31 – Make Your Own Pre Filter for MDF Fumes (17:31)

The Lightblade Learning Lab with Russ Sadler

The Lightblade Learning Lab is a series of videos that Russ did for Thinklaser Limited based on using the Lightblade 4060 Laser Cutting and Engraving Machine. Thinklasers Lightblade 4060 has a 400 x 600mm bed size and was supplied with a 60W EFR laser tube. In this session, Russ designs, builds, installs and tests a pre filter that stops sticky MDF fumes reaching the expensive filters of his Purex fume extraction unit.

Make Your Own Pre Filter for MDF Fumes
Make Your Own Pre Filter for MDF Fumes


  • Problems associated with cutting MDF (Medium-density Fibreboard) – external filters getting blocked.
  • Cutting one of Russ’s designs out of 5mm Perspex with a 2” lens, 8mm/s, 100% power
  • Mark 1 designs for the Pre-filter in this video are here:
    • Adobe Illustrator File (.ai)
    • DXF file (.dxf)
    • (see next video for Mark 2 designs)
  • Explanation of how the design mounts in the machine.
  • Assembling and gluing the main body of the filter unit.
  • Looking at the filter material.
  • Assembling the filter cover.
  • M4 plastic screws for holding the design together.
  • Filter material is 12-15mm thick quilting material bought from Dunelm
  • Cutting and trimming the material.
  • Fitting the filter unit into the machine.
  • Testing the filter unit.

My thanks go out to Tom at Thinklaser for giving permission to embed these videos on this site. If you are looking for a new laser machine from a quality supplier, then I would suggest you check out their website: www.thinklaser.com.

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Prefilter Mk 2

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What can a laser cutter cut?

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Transcript for Make Your Own Pre Filter for MDF Fumes

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0:14Welcome to another Lightblade Learning Lab in today’s session we’re going to make a

0:20new addition for this machine now I’ve been advised that quite a few people are

0:27having trouble with their either Bofa, or their Purex filter unit

0:32when they’re cutting MDF the debris and the smoke has been quite heavy and

0:39they’re blocking their filters up quickly I’ve been asked to look at the

0:42possibility of copying somebody else’s pre-filter well I’m afraid that’s in

0:50itself a bit of a challenge because I don’t like copying other things

0:53if there’s a problem I like to think about the problem and try and find a

0:57cost-effective solution so that’s what I’ve done hopefully I’m going to make

1:01a very simple cost effective pre-filter for this machine that will be

1:07easily either replaceable or washable which is the ultimate goal you don’t

1:13have to ever buy new filters what I’m going to do is dive straight in

1:17and cut the pieces then we’ll put them together and see how the thing works, Now I’m making this out of

1:24nominally five millimetre Perspex it’s white Perspex which I just happened to

1:28have some spare of so it’s whatever it is but you could make it out of a five

1:35 millimetre plywood or five millimetre MDF I don’t think it really matters

1:39now I’m using a two inch lens on here and I’m cutting this at maximum power

1:48running I think about eight millimetres a second

1:52well there’s our first pieces cut all the pieces are just falling apart which

1:58is very nice

Transcript for Make Your Own Pre Filter for MDF Fumes (Cont…)

2:01and yeah they fit in there nicely I’m only just about fits on the table I

2:06think it’s about 395 or 398 back-to-front so yeah this is a tight

2:13squeeze to fit this onto the table okay my second piece of material that I’m

2:18going to be cutting is big enough to do the job but it’s a very odd shape as

2:23you can see underneath it so what I’ve done I’ve purposely cut my first piece

2:28out of a nice square item where I can see exactly where it’s going to go and

2:33now what I’m going to do is to register where the start point is and make sure

2:38that this aperture fits over the material so I now know that the

2:45cut is going to fit onto that piece of material there we have the last part

2:50cutting and yes it’s going to come out of that funny shape and there we go

2:54that’s all fallen out nicely

2:57even all those little three millimeter holes

3:03if you’re making it from wood you might well be putting just ordinary wood screws or

3:09some self tappers in these little pilot holes I’m going to tap them m4. Up to now I’ve

3:16purposely been trying to hide what I’m going to do we’re going to start showing

