A while back there was a discussion about home made drum sanders and how to
build one. A search on the net didn't really come up with much so the wheels
or should I say drums in my head started turning and with my trusty pencil I
started sketching. First I listed the key features I wanted from the sander,
one was a drive mechanism for the material and second I wanted the drum to move
up and down and not the table. Seems most people want to follow deltas lead and
move the table which I find very undesirable. So after many sketches and scratching
my head I came up with a design I thought would work, but before I started I
wanted to see this thing in 3D so not having much cad experience I decided to
mock up the sander with wood like I wanted to build it. Prepping a bunch of one
by one stock I started assembling and before I knew it there it was the sander
I had envisioned in my head. As you can see in the picture below are the acme
screws attached to the take up bearings that will raise and lower the drum by
way of a chain drive.
At this point I was able to make changes and check dimensions in actual size,
now the lifting mechanism may be a bit cumbersome but it works pretty well.
This could be built out of wood fairly easy but I chose to use one by one steel
tube and weld the frame together, as you can see in the next photo is the sander
with parts installed.
As you can see it came out pretty much as it looked in the mock up. The drum
is constructed of oak and birch ply. I had just enough scrap pieces left over
from previous projects to make 29 4 1/2 inch round pieces then I laminated them
together to create a 22" drum.
The platen is made of two layers of 3/4" melamine, the drive belt was bought
from Klingspor it is a 100 grit paper back sanding belt that was specially made
to my specifications.
This is a close up of the gear motor for the drive belt. It's a 17 rpm 25 in/pound
gear motor, connected to the drive roller by a #25 roller chain.
Also seen is the drum height wheel assembly. This is attached to the two acme
screws by a #40 roller chain and sprockets.
The picture above is the height adjustment assembly. The acme nut is welded
to the sprocket and the sprocket sits in the flange bearing. The set screw at
the top of the acme screw which holds the screw to the take up bearing can be
loosened for a fine adjustment of the drum.
Here is the belt tensioner which keeps the belt tight as the drum is lowered
and raised. This set up works pretty well but still needs some tweaking.
Here I am truing the drum with some 60 grit sandpaper, I glued the sandpaper
to 1/4" ply and letting the drive belt run it through. Even though I used
a hole saw to cut all the discs they still came out a little uneven.
Still truing the drum but here I started putting together the dust hood. This
material is a poly carbonate plastic which is very durable, however it's very
hard to glue together. IM on my second attempt and IM still not happy with the
end result, there is a 4 inch dust port in the top center which isn't in this
picture.
Tue, 9/30/08 4:53 PM
This next picture shows the larger pulley installed on the drive shaft, which
in my estimation slowed the drum down to 2100 rpm it runs much smoother now.
Also you can see how I attached the sand paper to the drum. I cut a kerf in the
end and slipped the end of the sand paper in then inserted a screw to hold it.
Here is a interesting fact and something I didn't take into account, the drum
is 21" long and it took 7 wraps which is a total of 109.5 inches long. that
is 150 grit by 3" purchased from industrial abrasives for my initial tests.
Woohoo look at the dust go! this was an exciting moment after working on this
for the past month. Here I took a rocking horse blank that I had glued up and
ran thru, when I first sent it thru I forgot to turn the dc on and the dust
went every where but once turned on hardly any escaped. IM really not happy with
that dust hood and plan to make a new one this weekend. I made 6 passes on each
side and ended up a total thickness of 0.73, a little under but at the time I
made the parts for this horse I didn't have the drum sander and planed the stock
to roughly 0.76.
This next photo shows the enlace for the horse going thru, I needed to see
how it handled small pieces these on lays are about 6" long.
everything is working great so far so as I make changes ill update them here.
Below are some thumbnails to a few other pictures. Just click on them to get
the full size.
15
Meg. movie file
The tracking and belt tension assembly.
Above is a shot of the rear of the sander, the open space below the drive belt
will have a cabinet for supplies.
Here is a shot of the motor, this is a 1 1/2 HP. 3850 RPM pool pump motor that
surpluscenter is running a special on for 39 bucks. I thought this was a great
deal for this application.
I had to modify the shaft sorry no pictures, however the shaft has a threaded
end and all I had to do was cut off the threaded portion and put a 5/8 shaft
coupler on.
All the parts for the sander including the motor where bought from Surplus
center, the steel was bought from Metal Mart USA.
The gear motor I found on eBay with the speed control for 40.00
this is a 17 rpm gear motor with 25 inch pounds of torque. The motor is a
permanent magnet motor and runs on 90 volts dc. I have found that 17 rpm is
way to fast to run the motor, 5 rpm is about as fast as it should run and
slower. Some things to know about controlling the speed on a dc motor, you
cant just reduce the voltage to make the motor run slower without sacrificing
torque. So you need a speed control that has the ability to create PWM (pulse
width modulation) what PWM does in simple terms is turns the motor voltage
on and off in intervals to adjust the speed with out loosing torque. If your
handy with a soldering iron or know someone who is, there is a kit available
for the speed control. you can read more about PWM and the kit here. PDF
file keep in mind
I have no affiliation with this company IM just supplying information.
click here to learn about belt tracking.
The final cost of putting this all together is right around $500.00.
Some things that can be changed are the drive shaft, I used 1" and 3/4"
will work just as well. The frame can be made of wood and probably would look
nicer. I chose steel just because plus IM a half ass welder. The motor is a 1
1/2 hp. 3450 rpm, currently IM running this with a one to one ratio. IM thinking
of using a larger pulley on the drive shaft and slowing the drum down a bit.
This may also lesson some of the vibration that IM getting.
Ill Post more pictures in the next week or so when IM finished and I have done
some real world testing.
Thanks for looking.
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