Remember flash from early toy models that come attached to the sprue? As kids, we kind of accepted flash as a fact of life. But it's nice to see how technology and quality has improved.

I'm recently retired from the injection molding industry after nearly a 40yr career, sure have indeed witnessed the industry evolve over the years from when I first started in the business, good to see students of the trade being taught these simple straightforward fixes, keep up the good work RJG! I can't begin to number weird things I've discovered over the years as to the root causes of flash, from broken tie bars to molds being hung incorrectly some are just merely simple water cooling issues other tougher problems with fill and flash can be rather difficult to solve, especially on very complex parts :)

In this tutorial I learned a little about pac pressure, and you ask how else flash happens. Shot size, dirty tool, wrong die height, wrong material, or wet material, to name just a few. Love what you guys are doing keep it up.

Thanks for the presentation. Nicely done. Flash is also caused by tool defects at the parting line of the cavity.

Another cause I've seen with is silly is flakes of plastic build up in the mold caused it to flash and the tech kept upping pressure which caused it to really flash.

Great video Marty! Been trying to explain this to our process technicians since I took a course with you in January. Now I can just show them! Thanks! Looking forward to getting back to RJG for more training!

I worked in this field back in the late 1970's and early 1980's. There were no electronic controllers then. Everything had to be set by turning knobs and setting limit switches by hand. The majority of the machines I worked with were toggle clamped, not directly hydraulic. As time passed, the company bought more and larger hydraulic clamp machines. Still, no electronics. It was an interesting time in my life.

I have been working in plastic for over 10 years and started from zero knowledge to working up to supervisor and now learning process more and more each day. I can say everything in this video is well explained and true in every way. These are the exact steps I take to prevent flash in almost every case when you can tell you are overpacking pressure and blowing the tool open. Obviously sometimes it can be from clogged venting and in "some" cases even injection speed can play a huge factor. But at the root of it all, you have to see how much material you are truly trying to push into a tool and where your cut off point needs to be. Your machines are a lot different than mine but also a great point to make is your shot cushion should not be your exact transfer point. There should always be a little "room for pressure" between the sprue break and the injection nozzle as to not cause a bonnet

A great demo. would be nice to show the machine graphs

Description is very clear, the scenario to use the car is easy to understand, switchover point is the key point but not the injection speed to cause the flash, thanks!

Need to show a closer up of mold screen

Thank you for taking the time to make these videos.

FCS IM Machine getting certified by RJG, Excellent!

Great presentation! Keep up the great content!

It is appreciated if you make video explaining warpage, reasons and remedies

Nice video. Was the clamp force calculated for the resin used initially? Are the mould shut off faces ok? Is the mould cooling ok? High melt temperature could reduce the viscosity of the material. Assuming the gate size is correct then a rheology curve should be generated. This could then find the ideal injection speed and a process window . Applying full injection speed is not going to always give the best results. As you mentioned a second speed would reduce flash and also allow venting and a better transfer from injection pressure to holding pressure. Once the injection speed, holding time and pressure have been optimised I would then move on to checking the clamp force by using a DTI and weighing the parts.

Video is very helpful, thanks. I have a question though, Duponts nylon guide says to use the maximum pressure for the holding stage. This bottoms out the screw though. Or if I increase the shot size too far I get flash. Should I not use such a high pressure?

Good videos Marty!

I hope if you can provide us more videos for injection molding machine processing and how improve part quality.

thanks..very informative ..

Thank you RJG and marty for the wonderful explanation. Flash can be a result of any setting parameter in some sense. One of them that interests me is the cavity imbalance. I was able to eliminate flash by changing runner design. The root cause was nothing but one cavity being filled way earlier then the other.

Good explanation

Love good old decouple molding great experience learned how to process various materials using this method nice JSW all electric machine.

thank you so much for this explanation, will try these adjustments!

Would using a pre-loading hydraulic cylinder help eliminate issues with over pressurizing the tool? While also utilizing a smaller sized cylinder and also requiring less pressure? Like ones used on cores?

Former QC for here. As long as the flash wasn't too bad, we could take an exacto knife and trim it. But usually on the machines we had (the plant I worked at sold to China in 2004) it was too hot or too cold. It wasn't the speed. Also, dirty molds and molds that didn't like to release

nice presentation, please do a video to how to calculate tonnage of a mold

It is also possible to have fluctuations in the clamp force and dosing with worn machines. The mould temperature may also rise during the production run (tempering devices don't work well, cooling inside the mould is inadequate) and cause increasing flash. You can also have an explosive fill caused by a cold plug. Which may result in a flash or burned part. It may also be that the mould has flashed once after a fault and filled with a less viscous material than normally. In that case you have plastic stuck inside the mould not making it close well and requiring manual removal (knife and gas burner).

Nice video , do you prefer single point injection speed ? Thanks for sharing the knowledge 🙏

What about flashing the gate? Everything you said makes sense for flash on the part.

Nice presentation. At my plant, flash is usually caused by insufficient mold clamp pressure, 2nd stage pressure being too high, or the nozzle driving too deep into the bushing.

Clamp tonnage not set right and mold cooling working correctly will cause flash....now is the die-height set correctly is your lockup position correct. Do you have a broken tie-bar and is the mold there damage causing the flash?

Common processing without doing 98%fill. Slowing down on inject but not watching hold speed. So it slows down on last stage of inject, then goes in fast and hard on pack/hold. So hold speed is critical to watch as well.

