Thread: Just finished my CNC, a quick dust control question.

We will have to see some photos of the new machine first before making assessments.

I have some stuff on youtube, not too much but you can see the machine.

This one has it doing nothing but moving the ducting around to check the ducting can reach all around. The ducting is not complete and I will put pvc bends where there are bends so that the flexihose cant bend too much.

[ame=http://www.youtube.com/watch?v=ipxcYY3C-tE]YouTube - Testing rail for hanging ducting.[/ame]

Here it is cutting the temporary dust shoe until the one I ordered from Kent at Kentcnc.com arrives this week.

[ame=http://www.youtube.com/watch?v=hNSMoL-ZuMg]YouTube - cutting dust shoe on cnc[/ame]

its only just got going so speeds have been ramped down to about half of what I think it will do.

Thanks,
Jason

Hi Jason

Nice machine you have there. Hoem built or bought? What size, specs and if plans are available?

The question you have with regards to the dust is 2 fold. First is the type of material you are cutting/milling, and the second is how often the machine is being used.

If you are running it more than 4 hours per day and cutting/milling MDF the you would turn the handle on the pleated filter every second day to provide best airflow.

If you are using it less than that then once a week.

Eventually you will work out what you will require as you use it more and observe the filter and bag.

Hi Michael, thanks for that

I have been going over what I do so many times and in the end I decided to keep the whole unit outside and add the filter.

Turning the handle every other day is not problem, I wasn't sure if it would be every hour or every week.

This is the first CNC I have built so I ended up buy the plans for joes 4x4 hybrid. After seeing that nothing which made it easy to build was available in NZ I made it with what I could get at OK prices. 20mm linear rail, 16mm ballscrews etc from china and all aluminium/steel locally.

In the end it's not really like joes but does have some similarities with the carriages. The cutting area is around 1500x1300.

I am happy with it so far and it's had a couple of nice runs. At the same time its cut some bad pieces after finding I had the spindle running in reverse

One thing I am happy is that is seems to be solid. Now, what to make next

Nice job on the build. Looks solid and seems like it has plenty of speed to me. What do you estimate your rapid speed will be?
Sorry I know nothing about dust extraction, it is a little further down on my wish list than perhaps it should be.

um , one small word ,
1) mdf dust travelling through a plastic pipe causes static electricity ,
2 ) mdf dust in the right volume of air to dust , is an explosive ,
3 ) im not joking

all cabinet makers ducts are steel to conduct the electricity to ground , and avoid the problem , i recommend you run a bare copper wire down the inside top edge of your hose to wire it up to a good ground ( not in your control box ) , this wire will cause dust to stick and will probably block up the pipe every now and then

the chance of and explosion are very slim , a fire a bit more probable , still a bit less than bugger all chance , but there is a chance , every cabinet makers work shop has steel ducts for a reason

cheers ken

Originally Posted by SawDustSniffer

um , one small word ,
1) mdf dust travelling through a plastic pipe causes static electricity ,
2 ) mdf dust in the right volume of air to dust , is an explosive ,
3 ) im not joking

all cabinet makers ducts are steel to conduct the electricity to ground , and avoid the problem , i recommend you run a bare copper wire down the inside top edge of your hose to wire it up to a good ground ( not in your control box ) , this wire will cause dust to stick and will probably block up the pipe every now and then

the chance of and explosion are very slim , a fire a bit more probable , still a bit less than bugger all chance , but there is a chance , every cabinet makers work shop has steel ducts for a reason

cheers ken

Not this old hoary chestnut again.

An explosion has never been reported in a hobby level DC and as many fires happen in steel ducted DCs as plastic ones usually because someone sucked up something hot.

Read this to see this myth debunked.
PVC

The supposed Bare copper wire solution is complete BS.

Like Carba-Tec, I'd err on the side of caution.

Dust Extractor Safety
One hazard that is often overlooked in dust extraction equipment is the danger of the buildup of static electricity. The dry timber particles rubbing the inside of the flexible hose are constantly building a static charge, in the same way rubbing a plastic comb through your hair (if you have any) will build up a static charge. Static, when it discharges as a spark, is just one of three parts required to create an explosion. The other two parts are a fuel (in the form of fine dust particles), and air (which is being forced through the system). Explosions in dust extraction systems are rare, but they do happen. More often it's the large painful 'Crack' of the static finding its way to our finger tips that reminds us of this potential danger. A simple solution to avoid this situation is to ground your system. Fitting a grounding kit to the inside of the flexible hose and connecting the wire to both the machine and the dust extractor will minimise or eliminate static from the system.

