To understand back pressure here's a simple analogy - if you think of sliding a large wooden box down a stairs... you will need someone below the box pushing up against it to stop it from sliding freely down the steps and getting out of control. So while the box is sliding down the stairs, the person below the box is pushing up against it as if they were trying to push it up the stairs. The box is like the screw going backwards during plasticising and the back pressure is like the person below the box pushing up. The screw goes back and the (very badly named) back pressure pushes against the screw in the forward direction. Back pressure has some positive and negative effects. On the positive side, back pressure squeezes the air that comes in with the plastic granules back up through the hopper so you get less chance of bubbles and splash marks in the parts. Back pressure mixes in colourant better. It adds heat and helps to melt the material. On the negative side, it leaves the melt more compressed in the shot after plasticising so this can cause drool and strings as the mould opens (more decompression distance can counteract this), it also slows down plasticising so if the part walls are very thin and the part doesn't need much cooling you can potentially find the mould waiting for plasticising to finish after the cooling time is finished - giving slower cycle times. The temperature increase from higher back pressure can cause degraded melt if the material is very shear sensitive (eg PVC). Back pressure also affects shot size consistency and it's impossible to guess what back pressure will give the most consistent shots. So to optimise the shot size consistency you should run 10 short shots with different back pressure levels and see which back pressure gives the most consistent shot weight (range or standard deviation) over 10 shots. Back pressure does make the shot bigger by compressing more melt into the shot - typically I would expect to see around 0.3mm extra in the shot size if I doubled back pressure from 50 bar to 100 bar. In imperial that's about an increase of 0.012 inches in the shot if the back pressure is doubled from 750 to 1500 psi. We can see this increased shot size clearly as the melt cushion increases when the back pressure is increased.

So you make... technologies. I'll take two.

Wow, what a great idea to invite students to see this factory which helps to find many potential engineers for tooling. What an amazing movement!

Good job!

I have done this kind of slider mold design before, but I did not use a round ej to eject the part, I had to change to a stripper plate to eject the long part. And use the spring to push the plate back.

As a technician for process engineering with ten years of rolling in the industry, I would love to take a seat next to those lads and just listen to a different perspective. Go on, you do it right.

I dont necessarily agree with back pressure and part weight comparision you drawn in your video. Also, the other thing I noticed is the part weight only went down by 0.02grams or something. That's not big enough change to draw any conclusion.

Put the music louder, I could almost here the people speaking

Working like a slave for minimum wage, no thanks.

Back preasure puts more material in the flights of the screw not less.

Learn more about it at www.hymid.co.uk/case-studies/sustainable-partnership today!

www.hymid.co.uk/case-studies/sustainable-partnership

www.hymid.co.uk/case-studies/sustainable-partnership

www.hymid.co.uk/case-studies/sustainable-partnership

www.hymid.co.uk/case-studies/sustainable-partnership

www.hymid.co.uk/case-studies/sustainable-partnership

www.hymid.co.uk/case-studies/sustainable-partnership

www.hymid.co.uk/case-studies/sustainable-partnership

www.hymid.co.uk/case-studies/sustainable-partnership

www.hymid.co.uk/case-studies/sustainable-partnership

www.hymid.co.uk/case-studies/sustainable-partnership

fix your audio it's genuinely more important than the visuals people will put up with poor quality videos for longer than they will poor quality audio

Great vid!

Make sure you subscribe to our channel! If you'd like to find out more about our collaboration with SageTech, head to www.hymid.co.uk

Nice video production and song choice however a lot of people don’t know what this is or means 😅 maybe upload a video on what is happening

you cut the best part😭

gotta cut the runners off

hope that you make new video about maintenance molding machine

Gas leak detector

So interesting, how those machines operate

seems like a lens in an insert molding

There’s not enough context in the video dude

No explanation, no description, no pinned comment. Wtf are you even making?

@EltonJohn was sick last night at glasto! Farewell Rocket Man!

Cool vid

Sick

🔥🔥

Love my t90

TUNE!!!

sick

tune

❤

🎉

❤

😀

cool!

Sick

Love it!

tune