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  #61  
Old Mon 01 March 2010, 20:17
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
The overhang of the alu rail past the steel beam is very short and there are no concerns of it bending over such a short distance.
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  #62  
Old Mon 01 March 2010, 20:30
Zouave
Just call me: Eric #115
 
Sacramento, CA
United States of America
Alright, that's kind of what I figured, but wanted to confirm before I went ahead and settled on that design.

Btw, been a long-time lurker on here, will be getting started in my build, if all goes well, within the next month. Thanks for all the information and hard work you've put into this.
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  #63  
Old Tue 02 March 2010, 05:25
sailfl
Just call me: Nils #12
 
Winter Park, FL
United States of America
Eric,

I have aluminum rails and they work fine. You will not have any problem.
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  #64  
Old Mon 08 March 2010, 02:13
cvriv.charles
Just call me: charles
 
New Jersey
United States of America
What I would like to ask is why we have to use the size 3 v-cap's? I personally want the v-caps for the hardening and the easy of changing them out if they should get worn out. But I really do not wan to use the aluminum as the rail base for installing them. The inner radius is a problem with the steel angle. but the the size 2 rails are used,... the steel angle can be easily used. Dim B = .250" which is pretty much the width of the garage ground steel angle. Except the v-cap is hardened. From the pics the v-bearings arent even using the entire rail surface anyways. So whats the deal with having to use size 3?

Also,... do the shims remain at S1 during the use of the machine? Or are they only used for leveling and after the v-cap bolts are tightened they are removed?

Last edited by cvriv.charles; Mon 08 March 2010 at 02:21..
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  #65  
Old Mon 08 March 2010, 02:33
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
See post #59 above.
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  #66  
Old Mon 08 March 2010, 04:06
cvriv.charles
Just call me: charles
 
New Jersey
United States of America
Ok. But im sure it would be fine if bolt spacing was close enough. Some of the bolt spacing I have seen in some of these pics is kind of scary
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  #67  
Old Mon 08 March 2010, 07:29
cvriv.charles
Just call me: charles
 
New Jersey
United States of America
I think this is how Im going to go about it. A 3/16" x 2" iron flat bar to hang the rack and 2" x 2" x 1/8" angle iron to hold the V-Track vertical. The V-Track hangs on the side of the angle iron without the radius. Together they will hold up the gantry nicely. It looks pretty this wat too Both will have the same .5" mounting holes for adjustment. And the proxy holes too. Would I have to drill the proxy holes through both or just the angle? I dont even know how the proxies work yet,...
Attached Images
File Type: jpg xRailRack-600.jpg (6.5 KB, 1248 views)
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  #68  
Old Mon 08 March 2010, 10:16
sailfl
Just call me: Nils #12
 
Winter Park, FL
United States of America
Charles,

Why don't you want to use the aluminum?
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  #69  
Old Mon 08 March 2010, 12:54
cvriv.charles
Just call me: charles
 
New Jersey
United States of America
It just doesnt feel right to me I mean, we're constucting these machines that weigh nearly a ton out of steel and here are my rails or rail bases made of aluminum. It's just not sitting with me well. Im pretty sure this is what everyone is thinking that doesnt want to use aluminum.

Initially I was just going to grind my own rails out of angle iron. But I was worrying about them wearing down. I REALLY dont feel like changing them out any time soon. I read gerald's story about the height of the rails being 28mm. He said he was changing out his rails. Then was forced to use the hardened rails. This made me nervous. because he was changing out his rails probably because they got worn down.

I know he used his machine as a work horse,... but so will i. Im not using mine as a hobbist. My machine will be running almost everyday and all day. With the money I have allocted for this machine I will buy another laser/bent kit for another machine. I need this machine to be bullet proof. I need it to hold it's shape.

The method I have proposed will cost just about the same but will be stronger, look better,... it will be a little bit more work but im fine with that. And most importantly,... my gut is ok with it. I will report my results of course
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  #70  
Old Mon 08 March 2010, 19:23
cvriv.charles
Just call me: charles
 
New Jersey
United States of America
Here's my approach. I think I will do it because theres no reason it wont work.

