25 replies to this topic

[Bazzie]

I said I was going to build one so I did
I built it mostly out of left-over components from another machine I built. This was my project for the Christmas break, one of my more fun projects and very rewarding. It works great, very accurate repeatable process. It trims the donuts .5mm outside the rim and also grinds down to size. At the moment I just have an 80 grit sandpaper stuck onto a grinding wheel. The surface ends up a little rough but there is virtually no heat generated. I'm trying to get a diamond drum made up, that will improve the finish, and there are a few more software tweaks I want to make, just refinements.
This trimming vid was done when I still had the red emery paper on the grinding wheel, later replaced it with Flexovit paper that works better:
https://youtu.be/CFaN5i_RGKg

Following is a video of the grinding. You select the diameter you want by using the rotary encoders - one coarse and the other for fine adjustments. There is also a program that will do both the trimming and the grinding.
https://youtu.be/JLFjmaouVNw


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[Benno - SAC]

Very cool! 👍👍👍

[Courtney S]

That is so cool!

[Benno - SAC]

What I am wondering about:
What was that other machine, when these are just the "left overs"???

[gotboostedvr6]

You should check runout. With shafts that long I imagine it would present a problem.

[Bazzie]

Yup, I've fiddled with the shaft a lot and am getting one made up on a very expensive lathe by a friend. I threw out a lot of the cheap pillow blocks that were not running true. It was pretty shocking actually. It one point I considered making my own pillow blocks... I made this shaft myself and it's pretty accurate, better than my old ilpe truer.
The other machine I built for our business. It cuts polystyrene cornice/coving/scotia/architraves from XPS blocks, in 2m lengths, that's 80" so the machine is quite big


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[Bazzie]

Oh and those shafts are pretty accurate and with cutting as fast as it does there is little pressure or bend moment on the shaft. They're made from HSS and meant to be used for linear bearings, so they are true


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[Geary Carrier]

Love that engineering talk...

[Bazzie]

Well it is. Difference between an engineer and a mathematician is that a mathematician says if a man and a woman are a certain distance apart and you keep halving the distance then the man will never reach the woman. An engineer says he'll get close enough


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[Benno - SAC]

Cool, veeery cool!👍👍👍

[Bazzie]

Thanks Benno
I've since received my pink alu oxide grind wheel, and it gives a great finish, however still not course enough. Tyres still go up to 54deg on the surface while truing, so now I will go to the next step - add some diamond 'powder' to the surface. I bought 60-70 mesh off Aliexpress and have experimented with it with some good results. Will report back soon


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[gotboostedvr6]

What are you using as an adhesive for the diamond

[Nate Graham]

that...is...sweet!!!!

a lot of the dimensions could be reduced to make a smaller package and decrease those runout,etc. But that is nice. love the brushless motors and I recognize the controller. heh heh. build that with slot car axles or drill blanks and bearings and it could be quite portable .  

[gotboostedvr6]

Also are you using plated diamonds or natural surface?

[Bazzie]

What are you using as an adhesive for the diamond

I've played around with both 105 West Systems and Cyano, both work well enough for stripping rubber


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[Bazzie]

Oh, the 105 stuff is epoxy I used to used to build model airplanes- for composites work. It's a pretty high grade epoxy, and I used a very thin film


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[Bazzie]

that...is...sweet!!!!
a lot of the dimensions could be reduced to make a smaller package and decrease those runout,etc. But that is nice. love the brushless motors and I recognize the controller. heh heh. build that with slot car axles or drill blanks and bearings and it could be quite portable .  

Yes, I built this one large as it's a prototype. I was initially going to have 2 grind wheels, one coarse for a quick grind and the fine for final cut, but the runout would have been too much. It is minimal now, I've trimmed down the shaft on the machine from 8mm down to 3/32, so whatever error was in runout has been ground out. I've marked the shaft and bearings so it always goes in the same way. The wheels run very smoothly on the track, better than my old Ilpe tyre truer.


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[Bazzie]

that...is...sweet!!!!
a lot of the dimensions could be reduced to make a smaller package and decrease those runout,etc. But that is nice. love the brushless motors and I recognize the controller. heh heh. build that with slot car axles or drill blanks and bearings and it could be quite portable .  

Yes, I built this one large as it's a prototype. I was initially going to have 2 grind wheels, one coarse for a quick grind and the fine for final cut, but the runout would have been too much. It is minimal now, I've trimmed down the shaft on the machine from 8mm down to 3/32, so whatever error was in runout has been ground out. I've marked the shaft and bearings so it always goes in the same way. The wheels run very smoothly on the track, better than my old Ilpe tyre truer.


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[Bazzie]

Also are you using plated diamonds or natural surface?

https://www.aliexpre...2789991941.html
Possibly not the best but it works. Also just saw I bought the 70-80 mesh, not 60-70....


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[gotboostedvr6]

Unplated diamonds are a bugger to glue. They are even more difficult to do temperature sensitive work with.

Can your current grinding wheel be heated to 200 degrees f for 4 hours or 325 f for 1 hour?

If so I have a package I plan on sending to NZ. If your fellow countrymen doesn't mind sending a small package to you I'll include some adhesive that is vastly superior for you to test. No charge.

[NSwanberg]

Well it is. Difference between an engineer and a mathematician is that a mathematician says if a man and a woman are a certain distance apart and you keep halving the distance then the man will never reach the woman. An engineer says he'll get close enough


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A physics professor once explained to our class that in physics you get partial credit. In engineering you have to be correct or the bridge falls down.

[Bazzie]

Wow, thanks, I'm pretty sure the wheel would be ok @ 200C, it's meant to grind steel, so it gets a lot of hot sparks that don't affect it. That would be great thanks! 

 

What I will definitely do is to give the surface a light coat of epoxy first just to bind it a bit better, and then another very light coat after which the diamond powder gets sprinkled on. I may apply a slight bit of pressure to get better adherence from the resin, seems to work well. It's surprising how well it sticks, I've made a wheel that I used to trim the dogs' nails with a Dremel

Cutting tyres, no sweat

 

 

Unplated diamonds are a bugger to glue. They are even more difficult to do temperature sensitive work with.

Can your current grinding wheel be heated to 200 degrees f for 4 hours or 325 f for 1 hour?

If so I have a package I plan on sending to NZ. If your fellow countrymen doesn't mind sending a small package to you I'll include some adhesive that is vastly superior for you to test. No charge.

[Bazzie]

 

A physics professor once explained to our class that in physics you get partial credit. In engineering you have to be correct or the bridge falls down.

 

Haha, true... Still, approximations get made, but in the case where lives are at stake, safety factors get built in, e.g. lifts typically get designed to carry 5 x their rated cargos

[Bob Kurkowski]

I have never met a Engineer who is wrong....at least according to him.

 

Bob K.

[Terry]

Statement of the year for sure Bob!!! lol