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View Full Version : Next Project: Building A Thermolator (A what?!)



Liger Zero
12-28-2009, 06:46 PM
A thermolator is a device (in molding-babble) that regulates the temp of the mold... by circulating temp-controlled water through the mold cooling passages. See also: Budzar, Mokon, %&** Water Leak, Hose Break.)


After looking over the Mokon that I was given... I need two of them... I think I can build one. More or less it's a wee circulating pump, a heater block, fittings, and a control. In fact I can improve on it by using a pool-pump (for maximum flow!) and an immersion heater.

Question #1: Can a "stock" pool pump handle water at roughly 180-200 degrees or am I asking for trouble? The body and impellor are made of PVC which melts at around 400 or so... I'm worried about long term degredation at that temp. Anyone with "real world" practical experience using these materials at these temps exposed to water? Textbook answer is "no there shouldn't be an issue" but I defer to experience, don't want OMG HOT WATER all over the workshop. :)


Question #2: This involves a hopper for the back of the machine. The hopper I was given was built with "pop-lock" fasteners, and the whole thing is built out of steel. Plan to seal it up with welding-fu, and I constructed a distribution "thingy" (for the hot air) and am pondering where to cut to mount it.

That said, inexpensive non-FG insulation for an application like this... what are some good options? Wife-unit has been more active in Shop Related Activities lately, but she is allergic/phobic to FG and I don't want to discourage her participation out here.

Glenn Wegman
12-28-2009, 06:54 PM
Drive an automotive coolant pump with a electric motor.

Liger Zero
12-28-2009, 06:57 PM
The key to true precision molding is mold temp control... Lots of flow and an accurate picture of the true temps at the mold surface. Injection molding is the art of putting heat into a material, cramming it into a cavity, then sucking the heat out in a controlled manner.

If I go the pool-pump route I can be up and running in a week. Other method... requires fabrication and scrounging (HOORAY!) but would take much longer.

mechanicalmagic
12-28-2009, 07:19 PM
Real plumbing supply houses carry pumps that are used to circulate hot water in a loop, (instant hot water).

Styrofoam is rated to 170 f, (works in coffee cups), cheap too at the home center. Not sure what temp you need.

whitis
12-28-2009, 07:46 PM
Question #1: Can a "stock" pool pump handle water at roughly 180-200 degrees or am I asking for trouble? The body and impellor are made of PVC which melts at around 400 or so... I'm worried about long term degredation at that temp. Anyone with "real world" practical experience using these materials at these temps exposed to water? Textbook answer is "no there shouldn't be an issue" but I defer to experience, don't want OMG HOT WATER all over the workshop. :)


Garden variety PVC is NOT good to anywhere near 400. Melting point more like the boiling point of water. It isn't even good enough to handle hot tap water. Long before it officially melts, it will have no strength. There are special types of PVC that can handle higher temperatures but probably aren't used in a pool pump. Standard PVC pipe is only rated for 140degF (60C) and even at that temperature it has lost 80% of its strength.

I had a hot tub that ran mostly dry when the tub sprang a leak. The remaining water in the pump was thrashed to a boil (there was no pressure so it wasn't superheated steam) and the PVC plumbing melted.

Here is some data on strength vs temperature.
http://www.engineeringtoolbox.com/thermoplastic-pipes-temperature-strength-d_794.html

Black_Moons
12-28-2009, 10:05 PM
whitis: thanks for saving me the long post. PVC is definately NOT good for any high tempatures.

AFAIK lots of pumps (especialy the submersable) kind REQUIRE cold water to cool themselfs. others require it to keep the seals in the pump from melting.

At 100c (200f), afaik most motors and pumps will allready be past thier operation limits just from the water temp alone.

Many plastics soften as tempature incresses. Id seriously recommend looking into a cast iron body pump that looks highly seperated from the motor itself, and plumbing it with copper, or at the very least tubing rated for hot water use in homes.

Duffy
12-28-2009, 11:01 PM
I assume that you are not looking at a lot of head on this system, just moving water about. In that case, I recommend a hot water circulating pump. The kind used in residential, (apartment,) heating systems. These are designed to move hot water. In addition, since you are not looking at a mile of pipe, use copper, type M,to save money. Pex or CPVC MAY work, but copper WILL work. Duffy

Mcruff
12-28-2009, 11:23 PM
Some pool pumps can handle the temp, I have a friend that runs a pool pump and a swimming pool inside of a building to actually act as a chiller/heater and circulation pump for his 5 Cincinnatti Milacron presses.

Liger Zero
12-29-2009, 12:27 PM
Some pool pumps can handle the temp, I have a friend that runs a pool pump and a swimming pool inside of a building to actually act as a chiller/heater and circulation pump for his 5 Cincinnatti Milacron presses.

I'm happy with just the one. :D Its a fairly good press a bit quirky as it was C-M's first real attempt at a CNC-controlled servo driven molder.

My friend has a "proper" cooling system in his shop... it consists of a cooling tower that chills the water to 75 degrees this is fed to the thermolators which regulate the mold temp. The idea is to have a known baseline water temp to work from.



So the pool pump is out. Thanks for the advice... I *thought* the softening point of PVC was higher! :o

Next stop is the HVAC shop across town... they have a junk pile I rummage through from time to time maybe they have a circulating pump I could use.

digger_doug
12-29-2009, 12:32 PM
Do you mean like these ?

http://www.hgrindustrialsurplus.com/sub/product_detail.aspx?id=21-524-022&searchtable=2&sortExpression=&SortASC=&pageSize=50&currentPageIndex=0&searchNAP=

Poke around the site, they've got more of them floating around.

On that particular unit ($99) I'd offer $50.

Liger Zero
12-29-2009, 12:44 PM
Yes exactly. Dock Hardware might have them as well, but what fun is it to BUY something when you can make it yourself? :D

...if I can't design/build something within the next couple weeks I'll end up shelling out some cash for a used unit or three. (spares)


At a minimum you need one for the stationary half of the mold and one for the moving half of the mold (core and cavity). On some really complex molds individual sections of the mold would have separate loops... one mold I set up and ran years ago had four water loops (two for each half of the mold). These chilled the plate. Then there was "hot oil" at 350 circulated through a specific set of fittings to regulate the temp of a large core. The material was a heavy glass-filled high-temp resin.

Don't need anything that fancy, heck for what I'm looking to make water circulating from a radiator cooled by a fan would be good enough... I just want to build in the capability NOW so if an opportunity comes my way I can grab it. :)