5 axis Gantry style Milling Machine prototype

[ger21]

I think you'd be better off with a pair of these 100x200 extrusions with 20-25mm rails, rather than your 4 rails and smaller extrusions. More rigid, and less complex.

https://us.misumi-ec.com/vona2/detai...x180%2C100x200

[mikechandley]

I think you'd be better off with a pair of these 100x200 extrusions with 20-25mm rails, rather than your 4 rails and smaller extrusions. More rigid, and less complex.

https://us.misumi-ec.com/vona2/detai...x180%2C100x200

My mistake those are 20mm Hiwin rails in my drawing.

Do I use 2 100x200 in a one on top of other configuration or 1 across from each other, either way we are making a bigger footprint in the overall design and the X axis will have to be longer for the same inside working area.

I do like the 1 across from each other with 4 20 mm hiwin rails as it will reduce the Height but will it be better supporting a Z axis hanging 16" underneath plus 6" inches of travel?

My design has 14" of support above the Z axis. The 4 20 mm Hiwin rails will ad considerable strength to the 40 x 80 extrusions.

I will mock up a couple pics.

[ger21]

It's always been my understanding that the rails don't add any strength.

Do you need the 16" of clearance?

Keep in mind that anything I say are just guesses. But, I think the second pic you show.

[mikechandley]

see this...

[mikechandley]

It's always been my understanding that the rails don't add any strength.

Do you need the 16" of clearance?

Keep in mind that anything I say are just guesses. But, I think the second pic you show.

There is a lot of leverage under this Z axis

[mikechandley]

Maybe just redesign my original with 80 X 160?

Im no engineer but i think I need one for this lol.

[mikechandley]

Where are we at as far as torque? if we have 20 foot lbs at tool are we way less at the Y axis? If we do the multiplication from earlier on Y axis to the tool?

[ger21]

Maybe just redesign my original with 80 X 160?

No, use the 100x200, or even bigger if you can find it.

You can't make a machine too rigid.

[mikechandley]

I did a pounds per meter calculation on the three different profiles...
40-40x80 =9.12 lbs per meter X4=36.48 lbs
40-80x160 =25.877 lbs per meter x4=103.508 lbs
Misumi 100x200 = 45,085 lbs per meter x4=180.34 lbs

Holy cow thats alot weight difference on Y axis.

[NIC 77]

I did a pounds per meter calculation on the three different profiles...
40-40x80 =9.12 lbs per meter X4=36.48 lbs
40-80x160 =25.877 lbs per meter x4=103.508 lbs
Misumi 100x200 = 45,085 lbs per meter x4=180.34 lbs

Holy cow thats alot weight difference on Y axis.

Is each piece one meter long in your drawing on post 20?

You are too concerned about weight. 5 axis machine, you won't need or have super fast accel. The gantry will be driven with two motors? What kind of motors.

I'd say, Nema 34, 800 lbs total for the gantry, and Z without getting too concerned. So long as you can move the individual pieces in place. Lightening holes in the plate? Why? You'd also want bracing between the extrusions all the way across the length.

Ballscrew, rack and pinion?

How are you going to counterbalance the Z axis, pneumatic cylinder(s)?

IMO, this is all wrong. Too complex. Too much emphasis on the wrong things. Your Z would have to be a tube within another tube? Everything would need perfect alignment. Nice CAD work though!

I posted some pics to inspire you. I think you need to go back to the drawing board. Or, like I said, robot arm!






Your pics show alot of custom cut plate. Do you have a CNC to do this for you? Do you have any welding ability in aluminum? You could probably do something pretty awesome from thick aluminum plate that is welded, or even bolted together to make a tube structure with ribs, and give the T-Slot idea the heave ho.

Have you seen this thread?

http://www.cnczone.com/forums/vertic...rum-posts.html

He does something like that but with steel. Different type of machine, but it expresses what I'm trying to say to you.

Also, I really want to see a 5 axis DIY project with a used robot arm.

[mikechandley]

I can tig and Mig,
Have full access to any cnc equipment, Machine shop needed.
Planned on Nema 34 servos
Ball screws on all
post 20 yes one meter or approx, 40 inches

one big 7x14 x40 with a .375 wall steel tube is looking good right now lol

I agree to complicated....k.i.s.s.

Thanks for compliment on Cad Ive got 29 days on Fusion 360 right now free subscription runs out tomorrow.

[NIC 77]

I can tig and Mig,
Have full access to any cnc equipment, Machine shop needed.
Planned on Nema 34 servos
Ball screws on all
post 20 yes one meter or approx, 40 inches

one big 7x14 x40 with a .375 wall steel tube is looking good right now lol

I agree to complicated....k.i.s.s.

Thanks for compliment on Cad Ive got 29 days on Fusion 360 right now free subscription runs out tomorrow.

40" is a small span, and deflection is a function of the length cubed, so, yeah, 7 x 14 x 40 x 3/8 would be no problems! Way better idea! You could even drop it to 7 x 10. Not hard to weld in a couple of ribs too.

With the welding experience you have and the access to equipment, there's no need for T-Slot.

