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  #1  
Old Sun 27 August 2006, 08:11
Gerald_D
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The starting points for building your own MechMate - selecting table size, etc.

The very basic thing to do is to decide for yourself what size of MechMate you want to build. You need to pick your own X,Y table (or board) dimensions that you want to achieve and then my drawings will say "cut the rack to length Y plus 150mm" or something like that. The basic MechMate design will work with a fairly wide range of x-table_lengths and y-gantry_widths, but a narrow range of z-slide_heights, being essentially a machine for processing board materials...

Which brings us to the point that you need to know what size boards you want to process, and indirectly, what board you want to use as the table surface. Then you need to decide if you will have twin routers and how far apart they will be in the y-car. The plans will focus on a single router sitting off-center in the y-car, with a big dust hose using the space that others might eye for a second router. But I will give a priority to those building a MechMate similar in configuration to what we built in 2005/2006.

Back to board sizes....in South Africa, MDF is sold as 2750mm x 1830mm boards [9' x 6']. Masonite, Melamine-face chipboard and lots of other stuff also comes as "nine_by_sixes". Plywoods are not that popular, but they come in smaller sizes in any case (2440mmx1220mm or 8'x4'). Apparently the board sizes in America are narrower and gantries can be limited to 5 foot, but here, and in Europe, a 5 foot gantry is too short for most work.

In the plans, I will give dimensions of rails, racks, gantry beams, etc. as X_plus_1234 or Y_plus_567 where X and Y refer to board size. The MechMate will be capable of moving 50mm [2"] more in all directions. ie. a 100mm [4"] diam cutter will travel just clear of the spoilboard, while a smaller cutter can have up to 50mm [2"] breathing space off the edge of the support/spoilboard. (Only valid for a single router).

Out of curiosity, what board sizes will you guys want to be cutting?
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  #2  
Old Sun 27 August 2006, 10:31
Mike John
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My board sizes are 2070mm x 2800mm
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  #3  
Old Sun 27 August 2006, 10:48
Gerald_D
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Mike, how typical is that around Europe? Would you be interested in a gantry that managed to cut across the 2070mm?
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  #4  
Old Sun 27 August 2006, 22:41
Mike John
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Its very typical for mainland Europe.
I'm not certain for the UK.
To date I have never needed anything larger than my table size (1206mmx2560mm), and feel that lengthening the gantry might introduce an element of 'slop'.
The problem for me deciding size is that, at the moment I put 3 'pallets' up at a time for one common tasks, and have just enough room at 1206mm, so feel 1300mm would be nice. But then, am I going to want 1350mm later on?
At the moment I would stick to 1300mm.
How about the length?
Your trick cutting two side pieces from one 6m [ channel for my table saved a lot of money, making the 2560mm cutting a good choice. Does 'rack' come in certain standard lengths?

I already have my welder/fabricator standing by (my son), and a lazer cutting firm as well.
So I am awaiting the final plans with great anticipation.

.........Mike
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  #5  
Old Sat 02 September 2006, 10:08
Pete Wood
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I love this forum. Just like Mike, I can't wait to get started.

I am based in the UK, so tomorrow I will see what size boards are most readily available.
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  #6  
Old Sat 02 September 2006, 10:20
Gerald_D
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I know you guys can't wait, but there is some progress with drawings - while I'm not fiddling with other subjects on the forum
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  #7  
Old Tue 19 September 2006, 22:58
Gerald_D
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Board sizes in UK
Board sizes in Australia
more Australia

Valchromat coloured mdf sheet size 2500mm x 1250mm
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  #8  
Old Wed 20 September 2006, 18:50
David Rosenbleeth
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From Above:

I know you guys can't wait, but there is some progress with drawings - while I'm not fiddling with other subjects on the forum

Reply: Time flies when you're having a good time!!!
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  #9  
Old Wed 04 October 2006, 12:45
Bojan Regouc
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2070mm x 2800mm
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  #10  
Old Wed 04 October 2006, 13:08
Gerald_D
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Bojan, would you want a machine to cut full-size or half-size sheets? In other words, have you got workshop space for the big sheets and can you load the sheets with one or two people?
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  #11  
Old Sun 15 October 2006, 10:39
Holger Erendi
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Hello Gerald,

