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  #31  
Old Sat 29 March 2008, 10:32
Robert M
Just call me: Robert
 
Lac-Brome, Qc
Canada
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Laser part VS C Channels ?

Gerald,

Another alternative in material Iím wondering/considering for on the cross bearers (#1010302) & for the main beams (1010322) is; would it be seine to substitute those c-channels for some laser cut & bent ones !
Obviously with an appropriate gauge, witch btw I have no certainty on my estimated conversion, but say the 1010322 @21kg/m (14.08lb/ft) should be close to in std inches size to 3/8íí thick.
This is still bentable for some laser places that Iíve ask about !!
So, do you think it is seine and right to take that route?
No quote yet, but I estimate to be = or less cost than regular C-channels, with all itís benefitís we know about laser drawn parts !? ?!
Robert
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  #32  
Old Sat 29 March 2008, 16:00
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
The price will be much higher if laser cut and bent. Add the transport price from the laser cutter to your town. (Channels can normally be found in your town). The channels will normally be straighter than the bent parts.
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  #33  
Old Mon 31 March 2008, 13:42
IN-WondeR
Just call me: Kim
 
Randers
Denmark
Robert

You can have a look at my setup, it has been made by lasercut sheet metal and then bent, it works great for me.
Offcourse I have an advantage in the sense I'm working with lasers so I'm not paying much for something like that...
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  #34  
Old Mon 31 March 2008, 22:57
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
See post #14 in this thread
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  #35  
Old Fri 13 June 2008, 14:23
Barman
Just call me: Bart #36
 
antwerpen
Belgium
Hello ,

I'm thinking to make a MM for MDF boards of 122 x 244 cm.
The main beam will then 3040 mm and the cross bearer will be 1640 mm.
Today I have informed by the supplier of c-chanel's and the tube's.

The specified C-channel are not used in Belgium.
C-channel are called here UPN-profile.
I have some questions about these profiles because the sizes and weights do not fully match ,before I order these profiles.

About the router table.

For the main beam, I will order a c-channel 180 x 70 , but the weight is 22.4 kg/m instead 21kg/m.
Is that a problem? I do not think so.

For the cross bearer is the smallest c-channel 80 x 45 x 8.8 kg/m instead of 76 x 38 x 7 kg/m.
It is the smallest in their series. Are these profiles too heavy?

I would like to use 8 cross bearer or are 7 suffice?

About the gantry.

The cross member tube must be 100 x 50 x 2 mm but the thickness is 3 mm instead of 2 mm.
Is this a problem?

Thank you

Sincerely
Bart
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  #36  
Old Fri 13 June 2008, 21:05
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
Goeie MŰre Bart

About the router table.

For the main beam, I will order a c-channel 180 x 70 , but the weight is 22.4 kg/m instead 21kg/m.
Is that a problem? I do not think so. Absolutely no problem because that is static weight. Extra weight is better.

For the cross bearer is the smallest c-channel 80 x 45 x 8.8 kg/m instead of 76 x 38 x 7 kg/m.
It is the smallest in their series. Are these profiles too heavy? Again, there is no problem, same as above

I would like to use 8 cross bearer or are 7 suffice? If you prefer 8 cross bearers, that is better.

About the gantry.

The cross member tube must be 100 x 50 x 2 mm but the thickness is 3 mm instead of 2 mm.
Is this a problem? I think that will match the "more solid" table you are building. You will have a good industrial, tough machine and the heavier/stiffer mass will reduce the chance of vibrations. You might have a slight penalty on speed when cutting around a sharp corner, but overall you should have a better quality of cut finish. It is not a big difference either way - I have 2 gantries, 2mm and 3mm, and I can't say that one is better than the other.
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  #37  
Old Sat 14 June 2008, 01:52
Barman
Just call me: Bart #36
 
antwerpen
Belgium
Thank You,
Now I can order this at my work .
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  #38  
Old Sat 14 June 2008, 03:09
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
Quote:
Originally Posted by Gerald D View Post
. . . I have 2 gantries, 2mm and 3mm, and I can't say that one is better than the other. . .
I must add that the two gantries are different lengths:
Table width (Y) = 1830mm = 2mm thick gantry
Table width (Y) = 1220mm = 3mm thick gantry
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  #39  
Old Sun 24 August 2008, 06:01
kaartman
Just call me: Koning #20
 
Abu Dhabi
United Arab Emirates
First and last Cross Bearer placement

I need to understand the placement of the first and last cross bearer, on drawing 10 10 240 the stop block is X +205 apart, do I take 102.5 plus 29mm from the stop block or do I use half the width of the Y gantry from the stop block, On drawing 10 10 300 is it correct if I say the 0,0 stop block is inward from the spoil board edge ?

Regards
Koning
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  #40  
Old Sun 24 August 2008, 06:47
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
The stop-blocks are positioned to stop the gantry from running off the ends of the rails. Do not try and figure out the cross-support locations from the stop block locations.

