What does a parison programming system comprises of?

  1. The programming unit (Moog, Hunkar, Femit, Maco Breeze Profiloc PR30 etc..)
  2. A servo-actuator – the fancy name for the hydraulic cylinder- servo valve – LVDT (sometimes called DCDT)
  3. A hydraulic supply
  4. If it is an accumulator head or recip-screw machine then there will also be a long-stroke transducer measuring the shot position.

What are the typical Parison Programmer faults?

It is very rare that the parison programmer has a genuine fault – its nearly always something else!


Servo valves are high on the list of being the cause of problems, partly because they are dirt sensitive, and partly because so many companies have inadequate maintenance standards.

Cable damage

Cable damage is common. Cables melt when they touch the head or extruder barrel. Wires often get pulled out of plugs.

Hydraulic accumulator

If you are getting sluggish response it is worth checking the hydraulic accumulator.

Virgin-regrind mix

If you are trying to produce a much lighter container than normal you might find that there is a greater variation in weight than you can accept. On the subject of weight variation the biggest culprit is inevitably traced to variations in the virgin-regrind mix.

Are there any blow molding simulations or wall thickness prediction software packages?

There are various types of blow molding simulation software on the market. Because this software is so specialist it is usually quite expensive. Software to predict wall thickness change as a result of the parison stretching to the contours of the mold: Have a look at the site: https://www.t-sim.com/www/index.html. You can download the full working version, but only run their example files.

Polymer Training Ltd. Offer software to simulate the effect of process changes have a look at their site: https://www.polymertraining.co.uk/home.htm The software is called Picat.

Are older parison programmers repairable?

If the parison programmer is faulty and it is an old model it is very likely that the manufacturer will tell you it is obsolete and unrepairable. Of course this might be true, and it might also be that this is how the manufacturer gets you to buy a new ‘box’
Phone some of the independent repairers, like us 🙂 and get a second opinion. You might even pick up a refurbished unit. If you reflect, what is the point of putting a brand new parison programmer on a 20 year old machine?

Blow Moulding Soup of the Day 3

Some hints and tips relating to Moog parison programmers AND occasionally ‘weird stuff’ that won’t necessarily relate directly to the products or services we sell.

Blow Moulding Machines

  1. When you order a blow moulding machine give some thought to the ancillaries you will need. Don’t wait until the machine arrives.
  2. Thinking of buying a machine from China/Taiwan/India etc? There are some good machines, and a lot of really bad ones. If you order the machine directly from the manufacturer then you are legally the importer, and you have the legal responsibility to ensure that the machine complies with your countries safety laws. If the machine infringes any patents, it’s you that will get sued, not the Chinese producer.
  3. Spiral tube hopper loaders are great ! Really good with LDPE. Massive reduction of the dust that seems to get through the bag on vacuum hopper loaders
  4. Leak tester rejecting good bottles? The biggest cause is the simplest: not getting a good seal on the containers neck. Check the condition of the ‘rubber’ pad. The ‘rubber’ can actually be Polyurethane, Natural rubber, Silicone, and occasionally sponge neoprene. The hardness varies from 30 Shore ‘A’ to 75. Which is the best for your application? Sponge will seal on anything but wear out too quickly. Very soft materials will not pick up poor neck finishes, so generally medium hardness is better. Polyurethane has good tear strength, but beware this material can harden in time, so don’t buy more than a year’s supply!.

Blow Moulding Soup of the Day 2


  1. Cardboard is the biggest source of contamination in blow molding. It enters the system with the regrind, and all efforts should be made to prevent cardboard coming into contact with regrind. Use clean plastic ‘dustbins’ for storing scrap containers, tops+tails, regrind etc…
  2. Regrind is as valuable as new material. For every pound of regrind you don’t use, you will have to buy a pound of new stuff.
  3. Extrusion blow moulding of large containers in PET is a pig of a task.
  4. Have you tried Bi-modal H.D.P.E. yet? companies are reporting faster cycle times particularly on thick walled parts (jerry cans, drums)
  5. Never use ‘refurbished’ or ‘reconditioned oil. Everybody I know has more trouble with valves, pumps etc..