This is all steel we're looking at. There's a 1/8" thick base to hold up the rack. Then a 3/16" angle to hold the v-track. The rack is mounted to the 1/8" thick base using countersunk screws, 15 8-32's along the length of the rack in 8.25" intervals. No tape,... even though I didnt really have a problem with the tape. I did the screws because it works The holes in the rack do not pass completely through, .375". There is a very good reference surface forthe v-track too seeing there is no radius on the side in which its to be installed. I like it.
Attached Images
File Type: jpg xRailRack_2-600.jpg (6.4 KB, 1229 views)
File Type: jpg xRailRack_3-600.jpg (6.5 KB, 1226 views)
File Type: jpg xRailRack_4-600.jpg (8.4 KB, 1228 views)
File Type: jpg xRailRack_5-600.jpg (9.2 KB, 1229 views)
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  #71  
Old Mon 08 March 2010, 22:17
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
Quote:
Originally Posted by cvriv.charles View Post
. . . . I read gerald's story about the height of the rails being 28mm. He said he was changing out his rails. Then was forced to use the hardened rails. This made me nervous. because he was changing out his rails probably because they got worn down. . . .


I have never replaced (changed out) rails and I have never used hardened rails for the x and y axes. You may be confusing something I said about the old ShopBot z-axis that wore out.
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  #72  
Old Mon 08 March 2010, 22:27
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
Quote:
Originally Posted by cvriv.charles View Post
. . . . There's a 1/8" thick base to hold up the rack. Then a 3/16" angle to hold the v-track. .
I suspect that if you did the calcs, you are going to find that a sandwich of 1/8" steel and 3/16" steel might be more flexible than 1/4" aluminium. I don't think you have an appreciation for how flimsy your individual components are . . . . . pick up a length of any of those in the middle and watch the ends droop probably 6" or so. You might also see the thin stuff bow up between your fixing screws.
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  #73  
Old Tue 09 March 2010, 01:19
cvriv.charles
Just call me: charles
 
New Jersey
United States of America
Oh maybe your right about the rail changing being for the shopbot. But isnt a rail a rail?

Well,... I would still like to try this. If I fail I fail but I have to try. I have a feeling it would work good. If it does not I will report back. So that others may avoid it.

Thanks GD.
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  #74  
Old Tue 09 March 2010, 02:47
KenC
Just call me: Ken
 
Klang
Malaysia
Quote:
Originally Posted by cvriv.charles View Post
Oh maybe your right about the rail changing being for the shopbot. But isnt a rail a rail?
Charles,
Yes, a rail is a rail, a tire is a tire, ac car is a car... etc some tire last longer on the same car, some cars out perform others & some cheap crappy looking rails last longer in a mysterious way

I wish I don't have to come to this but I do suggest you focus on building & leave the design part out if your goal is "to build a MecaMate.... ". Do the mod/upgrade on your 2nd MM (since your ARE building a 2nd one)

MM is a good proven design; Radical in some way & using "crappy" components freely (which IMHO the beauty of it)... BUT don't judge the book by the cover, build & operate one before you pass any judgment... Even though my MM is still in the building process, I learn to appreciate the design ever more as the machine takes shape.

Some how, you got to trust somebody, some time...

I sound like leaking up to Gerald, but I'm not, its a fine line between appreciation & idol-ism.

Hope this help.
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  #75  
Old Tue 09 March 2010, 03:16
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
Quote:
Originally Posted by cvriv.charles View Post
Oh maybe your right about the rail changing being for the shopbot. But isnt a rail a rail?
The rail changing was only ever for a ShopBot Z-axis, which is quite different to the x and y axes. So, a rail isn't a rail.
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  #76  
Old Tue 09 March 2010, 11:06
cvriv.charles
Just call me: charles
 
New Jersey
United States of America
Quote:
Originally Posted by Gerald D View Post
The rail changing was only ever for a ShopBot Z-axis, which is quite different to the x and y axes. So, a rail isn't a rail.
Ok. That I understand. Thats why you recommend the hardened ground plate to be used for mounting/ rails for the z-axis.

I am a very stuborn person. I am going to try this regardless. Its human nature. It would only be a small price to pay if it failed. More of an annoyance really.

Everything else im ok with. It "feels" right. Dont really plan on changing anything else. Just this. Which isnt to far off from the plans.

I dont mean to offend by the change. I do have faith in GD. But this "feeling" of mine is what I call a sickness. even if I did the aluminum angle. After the machine was built and running. I wouldnt make it to my next machine but trying this. Because the idea eats at me.