Because the router is not in the center of the gantry, the cross-supports are offset by the same amount relative to the ends of the x-rails. Typically, the router is 100mm offset in the y-car/gantry, and that gives the 100mm offset mentioned on 10 10 300 W
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  #41  
Old Mon 25 May 2009, 13:24
cvriv.charles
Just call me: charles
 
New Jersey
United States of America
I have two questions.

I think I would rather use 4" x 7.25# as the 1010302SB with the legs facing downward instead of theway the 3" x 4.1# are install in the plans. Would this be fine?

Also,... the plans do not cover bolting the 1010302SB's to the 1010322SA's. What size bolts are being used for that task? I was thinking about using one big bolt but then again, having two smaller bolts per end I think maybe would be better? Maybe two 3/8" bolts?!?!
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  #42  
Old Mon 25 May 2009, 16:06
lumberjack_jeff
Just call me: Jeff #31
 
Montesano, WA
United States of America
I think the intent is to weld them instead of bolting. They also serve a role in preventing the table from going out of square, assuming a parallelogram shape, so for this reason, one bolt would be suboptimal. (Granted, the deck and the spoilboard will act to resist this deflection)

Also, a channel shape has most of its rigidity perpendicular to the plane of the flanges (the legs). The web (or the back) of a channel should be oriented parallel to the anticipated load, usually vertically.

If you place them with the legs down, they'll be less resistant to deflection when you load a sheet on it. Will they still be resistant *enough*?.... I dunno.

Short answer: I would weld them in the orientation shown on the plans.
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  #43  
Old Mon 25 May 2009, 21:48
cvriv.charles
Just call me: charles
 
New Jersey
United States of America
I can't weld them. I need to be able to dismantle the machine for transportation.

This is what I'm going to do,... I'm going to use the 3" x 4.1#. I am going to bolt them to the xBeam but,... I'm going to weld the channels together as two sets of 4. This way when I bolt these 2 sets to the xBeams, I won't have to worry about my table going out of square.
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  #44  
Old Tue 26 May 2009, 06:46
domino11
Just call me: Heath
 
Cornwall, Ontario
Canada
Charles,
Your spoilboard will do the same function and save you some work. You will need a spoilboard anyway.
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  #45  
Old Tue 26 May 2009, 08:44
J.R. Hatcher
Just call me: J.R. #4
 
Wilmington, North Carolina
United States of America
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My thoughts exactly Heath
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  #46  
Old Tue 26 May 2009, 12:19
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
Quote:
Originally Posted by cvriv.charles View Post
I think I would rather use 4" x 7.25# as the 1010302SB with the legs facing downward instead of theway the 3" x 4.1# are install in the plans. Would this be fine?
I am out of town and away from my data tables, but my gut feel is that you are reducing the strength by more than 50%
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  #47  
Old Tue 26 May 2009, 14:09
lumberjack_jeff
Just call me: Jeff #31
 
Montesano, WA
United States of America
Oriented legs down (or up), a C4x7.25 50" long with a uniform 150# load will deflect .026" at midspan. (the kind of loading from very heavy sheet goods)
The same C4x7.25 50" long with a single-point load of 150# will deflect .11" (the kind of loading resulting from standing on the crossmember to change a light bulb)

http://www.engineersedge.com/beam_be...flection_2.htm

Structural steel has a modulus of elasticity of 29,000,000.

In the y axis (legs down) C4x7.25 has a moment of inertia (I) of .432. It has a section modulus (Sy) of .343. It has a radius of gyration (Ry)of .45. It has a neutral axis distance (Z) of .459.

In the x axis (legs horizontal) it has an I of 4.59, an Sx of 2.29, an Rx of 1.47 and a Z of 2.

It's about 1/8th as strong oriented horizontally as it is vertically.

By comparison,, a 2x6 placed on edge experiencing the same point load at the same span will deflect .014"

Charles, in your other thread, you show the crossmembers oriented the traditional way. Am I misunderstanding your question?

Last edited by lumberjack_jeff; Tue 26 May 2009 at 14:37..
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  #48  
Old Tue 26 May 2009, 23:20
cvriv.charles
Just call me: charles
 
New Jersey
United States of America
Well,... im changing things around. i am going with the 3" x 4.1#. At the time I made the change back to the 3" beams because of the weight. the 3" is about half the weight of the 4" according to inventor.

Im just going to build according to plan.
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  #49  
Old Tue 26 May 2009, 23:34
sailfl
Just call me: Nils #12
 
Winter Park, FL
United States of America
Charles,

I think that following the plans is a great idea. It is a proven design and you will be happy with the machine you build. Gerald has designed an excellent machine.
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  #50  
Old Wed 27 May 2009, 23:57
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
Jeff, thanks for fielding that question - nice to have someone else around to explain "strength of materials"

Quote:
Originally Posted by Gerald D View Post
I am out of town and away from my data tables, but my gut feel is that you are reducing the strength by more than 50%
Back this morning and glanced through my tables. A channel typically loses 80% of its stiffness when rotated 90 degrees. That is a lot!
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