Heating Alum Molds And Stuff

[Delw]

its very Simple DON'T go above 250-300º

Sure you can probaly go hotter but your gong to loose the shineness in your molds after a bit is it worth it?

the baits after a while will start sticking more and more to the molds, you will start having to oil them to just get a good finish.

I've posted this before a few years ago.

NEVER LAY YOUR ALUM MOLD ON A BURNER, A TOASTER OVEN IS TOO CLOSE ALSO. Besides there is NO reason too. unless your pouring in a very cold climate.

I dont know how to explain it in technical terms but having a mold close to the element burns the surfaces of the mold and makes them more porus, causing the bait to stick. I know a guy that set his mold on a hot plate and it screwed them up big time. you have to scrape the plastic out.

heres kinda a exagerated example. a endmill that cuts the mold cuts on the outside edges of the tool but in the center of the tool it doesnt cut, its rubs the material off(machinist that have run lathes will undestand IE constant suface finish the center of the part is actually NOT spInning) anyway what happens is since the tool in the center is NOT cutting and more burnishing/rubbing is bends the material ( IE the surface of the mold)this is what gives you a very nice finish when you put it into an oven with direct heat those little bent/rubbed fragmets of alum that are smashed in will burn off opening the alum to a very porus state causeing a bad finished bait. Theres a process called heat deburing that machine shops use in the industry on critical corners. it burns the burr off on very critical parts.

This heating of the molds have gotten very carried away recently and people are messing up there molds.

Further more I have never seen an injection mold or injector that needs to be heated up EVER in order to get it to shoot. if you have to heat them up on injection you are doing something wrong. room temputure should be just fine.

The surface of alum will stay colder than the inner core, if you heat the surface of alum too hot you will have the problems.Alum is a big heat sink and of coarse the surface is what cools first.

an easier way to look at it is Prfessional injection machines use chilled/unchilled water to cool the mold, there plastic is the same as yours temp wide even cooler in some cases. they dont need to heat the molds to run 30-100 baits every 1-2min, so why do hand injections need it?

Delw

[TTDuckman]

I agree to all of the above.

Heat is the enemy. Heat will do nothing but slow you down in my opinion. Matter of fact, when my molds get to the point that I can't touch them with my bare hands, I switch to other molds. The reason for this is the the demold time has been extended due to heat retention and I can get back to production on room temperature molds. I think that people forget the entire reason for hand injection is "pressure". It allows the user to take plastic and force it into a cavity that gravity simply won't fill.

Tim

[GB GONE]

I will echo that Tim.

I may heat my BT blending block and injectors when I first start to get the cold out if the shop isn't warm yet but never my molds. The cooler the molds are, the more baits I can squeeze out before having to wait.

I will say, if I don't at least heat up the block and injectors on the 6oz duel set up initially, I will only get part of the way through the process and I either get a clogged block or clogged injectors. After one run though, things are good. I would guess I heat the block and injectors to 75-80 by setting them near my floor heater.

I have been adverse to heating my molds only because they cost so much! Never really thought about potential damage.

Thanks for the reminder Del.

Jim

[smallmouthaholic]

Delw-

Thank you for the informative post. Currently here in Eastern Pa. we're averaging 20-21 degrees @ night/ 30-35 daytime. I heat the insulated shop to 68 degrees during the day but shut the heater off @ night. The shop will remain 20 degrees warmer then the outside temperature in the morning. The molds and injectors on the shelf are c-o-l-d and need to be heated.Since the shop is not air tight,running the exhaust booth will drop shop temps 20 degrees w/out heat

Your technical advice is appreciated and after having the pyrometer re-calibrated and a new Infrared thermometer purchased, I will maintain accurate data concerning oven and mold temps. I have never set a mold onto a hot plate or burner of any type.

I can inject a single color into a cold,up to 16 multi-cavity injection mold w/o problems.It's the two-color injecting that causes the problems- especially in tube molds w/ their thin,narrow tails.

[nova]

The way that I preheat molds is I take old unsalted plastic(plastic that I use for making masters)and I melt it down then pour it into the molds and let it set there until I get my fresh plastic ready to pour.