Anyways. Just a quick question though. the angle iron im using is 3/16" thick. Thats only .0625" smaller. And it doesnt hang off the main beams as much as the one in the plans. My track is hanging from an 1/8" flat bar with 15 bolts holding it in place. It has to support the up force of the motor on the spring. No big deal. It extends out as far as the rails do in the plans. It also helps to support the bottom of the angle iron. I really feel this is rock solid.

You say that along they are weak and flimsy if I hold them at center the ends to sag. Again the angle iron isnt to far off from the rail in the plans. And I will have 15 bolts hold all that together. More if needed. I just dont see this as being a total failure.

Thanks for the input.
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  #77  
Old Tue 09 March 2010, 20:33
KenC
Just call me: Ken
 
Klang
Malaysia
Quote:
Originally Posted by cvriv.charles View Post

............I am a very stuborn person. I am going to try this regardless. Its human nature. It would only be a small price to pay if it failed. More of an annoyance really.

...... But this "feeling" of mine is what I call a sickness.

....... Because the idea eats at me.
Some how that sounded really familiar.... I feel a kin to you now...

Anyway, if that can put your mind to peace, give it a shot.

BTW, Having worked with steel long enough in my day job, I recon 1/8" flat bar IS flimsy & will not give you the flat you are looking for, you may (only may, no promises) have better luck with milled 25mm/1" thk high carbon steel. BUT I leave it to your own digression.

A side note, I taped my Y-rack onto the gantry rails last night & the 1mm the double sided tape filled the gaps as expected & held up beautifully. No sign of the problem that worries you so much
Y-rack on gantry 3.jpg
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  #78  
Old Tue 09 March 2010, 21:25
cvriv.charles
Just call me: charles
 
New Jersey
United States of America
Excellent. I feel better now that someone really understands where im coming from. As you said Im really doing it to ease my mind.

I really dont mind the tape all that much. I still might go ahead and use it. But I would erally like to try mounting the rack the way I showed. tapered bolts throughout the length of the rack. Non-penetrating holes. Why? because the setup is almost perfect. Atleast in my opinion.

You are right, 1/8" flat bar steel is pretty flimsy on its own. But I think with the way im going to mount it it will be ok. What forces do you think it will be subject to other than the weight of the rack, the upward force of the motor on a spring, and the back and forth x axis movement?

I could even drill and tap the angle underneath and bolt the 1/8" to the angle too. I really think this is doable one way or another. I might even add more bolts for mounting the angle and flat bar and the rack. I'll make it work.

Im really looking forward to starting my build. Im waiting for my funds to show up in my bank account right now im working on my garage getting it ready for this beast.
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  #79  
Old Tue 09 March 2010, 21:55
KenC
Just call me: Ken
 
Klang
Malaysia
You will be amaze how easy it is to tape the rack on. It is the perfect way for a lazy person like myself.

Anyway, I think we have a lot in common, I was waiting for fund to come in from some jobs I did earlier since July 09 & didn't have any work space until mid-Nov09. BUT I did what I could & do every bit of the work whenever I can by small purchases, doing leg works for better deal & sourcing equivalant spec items. If I were to wait for enough fund to do all the purchase I don't think the build would even take off in the first place.

My original intention was pre-ground rails, but the $$$ in flux wasn't that fast & shy in volum. I scraped around hard enough to come up with the money to buy the steel & started grinding the rails while waiting for the money & before I know it, the rails are completed & the table erected while the $$$ only trickled in slowly & other commitments are draining them quickly...

Well... I guess the only other way out other then saving up more fund is to make more money...
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  #80  
Old Wed 10 March 2010, 00:36
cvriv.charles
Just call me: charles
 
New Jersey
United States of America
Well,.. we do have a lot in common I didnt have any space for a machine like this until now. I recently bought a house with girlfriend. I made sure it had a huge garage. I have a huge 3 car garage with an upstairs loft. totally empty and ready to be filed I have to finish the inside though. No insulation or sheetrock. Hot during the sumer and cold during the winter. Im doing this all now. I was actually posting here a while ago saying i was purchasing a home etc etc. Hoping atleast. Well we got exactly what we wanted.

With the purchase of our home we get an $8000 incentive. Well atleast I do because its my first home. With some other money we paid toward the house Im getting back 10000. I will be able to purchase everything up front. If it wasnt for this I would be in your shoes. Saving slowly do what I can. Which im fine with because that all i know. I am very fortunate to be in the position I am now. For once atleast. Bummer thing though is that it could take up to 20 weeks to get my return So while I wait I will continue working on the garage and going through the mm plans building my machine on my pc.

