[greggv]

We have a hot glue machine at work that would be just the thing for you. It has adjustable temp pot, a pneumatic over hydraulic pump, heated hoses and a heated, air solenoid valve controlled discharge gun. I cannot for the life of me remember the name of the manufacturer, but I can get it Monday if it will help. I'm sure they sell seperate parts as well as complete systems. The name is something like Nordstrom. You migh try Google for hot glue equipment. It's a very well built, and trouble free system, and it runs your temps easily. When you're done with it, you just let the stuff harden up in it, then when needed again, just reheat.

[aadams]

Thanks for the suggestion! I had actually run across some parts on eBay for Nordson hot melt gun a while back but didn't realize what it was. I just went to their website and couldn't believe my eyes! Their machines would be perfect...however I'm assuming they are a bit out of my price range, but they have great looking machines that I can get many good ideas from!

It looks as if their XYZ system is very similar to my original plan (if equipped with a hot melt gun) of a gantry style machine. I would need to create a heater wrap for my hoses if I were to use pump/valve dispensing, but I think that could happen. I'm looking into some stepper driven pumps that are relatively inexpensive as well as solenoids valves.

If I went with stepper drivers for xyz, how difficult would it be/what would it consist of to control 3 on/off fluid pumps and 3 solenoid valves? Check out this video of the Nordson XYZ system and you'll see exactly how I want this machine to end up, only with three hot melt dispensers: http://www.efd-inc.com/media/index.html.

[greggv]

As far as how to control your stuff, I'm not the one to ask. I'm more of a commercial cnc guy. I would question the need for stepper driven pumps when pumping hot stuff, can you isolate the heat from the stepper? Or, if you do use stepped pumps, I don't think you'll need solenoid valves. Calculate the time the pump needs to run for your discharge amount, then back the motor up a few steps to eliminate the dripping. We use stepper pumps where I work also, and that's how we do it, in packaging of heavy, hard to deal with liquids or semi solids. Or if you're gonna use solenoid cutoff valves, just use a continous pressure system. You don't need both. I know our hot glue machines have the temp controls on the pump (constant pressure) for the tank, hose and the gun. I also remember that the company does sell replacement heated hoses of different lengths. They hook up with standard AN fittings, and an electrical plug to the machine and gun. Hope this helps.

[aadams]

Thanks for the info. So you recommend cutoff valves in my case? I thought perhaps I would need the steppers to increase/decrease pumping speed slightly to vary the amount of plastic being poured at different points in the cavity. I suppose I could increase/decrease speed of the xy axises to achieve this.

How would you recommend I make the constant pressure system? Thanks for the tip on the heated hoses. I'll be searching for a bargin to get my machine fitted with these (or something similar).

[greggv]

I would'nt say I reccomend cutoff valves, if you're going to use stepper driven pumps, I would start without cutoff valves, try reversing the stepper's rotation at the end of the cycle to eliminate dripping (if that's a problem) and then use cutoff valves as a last resort. The less things you have to heat up to use, the simpler it will be, and simple is almost allways better. If you choose to use a constant pressure system, then you'll need cutoff valves. The constand pressure can be obtained thru an air over hydraulic, or electrical type of pump, even pressurized containers will work. The hot glue machine uses constant pressure, I believe the pump is air over hydraulic, but it only pumps when the cutoff valve is opened.An on demand sort of thing. That still seems the easiest to me, having your heated resovoirs, with the pump built into the bottom of them, so you only have to heat one thing. Good luck

[JavaDog]

Those videos from that link are really damn cool.

When I was a lowly restaurant worker, I used to help the repair-main when our dish-machine would break down. They used Peristaltic pumps (like this guy) to give precise measured amounts of cleaning fluid, etc. Would that type of pump, with heated hose, work in your application? I would imagine it would make precise metering much easier (they are Stepper Driven), and since you don't need high-pressure it makes sense. Plus, since they are stepper driven, I don't see why you couldn't write G-Code that says "Move X-Axis blah blah, Move Z-axis blah blah, Move Y-axis (Pump) blah blah" you get the idea. Just a thought...