Nice job with Mechmate!! You got me to rebuild my PRT, I will try to make mine to cut in Y direction 2100mm.
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  #12  
Old Sun 15 October 2006, 10:51
Gerald_D
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Hi Holger, good to see you here! The 2100mm in the y-direction should be no problem. The MechMate you see in the photos is 1900mm y-travel for cutting boards up to 1830mm wide. Even with the longer, heavier gantry, we have a similar speed/acceleration to the old PRT 1300mm gantry. You might have to set your "ramps" a little bit slower for that long gantry, but you will still have a good performance.
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  #13  
Old Sun 15 October 2006, 11:07
Gerald_D
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If the MechMate were restricted to four table lengths (X) and four gantry lengths (Y), it would appear that most of the market could be served by the following capabilities: (max board sizes)....

X dimension equals:
1850mm [6.1 ft]
2500mm [8.2 ft]
2800mm [9.2 ft]
3660mm [12 ft]
....or would a 3050mm [10 ft] be a more popular length?

Y dimension equals:
1250mm [4.1 ft]
1530mm [5 ft]
1850mm [6.1 ft]
2070mm [6.8 ft]

(The design allows for 50mm [2 in] extra travel beyond all edges of the above board sizes)
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  #14  
Old Sun 15 October 2006, 11:51
Mike John
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Gerald
In manufacturing cost terms, is there a great deal between a 1850mm gantry and a 2070mm gantry?
Or for that matter between a 1250mm and a 2070mm?
It seems to be no more than the cost of the longitudal lengths of steel. All the cross pieces and end pieces, the Y carriage, all the manufacturing, the number of cuts and actual assembly, would all be the same.
And I guess this applies to the x direction.
Doubling the length of the table isn't going to double its cost, apart from maybe material. (I say maybe as you need 3 pairs of legs for a 2.5 m table, only 5 pairs for a 5m table.
I recognise you need twice the length of rack, but everything else remains the same.
So, what is the most economical way to go?
If I had the room, I can imagine loading one end of the table with a full sheet, let it cut, move to a sheet on the other end, then change the first sheet.
..........Mike
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  #15  
Old Sun 15 October 2006, 12:17
Gerald_D
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In manufacturing cost, you are right, it costs very little to up the size. (steel tubes, racks, cables, cable chain). But, the bigger the table, the more you have to walk to get around it. Getting small parts off the table are also an issue. (our 8x4' table is seldom climbed on - the 9x6' is climbed on often) If the table needs a vacuum system, then size matters a lot. A dust collector hose over a big area is also more difficult to handle.
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  #16  
Old Sun 15 October 2006, 23:22
Mike John
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Now I have to stop Roxana reading this!
She will want the biggest table possible to make me walk as far as possible. The thing is, if the table is so big that it is too close to the wall on any side, will I even be able to get around the table!


Just how big is your table?

............Mike
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  #17  
Old Wed 08 November 2006, 09:46
Gerald_D
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2750 x 1830mm [9 x 6 ft] board size - the movement is 50mm [2"] more on all four edges.
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  #18  
Old Mon 13 November 2006, 23:02
Bill McGuire
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Here in the US, plywood comes in 48" X 96", but Melamine covered particle board is 49" X 97"... don't know why...
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  #19  
Old Mon 13 November 2006, 23:08
Greg Waggy
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Bill, maybe for the same reason you can't find a 3/4" shhet of plywood any more, they are 15/32nds or something on that order. The 48" x 96" is a standard by which ceiling heights are and use to be stud centers in interior walls. As for the 49" by 97" maybe they have to build in a fudge factor for sloppy construction work or poor building materials. I know a 2" x 4" (3.75" x 1.75") stud has more water in it than a sponge floating in your wife's ketchen sink. Heck they'll spit at you most of the time when you hit them with a hammer.
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  #20  
Old Mon 13 November 2006, 23:18
Gerald_D
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Aren't those "odd" sizes because of some metric systems creeping up on you? A 2.5 meter board, ripped down the center with a 5mm kerf will give you 2 boards 49.1" wide.....

