Belt Grinder 2x72" and 50x2000 mm

[Boyan Silyavski]

Hi guys,
Now, whats that with the metal these days? Still have not finished my CNC as i have no free time, but already designing and making my metal belt grinder:joker:

I must be in my "heavy metal" period again, which i thought was long gone.

So after analyzing all on the market and most of the DIY plans, i decided to designe it from scratch but based on the successful designs.


-First decision was that it will accept standard metric and imperial belts at the same time - 2x75" and 50x2000mm. No need for wider belts.

-It will be overbuild. I hate vibrations from machines. if you know me you will be no surpised that it will be OTT. Come on, only 20 kilos more but a lot better. That 20-30 euro more in a project that will make me spend 400euro, so yeah..

-It will be a precision grinder. No surprise here also. All from calibrated cold drawn steel bars and plates / as they are the same price as the normal /, massive arms and steel shoulder screws for tightening the bearings and wheels.

- tilting 90 degrees. Thats a detail. Not that i intend tilting it but spending so much money i decided it should do all.


At a later time will start updating the build with pictures and more details. For now some snips of the design.


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[Lee Roberts]

Boyan, did you see this one:

https://youtu.be/ONH8BEp2dHE

Look at his other video's too.

.Me

[Boyan Silyavski]

Boyan, did you see this one:

https://youtu.be/ONH8BEp2dHE

Look at his other video's too.

.Me

Hi Lee,
i saw it and was tempted a bit but at the end decided from steel. This is may be the tool i use most and for everything / same for the 12" disc sander/ so i decided i would screw it very fast if not from steel. Plus the noise and vibrations when i sand 5 hours non stop. I looked at the 2 most expensive grinders and some nice builds which are proven designs and people use them from years.

[Boyan Silyavski]

Some update with pictures. I am actually making 3 machines, one for me, one for Jeff/ fellow forum member and friend, that lives around/ and one for sale. I think of that as prototyping :-)

Cut the steel and made some pieces:

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Jeff cut the main pieces ,that had to be precise, on the mill. In future all will be plasma cut on my machine but as i still have not finished it...

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So i started assembling this and that, welding , sanding and squaring:

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people go at restaurant Saturday night , instead 22.00h i was still welding brackets yesterday. Yeah, i was using olive oil for protection of surfaces when welding, drilling and threading, so it smelled like in restaurant around here


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sanding the bracket on my diy 12" disc sander made from 12" diamond disc welded to the pulley and 0.75kw motor.

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brackets ready

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the plate that goes on the bracket has 2 screws each, one side only, at the other side i sanded the weld and welded again until pits disappeared. not to speak of that even threaded the hole before welding, as i want all to be very precise

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The machines without the face plates and the pulleys. tomorrow jeff wil bring me the pulleys, bearings and so, so only thing left is motor mounts . Both motors are 3 phase with VFD.

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I think that will be one of the most used machines in my workshop, hence the idea to make it as good as possible. What do you guys think? You like them?

[Lee Roberts]

I like it!

.Me

[T0rnado69]

looks good,

more updates needed :)

[mekanik]

Very nice Boyan , thanks for sharing.

[toomast]

Sweet!

Sent from my LG-D605 using Tapatalk

[Boyan Silyavski]

OK, some more:

Welding the motor mount bracket that i cut from the original machine, as i savaged the motor from the junk yard. Clamped both pieces to the table first and then to a bar, then welded very carefully so not to distort the piece, as all wheels must be on one surface flat, otherwise belt will want to go left or right.

This is or ideally must be a very precise machine. First to be functional at all, then to be quiet and free of vibrations.

