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This informative blog allows plastics professionals to discuss plastics training and technology. Brought to you by Routsis Training: the plastic industry's premiere training provider.

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Establishing A Schedule For Machine Levelling

In a recent webinar, I received this question form one of our participants…
Jason
How often should my maintenance department level our injection molding machines?
My Response
It depends… but typically larger machines should be levelled every 6 months. The smaller machines tend to be more stable and rigid, requiring levelling every 12 months.
What is even more important is the fact that you need to measure any machine that is new to your facility every 3 months for the first year. Many molders assume that newer machines require less attention, but it may take up to a year for the machine to settle in.
Additional Thoughts
Keep in mind, you should always level the machine by placing the level on the tie bars. Although bubble levels can be used, a laser level is significantly more effective at measuring the levelness of the machine. Clean off the tie bar before measuring and use a grooved level so that it properly rests on the tie bar.
-Andy

Example: Calculating Clamp Tonnage

A customer of ours asked this great question the other day…
Jim
I am trying to determine, technically, what tonnage I need for a given job:
  • Area of part & cold runner is 19 in.sq.
  • Fill Pressure Actual (@ 1”/s fill speed) = 900psi hydraulic
  • Hold/Pack Pressure Actual = 650psi hydraulic
  • Intensification ratio for the press is 15.88.
Does this mean that the plastic pressure in the mould is ~900 X 15.88 = 14,292 psi?  Or it never reaches that, and the hold pressure of 650 X 15.88 = 10,322 psi plastic pressure is what’s seen in the mould?

If I take the 14,292 psi X 19 in. sq. / 2000 lb./ ton = 135T.  Is this the right approach on what tonnage is needed in this case to hold the mould closed? I am also wondering about the logic.
My Response
Assuming you are not 100% full during first stage… the 10,322 psi calculation would be more correct.
(10,322 lbs/in*in) x (19 in*in) / (2000 lbs/ton) =  ~98 tons.
This is because the pressure is not distributed across the mold cavity until the mold cavity is full… assuming mold filling is completed during 2nd stage packing.
Ultimately, the pressure losses that occur during fill actually reduce the actual pressure the mold cavity realizes so the 98 tons calculation would actually include a fudge factor for safety.
Additional Thoughts
If you were to take a more exacting approach to this calculation, you could preform a pressure loss study to determine the actual pressure loss through the nozzle and sprue as well as during fill. From this pressure loss data you could estimate the average pressure distribution across the mold cavity and relate it to the 2nd stage packing pressure distribution.
In most cases, the simple approach used above would be satisfactory for the typical custom molder.. especially since it would accommodate a small fudge factor to compensate for variability and machine inconsistency.
Molders who perform fewer mold changes… or are purchasing a machine specifically for an application should perform a more detailed pressure study.
-Andy

Time to Learn; Time to Save

A contributor at engineering.com posted an optimistic blog entry entitled ‘Time to Learn; Time to Save’. This entry addresses employment and professional development during recessionary times.
Corporal Willy (excerpt) 
The worst time to do nothing is when nothing is being done.  Economic Recovery is being talked about but when you are unemployed that can seem like an eternity.  I suffered through a few recessionary periods in my working career and in my career choice if the “Stock Market Coughed and Sneezed, then Big Construction got a Severe Cold.”  Because of things like the prime interest rate and some other factors all governed by the Stock Market, Banking industries and Material Suppliers, our jobs could be here today and gone tomorrow.  I have had to travel far away like many others in the building trades to get construction jobs. Many brother members of my local worked on the Alaskan Pipeline when there wasn’t any other work available.  “Have tools will travel” was kind of a war cry back then and still is today.  But armed guards had to watch over you at times because of the polar bears in the area that were suffering hard times too.  It wasn’t an easy career and it was very hard on marriages and all the other things that a normal kind of living should be like.  Yet it was rewarding too.  It fostered a way of life in most of us that could be summed up in this aphorism, “never put a wishbone where your backbone ought to be.”  We made our own futures…
The entire entry can be read here:
-Andy

What Do You Hope To Achieve Through Training?

During the NPE 2009 trade show, an attendee asked me an insightfull question…
Paul
If I intend to get serious about training my employees, what factors should I take into consideration.
My Response
I answered, if you’re serious about improving the skills of your production workforce, you need to begin by asking yourself a few questions:
1. What training methods have you used in the past? Were any of these methods effective? Which metrics did you use to measure their effectiveness?
2. What about now…how much time do you devote to training? Which training methods are you currently using and are they working?
3. More importantly, what effect has the current training plan had on your bottom line?
4. Lastly, what are your training goals? What do you hope to achieve by training your workforce? 
Additional Thoughts
Training needs to take place regularly, and time needs to be allocated for this purpose. Proper training requires resources, so it is essential to have the support of management when establishing a training system for your workplace. Make sure that management, as a whole, understands the scope of the training plan – and which metrics can be used to verify its effectiveness.
In the end, training should be purchased to help meet your company’s specific employee development goals. 
-Andy

NPE 2009 Technological Highlights

At NPE 2009, I teamed up with Josh from IDES to acquire footage of different technologies featured at the show. Back here at the office, we cleaned up the footage and added some explainations to make it more interesting to your employees…

These can be viewed here:
After viewing these yourself, I recommend you use it as a teaching tool to introduce some of your employees to these great technologies.
Also, feel free to forward the link to anyone who might be interested.
-Andy

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