[Coyotey]

I recently took the plunge and ordered a Omni 1218 machine in order to drag my small wood carving business into this century. Along with the machine I bought a 2.2kw "one bag" Chinese dust collector (the green one). I plan on having the collector in a small room just beside the router and stick the hose through the wall. Nice and tidy, out of the way, and not to mention quiet.

By the way, does anyone have any experience with this type of dust collector? I'm going to run an upgraded 3.5kw aircooled spindle and will be working on all kinds of wood and MDF. Is 2.2kw strong enough?

So while I wait for my machine to arrive, it is only natural to research the hell out of all things cnc routers and I came across a theme that quite frankly freaks me out and chills my blood: The real possibility of fire due to friction. All the ingredients for disaster are present: plenty of fuel, fresh air, and wind. It is my understanding that there are 3 main reasons for this happening: 1). general friction of anything running at high speed over anything. 2). MDF consists of a lot of garbage (including often metal particles) glued together. 3). Wrong speed and feed.

Now here is the nightmare scenario: a glowing piece of whatever gets sucked up into the dust hood, through the hose and lands smack dab in the middle of the collector onto a nice soft pile of wood chips and dust! My work will include running the machine for very long stretches on large pieces. Lots and lots of dust. I would imagine that in a case like this, it could take a long time before any outward sign of danger is detected, and then suddenly BOOOF! My workshop is in a wooden building. Sure I have plenty of fire extinguishers around, but I can't afford a sprinkle system. I don't think I'd be able to put out a 10 minute old fire with my squirt bottles!

I guess I just would like for experienced people to weigh in on this. Is this risk constantly on your minds? Is my shop going to be in constant danger? Am I over-exaggerating this?! (flame2)

Forgive me if this topic has been covered before, or if I'm posting this in the wrong place.

[ger21]

It is my understanding that there are 3 main reasons for this happening:
1). general friction of anything running at high speed over anything.
2). MDF consists of a lot of garbage (including often metal particles) glued together.
3). Wrong speed and feed.

Imo, none of these are really reasons for a fire. Although #1 is very vague.

MDF is no more likely to burn then anything else.

To start a fire from the wrong feedrate, you'd need to be moving incredibly slow, with an incredibly dull bit, at very high rpm. As long as it's still cutting, it's unlikely to stat a fire.

Fire's tend to start from unforseen events.
The other day I was cutting small parts from a sheet of plywood. A small piece came loose, and ended up on top of the sheet. When the router came down to make the next cut, the collet pushed into the lose scrap piece. Friction from the collet burned 1/8" deep into the plywood in about 1 second. But it didn't start a fire

I've also seen collets pushed into the table from erroneous g-code.
So to me, the biggest issue is collet nuts and toolholoders rubbing into wood.These can start a fire in seconds. It would be extremely rare to start a fire from the actual cutting process.

Also, if you have a vacuum table, that is more of a fire hazard than a dust collector. With a vacuum table, the MDF spoilboard itself can start on fire, and will burn on the inside from the airflow of the vacuum. Generally, loose material that could get sucked into a dust collector will be pushed aside and not see enough friction to start a fire. Plunging the collet into the spoilboard can start a fire almost instantly, and it can burn quite a bit before you see or smell it, as the smoke and fumes are sucked away by the vacuum system.

You mention 10 minutes. A fire in a spoilboard will be much, much faster than 10 minutes.

[Coyotey]

Thanks for the informative reply ger. This certainly puts my mind at ease.
I was under the impression that conditions created by wrong RPM's and feed rate were far less forgiving on wood based on some articles I have read, hence my concern. Also, the issue of MDF containing surprising amounts of metal has "sparked" concern from others. As you write though, it stands to reason that as long as the bit is cutting, then it is safely doing what it is designed to do. I guess I just wanted to get a feeler out there as to how vigilant an experienced cnc router operator is at any given time to this risk. Cheers!

[daniellyall]

it get`s very exciting when the dust extractor and pipes are on fire seen it twice reason blunt cutter and wrong feed and speed`s more likely blunt cutter caused it,

[ger21]

I cut hundreds of sheets of MDF a year, and have never seen any metal in it. MDF is made from fine dust, so it would be difficult for metal to slip through the cracks of the manufacturing process.
Now, particle board is another story. I routinely see small pieces of stone, and the very occasional small piece of metal in particle board. But they are small, and rarely cause any damage to the bits.

[underthetire]

I'd be more worried about static electricity. Make sure you use metal ducting or the flexible stuff made for this.

[wolff2018]

A few years late for the opening poster, but our experience was the dust collector caught fire and burned all 4 buildings down to the ground, contents and all, while I rec'd 2nd degree burns on my arms requiring skin grafts tryin to put it out with an extinguisher.
We had an Oneida dust collector bought as part of the Cobra CNC initial install, what struck me was the dust collector body was all black PLASTIC, and a cardboard barrel!
All was fine for about 3 years.

I was using the CNC on plywood, the dust collector was behind a partition wall that enclosed the CNC room, the room was open to the dock but the collector could not be seen from inside the room.
It was all installed by a master electrician and properly grounded, long story short without all the details- I saw a little smoke come thru a crack at the top of the wall followed by a little flame, I ran out of the room to look and could see the motor on the collector was on fire.

The fire investigators were never able to pinpoint what exactly caused the fire- the motor itself, an electrical fault or something else because the whole thing melted down into a burned puddle with what was left of the motor sitting there.
I KNOW what I saw, and was asked about every detail- the flame was not in the barrel, the motor itself was on fire along with the plastic turbine section, and it was still running with flames until the plastic softened enough about the time I saw the fire, that the whole top motor and all fell on the floor shortly after I started hitting it with the extinguisher.
By then the chipboard partition wall next to the collector around the CNC room was on fire and flames touching the ceiling, way too much for any hope of an extinguisher.

