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11th January 2021, 10:36 PM #1Intermediate Member
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Improving benchtop thicknesser dust port
Hi everyone,
I am looking for some advice on ways to improve dust collection on a lunchbox type benchtop thicknesser. I have a modified generic 2HP DC venting outside, with 150mm ducting.
The thicknesser has this configuration:
IMG_20210111_172634.jpg
There is a detachable cover/sheath (red) which takes air from the motor fan and distributes it via two passage above the spindle and rollers. The only other inlet is via the gap by the cutters/spindle which varies from 2-15mm due to the fluted spindle.
A connector (yellow) piece then connects at the outlet of the machine and has a 47mm outlet at 90 deg. to the airflow direction. Whilst the interface of the connector to the thicknesser is 52mm in the shortest dimension, the outlet from the thicknesser is only 40mm, and 7mm of that is covered when the connector is attached (lower edge).
Here are some pics of it in the flesh:
IMG_20201026_171642.jpgIMG_20201026_171630.jpgIMG_20201026_171611.jpg
The cross sections of B (80cm2) and C (138cm2) are both substantially lower than that for the 150mm ducting I have (176cm2), and A is even less again. The cross section of B is similar to that of 100mm ducting (79cm2), however I would expect the airflow to be less due to the rectangular shape. Whilst the height of the the cover/sheath could be raised to increase B and C, the inlet via the cutters/spindle will remain the choke point, unless the cover/sheath is raised to allow airflow in from above the motor. This would most likely compromise the safety of the machine so isn't really on the cards, and may not be providing the extra airflow where it is actually needed.
As as I see it the options are:
A) replace the cover with a new connector with a transition from rectangle to 150mm diam. (I can't see this having any extra effect over option B).
B) replace the cover with a new connector with a transition from rectangle to 100mm diam.
C) split the 150mm ducting into 3x100mm, with one going to the connector and the others positioned at infeed/outfeed
D) purchase life insurance and screw with the cover/sheath
E) invent time machine, go back in time and research dust extraction before purchasing a thicknesser
Any thoughts, suggestions, criticisms etc. would be very much welcomed
Cheers,
Darcy
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11th January 2021, 11:09 PM #2SENIOR MEMBER
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I'm sure the dust extraction gurus will chime in but on a slight pull off topic, how do you like the actually job the sherwood unit does with that helical head, very nearly hit buy on one today.
Back to the dust .. to me option b would be the starting point and than transition immediately again to the 6" ducting of the air flow is fast enough to pull the chips away .... I notice that they don't show that shroud in any detail on the website
One thing to consider is that the cutting head is throwing the chips at considerable force out of the unit, just look how far the chips will fly on an unshrouded unit. This says to me that you need a higher speed airstream to redirect the chips sideways and not have the shute/shroud clog up.
I was considering this if/when i buy one of these and like bitingmidge is doing for his jointer will look at designing a new unit that is a little more aerodynamic. I'l say again that I think turning the chips effectively 90 degrees to their propelled path is the challenge and why the wider body pro units all seem to center the port facing straight back.... The sales guy today was determined to tell me the right angle exit was better maybe it is
Cheers
Phil
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12th January 2021, 12:21 PM #3Woodworking mechanic
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I, personally, would go straight back - sloping upwards. The reason as I see for the right single outlet is to stop it getting in the way and to shoot chips out sideways rather than on the person that maybe standing at that end of the thicknesser, if it wasn’t hooked up to a dust extractor. Not all purchasers would have extraction systems.
A single 150mm outlet from the thicknesser might be a bit cumbersome given its size and the size of the thicknesser itself, so maybe multiple outlets going to a suspended manifold hooked to the 150mm system.
On my Dewalt, the internal outlet is 56mm with a 100mm surround. Thats hooked system via 100mm Flexi going to the 150mm system. It works great but the Dewalt has a chip ejection fan and that really helps
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12th January 2021, 07:31 PM #4Intermediate Member
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I haven't actually tried it, purchased a few months ago and having been sorting out DC since then. Timbecon sent me a 10% off code email randomly and that was enough for me . Hopefully have it hooked up soon, once I do I can post some pics.