This gets the molds plenty warm to avoid cold cracks.

www.novalures.com

Edited December 23, 2010 by nova

[Frank]

Thanks Del that reinforces my video with the temp gun showing the molds were room temp and shot well. I have posted before I pour on an aluminium plate that is up off the table so heat can be drawn away from the molds while I am working. I never stop from hot molds but have the ability to run a fan below the table to help get rid of some heat in the summer. It is a big heat sink. I also have one for my injectors to set on that does the same. Thanks Frank

[Delw]

The elements are too close to the mold using a toaster oven. best advice is to warm them up in the house before using them.

the other thing is that going from a cold mold to a hot mold also produces moisture aka sweating of the alum. qhich creates other problems. leave pins screws or what have you in there and they will corode/rust alot faster, and oxidation will happen much faster if your using salt on the cavity itself ie damaging it.

this also goes for when your done pouring and shut off the heat in cold climates, if they cool to fast and also your pins or bolts are in them your going to start the corrosion proccess.

Its always best not to rush pouring especially if you can damage a mold in doing so.,

Delw

Delw-

Thank you for the informative post. Currently here in Eastern Pa. we're averaging 20-21 degrees @ night/ 30-35 daytime. I heat the insulated shop to 68 degrees during the day but shut the heater off @ night. The shop will remain 20 degrees warmer then the outside temperature in the morning. The molds and injectors on the shelf are c-o-l-d and need to be heated.Since the shop is not air tight,running the exhaust booth will drop shop temps 20 degrees w/out heat

Your technical advice is appreciated and after having the pyrometer re-calibrated and a new Infrared thermometer purchased, I will maintain accurate data concerning oven and mold temps. I have never set a mold onto a hot plate or burner of any type.

I can inject a single color into a cold,up to 16 multi-cavity injection mold w/o problems.It's the two-color injecting that causes the problems- especially in tube molds w/ their thin,narrow tails.

[CrankinKing]

Great technical advice Del. This is contrary to a lot of other forums on this subject, through other sites. I will be using caution with my molds from here on out!

[mark poulson]

Del,

You just answered a question that has kept me from trying a mold I was given as a gift (thanks again Bob).

I have it here in the house, and it's always cold to the touch, even though my house is usually 68-70 degrees.

I was worried that it was too cold to inject.

To be totally honest, the cold, wet weather we've had in SoCal may have had something to do with my procrastination. My garage isn't heated, and 40+ degrees, although that may be balmy to you northern guys, just chills my bones.

[MuskyHunter]

A couple of comments on this topic:

1. I am not sure why the injectors are made from Aluminum. I would not chose this material to retain heat. Aluminum is used to remove heat in several different industries. (I.E. heat sinks on computers and such.) I would think that the injector would be made from a cold rolled steel. This can be purchased in tube form for this application. Steel would definately retain the heat much better instead of dissipating heat like Aluminum would.

2. The thing I would worry about most with Aluminum molds being heated and reheated would be distortion. The splitline would get warped very easily. (This would depend on the type of Aluminum used.) Yes, there will be an effect on surface finish over time of heating and reheating above the 250-300 deg range. In Aerospace, 300 deg is the range for a stress relief operation.

My experience comes from over 20 years of Manufacturing Engineering knowledge in the Aerosapce industry for those that don't know me.

[Vodkaman]

A couple of comments on this topic:

1. I am not sure why the injectors are made from Aluminum. I would not chose this material to retain heat. Aluminum is used to remove heat in several different industries. (I.E. heat sinks on computers and such.) I would think that the injector would be made from a cold rolled steel. This can be purchased in tube form for this application. Steel would definately retain the heat much better instead of dissipating heat like Aluminum would.

2. The thing I would worry about most with Aluminum molds being heated and reheated would be distortion. The splitline would get warped very easily. (This would depend on the type of Aluminum used.) Yes, there will be an effect on surface finish over time of heating and reheating above the 250-300 deg range. In Aerospace, 300 deg is the range for a stress relief operation.

My experience comes from over 20 years of Manufacturing Engineering knowledge in the Aerosapce industry for those that don't know me.

I agree, possibly the worst material for making molds, because of its thermal conductivity. Its main and attrubute for hand pourers, is its lightness. I have just designed some steel molds for pouring aluminium. They are heavy.

I too am aircraft background.

Dave

[mark poulson]

I'm not an aerospace engineer, but I did stay in a Motel 6 last night....

All kidding aside, I would guess the reason aluminum is used is that it is easily machined, and cheap.

Stainless steel would be great for injectors, but it would make them cost a fortune.

Same thing with molds.

I still have a two piece sst sand spike an old friend who welded for the local oil refinery made for me 30+ years ago, and it still looks and works great.

