Author Topic: Drum/ Thickness Sander  (Read 38949 times)

Offline S. Heslop

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Re: Drum/ Thickness Sander
« Reply #50 on: January 30, 2015, 11:57:03 AM »
Simon
             Probably your supplier at a reasonably  approachable price is Wickes. I bought a long roll- about 12 metres long but only 10cm wide. It's about 12 a roll. How to join it is any bodies guess. All that I can tell you is that I bought stuff for an old Picador but it was only about 3" wide. The firm was Davis Abrasives then in Byker and is now in Cramlington. The joints were diagonally cut and scarfed and glued.

Maybe this helps. Let me know

Norman

Hopefully this sanding belt is going to work fine, but i'll keep that in mind if it doesn't.

Offline S. Heslop

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Re: Drum/ Thickness Sander
« Reply #51 on: January 30, 2015, 02:12:19 PM »
Sanded more of a crown into the rollers (measures about 1mm wider diameter in the middle) and it seems to be tracking now. Although there's a strange squeaking/ knocking sound coming from the roller itself that I can't identify. My best guess is that it's the belt sort of slipping in parts due to the wider diameter in the middle.

Offline S. Heslop

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Re: Drum/ Thickness Sander
« Reply #52 on: January 31, 2015, 04:10:30 PM »
Went and bought some electric stuff today to build a PWM speed controller for a car windscreen wiper motor. I could've just bought a controller from ebay but i've been wanting to learn some electronics for a while, and this gives me an excuse.


It took a few tries to get something working. Keep in mind I really don't know alot about electronics besides the basics. I was first going with some more complicated diagrams i'd found online, specifically for PWM speed controllers, and I must've been mucking up the wiring somehow. So eventually I looked up some 555 timer stuff and found a very simple diagram that I was able to successfully build.



It's not without problems though. At about 75% duty cycle the wavelength of the signal starts to increase. I probably need to read up on 555 timers and play around with them more.

Glad I bought the oscilloscope though! I would've really been lost without it.

Offline Bluechip

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Re: Drum/ Thickness Sander
« Reply #53 on: January 31, 2015, 06:06:18 PM »
I presume your pot. is linear, not log or semi-log ???

Which is my usual antic ....  :loco:

Dave
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Offline S. Heslop

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Re: Drum/ Thickness Sander
« Reply #54 on: January 31, 2015, 06:22:55 PM »
Yeah, it's linear. I got some 47k and 100k ones. I was considering getting some log ones too but ended up being in a hurry making the shopping list and forgot to ask in the shop.

What difference would logarithmic pots make? Just give me an easier time fine adjusting the small range where the pot actually changes the motor speed?

Offline Bluechip

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Re: Drum/ Thickness Sander
« Reply #55 on: January 31, 2015, 06:34:17 PM »
Nope ...  Should be Linear. The frequency would drop very rapidly as the resistance increases.

eg ... say you had a 100k log pot the resistance change for the first ( say) 10 deg. would be a whole lot less than the last 10 deg.

Have not used 555's for PWM for ages, gone onto PIC uControllers .. Smartarse    :D

IIRC this is the cct. I used to use .. is it the same as yours ...

Dave

EDIT Rb is a linear Pot ....

Or it might have been this ...   :scratch:

« Last Edit: February 01, 2015, 05:31:21 AM by Bluechip »
I have a few modest talents. Knowing what I'm doing isn't one of them.

Offline S. Heslop

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Re: Drum/ Thickness Sander
« Reply #56 on: February 01, 2015, 06:22:04 AM »
Whew, was worried i'd bought the wrong kinds of pots.

Microcontrollers are my eventual goal with electronics, but I figured it'd be best to figure out how discrete components work first. In the past i've tried reading books on the subject, but i've never found much stuff that isn't either incredibly theory heavy with little practical stuff, or stuff that just shows circuit diagrams with no explanation as to what anything does.

Thanks for the diagrams though. I'll try them out and see how they go.

Offline Bluechip

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Re: Drum/ Thickness Sander
« Reply #57 on: February 01, 2015, 07:07:27 AM »
Most of the stuff you need to know about '555's in here  :thumbup:

http://www.amazon.co.uk/Integrated-Circuit-555-Projects-BP/dp/0859340473

PS The two BATxx Schottky diodes can be 1N4148's, makes no significant difference.

IIRC the 2nd circuit does not affect the base PWM frequency ...

Dave
I have a few modest talents. Knowing what I'm doing isn't one of them.

Offline S. Heslop

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Re: Drum/ Thickness Sander
« Reply #58 on: February 01, 2015, 10:30:41 AM »
That second diagram works much better at controlling the speed. Also produces a nicer square wave without the high points (inrush?). It does change the base frequency though, but i'm not sure if that is really a problem.

