Fingers crossed it'll cut ally

[blackburn mark]

75mm oil filter seals, iv no idea why i save them when i service my car?


1mm outside diameter hypodermic needles, i drilled the seals with a .75mm drill (by hand)

squash for unusual shape

plenty of holding force, the first seal is happily holding the weight of the second two blocks, i can slide each block around to square up but there is enough resistance for reasonable machining especially in acetal plate

i have used the smaller pads to cut 28mm washers out of 1mm alli, i had one failure with it creeping... it takes a light touch. they will be fine for my engraving job

[templecorran]

Some where on this forum I had a thread about vacuum tables. I suggested cling film to mask off the unused holes.
However, I like your solution. simple, elegant, and best of all, QUIET!

[blackburn mark]

I suggested cling film to mask off the unused holes

nice one ill give it a try, should work well with small holes, i was thinking latex but i guess over time you would build up a collection of anything that works
blu-tack might be an option for slighly larger holes, i think anything over 4 or 5mm would need a more sturdy plug

and best of all, QUIET!

high on my list, my router is running inside the house (thank god im not trying to cut wood)

[Jonathan]

blu-tack might be an option for slighly larger holes, i think anything over 4 or 5mm would need a more sturdy plug

Rubber test tube bung?

I got the syringes yesterday - thank you Bigger than I expected - I'm impressed at the pressure (or lack of pressure!) that they can hold. I'll do some experimenting over the next few days...

[blackburn mark]

yo jonathan, remember to put that one way valve as close to the tip of the syringe as you can, a mind like yours will work out why if you think about it, its not so important with the fish tank valves (almost zero resistance) iv had one of them fail so far, the one you have should be very robust
iv added the exsaust valve to my setup, makes life really easy :)
let us know if you have any eureka moments :)

[Tenson]

Mark, I've just skim read this thread in one turn, so forgive me if I missed the details. Have you got the PSU sorted for the big motor?

I also built a spindle with a large 270KV motor. I then modified a 750watt PC PSU to have a variable output voltage on what was originally the 12V line. Although I can make the PSU output any voltage unloaded, when the motor loads the PSU the voltage drops down the the point at which it can supply that amount of power*. I found that even driving the motor with 750watts didn't give a significant amount of cutting power; I can take 0.5mm cuts with a 6mm tool at 80mm/min but it is not very clean and the spindle RPM is too slow for 3mm cutters.

*The PSU will always limit at 750watts (this is a natural limit, not a protection circuit). Since the load of the motor is fixed (0.36 ohms), and the total power is fixed, the voltage must drop to 16.5V. I decided I need more power, but I'm not sure how to get it; even a budget ATX PSU >1000watts is not cheap.

[blackburn mark]

Mark, I've just skim read this thread in one turn,

owch! that must have taken a bit of doing.... well done.

750watt

that should be loads! something not right there... i used a 300w pc supply for quite a while (managed to trip the supply out a couple of times while using a hole saw... besides that its managed ok?)

im now on a cheap 12v 350w china special iv not tripped that one so far

im assuming your saying its to slow for 3mm tooling in wood ?
90% of my cutting is 3mm single flute in acetal between 1mm and 3mm DOC aprox 2000rpm between 200 and 300 feed

at 270kv you would need 48v to get aprox 13000rpm ... might be a tad fast if your using double row A/C bearings unless you have them swishing around in a nice light oil ?
you might have problems with the esc and windings getting hot

id be tempted to make a second spindle with a higher kv rating .... 890kv would give you 10680rpm at 12v

[Tenson]

Hi,

It doesn't do too bad in soft materials actually, but 3mm tooling in alu it didn't like. I assumed this was because the RPM was too low, but maybe it is just the CNC-3040 the spindle is attached to being too floppy for delicate tooling. Yes I think I should have gone for a higher KV motor; I had anticipated driving it with 30V.

Anyway here is a good tutorial I found about how to increase the PSU voltage - http://cyberfish.wecheer.com/blog/?p=769

[Tenson]

Oh I also forgot to say, the surface of anodized aluminium is non-conductive, but the surface is easily scratched through to the conductive bulk. It is most definitely worth earthing the chassis so if any high voltage comes in contact with it, the power can sink to ground instead of the person who might be touching it. Wherever you connect the earth tag make sure it is well connected to the bulk of the material since the surface layer does not conduct.

[Fivetide]

Love the vacuum pad idea Mark, will do something but a bit different, I am inspired though :) .. I went to school in Blackburn ...