Dispensing 'glue'/paint

[Pat2000]

anyone into dispensing glue or simular 'viscous' fluids - this is not necessarly for art!

This is an idea I'd love to 'play with' when the router type table is built.

I had an idea! (I don't know what the pro's use) for dispensing the glue (white - woodworking type of PVA stuff).

The simple idea was (sorry no piccy) a short length of perhaps PVC tube between two simple 'one-way' valves - sprung loaded ball type valves.

A simple solenoid type actuator would squeeze the short length of tube between the two valves and dispense a measured amount of glue, I'm relying on the plastic tube springing back into shape and drawing next amount of glue to be dispenced into the PVC tube ready for next squeeze by solenoid.

As I write this I'm remembering the very simple valves on the top of the 'liquid soap' type bottles - wonder if they would work.

In the back of my mind is - "if it all clogs up them I can throw away the simple mechanism with no great loss"!!

How do I get say Mach 3 to give appropiate pulses in the right place and dispense a nice line of glue? how do I stop dripping type probs - nice starts and ends!

Any Ideas very welcome, I won't be able to try then yet.. but my dreams won't go away LOL

Pat

[greybeard]

Hi Pat.
Thoughts -
Make the squeezable section from silicone rubber tubing - retains its flexibility.
Make the final outlet nozzle the disposable part.

Most pva glues that I use seem to form a thin film of glue hardening on the inner surface of any tubing. May be true only for pvc tubes, so perhaps metal tube with only the squeeze section and the nozzle out of SiR ?
What size line/quantity of glue to lay down ?

I will need something like this eventually for the process line I'm assembling, so I'll follow your dreams

[ger21]

Originally Posted by Pat2000 How do I get say Mach 3 to give appropiate pulses in the right place and dispense a nice line of glue? how do I stop dripping type probs - nice starts and ends!

Use relays to open and close a valve using the coolant commands in Mach3. M7 or M8 on, M9 off. Keep the glue slightly pressurized with compressed air. Ideally you'd want a solenoid controlled nozzle to shut off the glue at the nozzle to stop drips.

[cbass]

This the expensive way to do it...

http://www.dltechnology.com/pumps/default.asp

I was surprized to discover that they use servos and feedback to precisely control auger rotation.

It may give you some more ideas.

Carlo

[mxtras]

Look at metering pumps or tubing pumps at coleparmer.com - they are pricey but it may give you ideas on a homebrew that you could make. This would allow you to vary the output volume by making the pump another axis and it would be a limitless stream that would not require interruption.

You may have already thought of this.

Scott

[Pat2000]

yes... thanks guy's

I think... thinking out loud again !!! that some form of metering device would be the best solution.

umm food for thought.

I reckon they could be made for very cheap me thinks the Peristaltic device - see piccy is not exactly complex

http://www.animatedsoftware.com/pumpglos/peristal.htm


thanks scott - somehow you just jogged my memory - the problem Gerry with just switching the flow of a fluid simply on and off is that you cannot reckon on the flow rate remaining consistant, the slight pressure would have to be very consistant, any build up inside the tube impedes the flow and perhaps? very important? the viscosity of the Glue/fluid, particularly glue would change with temperature, any build up/ restriction at the nozzle would again slow the flow.

so umm, extra axis - ok best, but whats needed is just an adjustable/preset speed motor or a series of pulses operating a diaphragm switched as per coolant command?

is just a vertical needle type outlet nozzle good enough?

I guess the outlet should be quite close to the 'deck'?

I'd want to lay say 0.5mm (0.020in) wide lines/bead

[cbass]

Originally Posted by Pat2000 you cannot reckon on the flow rate remaining consistant...the viscosity of the Glue/fluid, particularly glue would change with temperature, any build up/ restriction at the nozzle would again slow the flow.

I think you are right on here. Viscosity will change not only based on temperature but also depending on how the material reacts to shear forces. Some materials thicken as they are sheared (moved) while others thin.

I would seriously look into using an auger-type pump controlled by a stepper/servo on a fourth axis (see image). This will give you precise control of pressure, which may be important given how small the nozel will be (.5 mm). The last thing you want is a pump that doesn't have the strength to extrude your material.

