Tip of the Day 156: No negatives on stroke scaling, please

“Always with the negative waves, Moriarty…”        ( from…? )

A customer found a way to confuse an eDART™ by entering a negative number in the scaling for the stroke analog input (from the machine). If you are taking injection stroke from the machine instead of the LER-30, always enter a positive number for the stroke full scale like this:

We will probably lock out negative values for stroke on the next release.

The eDART figures out the correct stroke direction using the Screw Run signal and watching the direction of motion^†. It will invert the signal automatically if necessary to get a positive volume and stroke curves. That way we can analyze flow of material from the plastic’s point of view: How much went IN to the mold rather than how much is left in the barrel.

Also, the wiring should be such that the (+) terminal on the analog input always goes above the (-) terminal and not the reverse. The analog input module cannot see negative voltages.

^† If there is no Seq. Module Input / Screw Run going into the eDART then you still need to use positive numbers for full scale. Then set the direction correctly in “Sequence Settings”. The correct direction is that the stroke signal should go positive while the material is being injected into the mold. You also need to set zero at the point just before suckback.

Tip of the Day 138: Redundant Id Names

We have found that in the naming of sensors some people are duplication the location into the “Identifier” column of Sensor Locations. For example, thus:

This duplicates the information that the sensors are located at the end of the cavity (end of flow). Or sometimes people put “Cavity 1”, “Cavity 2” etc.

In the Alarm Settings and other tools the locations will show up like this:

We recommend that you simply place number or letters in the identifier column because the location is already indicated under the “Sensor Location” column. The simpler version looks like this:

Tip of the Day 132: The “Save Notes” tool for the eDART™

1. Clear the previous note by clicking “New Note”. This places the cursor in the white area.
2. Type your note.
3. Click “Save Note”

• You could you set up security for saving notes to put the operators name into the change log.
• Or you could just request that they put their initials into the note.
• If you intend to use the tool across the plant you could set up a view with the notes tool in a convenient location. Here is the view used by the “Conx” (machine-only) eDART showing the Save Notes tool circled in yellow:

• When using the Analyzer you can export all notes for a given period by clicking “Export” and adding the type “Text” and the location “Summary Note” as shown here:

Once opened in Excel sort on the “Note” column and all of the actual notes will rise to the top.

Tip of the Day 131: Naming Temperature Sensors

I recently discovered that a customer had made an error in naming the locations of in-cavity temperature sensors. The rules are these:

• If the plastic contacts the sensor or the sensor is just behind the cavity wall use one of the in-cavity locations:

  Post Gate, Mid Cavity or End of Cavity. Then add an id for each cavity in multi-cavity applications.

• For in-cavity sensors pick a location name relative to the flow path.
• If the sensors are on the mold steel elsewhere you can use Parting Line or Mold Surface.

Tip of the Day 129: Use Descriptive Cavity ID’s

I discovered recently that someone thought you could only put numbers in the “Id” column on sensor locations. This is not true. You can use letters, numbers, spaces and some punctuation.

Use descriptive identifiers for cavities, valve gates and individual sorting outputs (tip #’s 68 and 69). Using letters and numbers describe these sensors and locations in a way that best identifies where the sensor is located. First select the “Location” in terms of the flow path through the mold:

• “Runner“: before the gate
• “Post Gate“: right after the gate inside the cavity
• “Mid Cavity” somewhere between the gate and the end
• quot;End of Cavity” near the last point to fill

The select an identifier that adds to the location described. In a multi-cavity mold these will often be simply numbered cavities. In family tools such as those making two auto lenses you might have a “Left” and “Right“. In multi-gated cavities we have used “Op-Top” for “Operator Side – Top” and so on.

Choose locations and identifier names that help you best visualize the inside of the cavity from the plastic’s point of view and from your view of the mold in the machine.

Tip of the Day 122: Set Screw Bottom to Get Cushion

Recently a customer asked if the eDART could compute the cushion. It can. But there is a manual procedure required that is sometimes forgotten. It looks like this:

1. Start the job on the eDART before purging the machine.


2. Sometime during the purge sequence pause while the screw is all the way to bottom (machine’s stroke indicator = 0).


3. 
   
   Open “Set Screw Bottom” from the main menu and click the button that says “”.
   
   
   
   
   
   


4. Continue starting up the process on the machine.

• The eDART remembers screw bottom between jobs. So technically you don’t have to re-set it on each job start. I suggested a re-set at each job start because the tech starting the job may not know that sensors were unplugged or the eDART restarted or powered down; all events that require a reset.


• Un-plugging the stroke sensor looses the location of screw bottom. Also, if the ports are not split (tip # 111 ) and the stroke sensor is on the same Lynx port as the mold sensors then plugging and unplugging mold sensors can confuse the stroke sensor as to where bottom is. Split the sensors so that mold sensors are on one port and machine (including stroke) are on the other.


• The reason that the eDART requires a screw bottom reset is that the stroke encoder is a “relative” device. It has no marker on the cable for an exact position of extension after power up. While this requires the extra step it makes the stroke sensor a very precise solution for a wide variety of machine sizes without the need to carry a whole line of absolute encoders of different lengths.

Tip of the Day 121: If you get a shock, STOP!

One of our consultants was in Malaysia last week. While hooking up his Lynx cable to an eDART he got a shock or at least a tingle from the eDART. He was holding the Lynx cable in one hand and the eDART was plugged in and perched on a table.

There are many explanations for why this can happen, generally having something to do with grounding; or lack of it. These can get rather technical. So, as not to distract from the main point, the short story is this:

If you feel a shock while working on an eDART installation, STOP and get an electrician to check the wiring before proceeding. This is a safety issue and should not be ignored.