Offline Bluechip

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Re: Drum/ Thickness Sander
« Reply #59 on: February 01, 2015, 11:36:01 AM »
It may well alter the frequency a bit ... it's a good few years since I did PWM with a 555.

Once you get into PWM on PICs its much more stable and very easy to change by code rather than oiking out the soldering iron.

If you're using breadboards I wouldn't bother about the glitching .. it does happen as you have a poor layout and contacts. Been there many times looking for non-existent problems ...  :palm:

If you want to 'scope it I would swap the motor for a resistor, no noise/ spikes from the commutator, and the sync. is better.

Post your original circuit ???

Dave
I have a few modest talents. Knowing what I'm doing isn't one of them.

Offline S. Heslop

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Re: Drum/ Thickness Sander
« Reply #60 on: February 01, 2015, 01:21:02 PM »
I'm not even sure where the original circuit was. I just found it via a Google image search.

I was looking up more 555 stuff and took another look at that website I got the real simple diagram from and found a more specific one.

http://www.555-timer-circuits.com/motor-pwm.html

And built it! There's an error in the diagram with one of the diodes backwards, that I wouldn't have noticed except that the two diode thing looked similar to the one in your second diagram.


The results are pretty good. The wavelength stays the same for most of the range, plus the pulse width ranges from very narrow to almost fully on.




The slight sawtooth shape disappeared with a resistor connected in place of the motor like suggested.

I think I might stick with this one since it seems to be working fine. I'll have to leave soldering it up properly till tomorrow since I'll need the daylight for recording it.

Offline Bluechip

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Re: Drum/ Thickness Sander
« Reply #61 on: February 01, 2015, 03:12:39 PM »
Have a look at the power rail while it's working.

The spikes may well be coming from there, you should really put a decoupling capacitor ( 22uF - ish ? ) right next to the chip Vcc pin to deck. The non-cmos 555's crowbar supplies like the devil.

IIRC the 7555 is the cmos version which does not do it so much ...  :thumbup:

It'll work  :ddb:  in my working life I've scoped industrial stuff and it's grim  :zap: but it ekkles ...  :lol:

Dave
I have a few modest talents. Knowing what I'm doing isn't one of them.

Offline S. Heslop

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Re: Drum/ Thickness Sander
« Reply #62 on: February 02, 2015, 11:06:29 AM »
Got the circuit made, with the decoupling cap and all which really helped reduce the spikes. Hopefully it'll work just fine with the bigger motor, that i've yet to buy.

It's ugly but i'm still really pleased with it. I should probably try get the flux off. I wonder if methylated spirits will work.




Thanks Dave for the help while building it!

Offline vtsteam

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Re: Drum/ Thickness Sander
« Reply #63 on: February 02, 2015, 11:24:27 AM »
I've been following along with great interest, Simon, just not a lot to say, except keep up the good work!  :coffee: :thumbup: :beer:
I love it when a Plan B comes together!
Steve
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Offline awemawson

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Re: Drum/ Thickness Sander
« Reply #64 on: February 02, 2015, 12:15:48 PM »
I use spray carburetor cleaner and an old toothbrush to remove flux residues after soldering. If you are neat changing a component it's hard to tell you've been there  :clap:
Andrew Mawson
East Sussex

Offline S. Heslop

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Re: Drum/ Thickness Sander
« Reply #65 on: February 04, 2015, 12:30:03 PM »
I've been following along with great interest, Simon, just not a lot to say, except keep up the good work!  :coffee: :thumbup: :beer:

Thanks! I'm more than familiar with that feeling too.

Did some stuff on the body today. Sides were cut out with paper templates and an assortment of tools.


And the base was cut with rabbets to match the width of the tilting table part. Wasn't sure if I should've made it a little oversize or not, but I just ended up making it match. I figure if the sides have to pull in a millimeter when clamping the table in place, it might pull the drum out of alignment a bit.


It's all just dry assembled here. I'll leave glueing it up for tomorrow. I've also managed to misplace the third 12mm bar for the table pivot, which I can't find anywhere. It's probably rolled under a bench or something.

Offline S. Heslop

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Re: Drum/ Thickness Sander
« Reply #66 on: February 04, 2015, 02:55:34 PM »
I found the third bar. It was on the floor and buried in sawdust.

Offline vtsteam

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Re: Drum/ Thickness Sander
« Reply #67 on: February 04, 2015, 08:11:27 PM »
I found the third bar. It was on the floor and buried in sawdust.

And I'm more than familiar with THAT feeling!!!  :lol:
I love it when a Plan B comes together!
Steve
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Offline S. Heslop

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Re: Drum/ Thickness Sander
« Reply #68 on: February 05, 2015, 11:23:17 AM »


Went into the garage to measure a thing and ended up making this. It's a hole cutter, for cutting holes about the right size for the 47mm bearings. Still need to grind the toolbit, as well as buy a drill bit that's a good fit with the hole.