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The belt grinder is meant to be used with using minimum 1.5kw 3 phase 4 pole motor and VFD. Now i had 3kw motor and in the same size and frame,plus Siemens 3kw VFD, so can you guess what happened :-)

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Now as i dont have physical grinder to see in real life, judge or copy from, some things are not clear, so instead of finishing all 3 machines i will leave it here and start trying this one to see how it works.
For example:
-welding the bracket made so that the tooling arm could not pass through further from the end of the square cage, and according to my calcs there is no need to. The motor bracket and motor are there as i put them there for the reason of when 1.5kw motor its easy to flip machine to horizontal. It could be made more compact but then it must be much higher, so some decisions have to be made for future ones.



The paint. Probably industrial epoxy as its the best i could do here. The color is clear though as Jeff like that color, so i decided i would not insist on strange colors. It would be the aquamarine of Myfords and Bridgeport. Does any body know the exact color name or code?

Asking cause on all pictures they look to have different color/ poor white balance on camera/ . The second one seems right to me on my color calibrated monitor.

So any hint on the color?

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[Noplace]

very nice, just curious how much would it cost to build one if you were willing to build in the future to sell it?

[Boyan Silyavski]

very nice, just curious how much would it cost to build one if you were willing to build in the future to sell it?

Difficult thing to say at this stage. But the KMG grinder sells for 1800$ and can not flip to horizontal. The best one sells for 3000$ and can flip and more . The ebay clones made from box section or/and 6mm laser cut pieces go for 800-1000. That without the wheels especially made for knife making.

On my prototypes all parts are milled/for now/ , so i have still to decide which ones are to be milled and which to be laser cut. Have in mind the price of the VFD and the 1.5kw 3 phase motor. Also welding things aligned precisely takes its time, so still not sure where to weld and where to bolt.

But the way i see it i want to have one model at ~1000euro /+30% if-when sold legally as a company / that beats all basic models around. But it may be high end 2000euro .

Cause its very simple. You want to make knifes, you need a grinder.You need a knife grinder. Thats it. FIY one way or another even if you totally DIY you will spend 500-800 euro on the complete machine. If you have lathe and mill and mig welder ~400euro at least.

By the way its a very useful machine even if you dont intend to make knifes.

So my idea is to make it accessible priced but not sure for now if it will be easily achieved. I started making changes on the drawing even while i am welding it together for this and that reason. So as i said this is a prototype to study whats working on the market and eventually make something better.

[JAZZCNC]

So as i said this is a prototype to study whats working on the market and eventually make something better.

Surprised you have made 3 identical when it's still in prototype. I Prototype lots of stuff and first version nearly always gets changed or improved in some way. Hell with my little router design I see ways to improve or make building easier just about every time I make one.

Surely would have made more sense to build one and test then improve second and test again etc.?

[Boyan Silyavski]

Surprised you have made 3 identical when it's still in prototype. I Prototype lots of stuff and first version nearly always gets changed or improved in some way. Hell with my little router design I see ways to improve or make building easier just about every time I make one.

Surely would have made more sense to build one and test then improve second and test again etc.?


I make one small wooden musical instrum (http://kalimbaa.com/)ent as a side hobby and every now and then i have a whole day or 2 day, when i do sanding all day long. So the faster the better.

I needed a serious sander also for all the steel projects. I have a nice DIY 12" sander but what i am making here is a "grinder" not "sander" meanung it will have very serious surface speed with 120mm OD wheel at he motor spinning at 300rpm / 4 pole 3 phase 1420 rpm motor with VFD/

The other thing is that i have a knife project where i am at the stage of needing the grinder. I made the prototypes using small bench sander but as i am using one of the bad ass tool steels its very difficult to grind with belt sander to shape.

Plus as i found the typical paradox- " To make a grinder you need a grinder"


The design is more or less clear, a lot of DIY copies of the KMG grinder with plans in internet. The KMG is also a copy of an older machine, so i understood while looking at the plans that these are not just copies, but a concept proven through the years of abuse, that works. So i directly started building on it knowing that it will work.

Jeff needed a grinder, all of the above+ that they sell material in 6m, packets of 10, etc., so doing 3 machines at once made sense to me.


The next step from here is next week machine is ready, i continue my knife project and while having actual experience using it for knifes, i will meditate upon a much more brave design.


