Newbie- Multi function machine

[StevecGarry]

Hi Folks,

Been putting together thoughts over a number of weeks on the sort of machine I want to build, and coming to the conclusion that it's going to be a multi function machine. The initial items will be routing and a hot wire cutter.

So, the basics.
I have some reasonable woodworking tools, a small 3.5" lathe, and a mig welder, so I can tackle some things that might not be possible for a lot of people.

The initial interest is radio control models, but there is also interest in possibly being able to machine aluminium, and maybe even steel, so that's ( I hope) been taken into consideration when putting together these thoughts. Other possibilites include some aluminium engraving and similar sign work, and maybe even some wood routing for whatever comes along.

The cutting bed will be a sheet, at least one, or more likely a base sheet with a sacrificial cover sheet of OSB, 8' x 4' with an overrun facility at one end to allow for the other function, and for a tool align sensor to be off sheet, and mounting of a rotary axis at a later stage.

The main side frames will be "donated" by a scrap fork lift, 2 of the lifting mast main frames rails will become the main (X) rail mounts. The plan is to install this in my garage, and if necessary, I can straighten things out by using appropriate blocks on the floor, so weight on the bed, or machine pressures won't distort the bed. There will be multiple support rails under the bed to prevent flexing.

I'm anticipating that the side rails will be sufficiently strong that flexing of the base or side rails won't be an issue. I will have to check that they are not bent before mounting the gantry bearings on them.

The travelling gantry will be steel box, I have a number of things here that have been made out of 50 x 25 box, and several of them are now not needed, so there are significant numbers of pieces of 50 x 25 that will come from those sources, and I plan to make some cross bracers out of some pieces of 25 x 25 box, so by the time it's finished, the gantry won't be that light, which will hopefully reduce any issues with flexing or bending, and reduce any problems with chatter on routing.

The Long (X) side bearings will be Hiwin profile rails, and the motion drives will be rack and pinion to avoid any bending problems with the length.

I've not yet decided if it will be driven by one motor on the gantry with a cross shaft and toothed belts, or if it will be 2 motors, I've seen references to slave motors, but not seen any theoretical circuits for that, and I won't have a "spare" axis on this project, as will (I hope) become clear in a moment.

The travelling gantry will have Y & Z. the Y also being HiWin and rack & pinion, the Z ball screw, to avoid the problems of keeping the Z from dropping.


Not sure what spindle I will use, that's going to depend on what's available at the time, and the costs.

It's looking like Gecko cards are an expensive but worthwhile plan, if for no other reason than they seem to be reliable, and have better micro step options than most of the chinese boards.

I've seen some very powerful stepper motors from Wantai motors, but I may not need them that powerful, I won't be sure until I have some more accurate weights of the gantry. Ideally, I'd like to be able to work aluminium and steel on this, and later, possibly add a plasma cutter. The other possibility is the potential to add another rotating axis on the base to allow rotational milling.

The gantry will be capable of allowing maching over any point on the 8 x 4, with sufficient overhang capability to allow machining over any edge.

The other early plan is to have an option to attach one end of a hot wire cutter to an arm that is in a similar position to the spindle tool point, and that would work in conjunction with another pillar at the "opposite" end of the 4' wide (Y) direction, which would give me a double X double Y hot wire cutter, solving things like foam wing problems nicely. The rigidity etc of the pillar will not need to be anything like the same as the gantry, but I guess that a lot of the drive side will have to be common with the gantry to avoid all sorts of problems with scaling of the axes. The gantry would not move in the X direction when hot wire cutting, the Y & Z would be the hot wire motions, with a Y2 & z2 being provided by a (removable) pillar at the opposite end of the bed. That would give me 8' cutting length for wings and the like, which will cover anything I can envisage at the moment.

DC power should be relatively easy, I have access to a lot of redundant battery chargers from things like fork lifts, and they are anything from 12 V up to 96 V, and current ratings up to 60 Amps, which makes life a lot simpler.

I've plenty of micro switches and the like here that can be used for limit and home sense switches, and I'm reasonably sure I still have a spare emergency stop switch from a project I did a while ago.

Initially, I'm thinking that hold down points will be by fixing into the sacrificial sheet, but I'm open to suggestions on that, and vacuum hold is another possible. If I can find some cheap slotted aluminium sheet, I might go that route, but it will depend on a bit of luck at the right time.

So, that's the thinking, before I go too much further, does anyone with more experience want to shoot any of this down, or suggest alternative methods that might be more appropriate.

Thanks

Steve