That is all.

For those of you interested in the basic explanation here is a link to a short video to show what happens when grounds are not connected.

[youtube=Jmg6zQWIH-s]

Notice that using a 3-prong to 2-prong plug adapter effectively disconnects the ground wire and so is also not safe.

Tip of the Day 111: Splitting eDART Port Load for Speed

In tip # 110 you probably noticed that the eDARTreaction time depends on the sample rate of all the sensors attached to the Lynx port. We recommend that you split the sensor load between the two Lynx ports on the eDART in order to get the fastest reaction time possible. The sketches below demonstrate this idea based on the sample rate calculations in the spreadsheet in tip # 46 (see latest version on web site).

Another Big Advantage of Splitting Sensor Load: Keeping the “Cushion” Computation Correct

As you see we suggest splitting the ports between mold and machine sensors. The other good reason for this is that the operator disconnects and reconnects mold sensor cables with every mold change. In the process of breaking the data stream the sensors have to re-organize themselves in the data stream, like a chain of elephants after a stampede. If the stroke encoder (LE-R-30) is on the same port where the mold sensors are swapped it can loose power momentarily or reset itself. Then, if you have used “Set Screw Bottom” on the eDART it has forgotten where screw bottom is. When it reconnects itself the eDART can still work stroke and volume but can no longer figure out the correct cushion.

Tip of the Day 104: Bypassing Inject Enable in Manual Mode

There are strange things done in manual mode

By those who presses wrangle;

Or so I’m told by molders bold

Who use Inject Enable.

They purge, retract or build a shot

Or even pull the barrel

While the eDART, sleeping or just awake,

Makes trouble sure to rankle.

(apologies to Robert Service)

As noted in tip # 96 the Control Output / Inject Enable provides value by preventing damage in case a controlling sensor fails or becomes disconnected. But I have heard that this can be quite frustrating to those trying to maintain the machine or operate it when there is no real job or mold there. In fact the eDART™ may be turned off or just powered on and the Inject Enable output is not even defined yet. So the relay contact remains open.

A press with a programmable controller could be programmed to ignore that input when in manual mode. But often presses are not programmable or it is very expensive to change a program. So customers sometimes wire the Inject Enable output in series with the purge guard switch or some other safety circuit. With the eDART off they can do nothing, even with the press in Manual mode.

Here is a suggested circuit to bypass the Inject Enable when in manual mode. A relay is driven by the signal from the controller that is on while in manual (also fed into the eDART‘s Sequence Module, or ID-7). When in manual the relay closes a contact that goes around the Inject Enable circuit. This lets the operator do whatever is necessary in manual mode.

If your machine puts out a “Machine in Auto/Semi” signal instead of manual then you can use the same wiring scheme except that CR1 would need to have SPDT contacts and you would wire the bypass across the normally closed contacts (  ).

Tip of the Day 98: Auto-Starting Jobs

A reader of tip # 97 noticed that I mentioned “auto-start” and wanted to know more about it. Here goes…

Philosophy

The initial idea behind the eDART™ was to remove user interaction with the eDART from the untrained user as much as possible. This is why we “stick” software to the mold with the Architect, why the Lynx sensors identify the mold and machine and why cross-copy was concieved to keep the plant-wide records straight. The idea is that the operator should only need to plug a Lynx cable into the mold and the system would take care of itself.

Auto-Start

The icing on the cake for this automated ( ) operation is that the eDART can be set up to start the job automatically if it recognizes Lynx sensors being plugged in that identify a previously run mold. If auto-start is turned on then, after a period of time, if the mold and machine are identified the job starts automatically, just as if you pressed “Accept”.

Furthermore the Sensor Locations can also be set to auto-start after a short period. If all of the sensor types and locations are filled in (not blank) then Sensor Locations will push its own “Accept” button like Job Setup and the rest of the software will then start up.

Note that if you are using auto-start and have a power outage all of the eDARTs connected to sensors should start up and start the same job where they left off without any action from the operator.

Warnings for Using Auto-Start

• • Changing Materials: The eDART auto-starts with the last process assigned to the mold when it identifies the mold sensor. It cannot identify the material automatically. If the mold is likely to run with different materials each time then auto-start of the job is not for you. You could still auto-start the sensor locations.

• • Not plugging in the Lynx cable: Since auto-start is based on identifying the mold then if operators do not plug in the cable it will not work. The previous job will continue to run until someone either plugs in the cable or changes it by hand.

• • Mixed molds with and without Lynx sensors: If you have some molds without sensors and some with then operators will still need to know to start the job by hand on those molds without sensors. If they do not then the job will continue to run under the previous setup and all data will be recorded there.

• • Not Stopping the Job: The auto-start does not auto-stop when the Lynx cable is unplugged (a risky proposition at best). So your system overview will show the job as “Down” when the mold is removed and no other mold is installed. You should encourage operators to stop the job if you want overview to show “No Job” when there really is no job scheduled for the press.

• • Training for First Time Mold / Sensor Selection: Auto-start will not auto-start unless it knows the mold, machine and all of the sensors have been set up. So someone will still need to be trained how to choose the right mold / material / cavitation, sensor locations, press on sensors to check set the pin sizes etc. If you have the eDART Data Manager (or server with cross-copy) then once set on one eDART the setup will be ready for auto-start on any eDART.

Setting up Auto-Start

Turning on the auto-start is done by setting a pair of software switches in the system configuration file (system.cfg). Since we do not encourage customers to edit the file themselves we have a software installer (and un-install or “turn off”) that can be used to turn it on and off. Contact RJG Customer support if you are interested.

See Art’s Tips to find earlier Tips of the Day.