operation cnc

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Originally Posted by Jonathan

Jazz will now vote for option 1.

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Won't go there regards stalling/racking has it's all been said.!! But there is more to this than just Stalling motors racking gantry's.?

The Main reason why I like it is Synchronization.?
My machine never loses position and the two ball-screws are synchronized exactly the same today has they were when first installed.
I don't have to worry that on long Jobs the machine will lose sync has the slaved steppers drop the odd step here or there running out of sync with each other slowly racking the gantry.

Don't have to worry that after 10-12 hours cutting I'm going to find that holes aren't where there supposed to be.!! Or the part isn't actually square after cutting profile out because the gantry slowly racked fraction of degree.!

The only way to ensure slaved steppers stay in sync is to either have very accurate Home switches or Home to hard stop and do it often. Certainly after every Job to be safe.
Even then if motors are tuned anywhere near close to the edge, esp regards Acceleration, they can easily lose steps without realising on jobs just a few hours long.
On Jobs that run non stop for 10-12 plus hours like litho-pains this could and has been for some slaved stepper users disastrous often resulting in not just in in-accurate work but stalls thru accumulative error over hours.!

Both work and won't argue that fact but I know which works best.!!

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Originally Posted by JAZZCNC

has the slaved steppers drop the odd step here or there
[...]
On Jobs that run non stop for 10-12 plus hours like litho-pains this could and has been for some slaved stepper users disastrous often resulting in not just in in-accurate work but stalls thru accumulative error over hours.!

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I have never seen any evidence of stepper motors on any of my machines loosing 'the odd step'. If it did they would be practically useless - it's either stall and loose lots of step or run perfectly.

If a motor does stall (which it wont if set properly) then it will only start moving when the step frequency has dropped to a low frequency, so it is possible to loose maybe a few steps (or tens of microsteps) if the motion is very small movements which constantly accelerate each motor, but that's still likely to damage the part whether it's one motor or two. Again, if the motors are tuned properly then, just like on Jazz's machine, you wont loose position so it doesn't matter if it's one motor or two. The only difference worth discussing is the input power considered with the whole system - if the basic calculations show that the motor and driver you can afford to use if just using one will perform better than the same calculation with two motors then go for it. If not it's illogical to use one.

from a neutral point of view with no experience just thinking about it logically. i'd want to reduce anything that could complicate things.. and to me that means running 1 motor even if that means on this axis you have to buy a big ass one to cope with it.

if your BoB/drivers are running 2 steppers on the same axis then you have 3 circuits there straight away that have room for error... the data comes along in 0's and 1's and all it takes is for a little interference on one driver circuit and one stepper didnt move as quick as the other.. bam your work is knackered and the machine is out of line....

now a single stepper has the same interference but this time the whole gantry didnt move.. only problem you have this time is take the wrecked piece of material shove where you like put a new piece down and start again as the machine is still straight


i'm not saying it wouldnt work.. and i have no doubt that yours works flawlessly jonathan, but my mind tells me to simplify to reduce the chance of error

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Originally Posted by wilfy

from a neutral point of view with no experience just thinking about it logically.
[...]
i'm not saying it wouldn't work.. and i have no doubt that yours works flawlessly jonathan, but my mind tells me to simplify to reduce the chance of error

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That's the point though - by agreeing with that you're agreeing that your logical thinking earlier in the post is based on a false premise, therefore you may not be arriving at the correct conclusion even if the points you are valid. In other words, if my system did have a 'little interference' which caused one stepper to slightly loose position we wouldn't describe it as working flawlessly.

Either way, if you buy the right electrical parts either system can work flawlessly, so in the end it's just a case of working out which is the most economical.

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Originally Posted by Jonathan

I have never seen any evidence of stepper motors on any of my machines loosing 'the odd step'. If it did they would be practically useless - it's either stall and loose lots of step or run perfectly.

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Jonathan I've had to correct stuff you made because the fucking things weren't square or correct so don't give me that bollocks.!!