The other option is to make something in a similar way to the build log I posted made by Stef110 (http://www.cnczone.com/forums/vertic...rum-posts.html) using either steel or aluminum flat plate that is welded together to make the gantry structure. With the tools you have available you could make something that is totally awesome where the motor and ballscrew are recessed into the gantry.

Similar to this shape:



Also, it sounds like your x and y working areas are small, so you may even want to consider a moving table, which would simplify it more.

Nema 34 size servos, what are those, 750 Watts? There is a DMM nema 34 750 watts, actually two models for Nema 34 size, one has lower power output.

You could use SYK MBA 15F or 20F mounts for Nema 34 using a direct drive and not have to worry about belts and such that would simplify things further, assuming these are 750W servos. And 10mm lead ballscrews on all axis. Two small diameter pneumatic cylinders with a small reservoir at the back of the Z axis running at 80 - 90 PSI might work for a counterbalance. I don't know how much your Z assembly will weigh. If you drop to 40 PSI with larger cylinders, you'd need a larger reservoir.

I forsee lots of design work ahead of you, but in the end, it is far better to spend extra time designing than starting a build too soon.

Have you looked for a used robot arm?

[mikechandley]

working area 21x31 But cant move z it will be on top of a granite countertop for cutting out the hole.
Many more complex problems coming lol.

Great looking Machine there. Ill check out the thread.

[mikechandley]

a quick sketch of the 10"x14"x52" steel gantry
7x7 legs 20 in long in pic should be 11" 9 inches to long oh well you get idea
1 inch steel plate for the X bearings
2 half inch plates to bolt the 10x14 to the 7x7 legs

[mikechandley]

This is very close to scale size

[mikechandley]

one more
X axis is 7x10x30 x.375

[ger21]

Is the countertop going to slide in between the uprights?

Where are we at as far as torque? if we have 20 foot lbs at tool are we way less at the Y axis? If we do the multiplication from earlier on Y axis to the tool?

The farther you get from the tool, the higher the forces are.

[mikechandley]

Is the countertop going to slide in between the uprights?




The farther you get from the tool, the higher the forces are.

No its not going to slide between.
I have a better idea when we get there your going to have to scratch your head on that one for a bit lol.

[NIC 77]

Guys, I'm getting really confused here, I want to help you sort out a few things.

2 Im no engineer but I can tell you if you pull 35 lbs of force with your hand against a custom made tool cutting into the stone you will be taking a very deep cut of .250 of material at a time.

Think of it as pulling a 1/2 end mill into the side of a solid aluminum 1.25 thick block at full depth of 1.25 inches not step cutting.

Actually, according to HSM advisor, a nice free feeds and speeds calculator, a 1/2" end mill slotting aluminum 1" deep (it won't let you select over 1" LOL, because you would never do this, with a 2 flute solid carbide end mill at 32 IPM, the cutting force is 145lbs.

I'll have to take your word for the stone, I have no idea, I haven't seen it as an option in HSM advisor.

2 So if im pulling 20 lbs of force against a tool is that ft lbs?

No, that's lbs. If you have a torque of 20 ft*lbs then that is 20 lbs @ 1 foot away from the center of the planetary to the tool tip.

You need to make angled (beveled?) cuts for sink holes? What happens in the corners? What I'm getting at, is do you need 5 axis? Or just 4?

Yes, or just some custom made tooling on a powerful drill press? Can you not get some custom shapes for your tooling with the curves you need built into the cutting bit? Is something undercut? I'm also not understanding why you need to build a 5 axis machine for sink holes. Perhaps if you can show us some drawings of what the sink holes should look like after they have been cut we can understand?

Also, could it be easier to incorporate a rotary table that the piece sits on as one of the axis? How big are these sinks?

No, it's not a straight conversion from force to torque.
Divide the force by 1/(distance from pivot point to where the force is applied.)

So, if your blade is 6" from the center of the harmonic drive, it's 20lbs / (1/0.5ft), or 10 ft-lbs.

No, I'm sorry, I believe you are mistaken. Torque = force x distance

So if you have 20 ft-lbs of torque then at 6 inches, 20 ft*lbs= 40 lbs x (1/2 foot), that would be 40 lbs of force at the tool tip, with 6 inches between the center of the planetary and the tool tip.

Also, when I asked about flanged output, I meant to suggest that you look at the specs for the planetary or harmonic drive, and you could attach the spindle directly to the flanged output, no bearing on the other side. There may already be enough bearings inside the gear, but you need to look at the specs to see what kinds of forces and moments you can subject the gear to.

The 2nd planetary could also be attached directly via the flange output to the lower assembly without additional bearings, it depends on the specs of the drives on whether you need additional bearings to isolate the drives from the forces.

[ger21]

No, I'm sorry, I believe you are mistaken. Torque = force x distance

So if you have 20 ft-lbs of torque then at 6 inches, 20 ft*lbs= 40 lbs x (1/2 foot), that would be 40 lbs of force at the tool tip, with 6 inches between the center of the planetary and the tool tip.

No, I was just coming at it from the other direction.

Also, could it be easier to incorporate a rotary table that the piece sits on as one of the axis? How big are these sinks?

I'm assuming these cutouts are in 6-8ft long countertops.

A big problem here is that you are asking for help from people that don't really know all of the parameters.