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  #1  
Old Thu 25 February 2010, 06:40
ddoggett
Just call me: Dan
 
Ottumwa, IA
United States of America
Bearing Skates for multiple uses.

I think Gerald would approve of the the linear skets supplied by this company. They would surely save a lot of time over grinding the rails I think anyway.

website: www.cncrouterparts.com

All input is welcome. And thank you Claus Dybdal from Zapp Automation for his energetic help!
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  #2  
Old Thu 25 February 2010, 07:18
KenC
Just call me: Ken
 
Klang
Malaysia
I find the belt reduction design interesting & the rack & gear drive very familiar
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  #3  
Old Thu 25 February 2010, 07:58
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
Sorry Dan, I don't see anything there that appeals to me.
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  #4  
Old Fri 26 February 2010, 07:15
ddoggett
Just call me: Dan
 
Ottumwa, IA
United States of America
That's certainly OK Gerald, just a thought. I was thinking the same theory but running on extruded aluminum angle just as a time saver. And mounting the R&P setup under the main rails to get them down and out of the way. Your design is GREAT to say the least.
Let me ask this... do you have any objection to a MM hybrid?? i was also thinking of the 8020 type extruded material for the main rails. The reason for this is because the extrusions are much more true in straightness. This would be more expensive but allows for more diversity in mounting the other original components. just my thoughts. I look forward to your input here.
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  #5  
Old Fri 26 February 2010, 08:02
sailfl
Just call me: Nils #12
 
Winter Park, FL
United States of America
Dan,

One of the things that makes this site so nice is that every one is building the same machine. There are some variations but the basic design and components are the same. If you are building it makes it easy to know what you need. If you need help, any one that has built a machine can help you. Gerald has stopped people from going to far from the basic design and I hope Mike does the same thing.

The CNCZone is perfect for those that want to build a hybrid. But that is Mike's call.
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  #6  
Old Fri 26 February 2010, 08:35
Regnar
Just call me: Russell #69
 
Mobile, Alabama
United States of America
Dan although I am not Gerald I think I can answer this question for you.

The Extruded aluminum is definitely a lot more expensive. I am pretty sure you have to ship freight on anything over 8 feet with UPS. So the shipping price is going to be significantly higher the 40.00 dollars. Not to mention that an 8 foot piece is 284.00 http://cgi.ebay.com/80-20-T-Slot-Alu...item334bf9aa60

From the local steel guy down the street I was quoted 154.00 for a 20 foot 4"x8" I beam. I was also quoted 122.00 for a 20 foot 4"x4" I beam for the legs. This is a big difference in price almost half the cost.

The second problem you are going to run into is the light weight. Almost everyone here is around 14-15lbs a foot. The 3060 weights about 6 pounds a foot. The lighter weight is going to cause resonance issues.

Im not trying to shoot you down I am just giving you a low down of what I have read through out the forum.

I have read of guys filling the extruded aluminum with epoxy granite to make them stiffer and heavier but that just adds to the time and cost.

You should also take into account that all of the t slot that are not covered are going to fill with dust and the cost of the tnuts. The nuts are ridiculously overpriced!


As far as the bearing go. They are not that bad of a design I have to admit. I built 8 custom ones for my brother so he could have a small cnc machine in his apartment. He makes custom computer cases and windows. The small bearings "roller skate" might be able to do the y and z axis but they would probably be short lived on the x axis due to weight.

If you have a decent drill press and a file you can make the bearings yourself. I made exact replicas of the bearing on my mill and most of the operations was drilling. Only the countersunk nut and vertical bearing needed milling operations. Also use 12mm bolts and not 5/16
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  #7  
Old Fri 26 February 2010, 09:26
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
Dan, after trying to put words in my mouth, you try and drag me into a typical CNCzone discussion? Sorry, I am not biting on that one.
It is not because I in any way think that the MM is the ultimate in designs (not by a long shot!), I just sometimes don't feel like discussing other schemes. . . . . and then get misunderstood and misquoted for what I said there.
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  #8  
Old Fri 26 February 2010, 09:35
KenC
Just call me: Ken
 
Klang
Malaysia
Dan,
Fist of all, you have all the right to build from what ever material & what ever design you see fit, you don't need anyone's approval

BUT since you asked...

Nils pointed out the philosophical factor & Russel pointed out some of the physical factors for not going your intention.
I would like to add the efficiency/productivity factor.

First & foremost, you gotta set your goal right, is your goal to
1) design a CNC router,
2) Design & build a CNC router that doesn't work
3) Design & never complete building the CNC router that doesn't work.
4) Build & complete a CNC router that actually works

ALSO,
1) How much time do you think that would save you?

I took about 80~100 man hour to cut & grind the rails... & a month for the table, Almost without a hick during the process thanks to the great support I get from this community. There are many who did it a lot less time.
Does that warrens the risk of running into unknown territory for saving 80hrs? It may be a false presumption as you may run into other unknown practical issues...
AND With Al extrusion, do you think you could really save any meaningful time to align the rail as straight as within 0.1mm? From my experience learn in my day job, aligning from +/- 1mm to +/-0.05 takes as much time as from +/-10mm to +/-0.05mm... maybe an hour saving is possible, but that rarely happens...