3:21you now how things work now look these two pieces here have got some

3:28interesting cutouts in them these cutouts here are flexible tongues

3:33they’re quite stiff but they do flex and the idea is that that’s these two pieces

3:40click together like this and then they will actually go in the extract tube at the

3:48back there and they’ll go in easily until they reach those little barbs when

3:54I shall have to go and push it in so once the whole thing is assembled that

4:00will sit snugly in there but you’ll be able to take it out so that begins to

Transcript for Make Your Own Pre Filter for MDF Fumes (Cont…)

4:09give you a little bit of a clue as to what I’m trying to do now we’re gonna

4:16build the next part well here are the eight parts that are going to make up this

4:21filter now I need to assemble them in the right manner so I need to start with

4:29that one and as I said these crossover they will poke

4:37through there

4:41like that they are quite loose but that’s because this material can very

4:47anything from 4.5 to nearly 6 milliliters so it’s incredibly difficult

4:53to get these holes to fit perfectly I made the holes four point seven knowing

4:59that quite a lot of this material was undersized but I came across some stuff

5:03that was nearly six mil I think the first thing we do is to pop this piece

5:06on we’ll put it on first and we’ll glue it on from this side so using my PDTG

5:14glue which seems to work extremely well on acrylic now I’m not going to be too fussy

5:20about the glue this time because nobody’s going to see this piece okay so

5:25that’s it sits nicely on my box now I can put just another little bit of glue

5:31along the bottom corners here as well I mean this is an incredibly simple

5:36assembly what we’re now going to do is just drop that on there like that these

5:45are all exactly the same and they just work they way around nose to tail

6:00like that now if i’ve got all these bits designed correctly this bit will now sit

Transcript for Make Your Own Pre Filter for MDF Fumes (Cont…)

6:09on top here and there we go that’s the complete assembly. Now all I’ve got to

6:18do now is to go around and just glue these joints and the whole thing will be mmm

6:28almost finished just give these another few minutes to dry another minute or so

6:37then I can turn the whole thing over and I can finish off the tabs underneath and then

6:45just to make sure it’s nice and really strong I’m gonna run a bead of glue

6:54around the edges and when that’s dry I should do this edge here as well I

7:02should wait for that to fully dry before I assemble the last parts well here we

7:11are next day and I’ve just been and bought what I thought were going to be

7:16the ideal thing to fit on there that’s what I’ve designed and then these things

7:20which are standard computer filters the day plan was to just stack nine of those

7:29up but now that I’ve got them and I take them apart and have a look at the

7:36filter material look you can see it’s probably pretty next to useless it’s

7:44probably fine for taking lumps of sugar out of the air but not for very fine

7:49particles of MDF smoke so plan A in the bin but fortunately I always did have a

8:01plan B when I designed this but Plan B involves making a few more pieces now I

Transcript for Make Your Own Pre Filter for MDF Fumes (Cont…)

8:09didn’t have enough material to make that in one piece so I have to make it

8:15in two pieces but what we’re going to do is we’ve got these extra pieces as well

8:29so let’s make sure we get them all the same way because there’s a long end and

8:33there’s a short end as you can see so I need all the long ends working the same

8:38way so that I can put them in long end log in that way we should just turn that

8:48over and assemble at the other way because I can’t glue it this way okay so

8:57now we’ll just pop some glue on those and get that held together now the most

9:02important thing at the moment is probably these joints here because

9:07goodness me that’s raining outside now I can just hear it

9:14so I should just hold those two joints together

9:23just make sure they press together and then I should be able to just gently put

9:32a little bit of stuff along those joints there to get those to bond together

9:42right so now that we’ve got that upside down or just do what we normally do and

9:47just run round all these joints here just to make sure that we’ve got them

9:53nice and strong well okay what’s it cost us so far

10:00some design time and either some MDF and maybe a few screws now screws are

Transcript for Make Your Own Pre Filter for MDF Fumes (Cont…)

10:08the interesting thing because I happen to have some very nice M4 plastic

10:14screws which is why I designed these holes with M4 just look I’ve got a bag

10:19of these that’s been kicking around for about twenty years so I have to find

10:23useful on sometime when my other filter system failed I went to a store which

10:33I’m sure you’ve all come across called Dunelm

10:36now it’s not the sort of place you’d normally go for engineering equipment

10:41but look what I’ve got for four pound I bought a meter and it’s material that