The material was free, scraps from his work, and so was his labor. Today, that setup would cost a lot, I'm sure.

I have friends who've poured the same aluminum molds for years, and thousands of baits, and don't have problems, so I think it is all a matter of how you handle both the injectors and the molds.

I am not really qualified to address the technical issues involved with aluminum as a mold and injector material.

That's why I appreciate Vodkaman. He actually knows what he's talking about!

[Delw]

A couple of comments on this topic:

1. I am not sure why the injectors are made from Aluminum. I would not chose this material to retain heat. Aluminum is used to remove heat in several different industries. (I.E. heat sinks on computers and such.) I would think that the injector would be made from a cold rolled steel. This can be purchased in tube form for this application. Steel would definately retain the heat much better instead of dissipating heat like Aluminum would.

2. The thing I would worry about most with Aluminum molds being heated and reheated would be distortion. The splitline would get warped very easily. (This would depend on the type of Aluminum used.) Yes, there will be an effect on surface finish over time of heating and reheating above the 250-300 deg range. In Aerospace, 300 deg is the range for a stress relief operation.

My experience comes from over 20 years of Manufacturing Engineering knowledge in the Aerosapce industry for those that don't know me.

Heres some main reasons why bait molds are made from alum and not steel.

COST of material

Cost of cutting

Tooling cost

also its a benifit that they cool off faster, as you can pull a finished bait out faster.

Ive made molds out of almost everything from CRS, Plastic, Alloy steels and even wood. Alum is the best ffor the situation that our bait pouring process is in.

for injectors the best one ever made was/is from NAPA, its steel with threads and holds well over a pint all this for 10 bucks, guys have been using them for a long along time well before hand injection came to the hobbiest. Just dont mention it on any forum or you will get chastised

seamless tubing in steel is pricey and the finish on others is not good enough to run O-rings in on most of it, without hoing it first, then it has to be polished. as if its not the plastic will stick, where as alum tubing the ID is already polished pretty much.

the draw Back of steel molds are plenty of over pours in 1 pcs molds. ie requiring lots of trimming. the weight of the mold and believe it or not a CRS mold will warp far faster than a aluminum will.steel will also rust faster and pit faster than alum will with salt content.

Alum molds for the hobbiest( even commercial aplications) wont warp under heavy use in the heats we use.

I been into areospace, commercial and Real molds (not bait molds) since the 80's The "Areospace" industry just like the "Mold" Industy are a completely different ball game with totally different needs and uses other than the fact of tolorancing. everything else that applies to the areospace business can be throw out the door as it really had no place in the mold industry.

when one talked about areospace its generally just the metals that are used, Inconell titanium, stelite, (hanse, mar, aka Ball Bustrium) waspoly and the list goes on then its just turning milling, grinding to hold the tolorances to those specs, As you know warpage and the hard spots of the high nickle alloys are sometimes a pain in the butt to machine, plus they have to hold in high pressure, high temps,High stress, and alot of not so metal friendy conditions

The bottom line still runs he same COST. you wants to make the perfect mold get d2/o6 machine it heat treat it then edm it and Polish it. while the mold will last for ever maybe 100+ years do you want to buy one for $2000-$3000 that would be a little 2-4 cavity one.

There are hundreds of molds that are alum that are 20-40 years old and used in production and they still look as good as they did when new other than cosmetics. I've seen them one of my customers has a few(made from zorn I think) and they still produce perfect baits.

Delw

[Delw]

I agree, possibly the worst material for making molds, because of its thermal conductivity. Its main and attrubute for hand pourers, is its lightness. I have just designed some steel molds for pouring aluminium. They are heavy.

I too am aircraft background.

Dave

Dave I disagree.

the "thermal conductivity" of alum is best for baits, mainly due to speed

heres an example.

take any steel dont care what it it make a simple dropshot worm open pour do the same with alum. pour them and tell me which one is better.

they will be Identical in the out put of the bait, the only difference you will have it lets say you want to round off the body ( the top where you pour in) because Steel stays hot if you pour higher than the cavity top surface it will flow over and you will have to trim baits like you do with RTV and POP, with Alum its not a problem and you can build it up pretty high and almost right away. as the thing corner of alum Thanks to the thermal conductivity Properties will col the edge almost immediatly cause the edge to cool the plastic allowing you not to over flow and requiring a trimming session.

