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Message |
    
Robert Cheal
Registered
Username: Robert_cheal
Post Number: 8
Registered: 08-2006
| | Posted on Sunday, October 08, 2006 - 01:35 am: | 
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Gerald,
I have some surplus Galv. steel left over from some idustrial projects in the yard and I wonder if some of it would make sense to use until I get to the: main beams, XY-gantry, and YZ-car.
For example I have 7 ea. of 4x4- L -1/2" thick 78" long and I wonder if they could be used for cross supports or would they be to heavy for the main beams to support.
I have only briefly looked at some of your drawings as I am just starting look deeper into buiding another machine. When I see steel lying around that will likely end up hauled as scrap it makes me think of a friend who like to say "free goes along ways."
I admire your work on this forum and forward to learning more.
Thanks, Robert |
Gerald_D
Registered
Username: Gerald_d
Post Number: 266
Registered: 11-2005
| | Posted on Sunday, October 08, 2006 - 08:07 am: |
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Hi Robert. The idea of L-section as a cross-support puts me off a little. C-section is just so much better. My book on "sections" is at the office and I'll have a look at the numbers there tomorrow. The weight doesn't worry me because it is static. When the main x-beams sag a little under that weight, the x-rails are shimmed to get them straight. |
Gerald_D
Registered
Username: Gerald_d
Post Number: 271
Registered: 11-2005
| | Posted on Monday, October 09, 2006 - 08:32 am: |
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Hi again Robert. Had a look at the data tables and seen that those angles would be great as cross-supports. Have fun drilling them!  |
Robert Cheal
Registered
Username: Robert_cheal
Post Number: 9
Registered: 08-2006
| | Posted on Monday, October 09, 2006 - 04:41 pm: |
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Gerald,
Thanks for your response and I agree in the first person drilling will not be the fun part of possibly using them. I am going to take stock of what is lying around before it all gets hauled off. And just because it is free does not mean it has to be used at all costs. The fun part is finding workable pieces... then the work begins $500 worth a drill bits for $200 work of steel. |
ralph hampton
Registered
Username: Rhfurniture
Post Number: 34
Registered: 08-2006
| | Posted on Monday, December 04, 2006 - 11:23 pm: |
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Gerald,
I have in my mind a system that has a work area of bout 2500 x 500 x 200 (xyz) for joinery and small solid wood part work - 99% of my work would fit into 1000 of the x of such a table. How well would your system adapt to such a size, and what could the minimum footprint be (seriously teeny workshop).
Just fishing at present, regards, r./ |
Gerald_D
Registered
Username: Gerald_d
Post Number: 582
Registered: 11-2005
| | Posted on Tuesday, December 05, 2006 - 07:47 am: |
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Ralph, the motor/gantry arrangement of a ShopBot or MechMate must make them of the worst systems for small footprints. Inboard motors would help a lot. A single-beam gantry would also help.
However, I don't see a serious obstacle in adapting the MechMate down to that size. A lot of the x-rails would probably be covered by a board to serve as a general purpose worktop most of the time. Therefore, you might build the whole thing lower so that this worktop is at a convenient height.
I have a design brewing in the background for a wall-mounted system..... The x-rails fixed to the wall (one high, one low). The "car" running on them to have an arm (ala radial arm saw) extending horizontally over a standard workbench, with the y-rails. Then a y-car and z-slide running on this y-arm... |
ralph hampton
Registered
Username: Rhfurniture
Post Number: 35
Registered: 08-2006
| | Posted on Tuesday, December 05, 2006 - 08:49 am: |
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(:
Will ponder a while... |
Paul A
Registered
Username: Paul_a
Post Number: 3
Registered: 12-2005
| | Posted on Tuesday, December 05, 2006 - 09:09 am: |
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Hi Gerald
There was a school teacher in the UK who built a wall mounted router as you described, the guy posted a build history on cnczone.com. |
Lee Wenger
Registered
Username: Wenger
Post Number: 1
Registered: 04-2007
| | Posted on Wednesday, April 04, 2007 - 04:51 am: |
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CamTech makes a router that generally fits the description... http://www.camtech.ca/products/routers/spacemaker/SpaceOverview.cfm
Is that what you were thinking?
