Mold Clamping Issue

[RSullivan]

I am looking for a way to clamp molds.
I have a dual jacobs injection machine.

 

I do not like to put the C-Clamps against the molds itself.
I believe that this causes un-even pressure down the length of the mold.
It also scratches / scars the outside of the molds.

 

So as an example, here is what I do (example is for a single cavity mold):
I use 2 peices of wood (The length of the mold, 2" wide, 3/4" thick) on the
outsides of the molds as clamp pads. I use 2 C-clamps.
I believe that the 2 peices of wood acting as clamp pads distributes the pressure
from the clamps better than just using the clamps. It also prevents scratching the outside
of the mold.

 

My problem is that the adjusting screw (the end with the handle) then sticks out to far and I cannot
center the mold perpindicular to the nozzle for dual injecting (it will be offset).

 

This of course is not an issue when I am not using the peices of wood (just the C-clamps).

 

I am using the smallest C-clamp possible

 

So:
- I am thinking of buying Aluminum bar to replace the peices of wood.
- I would have the aluminum bars 2" longer than my mold.
- I would drill holes at the ends of the bar.
- Bolt, washer, washer, nut to clamp them together.

 

This would solve my clearance problem.

 

But these solution seems sort of expensive to me. As an example priced six 9" x 2" x 3/4" 6061-T6511 bars
for my 3 senko molds. (Note, I am aware I could use the same 2 bars for all three molds but I would
much rather have a pair for each mold, makes things go faster.) and came up with a price of
$55.98 + $27.23 shipping. Ouch! I did not even bother to take the time to price out bars for the rest
of my molds.

 

Anyone have any ingenuise ideas to solve my clamping problem?

 

Or maybe there is an industriouse tool & die type member here who would be willing to cut stock and drill
holes for a better price?

 

I have though of doind this with wood but I believe that the wood would just flex (bow) outward
towards the center.
Thanks.

 

[emptystringer81]

I use a vise and tape card board on it so the vise teeth don't damage the molds, problem solved

[RSullivan]

That's a good idea, but I am using a Jacobs injection machine. A vice will not fit under the nozzle with a mold in it (I have some tall 12 cavity molds).

Thanks

[JRammit]

http://m.homedepot.com/p/HDX-2-in-Spring-Clamp-80002/100027346?cm_mmc=SEM%7CTHD%7CG%7C0%7CG-PLA-BT3-HDX-D25T-Tools%7C&gclid=Cj0KEQjw_9-9BRCqpZeZhLeOg68BEiQAOviWAkeW1HKgRbKyTb0HpnZ8Koln7yOCPeFcxUhPL716Wg8aAgPt8P8HAQ&gclsrc=aw.ds

Quick, ez, no mold damage... I use them for plaster molds, usually 4 at a time... They work fine once you figure out the best way to place them

[mark poulson]

I use these, and they don't scar my molds:

 

http://www.ebay.com/itm/Jorgensen-3706-6-Bar-Clamp-Standard-Duty-USA-/401172567327

[archery1]

the dewalt or irwin quick clamps work good also

HAVE NOT HAD GOOD LUCK WITH THE HARBOR FREIGHT CLAMPS

Edited August 20, 2016 by archery1

[emptystringer81]

The Irwin clamps work good, and they have rubber pads on them so they won't scratch. Wouldn't think u would need a piece of wood, most molds are strong enough not to flex.

[RSullivan]

Clarification:

Though I mentioned the perceived issue of the clamp feet scratching the molds, it is not the issue I am trying to resolve.

 

First of all thanks for all of the responses,

 

Spring Clamps:

I have tried these before.

I have some larger molds (12 cavity) so I need to run my injection machine with about 20lbs of pressure in order for all of the cavities and

appendages in the cavities to actually fill. The spring clamps (4 of them) do not have enough clamping pressure. When I did this it resulted

in a whole lot of 'flashing; occurring so I had to spend a lot of time trimming baits.

 

Standard C-clamps:

These are all to long ('wide'), see below (If this existed it would solve my issue)..

 

Wood working F-clamps (Jorgenson, Pony, Bessey):

These are also to long ('wide'), see below (If this existed it would solve my issue)..

 

 

The reason I like to use the pieces of wood (cauls) is that I have many molds with small / thin appendages in them. As we know some times

the appendages will not fill when shooting, so one must vary the pressure of the clamps in order to get the appendages to fill correctly. When I use the pieces of wood I never have this issue. I simply put the pieces of wood in position, put the clamps on, tighten them up and shoot. This works very well for me.

 

Now the real issue is the width of the pieces of wood, mold and clamp (specifically the length that the adjusting screw that ends up sticking out). The entire width is ~1" to wide to fit under my injection machine when I am trying to shoot dual color (i.e. 'laminates') baits. When I am shooting singe color baits I have no issues as I can simply cock the assembly at about 30 degrees.

