Wonder if it would work with my current VFD?. No UK or Ebay suppliers as i can see.
Back to my ali cutting wows does it matter which way spindle is rotating? . As it is i have no idea which way its going will have a closer look at some point .
D1


Thu Dec 28, 2017 11:14 am
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Post Re: CNC Router Build
Well, I'm sure a properly made enclosure will cut the noise considerably, and double glaze sounds fine, so long as the glass doesn't shatter with impact, that's why I mentioned polycarbonate. Maybe you can add an extra layer of polycarbonate to the glass to protect it. I've seen a few of the large enclosed CNC centres with spindles that go at considerable speeds and you could hardly hear them.

Re your spindle rotating direction, it should be clockwise, but it doesn't mater so long as you know that if you spin it in reverse, your conventional milling will become climb milling and vice-versa. I just hope you are using climb milling. Strange that you can't see it rotate, I remember I could go very low revs with the potentiometer. You can set your minimum cut off revs in your VDF, maybe you have them set too high. You can also set how long it will take to stop after you press stop and how long it will take to accelerate to your desired revs, and so much more!

The YouTube video above with the slower spindle received a few bad comments, I seem to remember, mostly from people who said it sounded pretty bad. Unless I was looking at another one, but I think it was this one and that's maybe why they have disabled the comments.

The lathe photo, yes, very nice in the photo but appearances can be deceptive i.e. just the fact that the lathe is called Swisstec doesn't mean that it has been made in Switzerland, it may be a re-badged Chinese brand just painted differently, so best to look carefully and do some research before buying, the cheap price is usually a telling sign.


Thu Dec 28, 2017 1:17 pm
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Post Re: CNC Router Build
Edward,
I'd agree with the warning re the lathe. It does look suspiciously like the D180x300 from the SMT machine company in China. This is a step up from the standard 7" eBay lathe with having a twin-vee bed but is only the 12 inches between centres version which could get a bit cramped once you have a conventional chuck on it and are trying to get the tailstock with it's own chuck and a drill bit far enough back to start a hole. Drilling is a common task on the lathe but it's also where the bed length will catch you out the most. Though you can buy special, short drill bits especially designed for this job.

Kit


Fri Dec 29, 2017 12:47 am
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Post Re: CNC Router Build
Well that been a revelation day :D
Yes the spindle was running in the wrong direction and yes is does matter Edward . Imagine if it was a standard twist drill we all know what it like to drill in reverse . A milling cutter is the same as a twist drill it as a spiral that as to be going the right way to cut into the material on the initial plunge .This is why my cutters were gumming up and not biting into the surface and just over heating .
I assumed because the spindle was running then it was automatically going in the right direction. Lesson one never assume, if pins 1 and 2 are reversed this changes direction of rotation i was just unlucky .
So checked it this morning just by turning the speed down to almost zero and yes backwards . This may explain unpleasant wine when cutting timber i have yet to test that. But it was cutting even in reverse so i imagine its going to be so much nicer :D
So first cut of ali at 8000 rpm with a feed of 600mm/m and 1mm depth of cut . No problem at all and cutter hardly warm . Think a bit of WD40 would help the processes but dont want to use my mister until i get a ali bed in that area . As it is just MDF at mo that would just soak up the WD40 and bloat out.
Def leaning to slower spindle speed and the one i have got should be fine . A closer look at the spec says a minimum cutting RPM of 4000 which is about right . I believe you can tune the VDF for a more lower speed bias so that might be something to look into in the future .
Also no problem with gantry now i am running well within its tolerance 2000mm/m max . Would still like to improve that so a bigger motor will be turning up at some point .
As for encloser you can get sealed units to what ever spec ya want toughened acoustic etc just depends how much ya want to pay https://www.sealedunitsonline.co.uk/reg ... mlEALw_wcB
Think a big piece of polycarbonate might just act like a drum and make the problem worse .
D1


Fri Dec 29, 2017 8:53 am
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Post Re: CNC Router Build
I think you're right, rotation direction does matter, I was thinking of the rotational relationship of endmill and stock when climb milling, but only in my head. Glad to hear that it's running much better now.

I took a look at the double glazing made to size, with front toughened glass, not too bad for price, considering that you just need part of the front to be glass, not all of the front plane, just a window big enough to take a look now and then and see how it's all going. The rest of the box can just be acoustic foam with some hard backing. The thing is to plan how you want the front to open, hinged or sliding, both ways get in the way and take up space. Then some cheap extrusion and you are good to go. Nice project for the new year, your lug holes will be thankful:)


Fri Dec 29, 2017 12:45 pm
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Post Re: CNC Router Build
having your spindle running backwards comes under the class of faults known as 'Finger Trouble'. Can be very embarrassing but are the quickest and easiest to fix.

Kit


Fri Dec 29, 2017 3:19 pm
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Post Re: CNC Router Build
D1, hang on, are you saying that you are machining ali at 8000rpm at 600mm/m and plunging/cutting 1mm depth with a 3mm endmill? Or is it with a 6mm?