I've always liked this idea due to the improved space utilization of this design but it seems to me that the idea is reliant on having a vacuum table. Or maybe a t-slot table at a minimum. I've also wondered about how beefy of a Y motor you'd need for such a design either that or a hefty gas spring or counter-weight. |
Gerald_D
Registered
Username: Gerald_d
Post Number: 1214
Registered: 11-2005
| | Posted on Wednesday, April 04, 2007 - 07:21 am: |
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Lee, we are talking of something quite different....
Imagine a standard workbench against a wall in a small workshop....and then a CNC machine that is attached to the wall above the bench, cutting a workpiece that is lying horizontally on the workbench. Naturally this is for smaller stuff, but these are mostly the type of guys that need "spacesavers". One-man sign companies, for example. Or guys using high-end natural timber planks. The really big machines are for the MDF brigade.
(Attaching to the wall implies a solid brick_&_mortar wall, which is common around here.) |
Kim Mortensen
Registered
Username: Inwonder
Post Number: 85
Registered: 12-2006
| | Posted on Wednesday, April 04, 2007 - 07:01 pm: |
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Gerald.. I'm thinking of making my own crossmember bearers. I'm going to cut them in 5mm mild steel, and then bend them 2 places to make a C-channel like piece. it will be 40mm high and 80mm wide, the main board is going to lay on the 80mm side of the beam. is this possible.??? If you want a picture pls. let me know... |
Gerald_D
Registered
Username: Gerald_d
Post Number: 1217
Registered: 11-2005
| | Posted on Wednesday, April 04, 2007 - 07:08 pm: |
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I have a difficulty to understand your description (main board?) - a rough picture will be appreciated. |
Kim Mortensen
Registered
Username: Inwonder
Post Number: 87
Registered: 12-2006
| | Posted on Thursday, April 05, 2007 - 12:29 pm: |
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Gerald, offcourse I meant the Support board... Sorry, my mistake.... |
Gerald_D
Registered
Username: Gerald_d
Post Number: 1223
Registered: 11-2005
| | Posted on Thursday, April 05, 2007 - 12:36 pm: |
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Hi Kim, do mean with the 40mm legs pointing down and the 80mm horizontal? If so, that will unfortunately be quite weak.
Rotate that channel to the vertical and then it is about 5 times stronger to carry a vertical load. 80x40x5 Channel will be okay when vertical. |
Kim Mortensen
Registered
Username: Inwonder
Post Number: 89
Registered: 12-2006
| | Posted on Monday, April 09, 2007 - 02:11 am: |
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I'm not sure why this would be weak. I can't bend them, twist them or anything, If I stand on them they don't even bend. But now they have been bent, and pre drilled and such, so I'm going to use this setup for now, then I'm going to see how weak it really would be. And make changes later if needed. |
Paco
Registered
Username: Paco
Post Number: 19
Registered: 02-2007
| | Posted on Tuesday, May 01, 2007 - 01:39 am: |
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Gerald,
my local steel shop have 5 Kg/m (76mm X 38mm) channel (instead of 7 Kg/m); would that be stiff enough for my cross bearer. I intended to have 7 of them instead of 8 as per MechMate drawing... fit better on my already built frame... upgrading here... |
Gerald_D
Registered
Username: Gerald_d
Post Number: 1311
Registered: 11-2005
| | Posted on Tuesday, May 01, 2007 - 08:22 pm: |
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Hi Paco, what cross-bearers do you have now? I can tell you the difference in stiffness between your existing cross-bearers and the 5kg/m channel. That should give you a feeling of how much you are "upgrading" |
Paco
Registered
Username: Paco
Post Number: 20
Registered: 02-2007
| | Posted on Tuesday, May 01, 2007 - 08:39 pm: |
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Right now my frame has 2" X 2" X 3/16" angles over 64"; that's 51mm X 51mm X 4.76mm over 1626mm.