I found this out by accident years ago. being from the areospace/commercial machining background we like everythign debburred. I was using a cheaper not so sharp tool that kicked up a pretty nasty burr one day and one of my old employees came to help me out for a little while. He saw the molds and started to clean them up deburring the edge of the cavity buy lapping the face of the mold. They looked nice I mean really nice, however the ones that my customers got that had them before they mentioned now they have to trim baits. We thought it was the plastic.

one day I was pouring for a tourny I was going to in another state and actually paying attention, I had a few of those nicely finished molds and some older ones and over poured almost every bait on the nice finished faced molds compared to the old molds as I was trying to build it up.

Thats why I never ever sand the surface of a open mold(1 piece) that little .003-.005 burr that the cutter kicks up is NEEDED to keep people from over pouring and to round off open pour baits if someone elects to do so.

I have run a steel CRS mold of the same dropshot worm and if you try to over pour the bait(rounding it off) it wont work like the alum mold and needs to be trimmed.its kinde like using RTV

Delw

[MuskyHunter]

Wow. I didn't mean to offend anyone with my comments. Sorry if I did. The injector was the only thing I thought would benefit from being made of steel. An Aluminum injector will loose its heat much faster than a Aluminum one of the same design. The molds do make sense to make them out of Aluminum and as you say, "the baits will come out of the mold faster."

[Delw]

Wow. I didn't mean to offend anyone with my comments. Sorry if I did. The injector was the only thing I thought would benefit from being made of steel. An Aluminum injector will loose its heat much faster than a Aluminum one of the same design. The molds do make sense to make them out of Aluminum and as you say, "the baits will come out of the mold faster."

no you didnt I did because I mentioned "Suction gun" "Napa" and "10 bucks" all in the same sentence.

Making injections guns in my opinion are a waste of time and a waste of money on the customers part when you can buy one that works perfectly out of the box from your local hardware store for 10 bucks, and its SAFE and the tips dont fall off as they are screwed on, not to mention they hold alot of plastic. They also have a chamfered tip.

Delw

[Delw]

http://www.napaonline.com/Search/Detail.aspx?R=BK_7151245_0282450456

obviously you dont use the hose. the last year the cup washers changed havent held up to heat very well, you can get replacements from many stores that last longer, or you can get a insert made that uses O rings instead of cup washers

Suction Gun, 1 PT

Product Line: Balkamp

Part Number: BK 7151245

[Vodkaman]

Thanks for your input Del. I have noticed that in the last few weeks, your input has significantly changed some opinions, not just on this site.

The thermal conductivity thing has always been discussed as a disadvantage of aluminium molds compared to RTV and PoP. Even if the other factors were favorable, just the weight would kill it.

We haven't decided on a material for the aluminium pouring molds as yet, as we have not sat down with a machinist. I have already identified the warping as a possible problem with steel molds and to that end, we are considering cast iron. But I am sure that machining a material as brittle as cast iron would have its own set of problems, tool wear/breakages etc. I would appreciate it if you could email any thoughts on the subject, as I feel it would be a severe hijack in this thread. ( folicallychalled@aol.co.uk ). Thanks Del.

Dave

[MuskyHunter]

Thanks for your input Del. I have noticed that in the last few weeks, your input has significantly changed some opinions, not just on this site.

The thermal conductivity thing has always been discussed as a disadvantage of aluminium molds compared to RTV and PoP. Even if the other factors were favorable, just the weight would kill it.

We haven't decided on a material for the aluminium pouring molds as yet, as we have not sat down with a machinist. I have already identified the warping as a possible problem with steel molds and to that end, we are considering cast iron. But I am sure that machining a material as brittle as cast iron would have its own set of problems, tool wear/breakages etc. I would appreciate it if you could email any thoughts on the subject, as I feel it would be a severe hijack in this thread. ( folicallychalled@aol.co.uk ). Thanks Del.

Dave

Dave,

Molds

The choice of a tool steel would be an H13 or similar hot working material if you plan to go that route. I think the concensus from above and my opinion is to go with Aluminum for a mold. As Del stated above, thermal conductivity for aluminum cooling off is a good thing. The plastic can come out quicker because the Aluminum gets rid of the heat well.

Injector

The injector will loose heat quickly because it is made from Aluminum. This is what will cause some problems with injecting if it is not done quickly. We just need a small coil to keep the injectors warm...an elctric blanket of sorts.

All just my opinion..