Also if your going to quote me then make sure you quote the whole fucking picture not just what you want to make fit.!!

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Originally Posted by JAZZCNC

Even then if motors are tuned anywhere near close to the edge, esp regards Acceleration, they can easily lose steps without realising on jobs just a few hours long.
On Jobs that run non stop for 10-12 plus hours like litho-pains this could and has been for some slaved stepper users disastrous often resulting in not just in in-accurate work but stalls thru accumulative error over hours.!

Both work and won't argue that fact but I know which works best.!!

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Guys, I welcome all your comments, but really didnt mean to cause an argument. Lets just put the subject to bed.

Im in one of these junctions in the road now. Whatever I decide I dont want to alienate myself from advice from either of you.

I must say however, I think wilfy's comment summerises my present thought chain. and as I have genuinely lost, Yes Lost. one of my 3 steppers it was a case of buying two more for the X axis anyway. So simplifying the bits you cant bite (ie the electronics) and only having to buy one (bigger) stepper & a longer belt & some pulleys seems to me a favourable way forward.

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Don't have to worry that after 10-12 hours cutting I'm going to find that holes aren't where there supposed to be.!! Or the part isn't actually square after cutting profile out because the gantry slowly racked fraction of degree.!

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This machine has cost me an arm and a leg. Im worrying about lots of aspects of it all the time, so Simplifying this area I guess is one less thing to worry about.

On a seperate note; Im also worrying about how accurately I have mounted the gantry to the slide plates. I mean with my Set Square its bang on; when i slide it along the rails; the rails dont move out or in (however I havent yet bolted them down I think im looking to see if it gets tighter at one end) but if the gantry is not square like Jazz has mentioned above the work wont be square... I guess Il find out in time... Its this kind of think that is doing loops in my head everytime im down the workshop. I find myself standing there drinking coffee and smoking staring at it just thinking about (and questioning) the accuracy of my work.

I have not assembled a thing yet and this scares the hell out of me too, with buildings (what I'm used to on a day to day) the tolerances are like 5-10mm no 0.00 something! My thinking for what it's worth is that If you build enough adjustment into the design then you can shim things to perfection later...

Guys i really think you are worrying about very little. I've used twin steppers and it was fine. I have belts running my machine with a single stepper on the X axis. It works great for the home machining i do......But! i have two ballscrews sat there ready to change to once i get round to it. If i can make a belt fit to control the screws from one motor then i will, if can't then i will just use two motors. Stick to your budgets up most and don't let bling go to your head. At the end of the day you are machinists now whether you like it or not, your nature will want you to change things later. There is no right or wrong way just preferences? I like both!
:beer:

I'm glad to see that I'm not the only one worrying about how accurately the machine has been put together. I've just (mostly) finished one side of my frame so I've done a quick test fit. The bed rail and the guide rail are 0.1^o out of parallel. Doesn't sound like much but that equates to just over 3mm over the total length according to my calculation :-(.

It's looking great though KC, keep the good work.

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Originally Posted by JAZZCNC

Jonathan I've had to correct stuff you made because the **** things weren't square or correct so don't give me that ****

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Yes you have once because the machine started off not square and I didn't realise. When it finished cutting I'm sure it was just as far out as when it started! If the machine had gradually lost 'squareness' then the cutter would have broken and the finish would have been terrible since they were so far out. Since then I have corrected the problem.
Also, I should add that the customer you're referring to didn't even tell me there was something wrong with the parts before asking you to fix it. If anyone has a problem with something I make, then I will do my best to fix it, but I can only do that if they tell me there is a problem. He also lied about where he'd sent the parts, but that didn't take much working out.

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Originally Posted by JAZZCNC

Even then if motors are tuned anywhere near close to the edge, esp regards Acceleration, they can easily lose steps without realising on jobs just a few hours long.

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Easily solved - don't tune them anywhere near close to the edge. If you need to do that then you should have bought better motors or drivers.