 

See: http://www.visualdictionaryonline.com/house/do-it-yourself/carpentry-gripping-tightening-tools/c-clamp.php for a listing of C-clamp parts.

 

If this existed it would solve my issue:

A 3" C-clamp where the adjusting screw is only 1 1/2" long. Meaning that if the adjusting screw was completely closed the 'Swivel Head' on the adjusting screw would be at least 1" from the 'Fixed Jaw'. I.e. it does not close all the way.

 

I have been unable to find such a C-clamp. I believe such an animal does not exist.

 

Thanks for all of the suggestions.

[Basseducer]

Can't you take your clamp to a machine shop and have the end of the bolt redone? Send your drawing around and get some estimates.

[CNC Molds N Stuff]

I only hand inject my own baits, but I use the heck out of Harbor Freight bar clamps.  I feel like the average HF quality has gone down hill since the kid took over the company, but its pretty hard to screw up a bar clamp.  (Irwin actually managed to screw some up so they wouldn't hold though.  LOL)  I have a bunch of these http://www.harborfreight.com/6-in-quick-release-bar-clamp-62239.html hanging over my pouring bench.  Well actually at the moment they are packed up in boxes with the rest of my pouring supplies while I do some work in the shop. 

 

A few times I've done work where I needed a shorter clamp.  The bar just got in the way.  At $2.99 each throwing it in the band saw to shorten it bother's me not in the least.  I realize in your case the tightening handle may get in the way.  Cut it off, find the thread, and double nut the screw.  You can still quickly spin them down, and once you get the rhythm having a wrench the right size at hand on the bench to snug off will go just as quick as a slide bar on a C clamp. 

 

They come with plastic pads, but I take them off and toss them in a drawer in case I ever want to use them for something I do care about the finish on, but for my own personal molds I could care less what the outside looks like as long as the inside works right.   To be honest though they really don't do any damage you couldn't buff out by hand anyway. 

 

As to uniform pressure... if you really want to go there... a trick used in some types of wood working is a slightly arched board.  I hesitate to say uniform clamping, but it does spread the clamping force over a larger area.  If using two end clamps the board is arched away from the stock at the ends.  If using a single center clamp the board is arched away from the stock in the middle.  When I used to use my parrot vise for molds I use aluminum plates machined to do the same thing.  A slight arch, and close a hair past touching all the way across. 

 

And the last of the immediate thoughts I had when I read your post.  You mentioned having to run 20PSI on your pot(s).  I assume that is high.  Since I only hand inject I don't know.  I do however have some personal molds that are 20 cavities or more.  One little finesse worm I shoot has 30 cavities with fairly thin curly tails.  They all fill to the tips with modest steady hand pressure if I run the plastic just a little bit warmer.  I usually use 4 clamps on that mold when I first shoot it, but when I am making my personal summer stock of them, I get in the rhythm, and the mold gets warm I only need two.  Maybe a few degrees bump in temperature can help lower your required pressure to fill it.  Again I only hand inject for my own use so I can only say it might be worth a try, but I don't KNOW it will work for you. 

Edited August 21, 2016 by Bob La Londe

[walleyeking]

Cut the adjustment screw to the length you need and weld on a new end to your liking.

[CNC Molds N Stuff]

Cut the adjustment screw to the length you need and weld on a new end to your liking.

 

That is a great suggestion.  I tried to think of things that anybody could do with basic hand tools.  For my own use if I needed to do that I'd probably turn and thread the screw to fit a standard knob/handle so I wouldn't need a wrench, and then use a back stop nut to clamp it in place so it wouldn't back off when loosening the clamp.  That's if I couldn't find a modest priced knob that fit the stock thread.  Or I might thread an unthreaded knob to fit the stock thread. 

 

Between McMaster, Reid Supply (or whatever they are called now), Carr Lane, and maybe Zoro Tools you should be able to find a knob to fit just about any thread. 

 

Not everybody has a lathe or even a welder though. 

 

Since I hand inject it doesn't get in my way anyway. 

[mark poulson]

You can make lots of clamps for different sizes by using hardwood pads, all thread, washers, and locking nyloc nuts, or carriage bolts with nyloc nuts.  

Edited August 22, 2016 by mark poulson

[RSullivan]

Thanks for all of the suggestion guys.

 

I took 12 4" C-clamps (Jorgenson) to a local welding / machine shop.

They are going to charge me $40.00 to:

1.) Cut the adjusting screws down to 3".

2.) Weld a 9/16 nut on to the end.

 

This will work for me an I found it to be surprisingly cheap!