operation cnc

[wilfy]

if you ever struggle to think of electronics and need to use examples always use water... it's far easier.

i.e. example 1 you have 1 hose pipe(outgoing signal) with a splitter in the end to make 2 outlets (2xsteppers)... water reaches the splitter and splits equally between the 2(both steppers get the same signal)

example 2 you have 2 hose pipes connected straight to 2 outlets and the flow of these is restricted by a computer, something goes wrong with the first outlet and the flow is slightly restricted at the wrong time compared to outlet 2.. you now have one pipe pouring more water than the other (one stepper moving out of sync to the other.

it's just limiting the possibilities of things going wrong. i understand what jazz is on about and i "go way back" with computers

[D.C.]

if you ever struggle to think of electronics and need to use examples always use water... it's far easier.

i.e. example 1 you have 1 hose pipe(outgoing signal) with a splitter in the end to make 2 outlets (2xsteppers)... water reaches the splitter and splits equally between the 2(both steppers get the same signal)

example 2 you have 2 hose pipes connected straight to 2 outlets and the flow of these is restricted by a computer, something goes wrong with the first outlet and the flow is slightly restricted at the wrong time compared to outlet 2.. you now have one pipe pouring more water than the other (one stepper moving out of sync to the other.

it's just limiting the possibilities of things going wrong. i understand what jazz is on about and i "go way back" with computers

except this is a false analogy.

If you 'go way back' with computers and understand what you are talking about perhaps you can explain what is wrong with what either I or Jon said in this very specific instance.

Does a piece of software running on a computer have magical pixie hero men inside of it that create a 'magical physical hardware' perfect connection between the software and the cnc machine or does a computer use a piece of software (often called a driver) to decide in 'software' which signals to send to which lumps of metal?

If 'hardware' is somehow so much reliable than 'software' and desirable perhaps you could explain why mission critical systems use ECC ram, or why we need transactionable databases or why TCP has to sit on top of IP?

[kingcreaky]

if you search for 2.2kw spindle on ebay... you will notice they are all portsmouth based suppliers. It appears there are multiple suppliers but Im sure its just one place selling them.

Over the course of the past 4 days, I have messages 7 individual suppliers. asking them to confirm they have stock, are they shipping from the uk I have recieved NO responses.

Most of them are 'make an offer' so ive tried making an offer say a tenner below the asking price, again NO responses.

You will notice that essentially the price is £252, some of them are a straght 252, some of them are £162.00 with 90 postage and all the variations under the sun. However I just cant get a response from them so im hardly willing to send them money.

Which leaves me with cnc4you.. who are offering a bargain price of £369 however they are uk based and offering a direct warranty

or Chai has quoted me in his "best price" kinda way £310 plus £60 postage

are there any other options? ive googled 2.2kw spindle with not much luck... thought id check with you lot before I order

Matt

[martin54]

Matt, I suspect your right about the one seller using multiple ebay names, has been mentioned before either on this forum or another. Lack of a reply may be down to them being away at the moment. Apparently it's the Chinese Spring festival at the moment, I was looking for a cooling pump for a 2.2kw spindle & tried searching ebay for the one Robin suggested. Found a seller on the uk site (Chinese) who had a message saying he was closed from 7th to 17th feb for this festival.

[D.C.]

Sorry about the thread hijack and congrats on the progress btw.

martin is right, it is chinese new year which these days is apparenty the largest migration event in human history, hundreds of millions people moving from the cities back to their home villages to spend two weeks with the family. Give them a couple of weeks and it they will be back to business as usual.

Edit: On the plus side if you can find guys still trading as normal delivery times seem very impressive, two orders I placed for electronics stuff with bog standard freebie China post arrived in 4 days and 6 days. (Real days not working days)

[m_c]

D.C. in theory, everything should work, but in practice, things may not work quite right. It can be things like marginally different speeds between a pin switching high and low, which are then exaggerated by drives that respond slight differently to high/low inputs and/or slight lag due to the different switching speeds. However with modern drives, it's pretty much a non-issue, but why take the chance?

Personally, given the choice of doing something in hardware or software, I'd personally do it in hardware every time, as it helps eliminate potential issues.

[Jonathan]

D.C. in theory, everything should work, but in practice, things may not work quite right.

If it works in theory but not in practice, that just means your theory wasn't good enough.

It can be things like marginally different speeds between a pin switching high and low, which are then exaggerated by drives that respond slight differently to high/low inputs and/or slight lag due to the different switching speeds. However with modern drives, it's pretty much a non-issue, but why take the chance?

Personally, given the choice of doing something in hardware or software, I'd personally do it in hardware every time, as it helps eliminate potential issues.

Again, the answer is vague so I'll repeat what D.C. asked - what specifically is the problem? The timing delays you're talking about are completely negligible, so there is no potential issue to eliminate. Originally the question was if you should set the motor directions in software, or one of the motor phases round to invert the direction. There will not be any tangible difference between the two, unless the software is pathetic.

[m_c]

Jonathon, go and search the Mach Yahoo group for Art's posts about the intracies of parallel port timing, because I'm beginning to understand why Jazz gets so pissed of with you.

[D.C.]

Interesting, I would trust 'software' over 'hardware' everytime. I tend to see hardware as crap and dumb , you send a bunch of electrons down the wire and pray they get to their destination (why do we need shielded cable again?) when you add a bit of intelligence into the equation you can account for and correct errors, hence why people looking for better precision use closed loop steppers and absolute positioning systems to catch and correct the all the errors produced by the hardware.

Without the ability to fix all the hardware issues using cleverness the internet would be stuck in the telegraph age. :(

[m_c]

DC, I'd rather trust hardware, as hardware being dumb, should always do the same thing.
It's a bit like do you swap a motor phase on a VFD, or do you just change the setting in the VFD to change normal motor direction?
Both should work...