Another thought, why don't you look up Shopbot, that should save you a lot of time & you will barely dirty your fingers building one. & you can buy everything off the shelve without knowing what the hell they are for...


NO PAIN NO GAIN

Last edited by KenC; Fri 26 February 2010 at 09:41..
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  #9  
Old Fri 26 February 2010, 11:06
jehayes
Just call me: Joe #53
 
Whidbey Island, Washington
United States of America
Dan: Since we're piling on...

Cutting and grinding the rails is not a problem! Don't let it scare you! Once you get the system going it is really easy (just a little tedious). (This from a guy who never cut a piece of steel in his life until I started the MM.)

Have some fun with it!

Joe
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  #10  
Old Fri 26 February 2010, 12:53
ddoggett
Just call me: Dan
 
Ottumwa, IA
United States of America
Talking Ok Guys!

I really do appreciate all the input! And I seriously respect Gerald and what he has done. For the record, I do not oppose Gerald's design, it is a good one. I also am a project manger for a production based company, so some of that may be spilling over. I have an education as well as experience in the automation field all the way from design and build systems, from simple PLC controls to 7 axis welding systems using ABB robotics. I am sort of a maverick that tries to look for possible improvement on an already proven product. Take the basic and make it better. Again, spill over. I love the gantry design as well as the Z axis design, i would not change anything there.

I've even been looking at a wall mounted unit for space savings in small shops/mancaves.

Gerald I do not mean ill intent at all. Thank you for doing what you have done here. This a well thought out design.

Off subject, would not rubber or other types of non-metalic washers sandwiched between components that are bolted together, eliminate alot of the "resonance" issues?
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  #11  
Old Fri 26 February 2010, 15:18
bradm
Just call me: Brad #10
 
Somerville(MA)
United States of America
Dan, forgive me for being flip in response to a legitimate question. It's Friday night, I'm an ocean from home, and I've been away for a week.

Imagine a simple framing hammer. Cut the handle close to the head. Now, for reassembling said hammer, would you like a very solid threaded metal pin, or some rubber cement, and why?

Yes, this is reductio ad absurdum. However, regardless of the many ways we've compensated for impact resonance in hammers over the years, they don't generally involve compromising the major structural member. Similarly, the solution to resonance in a gantry router is not likely to involve adding flex.
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  #12  
Old Fri 26 February 2010, 17:10
ddoggett
Just call me: Dan
 
Ottumwa, IA
United States of America
Thats really actually profound!

OK, OK.......... I'll build as specified my first machine, however, the second one I plan to make the Hybrid version. I will not mention MM with it until the masters say I can. I have more respect than that for all before me. I might be making a mistake but without experimentation how do things improve? Trial and error is how we all got here. I'm sure the grand master didn't just build something and say "TADA" it's done! If he did.......he truly is the master.

Let me ask this.. could it be possible that the harmonics are contingient on the drive speeds and/or the RPMs of the spindle or router? And could the actual AC frequency be a variable? Do the plasma boys have the same problem? And if resonance is an issue why has no one addressed a design improvement besides weight increase? At least an improvement that I have read on yet. No offense Gerald!

One other change I'd like to make is the addition of a 4th axis at the end of the table along the the width, for cutting billiards table legs and such.
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  #13  
Old Fri 26 February 2010, 17:43
MetalHead
Just call me: Mike
 
Columbiana AL
United States of America
We have tables out there with indexers on the end and wider tables with long indexers built in.

We even have a system that is just an indexer http://www.mechmate.com/forums/showt...77&postcount=1

I would not worry to much on the resonance. I would just put good feet on the table, build it rigid (Many base table variants in the forum) with decent mass and you will be happy with the result.

As far as the 8020 main beams, Surf the web and you will find a comapny that uses this design and it really strays away from the core MM design. (Affordable easy to build system with easy to aquire parts). But again many variations are documented here in.

We are looking forward to see pictures of your build.

Mike
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  #14  
Old Fri 26 February 2010, 19:36
ddoggett
Just call me: Dan
 
Ottumwa, IA
United States of America
Thamks Mike.

And I will be ordering your laser parts for sure. I'm still up in the air about the motors and controllers yet. I have a cousin who has a SB and went ahead and built a 4x4 model of his own. I think he went with a Joes 4x4 hybrid design and bought his 3 axis system from www.candcnc.com. They semm pretty pricey compared to what you quoted me last week.

I suppose if a guy had a radial drill press and setup a long enough table, using a standard endmill and setting up the drill press to 45 degrees the machining of the rails would depend soully on the feedrate as for labor timing.