I am hoping that when im good enough with my router I will be able to make money with it to build another machine. and keep moving forward.

about the 1/8" flat bar being flimsy. If you hold it at the center of its length,... yes it will bow down. But if you hold it at the center of it's width,... that should be enuogh to hold the rack and deal with any forces. Same goes for the angle iron. The center of its width is what we worrying about with the rails.

Oh and should you hve painted your machine before sticking the rack to the rail? or should the tape be stuck to bare clean metal?
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  #81  
Old Wed 10 March 2010, 01:12
KenC
Just call me: Ken
 
Klang
Malaysia
Well, money isn't everything but we can do much without it... OK enough of the ranting, lets get back to the fun

I hand painted & recon it had cured enough (over 1 month) before I get to tape up the rack. Hope my paint job is good enough to hold.
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  #82  
Old Wed 10 March 2010, 02:06
cvriv.charles
Just call me: charles
 
New Jersey
United States of America
Quote:
Originally Posted by KenC View Post
Well, money isn't everything but we can do much without it... OK enough of the ranting, lets get back to the fun

I hand painted & recon it had cured enough (over 1 month) before I get to tape up the rack. Hope my paint job is good enough to hold.
Lordy thats one thing that scares me,... painting. I have a ton of patience but when it comes to painting,... I do not. dont know why. I would seriously have to try hard this time around because this just isnt an old rusted bicycle, lol. A lot of the machines I have seen on this site have amazing paint jobs. I didnt read to deep into their threads to find out if they had the parts painted or they did the parts themselves or what. Im think I will try myself. Get a nice spray gun and give it a go. I have to research all that though. Last thing I want is chipping.
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  #83  
Old Wed 10 March 2010, 02:28
KenC
Just call me: Ken
 
Klang
Malaysia
I hand painted using roller brush. prefer it this way. Even though I can borrow a set of spraying equipment as long as I bother to ask. & there is a paint shop less then 30m away.

My strategy is to choose all the methods that I know & well enough with the tools I have. If I need/want to learn a new skill, such as spray painting, I'll start another project for it.

Building the MM really doesn't need special skill, the only skill required I recon is to stay focus on build & stick to the plan as much as possible. Which is really a huge challange
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  #84  
Old Wed 10 March 2010, 04:25
cvriv.charles
Just call me: charles
 
New Jersey
United States of America
LOL. Good advice. Well I do agree with you on using what you know now to do what you need done now. But for me,... same as the rails. if theres somethnig I want to do i have to do it. if I dont it eats at me. I'll redo it. I have scrapped completed projects that were near perfect except for a tiny flaw. a dumb flaw. the kind of flaw whre your yelling and screaming "STUPID STUPID STUPID!" Its crazy. Totally ridiculous. I am extremely anal. A perfectionist.

I cant say that you dont need special skills to make a MM. Because you do. The only real skills I think someone needs to do ANYTHING is patience and perfectionism. Straight up.

Following plans 100% is a real problem for me too. LOL.
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  #85  
Old Wed 10 March 2010, 07:49
xraydude
Just call me: Ted
 
New Orleans, LA
United States of America
Quote:
Originally Posted by cvriv.charles View Post
Well,.. I recently bought a house with girlfriend. I made sure it had a huge garage.
Wait a second... your house came with a girlfriend?
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  #86  
Old Wed 10 March 2010, 08:34
cvriv.charles
Just call me: charles
 
New Jersey
United States of America
Quote:
Originally Posted by xraydude View Post
Wait a second... your house came with a girlfriend?
And a huge garage! What more can a guy ask for! LOL.
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  #87  
Old Wed 10 March 2010, 09:41
cvriv.charles
Just call me: charles
 
New Jersey
United States of America
Almost done with the details. Looks pretty much like the ground rail. A combo of the two options available. Theres a TON of bolts per rail. I believe there are 21 - 5/16" bolts hold the hold assembly to the main beams. Theres,... 21 - 8-32 bolts hold the rack to the flat bar. Theres 29 - 1/4" bolts holding the v-track to the angle iron.

I decided to mount the v-track to the angle iron flush, v-track lip resting ontop of angle iron vertical leg. At that point I will treat the entire assembly as if it was a MM ground rail. Meaning then I will shim up the whole thing as one piece until the v-tracks are true to one another.

