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Thread: CNC Router Build Steel & Ally
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28th May 2013, 07:27 PM #46SENIOR MEMBER
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Been busy but still managed to get some plates done. Just 2 small plates left to machine and then to start working on the table.
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28th May 2013, 07:40 PM #47
That is a solid looking bit of machinery there Chris.
Bob Willson
The term 'grammar nazi' was invented to make people, who don't know their grammar, feel OK about being uneducated.
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28th May 2013, 08:01 PM #48SENIOR MEMBER
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28th May 2013, 09:31 PM #49SENIOR MEMBER
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Awesome looking work - and having noticed your hold-down method, there's a length of DIN rail in the shed that's getting chopped up soon
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16th August 2013, 09:58 PM #50SENIOR MEMBER
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Veryyyyy slowly getting there.
Some pics of the table, 100x10 MS & 65x10 MS, just needing to machine up another 47 spacers in 8mm MS.
Used M8 nuts as spacers for 12.8mm spacing for T nuts, the nuts on my mill have a width of 12.3mm so I'll try buying more of those or machine some from scratch.
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18th August 2013, 07:45 PM #51GOLD MEMBER
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Lot of work in the table T slots. Keep up the good work.
Cheers,
Rod
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19th August 2013, 09:56 AM #52
Looking good Chris
Thanks for letting us have a close up look at your cnc....Must make a start on mine sooner or is that soonest....vapourforge.com
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19th August 2013, 07:25 PM #53SENIOR MEMBER
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Thanks rod and russell, once the shims are done, it's off to the sandblasters for the PFC, paint it all up, and finally assemble it for the last time.
It'll be good to see what you come up with russell, I learned a couple of new things when you dropped by so it's a win-win situation
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28th September 2013, 10:03 PM #54SENIOR MEMBER
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Table assembled. Now I'm just hoping the PFC doesn't bow too much and need a mid support, it's supporting 95-100KG.
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5th October 2013, 09:04 AM #55
Chris To stop your PFC bowing you could epoxy some carbon fibre tow on the bottom side Or just straight glass would also work. This would stiffen it up a lot with little inconvenience.
Just my 3 cents worth (note the inflation)
Rvapourforge.com
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8th October 2013, 05:37 PM #56SENIOR MEMBER
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I've never worked with fibreglass or kevlar before, I'd probably just make a mess
Took some measurements with the dial indicator (weight was within a 15cm radius of the dial)
Front row - middle (weakest point)
12.5kg - 0.04mm drop
27kg 0.1mm drop
100kg 0.38mm drop
3rd slat from side, 2nd row
12.5kg 0.01mm drop
27kg 0.04mm drop
100kg 0.1mm drop
I'm pretty happy with those figures, but if I decide to add a mid table support it wont be any harder to do at a later date.
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9th October 2013, 01:07 AM #57Intermediate Member
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Hi Chris,
Your measurements are probably torsional deformation and local bending of the channel top flange. Your channel flexural bending deflection should be less because of the very short span. Shear center of channels doesn't line up with their web (or your load line). This introduces local flange bending and O/A section torsion. Both I beams and channels have low torsional stiffnes (compared to say hollow sections).
Regards
Zvon
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9th October 2013, 01:02 PM #58SENIOR MEMBER
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10th October 2013, 02:52 AM #59Intermediate Member
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Ups, (red face) it seems that my fingers are quicker than my brain as I typed the comment above without reviewieng the photos on previous pages of this thread. The side channels cannot twist much because they are restrained by the table support channels. Correct me if I'm wrong - your table flat bars are supported by four (4) channels (PFC's) that span between the bottom flanges of side supports (white PFC's). The table support (blue PFC's) are toes down.
Your deflection measurements are logical because of the load shedding - the flat bars shed load sideways and engagge adjacent channels. The edge (front and rear) channels can shed load in one direction only and the central ones in both directions.
In regard to the table stiffeneing you can:
- Epoxy carbon fibres to the channel toes as sugessted above, however it would increase the section strenght more than stiffness which you would be after.
- You can box the table channels by welding a flat plate/bar 6-8mm thick between the channel toes (creating a RHS section) however it would require a lot of welding. The stifness should be increased and deflections reduced by about 2 times.
- The most effective way of stiffeneing the table would be provision of a midspan support which may be supported by the blue framing SHS (I'm not sure if you have a rear SHS)
If you give me a rough sketch with members sizes I can model the frame and give you theoretical improvements (deflections) before you embark on a major table rework.
Sorry about my previous post, I was under impression that you were concerned about the side PFC's (white).
And yes, I prefer hollow sections (RHS/SHS) to open section (PFC/I). The trosional stiffness of hollow sections is an order of magnitude higher than for open sections.
Regards,
Zvon
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10th October 2013, 11:50 AM #60SENIOR MEMBER
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