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Topic: Mixing epoxy (Read 1 time) previous topic - next topic

skatun

Hi
I am getting sick of mixing epoxy by hand, so I thought I would try to make a mixing device with arduino.

My idea is to use a scale and two pumps and a mixer.

Does anyone know suitable items for this task?

http://www.webac.com/pictures/JM2BLACKSIDE400.jpg

Kim

CrossRoads

Damn, that's a lot of epoxy! What are you making?
Designing & building electrical circuits for over 25 years. Check out the ATMega1284P based Bobuino and other '328P & '1284P creations & offerings at  www.crossroadsfencing.com/BobuinoRev17.
Arduino for Teens available at Amazon.com.

retrolefty

Pretty specialized application. Different epoxy formulas have different setup times so you really need to know what you are doing or you could end up with a mess quickly. Anyway I suspect that trying to pump epoxy ingredients would be pretty difficult because of the viscosity of the material. A better method might be to use pressure to force material through the mixing orifice maybe?  This sounds like a very difficult project with lots of experimentation required to get it correct, unless you are working from a proven design that gives enough details to duplicate.

Good luck

Lefty

raalst

#3
Jun 05, 2011, 07:03 pm Last Edit: Jun 05, 2011, 09:04 pm by raalst Reason: 1
consider using peristaltic pumps.
these avoid having the epoxy mess in contact with the pump.
I know you can measure volume quite good with these but they might be too slow.
i.e. not enough throughput.
check google (and consider that they can be 3D printed for a prototype, check thingiverse)
http://www.thingiverse.com/image:56137

skatun

I have this epoxy here: http://www.vperseus.com/web/dgweixing/images/Infusion_brochure_09.pdf

How do you suggest to do it without pumps?

Kim

Chagrin

Look into peristaltic pumps as raalst suggested. They're pretty straightforward to construct from scratch and you should be able to get a pretty precise flow.

If you're using metering pumps you could create a crank mechanism (like how a steam engine converts linear to rotational motion) to push the pumps for you. Not sure how practical it would be but it'd certainly be entertaining to watch.

In both cases it would probably be best to use a single drive motor and a chain and sprocket to drive both pumps at the same time. By selecting the appropriate ratio of teeth for each sprocket you would then get the proper mix ratio for your epoxy. Changing the mix ratio would then just require a change of a sprocket.

gardner


worth the trouble to disassemble and clean it when you are done for the day.


West (and likely other epoxy systems) use plunger pumps than are primed up and left full of resin or hardener for as long as it takes to use the material -- months even.  There is no need to clean them between sessions.

It might be possible to rig up a linear actuator to the plunger style pumps.

But if it were me, I think I too would go with peristaltic.  If you are sufficiently handy, you could probably fabricate a peristaltic pump with a highly geared motor, a plywood frame and some tygon fuel tubing.  I remember a thread in the old BBS that included a link to some reasonably priced peristaltic pumps.

focalist

#7
Jun 07, 2011, 05:19 am Last Edit: Jun 07, 2011, 06:09 am by focalist Reason: 1
I first laughed at this, but it's a cute idea.  Not practical likely, but cute.

What occurs to me is the syringe-type two part epoxy sold on a card in hardware stores is pretty much what you want, at least dispensing.  You push the plunger, it dispenses the proper amounts of resin and hardener in proportion.  You just pop the cap on when done, it keeps once opened for months.

So, a stepper motor turning a screw with a static nut on the other end is all that you would need.  Total hack, but it would work, and cheap...  Scaling up really is just a matter of making it bigger.  The mixing point is the point where trouble could get bad fast.. but there's epoxies available with setting times from less than a minute to hours.  Your "syringe" can be made from PVC piping, using the proper diameter proportion to determine mixing ratio, just like the plastic-carded ones.  An epoxy with a ratio of 2:1 would use one pipe "piston" full, with a 2" inside diameter, the other with a 1" inside diameter (as an example.  It's the ratio of the pistons sizes to eachother that's important).  If a "plunger" is run equal distance down both, it will dispense out at a 2:1 ratio.  Changing mixing ratios then becomes changing in the right "piston", no calculation necessary.  Your motor/pump doesn't control the mixing ratio, it just controls how much of the properly-ratio'ed epoxy you pump out.  Typically, epoxies have only one ratio to be mixed at.. it's not like you vary amounts of resin and hardener to produce different types of epoxy, and their chemistries are probably unrelated enough that trying to have a Universal "A" to fit every "B" would just be silly.  Only when you entirely change epoxies would you change the mixing ratios.

It may just be easy enough to use a really cheap mixing nozzle that you expect to clog, and just take off and throw away just the mixing nozzle at the end of the day.  It could be made from cardboard or other relatively trash-friendly stuff I suppose...
When the testing is complete there will be... cake.

skatun

Quote
An epoxy with a ratio of 2:1 would use one pipe "piston" full, with a 2" inside diameter, the other with a 1" inside diameter
well its volume, and A = pi*D^2/4 ...

How do you suggest getting the epoxy in to the syringe? I have 1 barrel with hardener and one with resin. Why always focus on volume mixing rate and not use a scale and just stop at the required amount?

For the mixing part, what about a mix master or a magnetic stirrer or sth like that? How can u get a nozzle to mix it well?

Kim

focalist

How about the nozzle assembly includes a paddle at the mixing point, a shaft that extends back, which sockets into a motor?  The shaft extends back through a gasket (there's minimal pressure, ideally) and the paddle is rotated as the epoxy components are dispensed from their respective tanks, no matter how it's done.

                            Expoxy A
                                          \
Motor and gasket    ----]------{} =------ >>> mixed epoxy
                                          /
                               Epoxy B


The nozzle and paddle simply are removed and tossed.
When the testing is complete there will be... cake.

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