[OmegaNS]

I've been a long time lurker and this is my first post. My posts tend to get very 'wordy' on forums so I am trying hard to keep descriptions succinct and use pictures instead. And let me first say Thank You to all the regular members who post on here. I really look forward to hearing your comments/suggestions/criticism on this idea.

Overview: 3D Router; Steel and aluminum construction. Full 48" x 48" x 10"cutting envelope

Purpose: I need a 3D router for cutting foundry patterns. These are typically routed from polyurethane tooling board ( Alro Plastics Polyurethane Tooling Board). A casting pattern can have a lot of complex 3D contours and always has draft to release the sand from the pattern. I need something that is capable of Large and Fast Z axis movement to follow the bounding surface. Tooling board is roughly 80lb/ft^3 / 10,000psi tensile strength / 85 Shore D, so maybe a little harder to cut than wood but much easier than aluminum. Rough speed 1500RPM @70IPM and Finish at 10,000RPM @100IPM I would also like to be able to cut aluminum - mainly 2.5D motion (flanges, pockets, bolt holes).

Y-Axis 52.00" maximum travel. SBR25 Rail with 2 trucks per side (chinese rail/trucks). Motion using 2x CNC Router Parts Pro Rack and Pinion. Motors: 2 x Nema 23 unknown size
X-Axis 50.20" maximum travel. SBR20 Rail with 2 trucks per edge (chinese rail/trucks). Motion using 1x CNC Router Parts Pro Rack and Pinion. Motor: 1 x Nema 23 unknown size
Z-Axis 12.24" maximum travel. Hiwin 15mm profile rail with 2 flanged trucks per edge. Motion using 1x 2510 ballscrew (chinese ballscrew, bearings, anti-backlash ballnut) Motor: Offset mounted Nema 23 with timing belt. Counterbalanced using pneumatic cylinder. Spindle 2.2kw water cooled spindle ER20 collets


Construction: Box tubing for table 3" x 3" x 0.120". Gantry from 0.25" hot rolled steel using tab and slot for assembly. Fully TIG welded. Z -axis components from 1.0" and 0.5" 6061 Aluminum or MIC6 cast plate. Spindle tube is aluminum 4.0" OD with ~0.5" wall thickness.

Electronics/Software: MACH4 (although I'm weary of being a guinea pig and also no plugins seem to have been developed). PMDX 140 (PMDX.COM - Products for CNC and motion control applications) coupled with a PMDX 126 (PMDX.COM - Products for CNC and motion control applications) and PMDX 407 (PMDX.COM - Products for CNC and motion control applications) for spindle speed control. Geckodrive G540. I'm also open to suggestions. Something with ethernet and a ton of I/O would be great. Something with feedback or closed loop motion would be even better, but I think these are too expensive for my budget.

Concerns: Budget like everyone else. Other wise this would be 5' x 10' with linear profile rail for each axis. I'm also worried about the crane weight (over 300lbs with Z carriage and spindle) and whether that's too heavy? What motors I should run? Box tubing wall thickness @ 0.120"? The location of the X-axis rack and pinion and racking concerns? SPEED of Z axis with motor and 2510?

Not all hardware (nuts, bolts) has been modeled yet. Still to be modeled: axis limits/stops and homing switches, cable trays, table legs. I will update and upload pictures as I make the changes you guys suggest. Thanks again guys.



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[OmegaNS]

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[OmegaNS]

[wizard]

You say crane but I'm hoping you mean gantry! Your design is likely to be OK for the urethane board but Id have to question suitability for a great deal of production aluminum machining.

The first problem that strikes me is that the gantry is thin This will be a problem as ti don't see it resting twist well especially with a 12" long lever arm. You should seriously read the sticky that has much info in it related to gantry beam design. It would likely be of benefit to go through some of the calculations but I suspect that you would want to resize the beam into a more square structure. Further if you buy a rectangular beam or square beam from your still supplier you will save your self a lot of headaches trying to weld up a beam from scratch. It will have to be a larger beam, probably ten inch square at a minimum, even with the need for internal bracing it will be a lot easier to get to a usable gantry than trying to weld up one on your own.

In any event the gantry was the first thing that caught the eye as a potential problem, this especially as you move away from wood into harder to machine materials. You do have an advantage here, in that often 3D contouring doesn't load the spindle heavily but I would imagine you will have a certain amount of roughing out to do.

As for the rest go the machine I didn't look that closely! In general though the more you look towards machining aluminum the more I'd suggest beefing up the rest a bit. I'd also seriously consider making your machine upgradeable to profile rials in the future. That means a bit more thought in the arraignment of components. Or serious consider doing the Z in profile rails in the first rev.

I don't think you are off to a bad start here except for the welding up of your own beam. I just don't see a lot of value in that unless your goals are a unitized structure right down to the feet for the X axis linear bearings. I didn't see that in the drawings.

[ger21]

Exactly what spindle do you plan on using? Most of the 2.2Kw spindles have a minimum rpm of around 8,000, which is far above the 1500 you mention.

[OmegaNS]

Wizard,
I can change the 'thickness of the gantry. It is 5"x 11.87" currently. 10"x10"x0.25" is available but structural square tubing must be purchased in mill lengths (24ft) from my nearby supplier. That's roughly 780lbs of steel, but I'll call tomorrow and check on the price. I do have 5 bulkheads inside the current gantry.
The Z is profile rail (15mm). I have designed the router with provisions to upgrade the Y and X to profile rail in the future.

Ger21,
I had planned on the chinese 2.2kw spindle. The machining specifications I listed were from the tooling board supplier where they also suggested 1" ball end mill with up to 2" depth of cut on roughing (40% stepover). That's not realistic for a machine I can afford to build. I was hoping to 'get by' by taking many more passes and much smaller cuts. I'm open to suggestions.