From CARBA-TEC

OK, well the last piece of my dust extraction arrived today, the dust shoe from kentcnc.com

I am very impressed by it and I have been waiting for it to arrive so I can start the messy process of surfacing the table.

Then, on to the fun projects

Originally Posted by elkangorito

Like Carba-Tec, I'd err on the side of caution.

From CARBA-TEC

Fully agree, somewhere on one of the many forums, there is a picture of some poor bloke who lost part of his shed when his dust collector started on fire because of the static build up while running his cnc or doing woodwork. There is also another one where the router has caught fire on a cnc.

These problems should be taken seriously, they are IMPROBABLE events but not IMPOSSIBLE. Care should always be taken so as not to get bitten by Murphys Law. Its not hard to run grounding wire in a PVC pipe and although not many have them, a extinguisher nearby is a godsent. Spending half an hour doing a preventative is sure as hell, better than spending months repairing a silly mistake.

Daniel

Isn't it grounded at the DC. If a DC is wired properly then it should be grounded or are you guys suggesting it needs grounding every few meters or so?

As dust extractor itself is grounded quite well, its the pipes that you use to connect to it. The flexi-pipes they provide normally are wire wound already, the metal ducting is conductive so works great for grounding and the PVC stormwater pipes people use can build up alot of static. These are the ones to ground yourself.

Surprisingly, if you get a quote, the metal ducting can be installed fairly cheap if you speak to the right people or scavenge at the right places.

Daniel

Originally Posted by twistedfuse

Fully agree, somewhere on one of the many forums, there is a picture of some poor bloke who lost part of his shed when his dust collector started on fire because of the static build up while running his cnc or doing woodwork. There is also another one where the router has caught fire on a cnc.

These problems should be taken seriously, they are IMPROBABLE events but not IMPOSSIBLE. Care should always be taken so as not to get bitten by Murphys Law. Its not hard to run grounding wire in a PVC pipe and although not many have them, a extinguisher nearby is a godsent. Spending half an hour doing a preventative is sure as hell, better than spending months repairing a silly mistake.

Daniel

There are many risks in a home workshop but an explosion caused by static electricity in a hobby level DC is in the being hit by a meteorite category - do you always walk around with a hard hat? Lots of things are improbable but not impossible but if we run around attempting to prevent every possible scenario that is all we would do and there are many other things we should worry about.

There have been many challenges made on these and other forums and websites to provide a single verifiable example of this (explosion in a hobby level DC). Yes there are fires but there has not been a single example ever provided of an explosion in a home shop DC. And basic physic demonstrates that a grounding wire on any sort PVC system does nothing to prevent this unlikely event anyway. The wire inside flexipipe will not conduct ANY charge away because the plastic used is an insulator and the charges that build up are on the external plastic surfaces.

A far greater risk is a fire from other causes so having a fire extinguisher in a workshop shop makes sense. I wonder how many people who spent time adding a wire to their PVC ducting even have one in their shed?

Before worrying about static explosion everyone should worry about sealing powerpoints against inhabitation by ants? Some ants set up house in one of on the less used powerpoints in my shed, the corrosion caused by their waste and bodyfluids allowed a small current to flow which started melting and decomposing the plastic of the powerpoint and could have started a fire in in my shed. Luckily I saw the smoke and was able to prevent the fire from getting started. Even though this is a verifiable event have I or should anyone run around and seal all their power points against ant invasion - of course not.

The nice thing about this arrangement at the moment is that the investment is small. This wont be the permanent position for the machine so until I sort it out this looks like it will do the trick fine.

My dust shoe arrived this morning and I am really happy with it. I cut a couple of sample files from vcarve pro and I couldn't smell anything in the air so it's doing a good job of collecting at the source.

[ame=http://www.youtube.com/watch?v=3U1pB9GSK7g]YouTube - Dust shoe installed - cutting conrod sample[/ame]