Thanks for both your inputs, I think I will try option B first and see how it goes, and if heaps of dust and chips are coming out the front/end I will go to C. For fine dust C is probably necessary, although I do have some forced ventilation.
I will definitely be going straight back as is common in the bigger machines, either sloping up or out sideways at 15 deg. to get it out of the way. I can't see how the right angle exit is effective...
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13th January 2021, 09:05 AM #5SENIOR MEMBER
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Not sure if I have have the patience right now to wait on a discount code although the old GMC lunchbox is still functional be great to get your impressions after you have tried it out.
There are at least two threads that for the life of me i can't find at the moment on the site that provide some interesting food for thought on setting up effective dust collection that could be related to these units. The most relevant may be a discussion on router table dust collection where it is all being collected under the table using flow past as well suck, ie the front of the table provides enough open area to cater for full flow even if the router plate area is fully blocked.
I call it relevant as routers in general will expel chips and dust like a thickie at high speed.
The other thread was dealing with fine dust from a sanding setup where the best collection happened when the input piping was open at the end opposite the dc pipe.
For the lunchbox thicknessers apart from chip size the volume, direction and speed of the chips and dust should be similar between full length blades and segmented cutters. I've watched how the chips at least get expelled from the un dust collected GMC with the majority expelled in line with the board being put through, if its a two inch board you get mainly a 2" stream with some scatter to the sides. I have the video gear to collect some slower speed footage and will try to do that on the weekend.
So thinking about this we would always have a high speed stream of chips and dust to the width of the timber being put though and this has to have some effects on the DC setup. Straight back is no doubt highly effective because as users we tend to run boards through the middle area and we rarely run full width boards.
Now if you want the chip/dust stream to change direction it needs a reason to... open the far end of the pipe and create a high volume air stream that will by default capture the low inertia dust particles (fine dust) and also should turn the stream of chips. Ideally this air stream would be as laminar as possible at the start which is where a bell mouth hood on the open end would come into play.
I would think that combining 3 source back to the 150mm may end up being counterproductive though in practice taking the non full width use most of the time it may not appear so.
Anyway very interested in this as i'm likely to end up with the same unit and getting more concerned about DC all the time. Really enjoying not sweeping up besides the health benefits
Cheers
Phil
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13th January 2021, 11:42 AM #6Woodworking mechanic
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13th January 2021, 12:09 PM #7GOLD MEMBER
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If you haven't tried it yet how do you know it needs improving? I'd be hooking it up to a 100mm hose and see what it's like before contemplating any modifications. Very interested to hear how the thicknesser performs, those units look to be a best buy on the specs.
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13th January 2021, 12:36 PM #8SENIOR MEMBER
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I know it's a vendor video but it's interesting for a couple of things even if this isn't the true spiral unit, Choosing Your Thicknesser : Spiral Cutter or Straight Blade? - YouTube
For DC it seems the segmented cutters left more debris on the outfeed table though considering what went through it was minimal, so it would seem that some improvement might be had but it seems to be pretty good out of the box.
Here's one looking at the spiral head version: Sherwood 13" / 330mm Helical Spiral head Thicknesser Review - YouTube
Looking at the videos and specs on thing is the inserts on the spiral head have a small overlap and therefore shouldn't experience the ridges you see sometimes with the segmented cutters.
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13th January 2021, 09:04 PM #9Intermediate Member
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I'll try have a look for those threads. I suppose the issue at hand is the fine dust that escapes from the infeed/outfeed. The chips that escape are a pain in so far as they must be swept up, but shouldn't cause concerns to the machine or health. The fine dust however...
