Thread: The generic 2HP 10" planer/thicknesser dust control issues

Interested in this and will be watching.

The aim of this exercise was to make a collection hood that would double the size of the dust collection port and ensure that more air could enter the hood to generate more flow

After a few measurements I realised that space inside the machine is VERY tight.
The hood has to be able to rotate thru 180º so that when in thicknesser mode (table up) a microswitch engages to allows the motor to run.

The design was sort of fluid, changing as I went to over come a number of obstacles that I never knew about at the start, so lots of problem solving along the way.

I started with copying the basic external shape of sides and bottom of the existing hood onto a piece of sheet metal.

The material I used was the SS plate from a clothes dryer dryer drum.
I collect these drums because the SS is incredibly useful for many projects and it does not need protection or finishing.
The SS is quite thin (much thinner than the material the original is made of) but once assembled the new hood holds together pretty well.

I was going to TIG the whole thing together but I am so glad I didn't do that because;
a) I just knew I would have to remove and modify some parts (sometimes more than once) as I went along and
b) the pop rivet method means pretty well anyone can copy this once they see how it is done.

I basically lay the original hood side onto the SS and traced around the hood adding some metal tabs at various points to hold the hood together.
Below you can see the rectangular tabs I allowed for in the plan.
Eventually the two upper LHS tabs were reduce in length to about half that shown in the photo
Sketch.jpg
Thin SS cuts very easily with tin snips and leaves a clean safe edge (in contrast to an angle grinder)

Bending the tabs is done easily enough on this simple bending rig - a piece of 75 x 100 x 6 mm angle iron held in a vice.
I clamp along the tab line and use a wooden mallet to bend the tabs
DIYBender.jpg

The photo below shows the two sides and the base ready for pop riveting together.
Tip - drill the holes in the tabs on the sides before bending the tabs.
The rivets are also SS and all bar a few rivets can be inserted from inside the hood.
This means the flatter heads are on the inside and the rivet tails are outside the hood which provides a more streamlined internal path for the air flow.

parts.jpg

Below is the completed hood side by side with the original.
The most obvious difference is the size of the openings.

P1 (planer mode collection gap) and T1 (thicknesser mode collection gap) are significantly larger than the original PO and TO.
The original hood also uses a tilting panel that flips to direct the suck to the desired collection slot.
The problem is that if a 150 mm duct is use the panel robs the flow so I have completely done away with the tilting panel and both openings are fully open all the time.

The mode that has the biggest advantage is Thicknesser mode where the cutters are under T1. In this case, air will rush in through Pi and sweep over the back of the cutter heads and draw the dust away.
In planar mode (cutter above P1) air will preferably want to enter via the less restricted T1 but I'm banking on the fact that P1 is very large and the table will be enough of a cover to restrict some air preferably going into T1.

Comp1.jpg

In the photo below you can see how much larger the exit rectangle is from the new hood in comparison to the original which is placed on top.
Because of reflections etc Its quite hard to see the size of the new opening so I have shaded it purple.
The new opening is twice as large as the original and it is the maximum size that will fit in that space.

Opening.jpg

Here you can see the lock down mechanism that holds the hood down firmly in thicknesser mode.
Due to space limitations I could not copy the original hood mechanism exactly in this area and had to use a different method to register the hood onto that steel cross rod so that it stays steady while running.
The middle metal tab is a piece of spring steel drilled with a sharpened TC tipped masonry bit.
The spring steel tab holds the hood much firmer than the original - its a two handed operation for me to lift the tab.
Lockdown.jpg

When the hood flips over into planar mode all the locking mechanism shown above above has to fit under the table.
This required constant refinement e.g. timing the corners off the major triangular support braces..
Here you can also see how the locking tab is held in place with a couple of Hex bolts.
LockingMech.jpg


The micro switch actuator rod (MSR) is a steel rod that locks to the hood through a thickish Al brackets on the hood using 3mm split pins.
The MSR makes contact with a steel pin attached to a micro switch inside the cast iron frame.
This prevents the motor from running in thicknesser mode unless the hood is in the correct position

I have moved the MSR aside so you can see the split pin holes in MSR.
Given that space is a premium and needing everything to line up, this was by far the most difficult section to fabricate.
There are lots of little details in this section that are too difficult to explain in a few words - if you try it you will see how well everything has to fit.
My major problem was I ended up making the hood was about 2mm too wide so I ended up locating the left hand bracket(BL) inside the hood whereas the bracket on the right is outside the hood.
Ideally they should both be outside the hood.

Microswitch.jpg
I originally made the hood top connection strip of SS between BL and BR as a flat piece of SS but this was too floppy an left the whole hood floppy.
I remade that piece adding 10 mm wide full length tabs down each of the long sides, this stiffened the piece and the whole hood.

Here are a couple of views of the hood in thicknesser mode
OnTop.jpg

Top2.jpg

Now I need to make a new rectangular to 150 mm diameter round adapter so that the hood can be connected to 150 mm flexy.

I would classify this project as Tricky to Very Tricky.
If you decide to do it
- make sure you keep the old hood
- check clearances twice as often, or more, as you think you need to.
- carefully investigate how the hood microswitch works

As soon as I have progress on the adapter I will post a few pics.

OK here is the adapter.

I opened up another SS clothes drier drum as I needed more SS.
Normally I just cut 3 panels out of the sides of drum but this time I took the ends of the drum to get a continuous long sheet.
I needed that as the adapter required a piece of sheet metal longer than a single panel.
I flattened the 3 folds out in the sides of the SS using a wood mallet supporting the SS on a block of wood.