Thought I was being clever drilling the hole for the drill bit with the same drill, but it made a way oversized hole. I guess I didn't grind the bit very well!

Offline malbenbut

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Re: Drum/ Thickness Sander
« Reply #69 on: February 06, 2015, 04:40:25 AM »
I can buy a speed control up to 50v dc input from EBAY cheaper than I can buy the components in UK to make one.

MBB

Offline Fergus OMore

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Re: Drum/ Thickness Sander
« Reply #70 on: February 06, 2015, 12:19:29 PM »
Doing 'the shopping' at Aldi and Lidl. Next week, Lidl has a pillar drill for 49.99. I've got one when Aldi's had them( probably the same). Looked at mine and thought that I could put it on my lathe saddle. Mebbe bit of fiddling with the cast iron base but dead useful. Thought that you might be interested

Norman

Offline S. Heslop

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Re: Drum/ Thickness Sander
« Reply #71 on: February 08, 2015, 01:58:16 PM »
Squares II: Return of the squares



I spotted the middle with a spade bit.



I'm cutting off the excess so there's less to turn. It's also probably safer to be doing less of an interrupted cut.


And drilled all the way through. I need 23 of these and i've made that and one spare. I'd actually spent most of Saturday thinking about how i'd drill a 20mm hole without a 20mm bit, until I remembered I had the spade bits hidden somewhere.



I've also figured out how i'm going to hold the paper on. At first I was planning to use hook and loop sandpaper, but it's extraordinarily expensive. So I'm going to leave the two edge disks unglued, but held on with screws, so that after they're turned round I can remove them and cut segments out, and use the cutout to retain the edges of the paper.

Offline vtsteam

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Re: Drum/ Thickness Sander
« Reply #72 on: February 08, 2015, 02:38:55 PM »
Simon when roughing out squares to circles on the bandsaw, drill a tight hole in a piece of scrap for a nail, and press it through. Turn it over so it stands vertical, point up. Clamp the scrap to the bandsaw table with the nail sticking up. set the distance of the nail to the blade to equal the rough radius you want. Then put a hole through the center of your blanks for a slip fit on the nail.

To use, put a blank on the stationary nail axle, and rotate the blank into the blade to cut the circle. This works best if you have a groove for a miter gauge in your bandsaw table, and put a tongue on the bottom of the scrap base so you can slide it in toward the blade, rather than just clamp it. You can then cut circles of any diameter, just by sliding in or out.

You can also cut cone segments this way by tilting the table to give an angle cut.

And you can cut rings this way, too.

I love it when a Plan B comes together!
Steve
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Offline S. Heslop

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Re: Drum/ Thickness Sander
« Reply #73 on: February 08, 2015, 03:56:58 PM »
Simon when roughing out squares to circles on the bandsaw, drill a tight hole in a piece of scrap for a nail, and press it through. Turn it over so it stands vertical, point up. Clamp the scrap to the bandsaw table with the nail sticking up. set the distance of the nail to the blade to equal the rough radius you want. Then put a hole through the center of your blanks for a slip fit on the nail.

To use, put a blank on the stationary nail axle, and rotate the blank into the blade to cut the circle. This works best if you have a groove for a miter gauge in your bandsaw table, and put a tongue on the bottom of the scrap base so you can slide it in toward the blade, rather than just clamp it. You can then cut circles of any diameter, just by sliding in or out.

You can also cut cone segments this way by tilting the table to give an angle cut.

And you can cut rings this way, too.

Thanks for the tip but I don't think that'd work so well with my bandsaw. The blade likes to drift about so I need to cut freehand to try steer it. It's a pretty lousy bandsaw in general, the whole thing shakes as it runs since the three wheels are pretty far eccentric. Still beats using an upside down jigsaw!

A better bandsaw has been on my list of things to build for a while now. I think I still need to tidy up the garage a bunch after finishing this sander though. Still got the dust collector to finish, and I need to find a place to keep that bike (i'm thinking about strapping it to the ceiling).

Offline S. Heslop

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Re: Drum/ Thickness Sander
« Reply #74 on: February 09, 2015, 08:53:28 PM »
Nearly gave myself a hernia today trying to push the disks on.


Ended up making a rubbish reamer to get the holes a bit bigger. Now the whole stack is glued up and drying.


Been having trouble sleeping the last few days, spent an hour in bed thinking about how to re-arrange the garage to fit more stuff in. If I move that tool chest Rob Wilson gave me behind the drill press, I could fit the planer and sander onto the short bench at the back of the garage. It'd also put the chest in a more convenient location. I can barely get at it where it is now.


I've been using that corner of the garage as a sort of dumping ground for 'stuff that looks useful', as in stuff that will never be useful, so I'll make a trip to the tip at some point. I'm also still considering getting rid of that sheet metal forge. Or at least cutting it into chunks that can be hidden under a bench somewhere.