First time build - Steel Frame CNC Router

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Hi Everyone,

As this is my first post here, let me start by saying that I have never built a CNC machine before and other than a general college course on CNC/machining and reading this forum/CNCZone, I have had very little experience with either CNC or machining so hope you guys can keep me right

Following the advice given to others on here, I started reading through the build logs section of this forum and found a few designs I liked and also many handy tips that should help me along the way. I think I am now at the stage where I can start this build log to develop the design and hopefully soon start building! Please see following summary of the design:

Requirements -

• Machine profiles out of Wood/MDF
• Aluminium work ranging from machining profiles from plate and also machining blocks for which typical maximum total cutting depths are around 30mm
• Able to do some detailed work with both wood and aluminium like the Aztec calendar posted here

I understand that one machine cant suit all materials/requirements and so I will be more than happy if the machine is slow at cutting wood but is also strong/stiff enough to machine aluminium.

Design -
The attached is what I drew up based on what has been designed and seemed to work for others on this forum.

Attachment 17106Attachment 17103Attachment 17104Attachment 17101Attachment 17105Attachment 17102

• Cutting Area approx 750 x 400 x 100
• 2.2kW Chinese Water cooled spindle
• Rails are HGR20 on all axis (dimensions: 1000mm/600mm/300mm ) with wider type carriages on the X axis only
• Ball screws are 1050mm 1610 (double) on X Axis, 650mm 1610 (single) on Y Axis and 250mm 1605 (single) on Z Axis
• Motors are 3x NEMA 23 3.1Nm. One motor has been used with a belt drive for the double screws on the X Axis. This is mainly because I will be using LinuxCNC and have heard it doesn't support slaved motors.
• Frame is from 50 x 50 steel box section with larger sections being 100 x 50 (3 or 4mm thick). Side plates on the gantry are 10mm thick steel and all other plates including Z-Axis assembly and X-axis support bearing support plates are 20mm thick aluminium.

Some initial Questions -
1. Am I heading in the right direction with this setup or does it make more sense to look at something different?
2. Will 4x M8 bolts supported by the aluminium blocks tapped 15mm on each side of the gantry be enough to support the full gantry? Would it be better to make the supports from steel and weld the gantry box section to this with holes in the box section to get access to the carriage bolts?
3. What is the recommended thickness for the gantry box section? I will be using 3 of 4mm for the frame.
4. I have seen mention of Bearing spacing/aspect ratio on the forum so from the model, measurements taken between the inside of rail blocks and inside of rails are as follows:
X Axis - 42.74mm between blocks, 680mm between rails
Y Axis (Gantry) - 40.50mm between blocks, 150mm between rails
Z Axis - 30mm between blocks, 130mm between rails
Will this be OK or is adjustment of these dimensions required?
5. Is compressed air a requirement for when machining Ali? If so, I will need to build a compressor into my budget.

I haven't ordered anything yet as this is my first build and know for sure that I have cocked up on something somewhere! So I look forward to all the comments/guidance you guys can provide.