Tip of the Day 153: What’s in a Name? Machine + Template

Suppose you run a mold in more than one machine. And you use eDART™s to save templates between them, perhaps even just the machine template. Can you use one machine template (volume and injection pressure only) for both machines and get the same parts? Even if the machine curves are “normalized”? (see tip # 74)

Not likely.

There are simply too many variables: friction, check ring mechanisms, acceleration, transfer response etc. So you develop a method to have the technician pick the right template for the right machine. We suggested this in tip #87.

And that always works, right?

In order to remove that human error, Release 8.8 (July, 2009) prefixes the template name with the machine name. Now the best practice is to save the template with the same name on every machine. Then when the job starts it will look at the machine name on Job Setup and load that template with the previous name but with the machine name prefix.

Example:

When saving a template use a common name for templates that you designate as the correct standard like this:

Notice that the name of the template entered in the box above plus the machine name is limited to 35 characters.

Now you will notice on the cycle graph the machine name before the template name separated by a period as shown here with machine number „503B„:

When you start the mold on another machine there will be no template selected at first. When you go to select a saved template you will see the templates listed with the machine name in the left column as shown here:

You can select the template from the original machine as a starting point. This gives you a reasonable normalized machine template. Begin with fill-only parts matching the machine speed template. Also match hold pressure, hold time, screw run time and the other machine parameters (tip # 75). Have the parts checked for quality and adjust as necessary. If you have in-cavity sensors this process can be greatly shortened (assuming the same material) by matching the in-cavity templates.

Once you have a centered process producing quality parts on the new machine save the template using the same name; “QC Approved” in the above example. Now regardless of which machine the mold runs on the eDART will pick the “QC Approved” template for that machine. No human intervention is required except to choose the correct job setup at the start.

One additional advantage to the by-machine naming system is that you can show your cycle values template numbers in machine specific, non-normalized form: linear speeds and positions, hydraulic pressure and so on. This makes it easier for the technician to relate a change directly to the machine controller.

Note to EDM users who followed tip #87:

If you have prefixed machine names to your templates you can simply drill down into the „eDART Configurations“ folder to find your templates or do a search for „*.template“ from the „Groups“ folder. Then just change the template name so that the machine name prefix is followed by a dot (period) and then the template name. The templates always end with „.template“.

If you do this with all eDARTs on line the rename will be accomplished on all of them at once. While renaming you might also make your names consistent (like the „QC Approved“ in the example above).

At the next job start you will need to pick the template name the first time. The eDART will remember it on each subsequent job start.

Tip of the Day 143: Find the Root Cause Before Matching a Template

As you know we at RJG emphasize matching the template to return to the original process. The release of the Process Stability Dashboard encourages template matching of the machine settings if you have no cavity pressure sensors installed.


BUT, when restoring a process to template, think first. Find the cause before making a change.


Here is an example. What changed?

To match the template an operator might decide that the screw RPM is too slow because the screw recovery time is long. And he notices that the Effective Viscosity value on the eDART™ has not changed much from the template (only + 0.8%). So he might simply speed up the screw RPM.


The root cause here is NOT a change of screw RPM. Instead the change in screw run time is caused by a material change: 25% regrind mixed in where the template was made with virgin material. Changing the screw RPM could improperly change melt temperature, color mixing or break fibers differently and so change the part quality. Either the virgin material should be restored or a part quality check should be made with the new, mixed material. A new job setup could be made for the regrind and an appropriate template made after re-qualifying the new process.


Thinking through the above example the operator should first look on the setup sheet (or Setup Notes on the eDART) and see that RPM is set correctly. If it is and the template was matched after startup then it is likely that the material changed. Is this a different machine from the one on which the template was made? If so then perhaps the screw diameter or design is different and it takes longer to recover at the same RPM.

Tip of the Day 123: Why Cushion?

In response to tip #122 one of our customers asked, „Why bother with cushion when variations in Peak / Shot Volume would show you check-ring leakage and the like?“ Well, he was quite right. Variations in the forward motion of the screw can be seen very well in the peak volume. „Cushion“ as measured on machine controllers is a traditional way of looking for variation when no cavity information is present. With the eDART the peak volume can take its place. With an exception…

Suppose you are using eDARTs and their stored machine templates to transfer a mold (and its process) between two machines. And suppose you have no cavity pressure sensors. Because most thermoplastics are compressible the amount of stored energy at transfer depends partly on the volume of material left in front of the screw: the cushion. True, the cushion is actually the remaining volume with the screw furthest forward during hold, not just transfer. But we suggest that, in order to get a reasonable match between a process on different machines you should approximately match the cushion volume when the process is set up on the two presses.