In fact Dean next step would be directly producing them by the 10, cause of the fixtures on the mill and the lathe is makes sense to make 10 pieces at once.

Needless to say that the experience from building CNCs till the moment helped in in such way that the only error till now was just 1 spot weld not at the right place.

[JAZZCNC]

Needless to say that the experience from building CNCs till the moment helped in in such way that the only error till now was just 1 spot weld not at the right place.

Erm I'd say the error was the spot welding.! . . . Doesn't look good or strong. Great for proto typing but not for real thing. It needs proper welds to give it credabilty as industrial strength tool.!

[Boyan Silyavski]

Erm I'd say the error was the spot welding.! . . . Doesn't look good or strong. Great for proto typing but not for real thing. It needs proper welds to give it credabilty as industrial strength tool.!

I feel that too. Nothing will go out from here that could be broken by hand and a hammer. And you are absolutely right, now i could take the hammer and certain pieces could be broken apart for seconds. When all belts are spinning and i see everything is working correctly there would be proper welds where necessary. The other thing i will do is blacken all bare steel heating it with the gas torch to 315C.

[toomast]

...The other thing i will do is blacken all bare steel heating it with the gas torch to 315C.

What do you mean by that?

[Boyan Silyavski]

What do you mean by that?

There is a way to treat low carb steel / mild steel/ . You heat it at 315C, keep it there a couple of minutes, thin oxide layer forms in black, then you brush it with some oil and it goes even blacker. Result is much tougher part, even if not a high carbon steel. Black oxide layer is not real anti rust though it gives some protection


bellow you could compare bare cold drawn steel bar and treated.


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[toomast]

There is a way to treat low carb steel / mild steel/ . You heat it at 315C, keep it there a couple of minutes, thin oxide layer forms in black, then you brush it with some oil and it goes even blacker. Result is much tougher part, even if not a high carbon steel. Black oxide layer is not real anti rust though it gives some protection


bellow you could compare bare cold drawn steel bar and treated.


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Interesting. What is the "official" name of this process?

[JAZZCNC]

When all belts are spinning and i see everything is working correctly there would be proper welds where necessary.

Well next time do your self a favor and grind Chamfers on the edges will give stronger nicer welds. Created your self lot of grinding now or ugly proud welds.

[Boyan Silyavski]

Well next time do your self a favor and grind Chamfers on the edges will give stronger nicer welds. Created your self lot of grinding now or ugly proud welds.

Where was important and i was sure that will not need to break it apart its done like you say. The machine is still not finished.

[njhussey]

Instead of heating and quenching why don't you chemically black the steel? It doesn't add any hardening but does add a bit of rustproofing, not much but some!

[Boyan Silyavski]

Instead of heating and quenching why don't you chemically black the steel? It doesn't add any hardening but does add a bit of rustproofing, not much but some!


Cause it seems a bit expensive to buy the kit for blackening at the moment. The torch is easy,cheap and toughens the material. No quenching, air cooling. But that would be the next logical step



Now about Power.
Motor power. I was lead to believe / from forums/ that you need at least 1hp per inch belt, so i decided the machine to have 1.5kw motor. Mean while i had
made my self a 12" sander. 3 phase 0.75kw motor that run on 230VAC using capacitor, no VFD. The disc was easy to stop. See video below. So i decided to invest in a VFd cause i wanted to run it from 0-3000RPM depends what i am doing. I connected it yesterday. Man, i could not stop it in any way, its brutally strong combo. And only 0.75kw.

So i am starting to believe there is some misconception here. Cause belt is not wider than portion of disc i used for grinding yesterday.And as i said, i couldnt stop it pushing hard using steel bar. So i started to think thats the pulley mass is to blame. while all pulleys i designed are very much big bored and so they are light, the motor wheel is a whopping 1.6kg at 120mm. I started redrawing it recessed in the middle but could not lower the mass less than 1.1kg. So i went further and made all walls 8mm only. Weight dropped to 680g.