This dust collector- ALL of them in fact should NEVER be inside any building, this one was- the warehouse which had the CDC, the collector should NEVER be hidden behind any partition or wall when you cant visually see it at all times when it's operating.

There are safety dampers for the pipes that sense a fire and shut off the air and the power to the motor- get that and install it
Have larger than the 10# extinguisher we had by the CNC- at least two 20# ABC extinguishers.

I noticed after the fire that the Oneida web site appeared to no longer have that model OR the black PLASTIC type models with cardboard barrel, I found that very interesting and passed it along to the investigators. I cant fathom how UL could certify such a unit with flammable plastic and a freaking cardboard barrel for a use like this!
Here's what the results was before the fire spread to the 4th building- the one on the left containing the offices, computers, archives of records and photos, and much more.
There was also a large bridge crane installed only 3 years before the fire, the 17 of us lost all out personal tools etc and now its 2 years later and they are now rebuilding this week.

[jaguar36]

I don't see any issue with wood/plastic components in a dust collector. Regardless of what the housing is made of there is going to be a ton of flammable wood dust in the collector and the filter media will likely be flammable as well. If the motor catches on fire and you don't catch it fast enough its going to be a bad day regardless of what its made of. Sure a dust collector should be outside, but that's not feasible for most folks outside of industrial settings. Is it a risk? Sure, everything is a risk, but I don't think its significant.

[wolff2018]

I don't see any issue with wood/plastic components in a dust collector. Regardless of what the housing is made of there is going to be a ton of flammable wood dust in the collector and the filter media will likely be flammable as well. If the motor catches on fire and you don't catch it fast enough its going to be a bad day regardless of what its made of. Sure a dust collector should be outside, but that's not feasible for most folks outside of industrial settings. Is it a risk? Sure, everything is a risk, but I don't think its significant.

I'm sorry you are not seeing the bigger picture here, as well as the apparent fact that Oneida no longer has that black plastic housed turbine unit with the cardboard barrel- both are now STEEL, what does that suggest to you? I know what it suggests to me post fire investigators and insurance agents contacting the company about their product. Were talking here about a $5 million loss, plus an employee injury which when all was said and done likely hit the workers comp up for around $100,000 in costs.


I gave them all the information there was including a picture of the unit itself so they could see what it looked like and it's configuration;



The problem with plastic is it IS flammable itself while steel is not, the cardboard barrel is flammable but if a fire started in the sawdust it's not likely going to erupt into a wall of flames, it will smolder etc, once the plastic housing was ignited it took off and ignited the wall, that would not have happened if it was steel. The duct from the CNC was only about 6', 90 deg elbow, 6' and into the collector, it wasn't running like 45 feet all over the shop or something like that, so the amount of material was very limited, what did burn was the plastic housing which ignited the wall, once the wall was on fire it escalated drastically in seconds

In our temporary shops we are in, the new insurance carrier's agent did a walk-around, one thing he stated to me was that "there's the most dangerous piece of equipment in a woodshop right over there- pointing to the dust collector. We have two being used temporarily, both are all steel with steel drums and totally visible from all sides, unlike the one that burned which was behind a partition wall surrounding the CNC, so smoke or fire could not be seen when operating the CNC itself.

I could go on about a bunch of mistakes, starting with purchasing that plastic and cardboard collector in the first place, installing it INSIDE the building, and worse yet- having it obscured by a wall between the CNC operating station and it.
In such a situation there's no way the operator could see or smell anything in it's initial stage, but behind a wall out of view the fire could get going pretty well before any signs of something wrong were seen or heard. Inmy case the first signs was I heard a noise that sounded like someone outside banging on a car body with a rubber mallet to get dents out, I took my hearing protection off and the noise stopped so I had no idea, it sounded like it was ouside, but as I remember- the noise as well as what sounded like electrical shorting in a metal conduit started and then I saw a wisp of smoke followed by a tiny flame come thru a crack at the top of the wall, by then the motor was fully engulfed in fire and the plastic top was on fire.

I could add there are fire sensing devices for these that can automatically shut the duct off with dampers to stop the airflow, and shut the motor off, I absolutely would suggest having that on any such collector.

[wolff2018]

My advice would be make absolutely sure the entire unit and barrel are steel- no plastic, get an automatic device that senses fire on it that shuts the duct in/out off with dampers, and shuts the motor down, do not install the unit inside a building, have at least two 20# ABC extinguishers available, anything less than this- make sure you have loads of replacement cost insurance.

[pippin88]

When installing a dust collector in an enclosed cabinet (inside or outside a building) it is important to make sure the motor has enough airflow and ventilation. Sometimes these motors end up very close to the roof of an enclosure. Risk of overheating can be increased.

The motor should have a thermal cutoff.

[wolff2018]

When installing a dust collector in an enclosed cabinet (inside or outside a building) it is important to make sure the motor has enough airflow and ventilation. Sometimes these motors end up very close to the roof of an enclosure. Risk of overheating can be increased.

The motor should have a thermal cutoff.

Very true, in our case it was in a large warehouse with
A 14 foot ceiling, it was free standing but near a partition
Wall and it caught the wall on fire once it was on fire.
Big issue was it was positioned in a way it couldnt be seen
By the cnc operator from inside the cnc area

[wolff2018]

Some options for an automatic shutoff on dust collectors in case of fire;

https://www.robovent.com/learn/frequ...ust-collector/