Simply look at the cushion number in volume on the Cycle Values window (after settings screw bottom) and check to see that they are at least similar between the processes as run on the two different machines.

It probably is not possible to match cushion exactly, especially if the cushion is a very small percentage of the shot. Getting close (5 – 10%) will be better than guessing.

BTW: Tip #73 discusses some the rationale behind the machine values chosen for transfer of molds between machines.

Tip of the Day 89: In Decoupled 2 Use First Stage as End of Fill

This is a follow-up to the idea of using templates for machine setup (tip # 87). Here is a convenient method to let the machine tell the eDART where end of machine fill is instead of setting the fill volume on the eDART. In Decoupled 2 processing the end of First Stage (also known as „boost“) IS the end of the machine’s filling portion of the cycle. Using this signal and making a short shot you can use the eDART’s instrumentation to accurately match the filling (flow) part of a process even without cavity pressure sensors.

If you have wired the machine’s first stage output to the eDART’s sequence module then the eDART knows when machine fill ends. But you need to tell the eDART not to set the fill volume automatically. You can do this by setting a large number on the eDART’s Sequence Setting fill tab (but not 10,000 cu. in)

Once set, the eDART will not use the volume to figure out where fill ends but will instead always use the end of Seq. Module Input / First Stage. This is recorded with the process (mold/material/cavity combination) so that you do not need to set it again each time the process is run.

Now when you set up the process on a new machine you simply need to match the fill-only part weight and the fill time as computed by the eDART. In the fill-only shot below the eDART is using the volume zero crossing to determine the start of fill and the end of first stage for the end of fill. Thus the computed value Sequence Time / Fill is the length of time that Machine Sequence / Fill is on.

Notice that the injection pressure curve for the mold used above is one of those that prevents us from using peak injection pressure to figure out the end of fill. There is an early restriction in the mold that creates a first peak that is higher than the peak at the end of filling.

In order match a process on a different machine using the eDART you could use the following steps. Note that this will only work if all of your machines have Seq. Module Input / First Stage wired to the eDART’s sequence module. Use the cycle values set up as described in tip #73.

1. When the process is first set up be sure to set the Sequence Settings fill volume to some large number (not 10,000).


2. Record the fill-only part weight or size for the fill-only shot. Without cavity pressure sensors this is your only access to an „in-cavity“ measurement. You could use the „Setup Notes“ tool for this purpose and perhaps even add a photograph. (tips #71 and 72).


3. Save a template for the finished process on the first machine.


4. When the mold runs in a different machine adjust the machine and temperature controller to match the melt temperature, mold temperature (also recorded in Setup Notes).


5. Begin by making fill only shots.


6. Adjust machine to match decompression, backpressure, screw run time and fill flow rate in the template column of Cycle Values (tip #73).


7. Add Sequence Time / Fill to the Cycle Values on the eDART.


8. Adjust the transfer position to get the same fill-only part weight or size.


9. Re-adjust the machine’s fill speed to match the Sequence Time / Fill on the Cycle Values.


10. Repeat steps 8 and 9 until you get the same fill-only part in the same fill time shown by the eDART.


11. Complete the rest of the match by setting the machine to match the other values: hold pressure, hold time, cooling time (start of fill to end of mold clamped) and cycle time.


12. Check the parts for quality: no sinks, flash etc.


13. If desired, save a new template for this machine (as in tip #87)

Now that’s a rather long list. Let’s have a go at trying to do it in a numerical form from the eDART’s screen…

Tip of the Day 88: Using the Process Match Meter to Monitor Machine Setups

You can use the Process Match Meter tool on the eDART to look for machine setup changes even when you have no pressure sensors in a mold. This match number gets displayed by the eDART Data Manager on the „Advanced System Overview“ web page. Thus you can see at a glance whether all of the machines have been set to their standard process.

Step 1: Drag the Process Match Meter onto the Architect’s workspace. If you want to „attach“ the meter to all molds click the „eDART System / Molds“ folder under the Architect’s „System“ tab and drag it there.

Step 2: On the Process Match Meter click the „Process“ tab, select the „Injection Pressure“ sensor and then click „Accept“.