So in short i start to think that this could be driven using 0.75kw motor combined with VFD instead of the over sized 1.5kw, when pulleys weight is made minimum. yet to prove on next machine. of course i will see how much i need that low revs where is a small loss of power


Below video of the 0.75kw motor when runs on capacitor on 2 phase line


https://www.youtube.com/watch?v=zinGkNr1Nv0




And video of same motor that runs on VFD again 2 phase line. I could not stop it pushing very hard against it a 40x10mm steel bar.Trying seriously to abuse it . The disc itself is a very thick diamond cut disc and the blue sanding disc thats glued, is a 60 grit zirconia. So you judge what a beast it is now with the VFD connected.

Its very interesting to me if sb has a similar machine, 12" disc sander using 1400RPM mono phase motor, no VFD and if it could be stopped pushing hard against it?????


PS. Black lines on disc are from sharpening my pencils. Disc is new otherwise. First i run it at half speed and then at full speed at 100hz. It was scary to hold thebar with only one hand.


https://www.youtube.com/watch?v=UyCud1gSgEM

[Clive S]

Boyan I think you have answered your own question you can't compare using a 3 phase motor on single phase with caps against the VFD. You won't get the torque with the caps especially if they are not big enough.

[Boyan Silyavski]

Have almost finished the 3 grinders. There were some details that slowed the process, now more or less everything is clear.


Welding the motor mounts, trying to keep things on one same plane:
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Grinding away the spot welds, drilling holes, making stronger weld...only on one of them. Too much works and then i had to make it flat. So i decided to stop there and the other 2 only were reinforced where necessary.
Next time as i know now which weld first where and how, i will just do all pproperly.
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Then some painting:
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Too much paint mixed at once? No problem some but not all that was upgraded at home:
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Now the blackening, heating the steel at around 300C. Then brushed in olive oil when cooled down. The oil made them even darker after some time. Very happy with the result, last 2 pictures.
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Now why its called prototype, and why as Dean said it is good to be done one by one. I knew it could happen and was sure that i have avoided it but...as i have not designed the future 2 attachments, it happens that belt would interfere with one of them
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This is what took me most time. Deciding on the spring, finding the proper spring, tension, length and how to fit it on the machine correctly so it willnot mess with the belt and the future attachments. Main problem being is- this is the shortest spring i was able to find at that rating.
I finally was happy with the result, so version .01 was born On right picture is Jeffs grinder, we left his motor as he does not need it for making knifes so no future attachments.
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Finally mounted the handle, at the end it happens upper side of the arm is best and easiest. Then the VFD and motor. Cut some scrap belt and started the machine to program the VFD. Boom. The fuse goes down at home. Again, and again. Half day later after some research i went to the conclusion -"leak current" from input capacitor filter. Bloody hell, so i started reading the manual. Good old Toshiba. have made a switch on the VFD that can deal with that changing the capacitance. clicked the switch and all is working.

No vibrations. Super quiet. Not so when i mounted the old belt which is quite bumpy, the connection where is spliced. The belt tracked easily though but makes some noise.But as machine is heavy even that introduces no vibrations.

I am quite happy. Worked from first time. Tracking is perfect, speed is right. I dont see that machine without speed control though, i can not stress enough on that. Did some test grinding today and is super important to control exact speed at every moment.

The other important detail is that the 2 rollers at the front are fixed by spacers and shoulder bolts. So these 2 holes were drilled on the mill and hand tapped. That could not be. The must be machine tapped. hand tapping M10 is you could make it straight or not. Had to redo them a couple of times. As i have no M10 machine tap i bought yesterday. Next time will make tapping fixture similar to drilling holder, where shaft passes through a bearing and use driver to spin the shaft, so its clutch does the job of releasing when too much resistance.Though if needed, may be its the time for tapping head.

The video is a bit shaky but you could get idea what happens

https://www.youtube.com/watch?v=2WQmVcDUX-Y