10:53they use for quilting but look it’s absolutely amazing it’s exactly what

11:01we’re looking for by way of a filter material and I’ve got all this a meter

11:09of it for four pounds so that’s the only real cost of this project and I’ve got

11:18enough there to make probably six filters or replace the filter that’s in

11:24here six times whichever way you like to look at it so I don’t think it has to be

11:28cut all that accurately because it’s sufficiently flexible that

11:31it’ll push inside my frame here and if it doesn’t I’ll just trim it off looks

11:37like that might need a little bit of a trim but no big deal now I’ve made this

11:52dimension here 10 millimeters thick but this looks to be about probably 12 to 15

11:56millimeters thick so it will squash down you’ve only got to increase this by

11:59another 10 or 20 millimetres and you can put three or two thicknesses of this

Transcript for Make Your Own Pre Filter for MDF Fumes (Cont…)

12:04material in there I mean it’s just literally almost invisible to airflow

12:09what I have to do is just trim the corners off just to clear my screws I think I’m

12:19only going to need the four corners to hold this on and my over-enthusiastic

12:25use of holes is not in the least bit necessary that works perfectly okay with

12:32just four corner screws now what you’ve got to remember is that each one of

12:36these holes is the same size as the extract duct so the velocity of air or

12:43volume of air through these holes will be 1/9 of what it is down the extract

12:49duct so there’s virtually no air resistance through this filter at all so

12:53because there’s so little pressure loss across here you won’t need an additional

12:58extract motor you can use the fan that’s already there which is why this will

13:02just disappear in the machine and it will be seamless now this is so

13:06relatively cheap to make you could technically have two of these so that

13:11one of them is in your machine and the other one is out being replaced but it’s

13:17only going to take what, 20 minutes to take this out of the machine and put a new

13:21filter in it? okay well let’s take a look in the machine and see where we’re going

13:27to fix this now you had a bit of an idea because you saw me trying this little

13:32piece at the back here this is very asymmetric so we’ve got to fit it in one

13:36way only and it goes in this way but we have to be careful because at the top

13:42here there’s a bit of a ridge and so what

13:46I’ve got to do I’ve got to put it in basically flat like that get it beyond

13:50the ridge and then tip it upright and that will then get me past this belt

13:57there we go – clicked into place and you can now see the reason where I’ve got that little

Transcript for Make Your Own Pre Filter for MDF Fumes (Cont…)

14:08foot there just to keep it level we’ll just turn the extract system on to make

14:13sure that the filter doesn’t go off and suck in

14:26now I’m just going to do a 25 millimeter test square on some it’s it’s hard board

14:32which is sort of MDF type material

14:47we can see the fumes being drawn backwards

15:07that cut can go a lot faster because it smells smoky

15:12it smells smoky and it looks smoky and look it’s leaving marks on my hand

15:19just clean my fingers

15:25still a little bit

15:28but not as bad

15:33just try pushing it a little bit more 22 maybe or 24 lets try 24

15:42it hasn’t dropped out but it will pop out

15:49and now let’s try a clean finger

15:57there we go 24

16:01maybe it would go to 26

16:06just only just making it, look it’s pushed the bottom out now

16:14so that is not a good cut looks to be about 24 millimeters a second is the

16:19good speed to go for but the whole point there was we’re trying to generate some

16:24smoke now I doubt whether I’ve generated anywhere near enough smoke to see anything on

16:29the filter but let’s have a look I don’t know where it’s come from but

16:35we’ve definitely got some bits of debris on these two here which is approximately

16:42underwear we were dragging the the fumes from so this is something that I think will

16:47have to be field tested by somebody that uses a lot of MDF all day well I hope

16:53you found that another interesting session a practical problem and a

16:58practical solution I’ve enjoyed the design challenge and I think we’ve come

17:03up with something which is very cost effective and simple for virtually

17:06anybody to adapt and fit as I mentioned earlier the drawings will be available

17:11on the Thinklaser website so you can take those drawings and make it fit your

17:15own machine I’m certainly going to be leaving it attached to this machine

17:20because it can’t do any harm whether it’s going to do any good will be for

17:24other people to tell me so until the next session I’ll say cheerio

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Last updated April 25, 2024


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