» How to eliminate dirt problems in hot runner molds?
How to eliminate dirt problems in hot runner molds?
We are doing recycling process and use recycled material for production. We often have to clean material clogged at hot runner tip. Any ideas to eliminate this routines?
Herman, There are many quality issues of concern with the use of Recycled material if not handled properly. Is all the material being recycled being handled within your facility ? How is the recycled material being processed ? -----Is it simply chopped and reused, or is it extruded and made into pellets? Is the material being selected from the Runner System Tree, or are rejected parts being used in the regrind ? An easy QC Gate for checking the material is to use the MFI (Melt Flow Index) of the material as compared with Virgin Material----If there is a significant change, perhaps over 25%, you may have a degradation problem that results in your Hot Runner issue. Also, there are Shut Down routines that must be followed when using most Hot Runner Systems and you should contact the Manufacturer of your Hot Runner System
to get directions on the "Start Up/Shut Down" procedures.
there is way to use the re grinding material you have to make little bit changes in the machne nozzel you havto fit a fillte nozzel that has tobe cleaned peridecally we faced same problom while using the regrinding material i desigened a special nozzel to suite the machine barrel i got 2 desegen with us
@mark: yes i heard melt flow index is a good way to measure the quality of the recycled material, but it's more to high quality recycled materials. here in developing countries, we have to use more than 50% recycled material due to price issue. the challenge is then the dirt clogged in the hot runner system and yes, we do a lot of shut down routines because of that. i have been trying to solve this issue for years and still not satisfied with what i have achieved.
@sadasivasarma: this sounds like a good idea but isn't it affecting the injection pressure from the machine? how big is the holes in the filter? and what you mean by 'i got 2 desegen with us?'. i sometimes have problems with leaking nozzle if the nozzle changed too often, do you have this problem too?
yes i faced same problom as you are facing the fier design is that there will be no chang in the injection prssure of the machine the hole size dia willbe as 1.5 mm to 2.5 mm. there is no chance of leakage cleanng filter once in week for refer incoe hot runner system letature you can get compler details . you can manufacture your own to suit your machine if you want the design mail your mail address. youcn refer dme . and hosco moulding elemet leetrature,
thanks all, your comments definitely help me to understand better.. all the best.!!
Herman, With your high % of recycled material I am wondering what you see as the advantage to using a Hot Runner Manifold. It seems to me that you may be better off with a basic style sprue drop and eliminate the headaches of the Hot Runner.
hi Herman...recycling 50% will secure metallurgical quality problems .. think about whether the 'stop and downtime as well as the metallurgy NOK rejections really outweigh the proportion of scrap ...?
Herman, I fully understand the economics with recycled material and I support this for a number of reasons, however, I would point out that there is no good way to control the actual % of material fed back into the molding process
. If you say that 50% is used, what is the % during the next recycle ? And the next ? Although your material may very well meet your product demands, there is no doubt that it is being degraded and will result in various issues such as the clogged nozzles that you asked about.
@Herman ... You may be successful in moulding with 100% recycled!....hope the quality is ascertained in the product level. Also it varies from combinations of the recycled material 25%, 50%.....100%. How do you meet this with different products in line?
its all about the process. when we do good recycling process, the material will not be much different compared to new materials. and if we do good process, we can achieve stable quality for each product. in my opinion each material is unique and each product is unique. you just have to pay attention to every material and every product closely.
@Herman....In your opinion "when we do good recycling process, the material will not be much different compared to new materials". In my opinion, if the mixture of 25%, 50%, 75%.......are available in the barrel, we will find it difficult to control the degradation part. This problem is reduced if we use only 25% or 50% or 75% at a time. Practically it is difficult. Finally, the product will receive the effect of it. Very close attention can minimise such drawbacks.
Hallo Herman, i am not read all the comment,
However, based on our experienced that recycling material cause runner broken very low possibility. this more related with runner thickness size/mound design and mound temperature. Regarding recycle material process handling very importance, pls increase degassing and flushing frequency with correct fire burner with temperature during this according to what chemical used. pls try ... thanks
Hi Mr.Herman..i just start to read all comments..i had same problems on my production, specially on hot runner tools.. I use almost same hot runner supplier ( I do not know if we can make publicitie here) because is more easy to handle and also in terms of technical assistance as well for stock parts..
All that you said is common situation in all industry, every day we have more customer demands to degrease prices, forcing us to use more and more recycled materials. My industry is automotive and such demands start to be critical because recycled material is maintenance problems and as mr. Ramadhas said, many quality problems as well.
With my experience, what I can said to you is to focus on preventive maintenance on tools and also on HR..I had a strong preventive maintenance policy with my tool maintenance team and I can get good results on it.
Often tools are under maintenance and also HR.. A good overall cleaning, electric circuits check and use SISE to control hot runner temperatures stabefore start of production, avoid us to get problems on running production. Of course I still have problems, but I can assure that results are better as I was done before this procedures. I invest some money on a hot runner maintenance table and on SISE program, but it was a good investment because my daily problems degrease a lot.
If you want more details please send me an email, that we can discuss details as well by telephone..
It is still much cheaper to do recycled materials, some products use 100% recycled. It is our challenge to find ways to use the hot runner better. In developing countries price is very competitive, so 100% new material is not an option unfortunately.
Some products are successful, for example valve type hot runner is suitable for certain products. The downtime were not much. However some other products create bigger challenge and headache. We have spent some money to try different systems and techniques.
Just use a Nozzle filter as suggested by a previous post. If you need to use a very small grid OK you will get a pressure drop. But you usually have plenty of pressure in hand I have never found it a problem to compensate. They are easy to make if you just use a standard thread and truncate it to give the required gap and opposite cuts thro the thread for flow. I am sure you can find a design on the internet.