It will work. I just have to make damn sure that I am very precise with everything. Especially cutting/ grinding the angle down to size. Im going to purchase a horizontal bandsaw to make all my rough cuts. I think I will build some kind of jig like table to fine grind the angle to it target size making sure everything is precise. Might buy and extra to practice on,... or better yet if I mess up i'll just buy another.

The v-track is bolted with 29 - 1/4-20's that screw right into the angle iron. No bolts. I read that 1/4 - 20's can be torqued to about 125 in/lb or about 10.4 ft/lb. Thats more than 290 ft/lb total hold the track to the angle. A lot of the weight will be rest on teh track lip. So im not worried about the track moving. I believe the bolt interval is 4.3125". v-track is T3.

This is my plan.
Attached Images
File Type: jpg xRailRack_1-600.jpg (17.5 KB, 1171 views)
File Type: jpg xRailRack_2-600.jpg (15.3 KB, 1167 views)
File Type: jpg xRailRack_3-600.jpg (10.8 KB, 1172 views)
File Type: jpg xRailRack_4-600.jpg (8.9 KB, 1171 views)

Last edited by cvriv.charles; Wed 10 March 2010 at 09:46..
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  #88  
Old Fri 09 July 2010, 21:47
David Bryant
Just call me: David #99
 
Western Australia
Australia
Hi
In post #10 it suggests shimming at S1. Is this necessary in the set up phase? Or is it easier to keep the steel and al tight and do any shimming between the Al and the steel channels?
I am not sure if I should locktite the rails to the Al and keep my 6mm holes or drill to the 8mm clearance holes suggested on the plans to allow for shimming.

Thanks
David
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  #89  
Old Sat 30 June 2012, 10:45
Mr Ron
Just call me: Mr Ron
 
Vancleave, Ms
United States of America
I am in the process of building my own CNC machine (not a MM) and I'm trying to incorporate lessons learned by others into my final design. After reading all the replies to this post, I find one flaw to the use of capped rails. Capped rails are nice and straight, but the surface you bolt them to must also be nice and straight. I suppose you could shim the rails at each bolt hole (tedious), but if you are going to go to the trouble of using capped rails, which are expensive, a better way is to use steel angle rail and grind the V profile with the skate fixture. I could see rails for the Z-axis, being much shorter than the X or Y axis, could be made perfectly straight on a milling setup, but 8 foot rails? I can't see any advantage to capped rails.

I would like to have gone the MM route, but I started my current machine over a year ago and I have much time invested in it's design. My agenda for building a CNC machine is different from most other constructors. Aside from cost, I am trying to educate myself about how to build CNC machines. Getting one built in the shortest amount of time regardless of cost is not my agenda. To me this is a learning experience. I want to start from the bottom and work my way up.

So far, I have seen many different designs and ideas, some good, some not so good. I'm trying to approach this in the same manner as learning another language. I find the MM design is a very good one. The main good point is the location of the router, between the gantry rails. Other conventional designs have the router and carriage canterlevered from the gantry which places much stress on the gantry and the Y and Z bearings. My design, although of plywood construction, will incorporate the MM router location. The Z-axis bearings will still have an off center load on them, but I am working on that.

My being on this forum, is not so much to ask for advise, but is to present my ideas for your evaluation. My approach to building a CNC machine is from an engineering point of view and although the MM is well engineered, I have committed myself to keeping the cost down as much as possible without ignoring good engineering practice. I know cost is a concern for many as it is for me and even the relatively low cost of the MM is still out of my range. Those who have committed to MM and are happy with the results, shouldn't be concerned by my comments.
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  #90  
Old Mon 02 July 2012, 13:04
smreish
Just call me: Sean - #5, 28, 58 and others
 
Orlando, Florida
United States of America
Ron,
Not to be difficult, but this site is dedicated to MM fabrication and use.
The Use of Cap rails, or ground rails in the MM design - for the MM design - are proven and accurate when applied to this design.
The use of the MM method in other machines is not a point of discussion due the all the variables involved. The forum is not "closed to other ideologies", but only in the need to focus on those committed to the MM design and not others.

You mention that some ideas are "good and not so good". I personally feel that is a relative opinion.

The MM design is final. It has 100+ units in production currently without many issues.

I wish you luck with your endeavor - but evaluation discussions might be best suited at the CNC Zone or others.

Best,
Sean
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