Step 3: Stabilize the process. Always make process matches after the process has been running long enough to become stable.

Step 4: Click „Reset Process Match“, enter a new match (and template) name and click accept.

The meter will make a template and a match file at the end of the current cycle. It then begins to match the injection pressure to the match file on every shot. It computes a number for the match that the Advanced System Overview (ASO) displays on any office web browser as a moving bar. Also the meter needle moves in sync with the number on the ASO.

Note that the injection pressure curve will vary with viscosity as well as with changes in machine setup. We will be improving this at a later date. At this time you could make a machine setup match for each significantly different viscosity material (say „Low“, „Medium“ and „High“).

If the match meter needle goes off center look at the cycle graph to see the cause. You can’t tell without a Post Gate cavity sensor but the gate may not be sealed any more and this could cause sink at the gate.

You can also make a process match by machine / process combination as described for templates in Tip # 87. The name I chose here reflects this.

Notes for the future:

We expect to release improvements in the process match with eDART software release 8.6 (summer, 2008). This version will automatically compute template matches for both machine and in-cavity process values whether the Process Match Meter is running or not. Thus you will not have a „match“ file separate from templates. Whether an eDART is using the match meter or just the cycle graph the ASO will always display a match indicator as long as a template is active.

Also the new „Setup Match“ (machine setup) will match the speed profile template (volume) until transfer and then injection pressure until the end of the cycle. Furthermore it will always make a „Setup Match“ for the machine curves and a „Process Match“ for the in-cavity curves.

Historical note:

When the Process Match Meter was created in December, 1999 the eDART Cycle Graph did not have a template. Or at least it did not share it. So the meter had to make its own match file. Now that the match concept has become part of the Advanced System Overview we plan to bring the two together.

Tip of the Day 87: Setting up Templates by Machine

At RJG we hold that the in-cavity conditions are what control the final part characteristics (plus melt preparation). In instrumented molding we make cavity pressure templates that, if matched, produce the parts closest to the original. In order to keep these in-cavity conditions the same when moving a mold to a different machine the controls on the new machine may need to be set up differently to match the cavity pressure template.

In conjunction with this we are finding more and more that the machine based injection template (speeds, pressures and times) has great value in re-setting a machine setup to its or original form. Sometimes machine maintenance, wear or mis-calibration cause the numbers entered on the controller to not produce the same machine response. Or sometimes the process setup sheets are not as „pure“ as you would like. The eDART lets you save more than one template for a given process. So here is a technique for using templates to reset machine setups each time a job is run so that you get as close as possible to the original cavity conditions the first time.

Step 1: Make a template on the first machine with the best, most centered process. Name the template with the machine’s name, possibly preceded by something descriptive; for example „503B – QC Approved“ where „503B“ is the machine name.

Step 2: Transfer the mold to a different machine, say „308A“.

Step 3: With cross-copy (running on the EDM or our older „Server“), starting the job on the new machine will automatically bring up the currently set template from the first machine as shown below. The process is shown set up exactly as the other machine (see „Normalizing“, tip #74). You can use the stroke and pressure curves or the cycle values as defined in tip # 73.

But you can see the cavity pressures don’t match. Here we are showing the condition of a leaky check-ring on the 308A machine. The machine’s volumetric flow rate is the same but the cavity fills later. Of course you need to make sure cooling and melting are the same.

Step 4: Adjust the 308A machine setup using systematic molding techniques: short shots, eDART data etc. to match the cavity pressures as shown below. You can see that the machine speed and volume had to be increased (transfer position decreased) to get the same short shot in the same fill time and then for the cavity to fill in the same time (Process Time / Cavity Fill).

Step 5: Set the Volume at Fill on the cycle graph to the new transfer point (tip #53). The cycle values window above has the two machine values that changed shown in red ovals.

Step 6: Save a new template with the name „308A – QC Approved“. The new setup for the machine will be different but the cavity pressure template will be approximately the same. Of course it will look quite similar when matched, as shown below.

Step 7: Train the operators who set processes to always select the template with the matching machine name. If you are going to use the cycle values instead of the curves for machine setup you will also need to have them reset the volume-at-fill using the cursor or by making a short shot.

Note for the future:

While step 7 above is a manual one we hope to release an automated method with eDART software release 8.6 (summer, 2008). This would use the machine name from the job setup to select the correct template without the extra manual step. It would also save the volume at fill with the template.