Can speed cause flash in some other cases? The runner is being filled faster than the material can pass through the gate. In this case, the runner actually flashes when overcoming the clamp pressure. it is like your garage wall has a window in it and you have to pass through it at 70 miles an hour and your car cannot get skinny enough to pass through the window. Can this be the result when pushing very low MFI material? Isn't it possible to go from a thick area of the part to a thinner area and material is pushed in faster than it can pass through the thin area?

Taking the high pressure to screw stop may be causing your flash too.

Decent analogy.

Yall need to come to my factory!! Teach us a thing or to

Thank you

What are common cause of dosing alarm?is it connected to material temp .?

Do you do any thermoset injection?

Blocked parts in other cavities caused by buttons, the left over material over fills the closest cavities causing hella flash and a list of other problems

Where I work, flash is a bad problem. We have to do slot of trimming daily.

I've been a Tech for a long time basically call it what you want to { I agree } I do call it decoupling { you have 1 / 2 / 3 } there is so much that goes into it people will say { basics } I also agree as far as flash so many ways // rolled parting line / like you said blow mold open / dirty mold { clean it before you become that dreaded button pusher } / psi / on n on I love being a tech I work with 2 shot molding al diff types of material Was a good vid Id like to see more

Flash could be caused by a lot. Over venting the mold, big shot size, barrel heates too high, or mold damage/tool damage. Shorts are usually just not a big enough shot but usually if you are short on one side and flasing on the other there is a problem with the mold or how the press is leveled.

Only two things I know of that cause flash - Overcoming clamp pressure (This could be mechanical problems, wrong cut off, etc.) and mold damage. Also I like to use hydraulic pressure at cut off to set the hold pressure.

Sir u mean we should fill the part by using two profiles?

Also mold temperature can cause flashing. If the temperature is too high, plastic don't freeze in time.

Lower heat profile, reduce first stage injection speed , inadequate vents. Wear and tear maintenance, increase tonnage, reduce speed time, reduce injection pressure and timers.

Thank you for sharing. Is it also possible for a unreasonable product design to cause flash during injection molding process?

Clamping pressure too low or high causing the mold to bow in the centre, barrel/ nozzle temperature too high, too much back pressure on screw during filling.

Too much hold pressure or hold time will cause flash also incorrect shot size and not enough tonnage

Other cause too much back pressure?

Not enough clamping pressure. Mold to hot or possibly over hesting of the nold. There are so mwny variables eheb it comes to plastics that's why i love it. Actual mold damahe cojld cause flashing too

The other causes of flash other than a to low change - over position are: 1, tool damage. 2, imbalance fill on multi cavity tools. 3, Clamp pressure to low. 4, broken tie bar. Jimbo🏴󠁧󠁢󠁥󠁮󠁧󠁿🇬🇧

Tonage tranfer pos and shot size also water temps Vacuum seal parting line gas build up and all be cause. Of flash u can shot a press as fast as u want if u have a good cushion and.Tranfer i been. A mold tech for years and years. This is childs play.

In regards to tonnage, we normally run max allowable by the machine, the exception is when your mold is, for example, a 1/3rd the size of the platen. Running too high of tonnage on a smaller mold will cause it to wear outwards.

Good video. I would like to see some videos of profiling speeds and holding pressure, and reasons why you may have to to profile/ use two stages.

God all these clean factories make me realize how shitty of s factory I worked in

been in processing about 14 years there are so many things and variations that can cause flash.i work with machines from 120 tons to 1100 tons.if youre process is where it is supposed to be to the original than obviously something changed.

Clogged or restricted vents can cause flash.

Worn shut off plates, mold design, low mfi could cause flash

You raised the transfer, god damn scientific shit right there. Could have just said hey dummy, don’t put that much plastic where it can’t fit.

Decoupled molding

Other main cause of flash is mold damage. And also, in some particular cases, mold deflection.

Mold cooling question. How much temperature difference between the halves of the mold is acceptable? In my workplace they set temps. up to 30 degrees celcius! Way too much in my opinion. Of course there is a lot of flashing due to thermal expansion/contraction of the mold parts/halves. Plus ejectors or slides seizing. Pseudo "process engineers" claim that they have to do this due to parts bending or being not spot-on on size, dimensions. How do you run your molds folks? I know, in theory whole mold should be run on the same temperature, both halves.

Hold/pack pressure too high could cause flash

A worn mold.

Answer.. parts out of spec?

Chilled water temperature to high

Part should I'll with 95% without holding time

Over packing, shot size, tonnage

Bad spot. #1 Mechanical problems, slides and lifter timing, wear plate alignment, manifold stack height issues just to name a few... alot of variables cause flash outside of the process

So speed doesn't cause flash... but speed causes flash. Got it. Anyone else remember when RJG used to preach "Its not the tool or the machine, its always the process that causes issues". Pepperidge farms remembers.

Another thing i have seen is guys increase the shot size when the shit goes short and i have to fix the fucking nozzle leak plastic everywhere!

Tool damage is the only other cause of flash.

We are professional supplier for injection machine spare parts.

Why is it called 'flash'?

Let me see u. Use a krussh With thremaset bmc Material. And get rid of the flash. Lol

Flash is natural die venting lol

I never was a big fan of flash… kind of a wimp, only power he had was speed, but Superman was just as fast if not even faster

What about the weld line at the underfilled frame shaped part? Visual appearance was obviously acceptable but what about dimension and function/durability?

If youre shot size is too big