First build - Mid-scale gantry router design

[Ellis]

Hi all,

As a little disclaimer, I have been researching building a machine for around 24 hours. I realise the learning curve is huge and the questions I am likely to ask will be the ones you're all dead bored with answering. With that in mind I will try to keep things to simple yes/no answered questions whilst I design my project.

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Basic parameters:

-I would be machining almost solely aluminium, often 6082T6 although I use 7075T6 and other aerospace grades regularly also.

-I'd like to shoot for 500x500 working area, a little smaller is fine. Unsure about bed to spindle distance, will know more as designing goes.

-High tolerances. I'd like to be able to machine bearing pockets and such and have some control over the fit. Hoping the relatively small scale using parts typically found on larger router builds, coupled with the right construction, will achieve this.

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I am aware that Hiwin type rails are ideal. I am pretty sold on using them for the Y and Z axis (HGR15 size?) as they are preloaded, which makes them infinitely more versatile. However, they aren't cheap and I'm afraid I do have a budget.

My first question is, assuming for a moment that my design is rigid and viable: is it realistic to expect high tolerances in aluminium if my X axis runs on supported round rails, such as SBR16s? I would mount them flat, so the weight of the gantry is what provides preload. I think this would be okay, opinions extremely welcome. This is purely a cost cutting measure, no point hiding it.

To add to that, casting an eye over the vague description above and yelling at me if I'm dreaming is also invited.

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I have yet to deeply research what steppers/drivers I'd need for this scale machine, I will come to that once I have designed a generic frame.

Always surprising how much you can write without actually saying much...

Cheers and thanks in advance,
Ellis

Edit: I suppose this is punishment for posting so early. I have since read that typically folks would recommend the HRG20 size over the 15s for several reasons, and that in fact via Aliexpress, even with import, they're pretty affordable. Although the supported round rails are even more extra affordable!