[victorofga]

omega

im watching this topic..
what you drew up that could work.. but.. either way you make the gantry of aluminum or steel, it require some serious machineshop..
on the end for this design you might pay off 15-20 K of your pocket..
because after welding together those elements, somewhere need to machining flat..

machineshops that can handle it they are not cheap at all..

try to approach this all differently..
do you have this patternmaking as a reliable future? it makes a living income?

if yes, then take into account those foams, regardless of density you can mill with a relatively simple router.. and on the front you wont work with aluminum.. maximum some wooden parts

then look around, check cnc routerparts example what you could put together, and how much..

check with ebay sellers.. this machine you could expect about 5K a ready built soemthing you hook on power and start to work..
when money coming because you can run the bussiness, then you ready to go out for a larger machine that can mill aluminum too..

there are many seller sells 4x4 machine with 8 in Z you dont need really vacum table but need a relatively high Z
send out a couple of request.. keeping your expectation low..
most important you need a machine and start to work..

SALE CNC Router Milling, CNC Laser, CNC plasma machine, China, Servo Motor Drive, UK, USA, Italy, Spain, Thailand

another one

4x8‘Cncwoodworking Machine Free SHIPMENT on Sale | eBay

they make you the Z to a height waht you need.. start to make patterns then money coming you can afford better machine..




patternmaking can be a wellpaying biz, also can be a fail..
building a machine takes you away from earning money..

order a ready machine and while you waiting its coming start to prepare.. make room in your shop, build shelves, try to figure how you going to build the patterns,,
look for materials sure working for you..
if you make it of parts, can you glue together,? (the patterns)

and again, be realistic.. without a machineshop behind you, you cant make this design with a hand drill and handtools..

[wizard]

Wizard,
I can change the 'thickness of the gantry. It is 5"x 11.87" currently.

That is an odd size. I doubt you would have any problems machining foam or wood with it. If you want to do high quality work in aluminum it may be a problem.

I'm more concerned about your desire to weld that beam up out of plate. It is possible to do of course but this isn't a trivial exercise. You will likely need stress relieving and post stress relief machining.

10"x10"x0.25" is available but structural square tubing must be purchased in mill lengths (24ft) from my nearby supplier. That's roughly 780lbs of steel, but I'll call tomorrow and check on the price.

Well that sucks! I'd seriously look for another supplier that offers full services. Getting stock this size cut to order shouldn't be an issue.

I do have 5 bulkheads inside the current gantry.
The Z is profile rail (15mm). I have designed the router with provisions to upgrade the Y and X to profile rail in the future.

In one of the stickies you should find a thread that has a number of spread sheets embedded in it, one of which should help you with linear rail sizing. Normally I wouldn't be concerned but You have a long working distance on that Z axis. Ultimately I don't know what you need accuracy wise for these foundry patterns.

Ger21,
I had planned on the chinese 2.2kw spindle. The machining specifications I listed were from the tooling board supplier where they also suggested 1" ball end mill with up to 2" depth of cut on roughing (40% stepover). That's not realistic for a machine I can afford to build. I was hoping to 'get by' by taking many more passes and much smaller cuts. I'm open to suggestions.

As for being realistic that depends upon just how difficult this material is to machine. Im not familiar with this material at all so I can only suggest making the machine as stiff as you can afford

[mbronkalla]

When looking for structural tube, don't ignore salvage. My local steel supplier ( Pal Steel , Palmyra WI) has both "new" and "salvage" and will torch cut to length . Salvage is 1/2-2/3 the price of new. my 6x6x1/4" gantry needed 6', I asked for 7' for clean up allowance. They had 8'+ and threw in the rest for free.

[wizard]

When looking for structural tube, don't ignore salvage. My local steel supplier ( Pal Steel , Palmyra WI) has both "new" and "salvage" and will torch cut to length . Salvage is 1/2-2/3 the price of new. my 6x6x1/4" gantry needed 6', I asked for 7' for clean up allowance. They had 8'+ and threw in the rest for free.

I forgot about this! In my case the local big upstate NY steel supplier runs a separate business selling off drops, cut outs and the like plus fresh stock for low volume buyer. They offer cut to length services so you can get a rough cut of what you need. They also sort drops by length. Nice operation really, it keeps the low volume customers out of the way of the main facility and the drops are sold by the pound.

I'm actually surprised that a full service steel supplier can't cut to order. The original poster might be better off looking for a new supplier.

[slopecarver]

blanchard grind will get you flat for cheap, but you cant do holes obviously.

[OmegaNS]

I should have included that I intended to use leveling epoxy for the parallel surfaces. I do quite a bit of welding, so the task of welding up the gantry really doesn't seem as daunting as some have warned. I'm working on the math currently to determine the stiffness at the cutter, so I guess that will be the true reveal on this design. I tried to follow the key elements (large spacing in gantry feet bearing, supported gantry beyond bearing edge with short stout uprights, very large tubular cross section for gantry with 11+ inches of vertical spacing on the x-axis bearings to minimize the torsional forces, etc.) in designing and overbuilt in my opinion.
I am having a hard time finding affordable motors though to accelerate the 300lb gantry and I may have to consider "adding lightness"

[victorofga]

you can find motors for even heavier gantries.. some large routers gantry weighing tons..
it all boiling down how much you can invest..

some scm or biesse window doormaking router carry half of ton only of tools.. so you it could give you an idea there are motors that can drive serious weight

[slopecarver]

And they are an order of magnitude outside his budget.