Sun Dec 31, 2017 3:34 am
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Post Re: CNC Router Build
Hello Edward yes 6mm cutter 8000 RPM 600mm/m and blunt cutter at that .Think you said G wizard suggested 10000 RPM at 700mm thought would just slow it down a bit .
Not done anymore testing but spindle seemed quite happy at that speed . A 1mm depth of cut not really loading the spindle to much suppose i should turn display to amps and see how much its been loaded.
Speaking of amps did you ever test how much your steppers are pulling ?
D1


Sun Dec 31, 2017 8:19 am
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Post Re: CNC Router Build
Ah, I see... it's a 6mm cutter, that should glide with no problems. The proof of the pudding is in using a 3mm cutter with no clogging, see how fast and deep you can go...

According to GWizard, you can do 10000rpm with a 3mm 2 flute at 360mm/m....just don't blame me for the broken bit:)

If you can do it at 1mm. depth with the 3mm cutter and no lube, I will enter you for next year's honours list, I promise!

I haven't tested the ammeter yet, it's of limited interest because the motors won't be cutting anything, so they'll have an easy ride. Things will change a bit with the cutting forces.


Sun Dec 31, 2017 10:49 am
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Post Re: CNC Router Build
Hi Edward think i am going to run the spindle as slow as i can until i get the hang of things . My little mill runs at 2500 max think the spindle will be fine at 4000 maybe even 3000 with very small cutters . Attempting deep cuts prob not a good idea my little mill was always .4mm spiral pockets etc not adaptive .
Need to use 1mm cutters at some point what does G wizard say on that one .
Been trying to use Fusion more for my CAM do you find it takes ages to generate tool paths . It also does odd things i do think its quite unstable and almost a work in progress will stick with it but hope it improves rapidly .
D1


Sun Dec 31, 2017 11:21 am
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Joined: Wed Feb 15, 2012 3:36 pm
Posts: 408
Post Re: CNC Router Build
For 1mm 2 flute at 5000rpm it's somewhere around 80mm/m

Fusion is a little buggy sometimes, but it is mostly fine. I've never lost anything. Toolpaths are generated in a couple of seconds, but I never do anything too complicated. Bear in mind that I use the Mac version and a very powerful computer, the Windows version may be different.


Mon Jan 01, 2018 11:50 am
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Joined: Mon Nov 22, 2010 1:18 pm
Posts: 1290
Post Re: CNC Router Build
Happy new year all .
Think Fusion slows down a lot when ya doing complicated tool paths. May not be a problem in general but try something with a lot of pockets etc you will really notice how slow it is .
5000 at 80 sounds about right i like slow . Been cutting some acrylic today a do this a lot for day job .6mm cutter 4000RPM at 450mm/m with 1m DC is great so quite i can hardly hear it . Spindle seems very happy at that speed doesn't get warm or anything . I know i could prob go a lot faster but never in that much of a hurry and the noise is a bigger issue.
On spindle front Edward you may have noticed on may control box i have isolator switches for both steppers and spindle. Nearly lost my finger once with a works CNC the spindle start button was ridiculously close to the tool zero button . Always knocked the spindle off at the mains power board after that and thats why theirs a isolator on mine . I just allow power to spindle when i am ready to cut . Better to be safe than sorry .
D1


Mon Jan 01, 2018 12:42 pm
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Joined: Thu Mar 10, 2011 11:38 pm
Posts: 571
Location: Exmouth, Western Australia
Post Re: CNC Router Build
So I finally got my upgraded MDF CNC router moving under it's own steam. A lot of the recent work has been stripping the electronics out of the same case as the PC and into a housing of it's own along with the new spindle PSU and controller.
The downsides are that I've failed to make the gantry side pieces as rigid as they needs to be and those 2mm lead leadscrews were a very bad idea!

I had thought that the bigger NEMA23 motors would run faster than the old 17s but (as all those in the know keep saying) torque drops as speed increases and I've proved that big time. The old machine had an 8mm lead screw on the gantry and belts up the long axis so the mm/step was OK. Even with these new motors I can stall them easily by gripping the leadscrew when the gantry is moving at only 50mm/sec (about all it can manage anyway). At much slower speeds I can't stall the motors by hand no matter how hard I try. This is not seriously affected by adjusting the current setting of the driver (which agrees with what I've read regarding motors running at high speed) or changing the microstepping or replacing the cheapo TB6600 based driver with a Leadshine unit.

A little maths says that moderate microstepping (800 steps/rev) can give a resolution of .025mm (that's one thou for our 19th century readers) with a pitch of 20mm/rev, which is plenty good enough for cutting wood, so I'm looking at changing to 1610 ballscrews (10mm pitch and less friction) or maybe use belts again, just bigger this time.

On the electronics front, I got the oscilloscope out today and my old PC running CNCLinux puts out step pulses with some pretty uneven timing at most frequencies. Pulses due at intervals of 125uS (8000 pulses/second, 80mm/sec with no microstepping) were output with intervals of 100, 150, 100, 150 and so on. Other groupings of errors (often plus/minus 25uS) were seen as well. I don't think this is the cause of the stalling but I'm going to look at an outboard controller, possibly a TinyG board or the same company's more advanced software running on a 32bit Arduino Due board. Plenty to get on with before I can actually make another clock!


Thu Jan 04, 2018 1:43 am
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