MultiCam dust collector - overflow


#1

At the request of the OP (@bertberaht) , I’m splitting the thread for the MultiCam dust collector; overflow, sensors, login, or what-not. This is the original post that started the discussion:


#2

I know this isn’t the first time. I personally observed it while an individual was running the MultiCam; I asked him to empty it and to his credit he did. It was so full/heavy that trying to transport the bag caused it to split. But for whatever reason he didn’t notice it was full when he started, or while he was running it, for that matter.

So, it’s easy for me to make suggestions because I’m not the person who’s going to volunteer the time to implement these. Having said that, here are my two suggestions, intended to be constructive:

  1. Could the login screen at the MultiCam be changed to ask the question “Is the dust bag less than half full?” (or similar - like the way that Laser has a checklist when you log onto a laser?)
  2. Is there a way to put a sensor on it? Perhaps a weight sensor under the abg and when it gets to a certain weight a light goes on or something?

Multicam SIG Category and 1st Post
Multicam SIG Category and 1st Post
#3

To answer the login screen question, not really possible. It uses the jump server. The terminal there is just a raspberry pi providing rdp.

As for the sensor, I believe this is possible. I don’t know that weight is the answer but surely ultrasonic or something else.


#4

It is. Not all of our members are capable of carrying a 50 pound bag of wood chips to the dumpster. Having an alarm that triggers at W pounds, where W is limited by the maximum weight our MultiCam users can comfortably carry, is a perfect solution.


#5

Basing the concept on this, I’m putting together a part list to provide a plc controlled setup where once can provide a switched limitation for controlling power to something(multicam, blower, etc) based on load cell calculation.


#6

Could we old school it with a pivot platform (think seesaw) for the bag that has a breakaway catch and interrupts power to the dust collector? I’d like to avoid complicating a simple dust collector on the scale of an electronic drill press in a woodshop.


#7

Could a catch be designed to be reasonably consistent even when surrounded by lots of sawdust?

Personally, my first thought is to use a load cell and a script running on the Pi to lock the Remote Desktop when the bag is too heavy. But I’m not all that familiar with the setup on the Pi so I can’t say how difficult that is from a software perspective.


#8

This doesn’t actually keep them from running the machine though. Once the G-code is created (even if using remote desktop from a laptop for instance (insert my photo here of laptop with way too much sawdust in it)), it’s just pointing the Multicam at the file in a certain directory.

If it’s not access control, then you can only shoot for notification (blinking, buzzing etc.).


#9

And/or logging.


#10

Under no conditions do we want to cut the power to the multicam when the dust collector limits. What we do want to do is turn off the dust collector.


#11

We could, my design takes into account least common knowledge(denominator) situations, it also takes into account administrative bypass and such.

In other words, the design I would propose is not going to be a drill press style implementation. It will be more an industrial implementation where the end user has no machine knowledge.

What I envision in its totality is as follows

4 load cells that the dust collector rests on, one jbox to sum the load cell output, one plc to do the smarts, one display that states the load dust collector is X full. A keypad for inputting a combination to access the bypass, a switch for turning on the dust collector, a switch for the by pass, one contactor to control power to the dust collector

Parts list

4 load cells
1 load cell sum box(jbox)
1 plc for computation
1 contactor for power to the dust collector
1 switch for overriding the load cell limitation
1 keypad for code input
1 switch for power to the plc
1 nema box for keeping out the dust
1 HMI display

It would work as follows

User turns on the switch for the dust collector, plc evaluates load cell input for weight, based on that input contactor is either turned on or message is displayed that the dust collector is full and must be dumped before proceeding.

There would be an override that could be key or code based to proceed without dumping it or to disable it.I would prefer a physical key for ease but a code could be used.

What occurs once the dust collector is on and it becomes full is up for discussion, it could display a message, it could start a timer to shut down the dust collector, etc.

The sky is the limit here.

As for why I’m choosing a basic PLC over PI or arduino, plain and simple reliability.


#12

As a very infrequent Multicam user, I am daunted by the dust collector. Large, heavy, messy, and stuck in a hard to access area are a bad combination for encouraging users to do a task. Hopefully the layout of the new wood shop will put the dust collector in a better position for easy emptying.


#13

I agree, I was hoping to avoid messing with AC power all together. As it’s been pointed out, it’s not an effective lockout.


#14

The impatient will simply remove chips from the bag until the weight threshold is reached pushing the problem onto the next user. I suggest adding deadband and state.

We have a persistent problem with dust in the woodshop. Please do not purposely make that problem worse.

On multiple occasions I was faced with a mostly full bag on the dust collector but no replacement bag. I suggest including a mechanism for the person dumping the bag to easily indicate they are installing the last bag.


#15

Can you expand on the deadband and state concept here?

I’m not following on the “Please do not purposely make that problem worse”, the statement you quoted was one of many options.

EDIT

I follow now, I’m used to hearing it as different terminology, adding this is of course an easy option.


#16

I’m sure I’ve missed lots of conversations (and I truly hate to give (or be given) “drive by criticism”), but even a buzzer/flasher would at least remove “plausible deniability” from someone using the machine. It’s also simpler and doesn’t involve dealing with controlling mains power.


#17

Buzzer’s and flashers are an option, mains power control is trivial and safe. The dust collector runs on 110. We already do this with our rfid interlocks.


#18

Did we make the interlocks?

I’m sure we have people who are more than capable of building a device to safely switch off mains power, but I’m pretty hesitant to set the precedent that it’s ok. In an industrial setting I’d agree in a heartbeat, but there’s liability, insurance, and fire code to worry about here. I don’t know enough to say we’re in the clear or not but I think it should at least be brought up beforehand.


#19

Yes, we did. Considering the risk here I think we will find it more than acceptable.


#20

Deadband + state: Once the device decides the bag is full the weight has to drop to a reasonable minimum that indicates the bag is empty (hopefully, has been replaced). Until that happens the bag is still considered full.

Please do not automatically shut off the dust collector once it has started.

Finally, I believe a third startup state would beneficial. You’ve proposed…

• Bag not full: OK to run.
• Bag full: do not run,

I suggest adding…

• Bag expected to become full soon: Warn the human / OK to run.