My reasoning essentially comes from the readings from this forum. The current outlet has a sharp 90 deg. turn and to a 2" outlet. That must provide two fifths of f all in terms of fine dust collection. Based on the Bill Pentz exhaust requirements, 400CFM is needed for chip collection for planers (thicknessers). It is possible that the fan power of the thicknesser makes up the difference between 2" CFM and the 400CFM required, but I couldn't say without trying. As Lappa said his works fine so it may be enough, but only for chip collection. For fine dust you need around 1000CFM, which is acheieved by 150mm ducting, or 3x100m. Since I can't really alter the thicknesser to increase the input airflow, the 3x100mm seems the best option theoretically, where 2 of the pipes would ideally have bell mouths and more-or-less unrestricted input airflow. The annoying thing about fine dust is that you can't see if, so I can only go off the advice from these forums. However, there is no harm in trying the standard 50mm outlet with 100mm adapter and seeing what happens for chip collection. If its not a problem then possibly I could use the standard connector and 2 extra 100mm on the infeed/outfeed if i'm really concerned about fine dust.
I can definitely take some videos of the different options, although I can't promise when they will be
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22nd March 2021, 06:01 PM #10
I'm sorry to have arrived so late to this party - not for the first time, I'm going through the old "does my (de)thicknesser really need an upgrade" and was about to launch the following into its own thread!
My thicknesser is a cheapie, around 25 years old, bought from Trade Tools who amazingly still stock parts for it, or did when I broke a sprocket a couple of years ago!
It came with a standard cowl and no provision for chip collection, and a bolt on variant which had a nominal 4" port. I can't for the life of me see why they stopped making them this way as it works very well indeed and gets over that immediate 90° turn problem. Presently it sits with a 3d printed sleeve which gives the PVC connection a tight push-fit, and one of my printed magnetic connectors - and that's the way it's going to stay. Below are the reasons why, and if anyone can provide a compelling argument for me to go ahead with the "improvements" I'll happily do so in the fullness of time.
21-03- 22 at 15-47-51.jpg
Because I had to model the machine to do what I was doing, here's a diagram of what it looks like "under the hood" - the limiting factor is always going to be the area of inlet air available. @BobL posted a table from Bill Penz on the above mentioned jointer thread from which states that to remove fine dust from a 20" planer requires around 900 cfm. With no basis for my assumption whatsoever, I guess that a 12" machine will probably require less than that, but note also my observation that the "smell of fresh-milled timber" that accompanies machining is most probably dust particles being drawn into my unwilling sinuses! (Note: out of habit I wear a respirator when using this machine and keep the exhaust fan on as well, but the problems does seem to be minimal).
21-02- 18 at 23-44-59.jpg
Some time in the past (around 15 or twenty years ago) I made a plywood copy of the connection modified to take a 6" pvc connection. It was a cumbersome thing to connect, completely out of scale with the machine and I gave it up after a short trial period, having seen no improvement whatsoever - (If you go back to the original thread from 2004 - you'll see a few "I told you so's"! Sadly no pics have survived there or on my files.
Recently, I wondered if by using a sort of cross between the "modern" cross-pickup and this one would work, and to give a bit more airflow to allow a 6" connection I thought I might add a 50mm wide slot at the back of the machine to enable a greater airflow - however I remain unconvinced that would happen without affecting the chip collection of the machine, but this is kind of what I was thinking:
21-02- 18 at 23-51-44.jpg
Finally - there's an option to provide a better air flow to the existing connection - I had originally also thought of incorporating a slot along the bottom connection to try to improve fine particle connection, but in the absence of any way of measuring the outcome I've abandoned that for the time being. Here's my current thought on improving the design of the hood - the articulated surface split into two are due to my drawing inadequacies but they serve the purpose for now.
21-02- 18 at 23-48-26.jpg 21-02- 18 at 23-50-24.jpg 21-02- 18 at 23-44-33.jpg
So, do I say "good enough" to my present setup? Or pursue the option of adding the slot, and getting more airflow? None of this will happen in the near future, but I'll eventually work my way round all of my gear and come back to this!