There is an easy way to check how square the machine is once it is assembled and working:

1. Set the machine to drill 3 holes of the same diameter at the corners of a right angled triangle in some scrap, with one side parallel to X.
2. Push drills or bar the same diameter into the holes.
3. Measure using digital calliper the side lengths of the triangle by measuring the centre distance of the drills.
4. There are now various ways to find how off-square the machine is. You can draw the triangle (which will be scalene if the machine is not square) in a CAD program and measure the angle that should be 90° to find how far off it is. There are of course several ways to calculate this angle, or you could just use Pythagoras' theorem to see if the hypotenuse is longer or shorter than expected, then at least you know which way to compensate.
5. Correct for the error, then repeat until error is acceptable.
6. If two motors set the home switches appropriately if you have them, or you can put marks on thepulleys you can accurately align.

I got mine within +-0.01° using this method, but that was with a 600mm calliper. Still with a 150mm digital calliper you can get it very close. Also when measuring the hole spacing parallel to X or Y you should find they're within a few tens of micrometers:

Attachment 7903Attachment 7904

There will be a slight error due to the lead error on C7 ballscrews, but as the images above show, at least in my case, this is very small - about 0.01mm in 600mm.

Dog with bone?

Ok... so where do I buy a long belt from? the distance between screws is approx (i need to measure) 1.1 meters. So assuming im looking at 'Pitch Length' I need one approximately 2.2 metres?

maxium i can find is about 1.8 metres (1870mm)

im not bothered what 'pitch' it is etc, so long as its a timing belt. once ive found one il buy pulleys to suite, then bolt my existing stepper drive pulley to the ballscrew pulley (ala jazz)

Attachment 7923

If you go to any decent bearing and belt supplier you can have belts made to any length you want, thats what I did. Cost be about £15+vat if I remember correct.

Why can't you use open belt? the gantry has to be fixed to one side of it any way?

Sorry just re read and you want the belt to cross the screws. Give ERIKS in Swindon a call

Address: Unit 2/Ravenseft Pk/Cheney Manor, Swindon SN2 2QP
Phone:01793 533181

The do belts of any size within reason and i found them to be the cheapest at the time.

had one of them nights tonight... first off dropped the ballscrew and bent the end

Attachment 7925

so, decided to fire up the big heavy green machine in the corner. I should perhaps at this point explain that the machine is jinxed. Every single time I use it, it ends up either hurting me, or my wallet

so spun it up.. the other end whipped round like a b*stard, I grabbed the ballscrew before it killed the dog and...

Attachment 7929

thats the tidy version... (all those bearings went everywhere... for a moment, it was like a scene from home-alone)


so, after a few beers of contemplation, and a motivational chat with jonathon on skype I formulated a plan...
Attachment 7926


Attachment 7927
better. Not quite jonathon standard of engineering, I agree but much straighter.

So being an 'engineer' :D now. I decided to use this useful bit of kit too bore the holes in my pulleys

Attachment 7928

decided to come up and finish my beer in the house before I broke anything else

Attachment 7930 Attachment 7931

Better change your name to wobblycogs, oh no - too late!! have a better day tomorrow. G.

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Originally Posted by kingcreaky

better. Not quite jonathon standard of engineering, I agree but much straighter.

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Oh I don't now looks about the same standard to me.!! . .:devilish:

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so spun it up.. the other end whipped round like a b*stard, I grabbed the ballscrew before it killed the dog and...

http://www.mycncuk.com/forums/attach...110_192526.jpg

thats the tidy version... (all those bearings went everywhere... for a moment, it was like a scene from home-alone)

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i'm sorry but this has had me pretty much pissing myself everytime i read it... i just cant keep a straight face when i read over it and i think i've done so 5 times now..

i'm such a bad person.. and whats funny... i know damn right i'm gonna lose them balls one day

Last time i bent my end and slung my balls out she gave me such a slap :hysterical:

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Originally Posted by 2e0poz

Last time i bent my end and slung my balls out she gave me such a slap :hysterical:

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The trick is to get your balls in the right hole mate. . .:hopelessness:

Garden full of snow, baltic weather. But not in my workshop ;)
Attachment 7948
properly cosy.