The adapter is 250 x 80 rectangular to 150 mm diameter round, over a distance of 300 mm.
I added 20 mm wide tabs along each end and the sides to allow for enough material for joining.
I used the Ductevolution spreadsheet to work out the measurements
then I transferred that to the SS which looks pretty crinkly but I did flatten it out a bit more before I joined it up.
Transitions2r.jpg

I though a wooden former would help with the folding so I spent an hour milling and turning up a large former from the only large block of wood I had on hand and that was a piece of tuart - crikey that wood is hard. I then turned the 150 mm end round on the lathe and also rounded over the long edges.

former.jpg

In the end I didn't even use the former as the natural curve of the SS from being part of the drum and a few deft squishes by hand was enough to bend it into shape.

I basically fitted the rectangular end over the rectangular opening of the hood and clamped it in place and the added rivets till I had the shape.

Here it is in planer mode.
Transition.jpg

And in thicknesser mode
Transition1.jpg

I have got a long piece of 6" flexy which I use in short lengths on machinery but as it is highly corrugated and I need to use about 1.5m of it I'd rather not used it for this machine so I will wait till I get some smooth bore stuff before I test.
Transition2.jpg

A

While waiting for the smooth bore 6" flexy to come in I thought I would do a quick test using the corrugated flexy I have on hand to at least see what a minimum flow rate would be.

One problem with performing this measurement is the air speed in the middle of a 6" duct is now too high for my anemometer (max speed is 32 m/s) so I need to use a 9" test duct to do the testing.
This is major mucking around for what is a Q&D test that I only want to do once and with the smooth bore flexy.

However, I could still measure the air speeds from near the sides of the duct (~15m/s) to about 1/3rd of the way into the duct where it reaches 30 m/s, so if use 32 m/s as the max speed in the middle that will give me a minimum flow rate result.

Cutting to the chase the flow rate is 940 mCFMs and it doesn't matter whether the machine is on or not or whether its in thicky or jointer mode. Don't forget that's a minimum value and should improve when smooth bore flexy is used.

So fron 385 to 940 CFM thats a 2.4 x improvement - that makes it definitely worth the headaches involved.

I will repeat the test when I get the new ducting - I doubt expect it to be a lot more than 940 CFM

Thanks for the excellent write-up Bob, on your great project. The results of your work look as if you had used new material and certainly don't show the result of using recycled sheet metal. I know from past experience just how difficult it can be to straighten out curved sheet, because in times past I worked at a minesite/concentrstor mill and we had access to stainless steel skins off magnetic separator drums, when they had been replaced with new skins. This skins would have been about 750mm in diameter and 2000mm long, and had been removed by air arcing from the drum. The first stage of straightening involved running over them with the fork lift on the workshop floor, to get as much curl out as possible. This would make it possible to fit them into the powered rolls, in their fully opened position. They were placed in the rolls in a sideways orientation, and run back and forth, as the rolls were gradually closed, and the sheet gradually flattened out. Sometimes the sheet needed flipping to remove some curl, but eventually a pretty straight sheet was the result. I sure missed that place when I left for the access to handy scrap, excellent workshop equipment like the already mentioned rolls, the guillotine with over 1/2" full sheet capacity, lathes, milling machine, welders, hydraulic presses, (Servex 60 tonne and a 500 tonne horizontal press, which I don't recall ever using for a foreigner)

Cheers RT. Most of those clothes dryer drums are in pretty good nick when I takes them apart however there was one one that looked like it had been been tumbling something heavy as the drum was quite dimpled - with the bumps pointing outwards. Sort of the opposite to what motor vehicle body work looks like after they have been caught in a severe hails storm. I have often tried to think of what it might have been.

My sheet metal worker mate is doing exactly the same thing for my Minimax CU 300 combo!

Bugger laughed when he saw some of my very rudimentary metal working skills. Will post soon....

Originally Posted by Jeff Leslie

My sheet metal worker mate is doing exactly the same thing for my Minimax CU 300 combo!

Bugger laughed when he saw some of my very rudimentary metal working skills. Will post soon....

Sheet metal working mates come in real handy, . . . . sometimes.

Since I built this new hood some 2 years ago I have only ever put small numbers of short stock though this machine so I've not really had a chance to try it out for an extended period.

Last weekend by Bro came over with 60m of 125mm wide 21mm thick Jarrah floor boards which we put through the thicknesser using the new hood while my dust monitors were running.

All up it took about an hour and a half and at no stage did the shed air show dust levels above that of outside air. The outside air was actually dustier than the shed air, almost certainly because I got my bro to scrape and brush as much grit and crap off the tongue and grooves outside the shed while I started to put the boards through the thicknesser inside the shed. Next day we also compared levels of nasal booger dust coming out in the shower (I've found this high technical comparison to correlate quite well with dust detector findings). I had none and bro had some, but not the typical red colour you see with Jarrah dust.

Originally Posted by BobL

Next day we also compared levels of nasal booger dust coming out in the shower .

A highly scientific experiment there BobL!!!

Originally Posted by BobL

Since I built this new hood some 2 years ago I have only ever put small numbers of short stock though this machine so I've not really had a chance to try it out for an extended period.

Last weekend by Bro came over with 60m of 125mm wide 21mm thick Jarrah floor boards which we put through the thicknesser using the new hood while my dust monitors were running.

All up it took about an hour and a half and at no stage did the shed air show dust levels above that of outside air. The outside air was actually dustier than the shed air, almost certainly because I got my bro to scrape and brush as much grit and crap off the tongue and grooves outside the shed while I started to put the boards through the thicknesser inside the shed. Next day we also compared levels of nasal booger dust coming out in the shower (I've found this high technical comparison to correlate quite well with dust detector findings). I had none and bro had some, but not the typical red colour you see with Jarrah dust.

I'm guessing that there won't be too many requests for photographic evidence of booger test samples!. Good test data probably though, testing the effectiveness at the point of consumption.
Rob.