[aadams]

Thanks again to all who are helping with this project! I really appreciate all the input I am getting. I would be lost without this place!

At this point I am back to my original idea of using pumps. With the xyz moving the mold and nozzle into place and then somehow controlling the three pumps (maybe on an "a" axis or whatever the 4th is called) one at a time, perhaps some kind of re-tooling sequence (switch to pump1-1st pass, switch to pump2-second pass, switch to pump3-third pass). This theoretically would be controlled by an on/off bit as discussed in an earlier post.

The pumps will be installed directly under the heating pots, which will be stationary above the z-axis with hoses (somehow heated) to the nozzles mounted on the z-axis. I don't have it figured out yet how to shield the pump motor from the heat...any suggestions?

I have a question now about stepper drivers/controllers. Searching ebay I found this interesting product that appears to be a 4 axis stepper driver/controller combo:
http://cgi.ebay.com/ws/eBayISAPI.dll...877761462&rd=1
Does anybody have any experience with this one? I'm curious as to if it would work for my machine. The price is right, but all too often you get what you pay for.

Also, when looking at stepper motors, what should I be looking for as far as specs? As you know I am new to this, so I'm not sure what would be too small, or just a waste of money.

[JavaDog]

I don't have it figured out yet how to shield the pump motor from the heat...any suggestions?

Did you look at my post?

[Evodyne]

I looked at the link. The main thin I saw is that it is full or half step-no microstepping. And you are limited to unipolar use. On the flip side the current limits are ample. I would wonder how they are handleing their current limiting if it isn't a chopper type drive.

I use the Geckodrives and love them. Go to www.geckodrive.com. Other use Rutex and like them too. There are other options-I'll try to look a few up this evening.

One thing you have going in your favor is that you are not trying to push a milling bit through material-your strictly positioning. This being the case, you can get by with less than the guys building routers or mills. You migh be fine with some stout little NEMA 23 motors (NEMA 23 refers to the motors frame size). Next size up is NEMA 34, then NEMA 42, and so on. For you more power will simply mean better acceleration and deceleration. If you don't need the speed, your OK with smaller motors.

At work and gotta go-I'm gonna get myself in a bind otherwise!

Bye for now.

[aadams]

JavaDog,
You're right. That pump would work great to shield from the heat. Would it be able to dispense small enough volume of the plastic? Probably would. Now if I can find 3...

Thanks Evodyne for the info.

[JavaDog]

JavaDog,
You're right. That pump would work great to shield from the heat. Would it be able to dispense small enough volume of the plastic? Probably would. Now if I can find 3...

Thanks Evodyne for the info.

Yeah, since they are driven by a stepper motor, I would imagine that they are pretty flexible when it comes to dispensing. They are used in the medical industry quite a bit as well.

You may even be able to make your own, as their design is pretty straight forward.

[aadams]

Okay, got my motors on the way. I went with powermax II Nema 23 motors, primarily because I found them cheap on ebay. Hope they will work!

I'm looking into a controller board and found a couple, but I'm not sure about them. This one:
http://www.hobbycnc.com/driverboards/4aupc/4aupc.htm
and either the 3 or 4 axis one from here:
http://www.xylotex.com/

Any suggestions? The price is right for this project, but will it work?

[MadMax]

Take a look at STAMP microprocessors (lots of Google links). Pretty cheap easy way to set up logical motor control based on switch/timing inputs. I really like them. They're very configurable and there's a lot of good user projects posted for you to steal code snippets from.

What plastic are you planning to use? A lot of plastics suffer from quite a lot of shrinkage. Especially the crystalline ones (PE, PP, nylon etc) Expect quite a lot of sink in the middle of your part. 1"x1" is quite a lot of cross section for thermoplastics.

[aadams]

MadMax,
Thanks for the info.

The plastics I use are a liquid plasitisol that sets to a rubbery plastic. The plastic does shrink as it sets, but I should be able to compensate for that with timing.