Right, quick update then.

Ordered replacement ballnut from Chai, aswell as four ballscrew blocks... Im also now waiting on more bandsaw blades.

Attachment 7949

Attachment 7950

not quite sure where im going to put the Y stepper... should of perservered with drawings.. but too impatient.




seperately, i have been given literally 2 tons of metal off-cuts. Its mainly 4mm and 5mm plate but some 3mm. all funny sizes but cut with machinery so all square. I think its galvanised?

anyway ive got far too much, and it was free so If anybody here needs any, come collect it. (leicester) The photo doesnt do how much ive got justice my estate car was on its arches with three loads. There is loads.

Attachment 7951

I have been looking for some scrap metal to practice welding but I guess galv isn't ideal? Not sure? I begged some scrap from a local fabby but have nearly run out...if it's suitable for arc welding practice I'd gladly take some off your hands!!

Love the burner btw !

Machine looks good too. G

ssssshhhhhhh******tttttttttt

so.... you guys always talk about planning planning planning... well ive made a big mistake

Attachment 8062

the ballscrew nut housing, that are bought paid for and on their way from china... are 86mm wide

Attachment 8063

WHAT a sausage.... I dont have that much space!!!

what am I going to do?

this is compounded by the fact ive ordered 4 of them, 2 for the x, 1 for y and 1 for z

Z dont fit

and guess what

Attachment 8064

so, when you've finished laughing... and can think of some constructive ideas... let me know


Plucked up the courage to finish the Y though...

Attachment 8065

If you've got the ballnut mounts from Chai they'll look nothing like the diagram he's sent you. They'll just be a steel block which you may be able to thin down the 86mm to less than 60mm. I dont have access to mine from Chai at the moment to get exact measurements but would say its deffo possible.

You can probably just saw off the two flanges then drill and tap some holes in the bottom, then it'll be 52mm wide.

Here's some I made earlier...I've got one left if that's any use to you? I just copied the dimensions of the ones on eBay.

Attachment 8066

KingCreaky,

I would try and mod the ones you have, but failing that this is a link to the mounts that I mentioned to you on Sunday.
Ball nut mount for 1605, 1610 ballscrew, free shipping to any country! | eBay

Jim

so, after sitting about feeling sorry for myself.. Ive made atleast a temporary measure... not sure if its good enough for the stresses of milling ali... but will be good enough for now I hope.

fortunately ive got that old ballnut... the one I broke previously... useful...

so; heres the plan

Attachment 8123

cut the circle out with the band saw (roughly). so it will go in my three jaw lathe chuck.

Attachment 8124
bore the center out with lathe
Attachment 8125

then get cutting and tapping...

Attachment 8126

seems to work... (Jonathon... if you need any help with your 'engineering' give me a shout :yahoo:

Why didn't you just make them in the first place if you have the gear to do it?? Sorry just being nosey lol

think its just lack of confidence martin. I think I mentioned before Ive had the lathe for a while but never really used it. Although your right now ive made one I do wonder why I bought the others... might sell them on or something (when they eventually turn up)

after Y comes?


Attachment 8133Attachment 8134Attachment 8135Attachment 8136

Looking really good and the ballless nut was just the ticket.

evening all... finding it hard to shut you lot up arent I... obviously your just lost for words ;D

anyway... get this.

So, I emailed chai, saying il have four of those ball nut housings to suite 1610 rails.

assuming he would send me the ones on his ebay shop er... these

Attachment 8144

but .... he must of read my previous posts.... or something because I actually recieved these

Attachment 8145

Im not having a moan, its not his fault. I didnt specify part numbers or whatever... these are actually the ones id prefer!.

anyway, so you may also notice the brand new ball-nut.....

how do I put that on the orphan screw? without dropping my balls everywhere?

Matt

Quote:

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Originally Posted by kingcreaky

how do I put that on the orphan screw? without dropping my balls everywhere?

