Efficiency Esimtation

Bill. don't you dare ask, "North or South"!

At the risk of not being PC, I want to say to Molders all over the world,"Merry Christmas and Happy (keeping on) Molding in the New Year"!

brent

Alecia

"mold Load" is the percentage of the machine year (month/week/etc) that the mold will consume producing parts to fulfill the customer's requirement.

Let's say the mold can produce acceptable 20,000 pcs per shift. (total parts less scrap)

Your customer wants 1,000,000 pcs/month. The mold must run 50 shifts/month There are 91.25 shifts per month. The mold load is 50/91.25 = .5479 or a 54.79% mold load.

This means that this one mold will consume a machine for 55% of the month at it's current output capacity.

The reason why this is useful is that if your customer increases his requirements to 2,000,000 per month the load is 1.09 or 109% of your capacity (because you only have one mold.)- you're overloaded at your current rate. If you had two molds you could split this requirement into two machines

In reality as soon as the load borders on 75%, you're risking missing the shipment because if the machine goes down, a cavity is blocked off or any of several other possibilities it will no longer produce enough parts (this is risk analysis a subset of materials planning). Further, all molds need maintenance. Running any mold 75% of the time generally will not leave enough time for the mold to be cycled through maintenance since you will have many molds in maintenance at the same time.

Keep in mind even with a 55% mold load, other molds are competing for machine time to produce different parts. This is why your spreadsheet first looks at available machine hours. Then you look at the individual mold loads for that machine and look at its usage.

Then you break it down, no longer looking at an annual load on your molds and machines and break it into your scheduling time frame - weeks, months, even days.

It is easy to add in a sub routine into the mold load calculation the number of boxes, bags, meters of tape for the boxes, labels AND kilos of materials all per percent of load.

Calculate the mold load for a period of time and it will come back and also tell you the additional materials required to ship the product.

This calculation is an interesting planning tool.

I hope this helped. I apologize for saying your were Chinese.

Dear Bill,

Thanks a lot for your reply. It does help a lot.
I would have a couple of additional question.

How is a mold load measured?
It's hard for me to imagine that you would measure it physically.
Can I do it by the following formula?

Volume/Cavities*Cycle Time

And a machine load would be sum of it?

What would be the optimal efficiency of a machine?

I would appreciate your reply.

Bye the way I am not Chinese, but Korean.

Alicia Shin

Alecia

This is a production control problem. The formula is a simple spreadsheet calculation:
Each production run is the sum of it's parts- the time the machine is open to the time (including setups, material change overs, production, setup and tear down) to the time it is open again.

This is based on available hours (you also have to include machine maintenance which is not part of production efficiency)

You start with the total hours in a year. You then subtract of hours for scheduled/unscheduled maintenance. This gives you an 'efficient year' - time available for production. You then add up the hours consumed for each job (the 'mold load' the total number of hours the mold will run annually). Create a fraction/percentage. This is called the 'machine load'. Machine load = total sum of mold loads.

If a machine has an annual load of .8 = 80% it is probably overloaded because production volumes are not predictable through the year. As the percentage goes down the easier it is to add additional jobs. Remember if you have (for example) three identical machines, each capable of running the same job, your 'machine load' calculation starts out with 3-machine years capacity for each year.

Improving efficiency now becomes an exercise in scheduling and common sense.
1. Can you schedule several jobs using the same material thereby avoiding material changes?
2. Longer runs make of better efficiencies BUT if you warehouse a year's worth of parts where you only have a 5% margin, you've tied up a lot of money and storage space.
3. Can you train your techs for shorter startups?
4. Can you minimize your rejects and therefore avoid rerunning the same job and/or shortening the time required to fulfill the order.
5. are you scheduling the volume to be run for each job (each with it's startup costs) based on your customer's orders or an economic order quantity run formula that balances requirements of the customer to the costs of unscheduled retained inventory?

There is a plant in the US who specializes in short runs. The can set a mold (a few of which are quite large), change material/color in one hour; make 50 parts then do another different job.

There are a few plants who will only run a small number of materials i.e. HIPS, ABS, PP, HDPE. They won't accept jobs with materials that are difficult to change i.e. PEEK to color matched HIPS.

There are other molders who have machines specifically reserved for optically clear parts. They don't change materials, they change the entire screw/barrel when they want to run lens molds. When the next part is a black ABS part, they pull the barrel/screw and put in one for conventional molding.

I've programmed this and many others have. You can do it yourself. Once you know how loaded your equipment is, you can model the addition of new jobs or the loss of existing ones.

While I know your next post will be to ask me to send you the spreadsheet (why do people in China do this?), it would be silly to give you something I spent many hours to develop. It's a good learning exercise to go through on your own.

Hope this helps.

Bill Tobin

Hi,

I meant production efficiency, which would equal to non productive(incl. set-up, material change-overs, colour change-overs, other downtime) verses productive time of a machine base on its product mix.

How is production scheduling managed to keep optimal eifficiency, when a new product is to be added. How can the impact of this new product on efficiency of this machine be calculated?

I would appreciate your feedback.

Thanks

Alicia Shin

What do you mean by efficiency?
1. Efficiency during the run?
2. Efficiency in getting the first useable part?
3. Efficiency in mold change overs?
4. Efficiencies in color changes?

Obviously if you charge your customer for all machine time use (productive + non productive) you are 100% efficient