Cheers,
P
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24th March 2021, 06:42 PM #11
Good Morning Darcy
I hesitate to post this as I "just know" that BobL will cringe when he sees my back of the envelope calculations.
The carrying capacity of your proposed extraction system depends on the diameter of the ducting and choke points less friction within the system. The DC extraction is fixed by your DC.
Nominal Calculations: The exit from the shroud appears to be 47mm giving a cross section area of 1,735 mm2. Increase the exit diameter to 100mm and the cross section area rises to 7,854 mm2, a gain of 450%. Increase the diameter to 150 mm and that area rises to 17,671 mm2, a bit more than double the capacity of the 100 mm duct. And so on.
Effect of Friction: There is a friction zone within any duct which reduces the effective diameter of that duct. Some will argue that it is around 3 mm, but I prefer a more conservative 5 mm to allow for Murphy and the unknown unknowns. The "effective area" of the 47 mm exit then drops to 1,075 mm2, a drop of almost 40%. This is significant.
The recalculated "effective area" of the 100 mm duct is than almost six times the area of the 47 mm, meaning it will carry six times the volume. The 150 mm duct will carry almost three times the volume of the 100 mm. I would suggest that this is a strong reason to go with the 150 mm duct. But the triple 100 mm system would only carry about a quarter more than the 150 mm duct - diminishing returns for effort?
Duct Friction.jpg
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24th March 2021, 08:42 PM #12.
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The biggest elephant in the corner on this machine is the gap between the thicknesser head and the dust collection shroud/cowling.
The amount of air through the motor etc will be minimal as motor fans don't move much air through the small restrictions around motors.
According to the diagram the gap is between 2 and 15 mm so unless something is done about A not a lot more air is going to be pulled through that gap.
The head will act like a little impeller but the added suck from one side is negated by losses on the other.
Opening this up has it positives and negatives - it should improve air through put but may also lose a few more chips
Thicky.jpg
My first effort would be to reverse the shape of that gap into something like this - ie semi BMHS shape
Thicky2.jpg
The next elephant, or maybe a Rhino, is B.
The cross sections of B (80cm2) and C (138cm2) are both substantially lower than that for the 150mm ducting I have (176cm2), and A is even less again. The cross section of B is similar to that of 100mm ducting (79cm2), however I would expect the airflow to be less due to the rectangular shape.
Then C has a similar problem.
In other words putting a 150 mm duct in this machine will be significantly stymied by A, B and C so unless these are enlarged there will be little gin in performance.
This is why I completely rebuilt the cowl ingon my planer/thicknesser combo.
The generic 2HP 10" planer/thicknesser dust control issues
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25th March 2021, 09:32 AM #13.
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25th March 2021, 12:48 PM #14GOLD MEMBER
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LickinChips, the OP, hasn't been seen since January. Perhaps he found that the dust extraction on his machine worked fine in its original guise, perhaps he's modified it and he's happy, who knows. So is all the chat about improving the dust extraction, choke points etc., etc. possibly totally pointless?
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25th March 2021, 01:46 PM #15
I think there is a point other than just continuing the conversation: One of the things I am finding frustrating with this forum at the moment is that searching is pretty difficult - Search <12" thicknesser dust connection> for instance and you'll get no result, so try < thicknesser dust connection> and this thread comes up first. If you dig deep enough, you will find info from decades ago, which is not always in line with current thought, so updates are never a waste of time.
So, when looking for somewhere to "dump" my post, this seemed logical - it's still current after a fashion and searchable for others in the future who may find it useful.
There may be other better threads buried somewhere, but I can't find them so I presume neither can others who are about to ask the same question.
That's why I've started separate threads of late for Jointer, Table Saw, Shed Ventilation and Router Fence, to enable others to find them at some point in time.
Still to come - Bandsaw and belt sander! (You have been warned.)
Cheers,
P
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