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Just screw the nut on to the screw. Make sure you push the tube that's in the ballnut against the end of the ballscrew (so it's covering the end machining) as that will ensure the balls cannot drop out. Just do it slowly and carefully and you shouldn't have any problems.

I doubt that Chai reads all the posts on every forum & even if he did would remember who had ordered what so I would think he has just sent you what he has got at the time.
That would annoy me, ok you didn't specify a part number but you did go by a picture in his webshop. I know that sellers have the right to substitute items if it's in their terms and conditions but if you had ordered these & had already done the work for this style to fit or were replacing existing units the new ones he has sent wouldn't fit.
I got caught out with some electronic components I bought from RS in a similar way, my fault I suppose for not reading the technical spec properly but not being a whizz with electronics I just went by the picture. RS were very quick to point that out to me so won't order from them again if I'm not 100% sure exactly what I need, what it looks like & how to use it properly lol.

A tip I was given for removing and replacing the nut, but have not yet tried is that standard airline hose not (curly-wurly) is a really good fit (tight but flexible) and the nut can be wound on and off the screw quite safely. G.

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Originally Posted by martin54

I doubt that Chai reads all the posts on every forum & even if he did would remember who had ordered what so I would think he has just sent you what he has got at the time.
That would annoy me, ok you didn't specify a part number but you did go by a picture in his webshop. I know that sellers have the right to substitute items if it's in their terms and conditions but if you had ordered these & had already done the work for this style to fit or were replacing existing units the new ones he has sent wouldn't fit.
I got caught out with some electronic components I bought from RS in a similar way, my fault I suppose for not reading the technical spec properly but not being a whizz with electronics I just went by the picture. RS were very quick to point that out to me so won't order from them again if I'm not 100% sure exactly what I need, what it looks like & how to use it properly lol.

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i can imagine what has happened here though

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So, I emailed chai, saying il have four of those ball nut housings to suite 1610 rails.

assuming he would send me the ones on his ebay shop er... these

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so creaky has noticed chai has ball nut housings in his ebay shop.. but then instead of going through the shop has contacted him direct and asked for 4 ball nut housings... yes maybe chai should have maybe said i have a few different types and asked which ones..

chai has likely just sent out the most popular ones. luckily though this worked out well any way

OK, Id like to have all the peaces together in order to get it moving at the weekend... or atleast try! assuming I can connect the X ballscrews and all the steppers this week I think it may be possible.

Ive also, for now decided to drive the X with dual steppers... rather than the single stepper long belt approach. Only because its easier (long story) Ultimately I may change my mind on this at a later date... but for the purpose of getting it initially going... 2 steppers it is...

So, I have already got
1 x 500w linear power supply from Zapp PS806-5 Linear power supply.
4 x DQ860MA 80v drives Stepper Motor Driver DQ860MA:Stepper Motor Driver DQ860MA wholesaler

Im going to buy hopefully today in order to get delivered for weekend
1.5mm2 cy cable CY Cable - 4 Core 1.5mm2
2 x steppers for X axis 3.1nm (will these be powerful enough? it weighs a ton!) Nema23 Stepper Motor 3.1Nm
this breakout board? Im open to advice Breakout board CNC Stepper Motor 5 Axis Spindle Relay HG07
1 x estop? Red Mushroom Emergency Stop push button switch NC 400V 6A

For now, until the machine is done and I can machine the face for the box all the electricery are in, im going to wire the steppers direct to the drivers rather than going via connector blocks. However I notice on some of the other builds fuse boxes are used... where about in the citcuit should I incorporate a fuse box (I assume after drivers and before steppers) What fuse box & how many fuses do I need etc?

Not sure if that breakout board is any good?

Can anybody recommend anything else im going to need.... or wish I had?

really appreciate your replies... reply even if you dont think you have anything to add... your probably going to know more about this subject that I and Id appreciate your thoughts....

ps - if anybody fancies a trip to leicester on sunday to be involved in a firing it up... all welcome pm me