Fingers crossed it'll cut ally

**Jonathan** · 11-01-2011

Interesting stuff. You could stick a sheet of whatever plastic you're using down to the bed and mill slots/holes for the air ... then flip it over and cut out a grid of rings to fit your O-rings. Might be worth thinking about what pattern of rings would hold things best - some bigger than others? Could have rectangular ones, all sorts!

I might have a go at this, got some 6mm acrylic that would do the trick. Got plenty of O rings from £1 shop. Some might be big enough.

With a sufficiently big syringe how many pads do you think could be served? Or are you sucking the air out of one at a time and swapping the syringe round?

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?

**blackburn mark** · 11-01-2011

You could stick a sheet of whatever plastic you're using down to the bed and mill slots/holes for the air

iv considered it for long runs, might be a pain to get the holes routed to each o-ring if its a complex pattern

the problem with mixing diffrent size o-rings is the diffrent surface arias would compress the o-rings diffrent amounts

With a sufficiently big syringe how many pads do you think could be served? Or are you sucking the air out of one at a time and swapping the syringe round?

im going to try using one syringe and fix one of the one way valves as an exsaust so you could pull the initial vacuum the pad valves will hold the vacuum ill press the syringe home and the air iv removed from the pads will be routed through the exsaust one way valve ?????? if you can get your head around that :)

i need to do a drawing to show you what i mean.... imagine you have two one way valves attached to the end of the syringe, youll work it out :)

am i sending you a large syringe ? (iv got a few from work)

**Jonathan** · 11-01-2011

Originally Posted by blackburn mark

imagine you have two one way valves attached to the end of the syringe, youll work it out :)

am i sending you a large syringe ? (iv got a few from work)

Oh, two valves ... you're using the syringe as a pump!
If you could send me a syringe that would be great, I've not got any that seal any more - found out they don't like concentrated sulfuric acid. I can papal you something for it.

I had better buy some valves and tube. What diameter are you using?

**blackburn mark** · 12-01-2011

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 :)