One thing I don't think you've mentioned yet is what kind of glue you plan on extruding. What consistency will it have?

[Pat2000]

Cbass , thanks I would have to study those Augers to understand the mechanism better, I'd prefer to make my own pump cos of cost.

the Idea I've been toying with is along the lines of what they call 'window clings' thats using window paint see piccys below, the out line (which will perhaps be all i want is made from a black line usually.

the Glue they use seems to be based on PVA type of wood glue (the white stuff!!) when it is semi-dry 1-2 hrs, the coloured infilling is added , thats of a runnier viscosity, flexable and semi translucent - its all done on a plastic backing and the 'cling' (rather like a sticker) is peeled off the backing and will self-stick on glass.

It is still All plans on the 'back burner' as they say.

chances are that I will use my cnc router for all kinds of other purposes lol!!

i'm pretty keen also to make a tangential knife

It would probably be OTT for me to use a stepper driven auger partly cos of running out of controlable axis, I'm using two steppers on my x axis so thats 4 axis spoken for - a rotary exta axis would almost certainly be one of my future projects.

so anyhow if say a small stepper - printer type can be fairly easily driven by a simplish electronic drive all I'd hopefully have to do would be turn it on & off? driving it at a pre-set speed?

I'd imagined that the auger was also or mainly used to mix 2-part Epoxy glues as they are 'extruded' is that right?

whey-hey boss mans says I can go in to work tomorrow and m/c parts for my router (on a days holiday) so I'm gonna fly me mill and rip-into a few parts!!

piccys from http://www.windowbutterflies.citymak...lyGallery.html

(site nothing to do with me!)

[greybeard]

Pat - I'm reading between the lines here. But re my earlier posting about pva depositing a layer in the tube. If your looking for an adhesive, the "waterproof" type like resinW in the blue bottle(I think) are catalysed so they will glue non-porous to porous surfaces(I use it for non- to non-). These will tend to give the build up that concerned me. However the other type, where your warned not to use them in damp situations, probably wont do this. At least much more slowly I'd guess.
If you are only using it as a barrier as in silk painting or glass painting, I'd guess the commercial products like Pebeo are thicker, but not catalysed.
I'd be inclined to leave samples in short lengths of whatever tubing you might use for a while and see what happens.
John

[andy_ck87028]

Pat

A different subject........

I also have been thinking of different tool head options for my CNC router and I have been intrigued about how to cut internal sharp corners; sharp sided internal right angle or, even more difficult acute angle internal corners. Clearly a router won't help.

I asked once before and broaching was suggested but that is no good for wood or plastic.

Looking at the vast array of power tools I was expecting to see a reciprocating file but I have yet to see one.

Any thoughts on how to fabricate a tool that would provide a solution to this need.

Andy

[Pat2000]

just found this on auger pumps - all a bit OTT (over the top) for my application but interesting for those following this - they reverse the auger slightly to stop/relieve pressure at the nozzle!

http://www.gpd-global.com/text/other/Back-end.htm

[Pat2000]

Originally Posted by andy_ck87028 Pat A different subject........ I also have been thinking of different tool head options for my CNC router and I have been intrigued about how to cut internal sharp corners; sharp sided internal right angle or, even more difficult acute angle internal corners. Clearly a router won't help. I asked once before and broaching was suggested but that is no good for wood or plastic. Looking at the vast array of power tools I was expecting to see a reciprocating file but I have yet to see one. Any thoughts on how to fabricate a tool that would provide a solution to this need. Andy

Broaching does work for plastic's particularly types like Delrin (Acetal) it broaches with a simple tool - would post details if you need piccys - I suggest you start a thread somewhere, However having said that it can be very fiddly to program - you'd basicly have to hand-code the broaching cycles - it's much easier to broach right through the material - to broach an internal 'blind' courner' is real tricky!!

I'm not much of a 'wood-man' but you've got the grain to contend with and so - very difficult.

you'll have to post details of what you propose to broach - how thick - what material - are there small details...

Pat