And a word to all who input to this forum. THANK YOU ALL! I have been reading for weeks and still am amzed at the talented folks worldwide that contribute. I am especially envious of those who build their own boards as well. Thumbs up to you! ShopBot never had it so good. (Personal opinion)
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  #15  
Old Fri 26 February 2010, 19:39
ddoggett
Just call me: Dan
 
Ottumwa, IA
United States of America
Excuse me!

Its "Thanks Mike" and seems not semms!
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  #16  
Old Fri 26 February 2010, 20:07
KenC
Just call me: Ken
 
Klang
Malaysia
Quote:
Originally Posted by ddoggett View Post
OK, OK.......... I'll build as specified my first machine, ............ without experimentation how do things improve? Trial and error is how we all got here.

This is the most sensible thing from you so far

As for the resonance, ask yourself again, is that a life & death situation that you MUST eliminate resonance? From a fellow project manager (well that was my last position as an employee), If your product spec is not compromised by the resonance, what warren the cost to "improve" it? & if adding a little weight can address the issue, why waste too much time on exotic & possibly expensive solution which you don't need?
IMHO, Harmonics is the main cause of frame resonance. I read about DSP tech integrated into motor drives to address this problem but I stop digging any further once I concluded the tech is not as mature as the conventional micro-stepping drivers. (## I did set my goal to build a CNC that work really well )

Looking forward to see your build soon.
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  #17  
Old Fri 26 February 2010, 20:18
KenC
Just call me: Ken
 
Klang
Malaysia
Quote:
Originally Posted by ddoggett View Post
I suppose if a guy had a radial drill press and setup a long enough table, using a standard endmill and setting up the drill press to 45 degrees the machining of the rails would depend soully on the feedrate as for labor timing.
If you read hard enough, you will find the instructions & examples of rail cutting & grinding using the laser cut grinder skate. I build a 8' long work bench for the grinding, but many did it without a bench.
Of course, surely you can mill the rail if that is what you wish.... There are examples of such procedure here in this forum too...

Now, hang up your phone, unplug the door bell, send your wife & kids to the in-laws, put a "gone fishing" sign on your door & start studying the forum thread by thread, & word by word....
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  #18  
Old Sat 27 February 2010, 04:57
J.R. Hatcher
Just call me: J.R. #4
 
Wilmington, North Carolina
United States of America
Send a message via Skype™ to J.R. Hatcher
Dan, grinding the rails was not that time consuming or difficult for me, and I was the first to grind this way .... with the skate. I spent a total of 9 hours, cutting down and grinding. It took almost that long to clean the workshop of all that black stuff . Take a look at this link ...... maybe it will help, also click the word "skateboard" within the page.
http://www.mechmate.com/forums/showt...5&postcount=17
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  #19  
Old Tue 02 March 2010, 11:21
TheDave
Just call me: dave
 
Toledo (Ohio)
United States of America
Quote:
Originally Posted by ddoggett View Post
I suppose if a guy had a radial drill press and setup a long enough table, using a standard endmill and setting up the drill press to 45 degrees the machining of the rails would depend soully on the feedrate as for labor timing.
Or if you have a standard drill press with an end mill chucked in, you could just clamp a piece of angle on the table (with the hypotenuse of the triangle on the face of the table). When you lay your piece to be milled against the clamped angle you will automatically get your 45 degrees.
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  #20  
Old Wed 03 March 2010, 02:33
ddoggett
Just call me: Dan
 
Ottumwa, IA
United States of America
Cool

Thats the ticket Dave! Believe thats the route I'll take. Thanks.
I love this forum!!!!!!!
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  #21  
Old Wed 03 March 2010, 20:38
swatkins
Just call me: Steve
 
Houston
United States of America
Quote:
Originally Posted by TheDave View Post
Or if you have a standard drill press with an end mill chucked in, you could just clamp a piece of angle on the table (with the hypotenuse of the triangle on the face of the table). When you lay your piece to be milled against the clamped angle you will automatically get your 45 degrees.

Do you think that method will give you an accurate edge profile? I think it would be hard to keep it uniform feeding it by hand...
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  #22  
Old Wed 03 March 2010, 20:49
KenC
Just call me: Ken
 
Klang
Malaysia
Quote:
Originally Posted by swatkins View Post
Do you think that method will give you an accurate edge profile? I think it would be hard to keep it uniform feeding it by hand...
piling on top of this,

Would like to point out that this angle iron flex a lot & the length magnifies the flex, this flex can go over 10cm if left overhung.
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  #23  
Old Thu 04 March 2010, 17:13
TheDave
Just call me: dave
 
Toledo (Ohio)
United States of America
Guys,

I merely suggested an approach someone could take. The accuracy of the results depends greatly on the skill of the person who sets it up and does the work. Someone who knows what size cutter to use, what speed it needs to turn, what the feed rate should be, and has proper support of the workpiece (which may include infeed and outfeed tables) should have no problems getting accurate results.

I wouldn't suggest this method for someone who has never done any metalworking - I would suggest the grinding method. But Dan seems to have some fabrication experience. Besides, it really isn't that hard. I've done similar processes myself with good results.
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