20mm is slightly thicker than 3/4".....
18mm is popular in some metric countries, slightly thinner than 3/4"........
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  #21  
Old Wed 15 November 2006, 00:05
vadeem
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The 49x97" sheet as found with MDF, is used so that even with the loss of the saw kerf, one can still get, for instance, two 48x48 pieces.

It indeed comes very square from the factory.
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  #22  
Old Tue 21 November 2006, 05:49
Gerald_D
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What is the smallest MechMate off the plans? Well, I am very tempted to do a 1200mm [4ft] gantry on a 600mm [2ft] table for making signs at home. In this case I would call the gantry x and the table y.

That gantry would easily transfer to a 2400mm [8ft] table if I want to sell it. I think there comes a point where one considers shortening the table instead of the gantry, since 95% of the MechMate's "engineering" and sweat are in the gantry (and control box) and not in the table. Tables are almost consumable/disposable - unless you are heavily invested in vacuum holddown.
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  #23  
Old Tue 21 November 2006, 06:18
Greg Waggy
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Gerald, Then what you are saying, build the width you want but the table length can be expanded. The gantry is the moving part(s) that have the milling motor/router attached?
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  #24  
Old Tue 21 November 2006, 06:31
Gerald_D
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Everything of any complexity sits on the gantry (the moving part). ALL the motors, ALL the switches, ALL the cables/wires (except one ground wire), etc. The static table only carries a pair of rails and racks.

The logic is that you build the gantry in a small corner of the garage, get the x-motors to turn, get the y-car to run, get the z-slide to move. etc. Thats 95% of the sweat. THEN you build the big table and explain to your wife that her car now has to sleep outside.
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  #25  
Old Thu 23 November 2006, 08:48
fabrica
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Gerald I have started on the base table. In all parts which use 50 mm dia round pipes can I replace them with 2"x1" 3 mm thick box iron . Is their any special reason for you to suggest round pipes.
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  #26  
Old Thu 23 November 2006, 08:56
Gerald_D
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2"x1"x3mm box section will be perfect. You also need a piece 490mm long for the Z-slide.

I used pipe for two reasons:
1. I had some pipe lying around that wasn't going to be used for anything else.
2. The sawdust doesn't collect on top of round pipe - the machine stays cleaner.
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  #27  
Old Thu 23 November 2006, 10:23
fabrica
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OK then I will go with the box iron option.
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  #28  
Old Mon 19 March 2007, 08:11
Sheldon Dingwall
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Gerald, I'm thinking 2' x 4' too. Or possibly smaller, say 20" x 40" with a dual Z.
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  #29  
Old Mon 19 March 2007, 09:42
Gerald_D
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Sheldon, I would make the gantry long (40-48") and table short (20-24"). It is easier to lengthen the table down the line if you want to go bigger. Also, the access to the job is easier with a long open X. (See this post above)

Also, I would build such a small table quite high off the ground. And give the table a sturdy vertical front "apron". This is for clamping vertical work where you need to do end work - like drawer sides.
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  #30  
Old Thu 05 April 2007, 09:59
Gerald_D
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A newbie is overwhelmed - where to start?

An exchange of mails today (slightly edited):

Received:
Can you advise how I might start out with a simple DIY CNC table?

What budget do I need?

Your forum is so detailled where is a good starting point?

Has anyone applied this to a wood lathe holding a router with only an x and Z axis?

My exposure to CNC is limited but am about to attend a control logics course, we have a few linear motion controlled converted grinders we use Rockwell electronics but the industrial stuff is V expensive I trust you have some home DIY tricks?

Replied:
Unfortunately I avoid getting into protracted 1 on 1 e-mail discussions because I think your questions (as a very good example) are asked by many, and the reply/discussion flowing from it could benefit many. Would you mind if I placed your questions on the open forum, with slight modifications to protect your identity?


And then he said:
No problem, thanks

So, here follows the replies.......
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