We already discuss this and you suggested me to go with channels and I look on the MechMate drawings and that's where I picked up the 7Kg/m (76mm X 38mm channel). I could do the upgrade this weekend with 5Kg/m 76mm X 38mm channel instead but I wonder if I would be as stiff as what the MechMate drawings suggest which I use as a reference.
Right now I have 7 of those angles as cross bearer so I would upgrade with the same number of 76mm X 38mm @ 5Kg/m if that's stiff enough.
I have problem with the vacuum that cup my machine bed up to 0.03" in the center over hours and mess up my pockets and sign carvings; that's why I need an upgrade. |
Gerald_D
Registered
Username: Gerald_d
Post Number: 1315
Registered: 11-2005
| | Posted on Tuesday, May 01, 2007 - 09:07 pm: |
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Paco, I do not have my reference tables here at home, but 5kg/m is probably about 85% the strength of 7kg/m and about 300% the strength of the 2x2x3/16". (I am guessing from my (big) stomach). Let us just say it is a HUGE improvement over the angle iron. |
Paco
Registered
Username: Paco
Post Number: 21
Registered: 02-2007
| | Posted on Wednesday, May 02, 2007 - 01:20 am: |
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I end up ordering 6.12Kg/m for a fast delivery (no 7Kg/m in stock)... I can't wait to have this part of my life resolved.
Thanks Gerald! |
Gerald_D
Registered
Username: Gerald_d
Post Number: 1317
Registered: 11-2005
| | Posted on Wednesday, May 02, 2007 - 07:48 am: |
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This morning at the office I see my tables only list one weight of 76x38 channel, 6.72kg/m
If I compare that channel to 50x50x4 angle (my handy table is metric only), the channel is 825% "stiffer". Compared to 50x50x5 it is 675% stiffer.
Even if we compare that 6.72kg/m 76x38 channel to the same mass of angle iron 70x70x6, then that channel is still 200% stiffer. The point is that channels are inherently a much stronger beam than an angle iron because of their shape.
When I talk of "stiffer" I am comparing the amount of deflection caused by a vertical load when the beam is horizontal and supported at the two ends. It is not true that channels are always better than angles, because the force directions and supports can be different. |
Paco
Registered
Username: Paco
Post Number: 22
Registered: 02-2007
| | Posted on Wednesday, May 02, 2007 - 04:25 pm: |
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Thanks a bunch for the details! It should help keep my bed straight even under this deformation force from the vacuum... I hope... it's a must... |
Gerald_D
Registered
Username: Gerald_d
Post Number: 1321
Registered: 11-2005
| | Posted on Wednesday, May 02, 2007 - 05:05 pm: |
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We had a 40mm thick MDF bed on our old ShopBot (96x48"), built up over the years of glueing on and skimming off "spoilboards" all of MDF, and we removed it after about 5 years because it had too many holes through it. Well, when we loosened the screws, that board curled up by about 30mm! Imagine if you try to pull a 40mm thick MDF, curled by 30mm, flat onto some 50x50x4 angle irons......you can be sure that angle iron will bend by about 10 to 15mm as it fights with the heavy MDF. We want to be sure that the cross-bearer always wins the fight with the table. |
Paco
Registered
Username: Paco
Post Number: 23
Registered: 02-2007
| | Posted on Wednesday, May 02, 2007 - 07:00 pm: |
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My problem happen with the vacuum usage; say I'm carving a sign (no matter what material) with intricate pockets (raising letters and logos from the background), as the vacuum hold flat the material, the bed start to cup upward. This happen over hours; I generally don't have problem with 15 minutes milling but when I pocket or 3D raster carve where the tool machine from one section to another the get back later over long period of time, I can see that the material slightly raised.
It doesn't help me look like a PRO in front of customers... |
10. Base Table