questions & suggestions for a (slightly) bigger 2.x build

[cerocca]

Hi there,
as mentioned in my "new member intro" post http://www.buildlog.net/forum/viewtopic.php?f=2&t=2103, I’m beginning to plan the build for my laser cutter, strongly based on buildlog 2.x design.

I started studying all the drawings , using the openscad model from thingiverse http://www.thingiverse.com/thing:12864 to enlarge the cutting area. I would like to reach a usable cutting envelope of about 34x24x4” (z dimension is not that important to me)

the main doubts I have are the following:

1) machine dimensions: is 34x24x4” a working area which makes the machine “too big to be built”?
in one thread I read that there should be no problems to increase the 2.x design upto 30x20” - which should be the older buildlog (2.0? 1.0?) working area. In another thread (http://www.buildlog.net/forum/viewtopic.php?f=17&t=1622&start=10) user JV4779 says he scaled up his 2.x to 780mm X 430mm, suggesting to don’t go bigger because of the makerslide.
So, according to this, can 34x24” be a critical size for the build or not? My target is to have a bigger working area which can work on bigger material sheets - see also point 2 - and which can house both a 40W laser (I will begin with this) OR a 60W laser (it will be a future improvement, with all the related issues such as proper cooling)

2) standard material size: here in Italy one of the bigger laser cutter services (vectorealism) offers a 800x394 mm as the biggest workable sheet (wood / acrylic). Is this a standard dimension in the market? Because if the standard dimensions are smaller, I can make my cutter smaller, anyhow not less than 30x20”

3) space for laser: if i’m correct, the 2.x design can house laser tubes upto 750mm long and 52mm diameter. If I plan to be able to house also a 60W laser, how much space has to be left at the laser tube’s sides in order to avoid problems? (60W is quite longer than the 40W...)

4) motors: I would like to keep using the NEMA17 motors, planning to drive them with properly cooled Pololu stepper driver boards (A4988 based) . Is the NEMA17 Ok for the dimensions I would like to reach? or I have absolutely to use a bigger - NEMA 21 - stepper, so making the Pololu stepper driver undersized for the machine I have in mind?

Please note that I can have metallic parts custom cutted and other stuff 3D printed - such as the laser holder - if needed.
These are all the doubts I have after some days of studying... of course any suggestion is more than welcome!

I think that's all.... thanks since now to anybody who can help me , bye!

C.

[jv4779]

How big you can go really depends on the precision of the makerslide you get. In my case 32" on the X axis is doable even with the slight bow in the middle. You could get better or worse. With the makerslide that I got it should be possible to go to 32" by 32". As the size gets bigger the X and Y axis need to be perpendicular to even greater tolerances. Distortion from having the Y axis gantry sides out of parallel adds up as well.

Jeremy

[kbob]

Addressing the motor size question, the X carriage weight will not change, so the X motor will have the same load as on a smaller machine. The Y motor moves the gantry, and you're adding nearly 50% to the gantry's weight. I think it would still be well within the capabilities of a NEMA 17 motor to move the gantry; you will just have to use a slower acceleration constant. The Z motor is geared very low, so it has plenty of torque for a heavier table.

[cerocca]

Thanks to both for your replies!
The more I go through the forum, the more I understand how to proceed with my build idea, so I started filling the BOM, trying to find as much local suppliers as possible.

I have still to figure out the "space for laser" matter, i.e. how much space to have at the laser tube’s sides in order to be able to use both 40W or 60W tubes.
Anybody has an idea about this?

Thanks again, bye
C

[cnc74]

Hello all,

I look forward to hearing how all that choose to extend there working space are progressing! I am just starting my own build and the first thing I htought of was "can I extend my working space?". Its always cheaper to do it the way you want it the first time around but with far too many unknowns (for me) I am chosing to go vanilla and build it to the predefined specifications so I can learn what works and move forward with my "plans to expand" at a later date!

Thanks in advance!!


-CNC74

[JValliere]

I based mine off the 1.x for the frame...with the limited supply/vendors for honeycomb, my actual cutting envelope worked out to be 16 1/2" x 24". I could push it to 18" x 28" with larger honeycomb bed. I also used Nema17 motors and they are more than powerful enough for this size.

-edit-

You cannot get too many of the spring loaded nut inserts when you build this. #6-32 square nuts will get you by, but, it's not ideal.