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  1. #171
    I can papal you something for it.
    dont worry about it man, work was scrapping old stock so i didnt pay anything myself :)
    found out they don't like concentrated sulfuric acid
    they dont like WD40 either

    i didnt manage to get much of the surgical tubing, i need to buy some more myself, it looks like 1.5 or 2mm ID and the brass tubing is 3mm
    i just used what i had lying around, if i was buying id go for the smallest diameter i could get

    Ps: the only reason you would need to use the syringe like a pump is if it failed to seal on the first draw, it would save you having to remove the syringe and start again, im pretty sure you could pull a pretty good vacuum on 4 double sided pads all in one stroke
    the 30mm pad held onto a un-polished block of alli for hours without the need for a top up, id top up every now and again if it was on the cnc though :)

  2. #172
    I'm looking at the servo controller now. I've traced the PCB and drawn circuit diagram of the interesting bits. The problem is the one you sent me has one significant difference to yours - mine gets 3.3v for the microcontroller and potentiometer via a 3.3v voltage regulator. I think yours is either a 5v microcontroller, or they're getting 3.3v via a voltage divider....

    Could you measure the maximum voltage from between R32 and ground on the PCB please? I may have asked you to do that already, this thread is so long I'm not sure!
    Also what resistance is your potentiometer - it says on the metal case (FB5k ... i.e 5k ohms for mine)?

    Edit: don't worry about the voltage, post #90! Except was that definitely the voltage from the resistor to ground, not across the resistor?
    ill try to get another the same as yours
    this thread is getting a bit long i guess i should have split it up into spindles router and vacuum stuff

  3. #173
    Quote Originally Posted by blackburn mark View Post
    ill try to get another the same as yours
    this thread is getting a bit long i guess i should have split it up into spindles router and vacuum stuff
    Wait a second. I can just make you one using a PIC ... it'll save you buying one and you won't have to modify it.

    If you just measure the voltage at the point I said earlier. Remove that resistor (R32), remove R31 and connect the parallel port pin to where R31 connected to the potentiometer, then set spindle in mach3 to highest, adjust the pot so you get the same voltage as measured at R32 earlier. Put R32 back in place and do not move the potentiometer ever again otherwise the microcontroller will probably break.

    Measure that voltage, if it's ok then I'll scribble a diagram over the picture you posted.

    It would be good if a moderator could split this thread up to save duplication? If not then I'll start a new one about the spindles.

  4. #174
    Just a note to say that the different size O-rings should all compress the same amount as long as they are all the of the same thickness, therein lies the problem getting the same thickness in different diameters.

    Peter

  5. #175
    Quote Originally Posted by Jonathan View Post
    Wait a second. I can just make you one using a PIC ... it'll save you buying one and you won't have to modify it.

    If you just measure the voltage at the point I said earlier. Remove that resistor (R32), remove R31 and connect the parallel port pin to where R31 connected to the potentiometer, then set spindle in mach3 to highest, adjust the pot so you get the same voltage as measured at R32 earlier. Put R32 back in place and do not move the potentiometer ever again otherwise the microcontroller will probably break.

    Measure that voltage, if it's ok then I'll scribble a diagram over the picture you posted.

    It would be good if a moderator could split this thread up to save duplication? If not then I'll start a new one about the spindles.
    great stuff, ill get on it as soon as i have time :)
    ill probably buy another servo controller so i can run the spindles without mach and for a backup in case i fry the one iv got

  6. #176
    Quote Originally Posted by ptjw7uk View Post
    Just a note to say that the different size O-rings should all compress the same amount as long as they are all the of the same thickness, therein lies the problem getting the same thickness in different diameters.
    sounds to good to be true, ill have to do some maths, iv got plenty of o-rings from 18mm ID to 50mm ID and they are all 3.5mm section

  7. #177
    Your right it is to good to be true, must have been asleeop when I did the calcs!!

    Peter

  8. #178
    Your right it is to good to be true, must have been asleeop when I did the calcs!!
    Darn it ! never mind, it would have been nice :)

  9. #179
    Yes Thats what you get when making quick calcs on the back of a fag packet while doing something else!
    Took some time to find my error in th calcs!
    Oh well seemed right at the time.
    On some vac tables they have a cross hatch of grooves that you run a length of rubber around so its under the piece you want to hold and cut of any excess, can also be fitted with stops for repeat parts.

    Peter

  10. #180
    i've done some testing with these vacuum pads up to 50mm, they will work fine for engraving or fine cuts however due to the tiny footprint of the stiff o-rings the friction is a little low and there is the risk of the part slipping latteraly

    jonathan, i've sent you a couple of syringes some tube (i found some more) and a one way valve, the valve is a medical job and it takes quite a bit of pressure before the seal is broken and it allows any flow so it needs to be mounted on the tip of the syringe to reduce pressure backlash, not perfect but it will give you something to experiment with, i'm leaning towards your idea of making a bolt down board unless i can find better seals, car oil filter seals might be much better for individual pads, they have a square section and a much larger contact area

    i've sent it to your uni address

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