1200 x 800 Gantry Router Build

[reotilemarine]

I have been a long time lurker on here reading the build logs and trying to get as much knowledge as I can about the subject of CNC routers. I am now in a posiiton where I would like to build a CNC router and look forward to feedback from you all for my ideas.

I am looking to build a CNC router to mainly cut wood / carbon fiber. I build a lot of RC models as a hobby and this this will aid in making them. I am constrained to 800mm frame width as it has to fit through a doorway into my workshop. I have chosen 1200mm length to maximise bed space. I am hopefull for 1000 x 600 workable bed space however I accept this will be limited by design.

The dimension that I think may add to the complexity of the build will be the Z axis. I would like to ideally have up to 300mm useable travel as I would like to use the router for machining plugs for composite moulding and as such require the large Z axis. Therefore the router has to be capable of reasonable quality 3D surfacing over the Z axis travel.

I would like to base my design along the lines of Joe Harris's / AndyUK

Some initial thoughts of materials would be

80x80x4 for the box section framework
60x60x4 adjustible bed
1610 ball screws for X, Y and Z axis with the Z axis connected to the motor with a HTD belt to allow for different ratio options.
X axis I am hoping to drive two ball screws with one motor and a large belt connecting the two together.
Linear rails for all axis
Expoxy leveling for the X axis
Gantry 90x45 in an L confuguration


So that is a brief summary for the beginnings of my design. I would be greatful for feedback on meterial sizes, z axis limitations for 300mm usable travel and any other glaringly obvious problems with me chosen materials.

[mekanik]

There is no need to restrict the width of the machine if you mount it verticaly, Dean has a video of one of his machines, sure he will post the link if he reads your post.
Regards
Mike

[reotilemarine]

Thanks for the advice Mike. I have seen Dean's verticle machines however I know very little about the differences/limitations of having the machine in this orientation and how this may affect tasks such as the 3D surfacing I mentioned.

I am quite happy with the working area I will have with my proposed bed size however open to any feedback from people and improvements.

[JAZZCNC]

Thanks for the advice Mike. I have seen Dean's verticle machines however I know very little about the differences/limitations of having the machine in this orientation and how this may affect tasks such as the 3D surfacing I mentioned.

There are very few limitations with a vertical machine and many advantages other than huge space savings. For 3D type work it's actually much better because gravity is helping with clearing chips so you are not recutting chips which impacts the surface finish and causes excessive wear on tools, even when using dust extraction.

[reotilemarine]

After thinking about my options and speaking to JAZZCNC I am changing my plans in terms of build method. I would like to keep the same overall bed size however I am now working towards designing the router using 45x90 extrusions and end plates. The reason for this is that it will be more than strong enough for the work I am proposing to do and reduces the complexity of welding and epoxy y - axis levelling.

I am working on a CAD design at the moment however having never used fusion 360 before it will be a steep learning curve however I feel it is necessary to get all dimensions and sizes of components correct.

So for now I will have to describe my intentions and go from there.

I am planning on using 45x90 extrusions. One down each side of the bed forming the supports for the 20mm linear rail recessed into the end plates.

I shall also include an extrusion down the centre of the bed to provide additional support for the end plates.

End plates and gantry side frames will be 20mm tool plate aluminium.

Gantry will be made up of 2 x 45x90 extrusions in an L configuration recessed into the gantry sides.

I am thinking of twin 1610 ball screws for the y axis, and single 1610 for the x and z.

20mm linear rails throughout.

One thing I am not sure of is whether it would be better to have twin motors for the y axis to aid in homing calibration or wether to utilise a serpentine belt on the two ball screws and rely on them moving the gantry in tandem once calibrated.

Drive motors I am hoping to use closed loop stepper motors so advice on the options regarding power would be great. I can then make a start on the CAD model and put these parts in as a starter for 10.

In terms of linear rail carriages. What is the difference between the standard size versions and the wide / thinner versions?

Image showing the style of machine I am proposing.

[reotilemarine]

I have managed to put together a first draught of the machine base. It is quite a steep learning curve with fusion 360. I have put in a grid of tapped holes at 50mm centres. This may be changed to 75mm in time as its a lot of holes. I will have a sacraficial top over this with clearance holes into the threads below.

Before I model the gantry I have looked through here for some parts I am unsure of but still undecide on -

• Optimum distance between the two carriages on the linear rail to give adiquate support without loosing too much Y travel.

• This may also have a bearing on the first query, suggested height of gantry. I would like to have a minimum 100mm of useable Z travel above my sacraficial bed if possible. Machine bed is 15mm and sacrifial bed will be similar. I understand different Z axis designs can give more travel but there is a trade off for a springy Z axis at shallower depths.

[JAZZCNC]

This might help.

This is the tallest gantry side out of this model I use. This would give you 230mm from the lowest point under the gantry, which is the bottom bearing plate, to the top of the profile. This doesn't account for the bed or spoil board.

[Soyb]

Hi reotilemariine

It sounds like we are on a similar journey, http://www.mycncuk.com/threads/14558...t?goto=newpost.

I am in the process of designing / building a desktop gantry machine based on simple obtainable components, I only have a Stepcraft machine and a 3D printer to make everything,