Skuba Router

[skubajon]

Well I have gotten tons of feedback from lots of people here so thanks.

I wanted to start a build log as Im getting really close to putting in my order for parts. I have a lot of the materials already and hoping to have this thing build by end of sept/oct of this year. I designed this machine to be expandable as needed. I'm starting out with some proprietary extrusions to build this machine, but in case I don't like having the extrusion, I can completely switch to steel beams. The linear rails are 1000mm long both x and y and 450mm long z. This is a slaved X axis machine running on 5mm lead ballscrews. It will be servo driven with a gear reduction (as of now with proposed motors) 3:1

As far as the main structure which I have yet to complete, this machine will sit on a base 4 foot from the ground, constructed of square steel tubing. The working table will be a piece of Epoxy Granite, 2 inches thick, complete with threaded inserts. The threaded inserts are going to be installed with extremely close tolerances by my local machine shop so that all the fixtures this will use will be plug and play as you could say.

For electronics I'm currently debating on some different parts. I'm really interested in the C23 board and the smooth stepper motion controller. I'm also debating on going with Gecko drives or the Dugong digital drives.

This machine has started out as a way for me to prototype products that I build as my machine shops that run products parts for me, do not do one off parts for testing and if they do, I'm spending 300 to 500 dollars to get a part made. So I opted to build a machine and now its turning into a time consuming ultra hobby! I manufacture fire arms and other items in that industry. I also wanted a nice means of engraving some tools that I currently sale with all my patent info. These tools are made from 4130 steel. Again this saves me about 4 to 5 dollars per part doing in house than sending out to be done and at 10000 parts a year, I figured it was time to build something. I also wanted to build some machines for customers and needed something with a wide footprint that my Grizzly mill just cant get me.

Any advice, suggestions or comments would be gladly appreciated! I don't even mind good constructive bashing on the design! I've been told by many, I cant do this so I'm either going to blow a whole bunch of money, or post my results with a smile!

I have been really interested in High Speed toolpaths as It allows me to build a much smaller machine and achieve some good results as the stress levels are a whole lot less than old school milling. I started modeling this after the datron but not on datrons budget. I won't have ATC or anything like that. I will have a few cool features built into this one though. I have build a prototype laser tool height tool that will be permanent on the machine. In fact, its working so good that I probably will be using lasers for homing and limits. 10 bux can't go wrong and they work flawless!

Well here are some photos of what I have done so far. I have also added some space incase I feel like I need a little more support for the y/z carriages that will allow another profile rail and set of bearings. I do estimate the final weight of the machine at about 1200 to 1500 lbs with the steel structure below.




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[skubajon]

Here is a little bit more work done on it. If I go with a little smaller wall tube for the structure, a save about 400 lbs!

[skubajon]

And another with all the axis hooked up to their screws. Got a little ways to go yet. Still have to design the limit and home switch stuff, and a good way to cover my ballscrews and servos. After that I need to finish up designing the water tank for spindle, coolant tank/pump for flood/mist cooling, and the electronics enclosure.

[pippin88]

I like your gantry risers! They will be nice and stiff.

[bill south]

The only concern I would have with this design is the placement of the head that far forward of the gantry. When the gantry x axis is at its most rearward position, the head appears to be at mid table so your effective working space is the forward half of the table. Of course if the table is quite large, that will not be a problem.
Nice work and just my opinion.
Bill

[ger21]

Personally, I think you'd be much better off with single 20mm or 25mm rails, vs the double 15mm rails. Unless your alignment is perfect, you'll get some binding, or premature wear on the bearings.

Also, the extrusion your using for the gantry tube will be the weak link in the machine. A single heavy wall steel tube with double the height would be cheaper, and stronger.

[skubajon]

I appreciate your feedback

So as far as the cutting head being forward, I definitely agree. I originally designed this machine to have about 2 foot by 3 foot cutting area. With this it was cutting off quite a bit so I extended the rails to 1000mm both axis. This actually gives me about 26 for x and 33 for y

For the rails the reason I chose these was because of price and avail. I had access to most of the materials here. My thoughts were right in line with what you're thinking. My friend builds automated type machinery and is extremely confident he can help me get them aligned right and with his full machine shop for access why not give it a shot! Each 1000mm rail and 2 blocks only cost me about 50 bux brand new through hiwin. If we struggle then these rails will be used on a small engraver and I'll opt for bigger rails

As far as the beam....I've been staring at that thing and don't have much confidence in it at all. And when I say I'm about to change the plans and go steel beam, the friend shows me some awesome things people are doing with less of a machine. I've seen some nice stuff done with an wooden build machine! So if it doesn't work we have 2 options we have already thought about and designed into the machine for future upgrade. I'll give him credit though on this extrusion. It's proprietary for his company and its used to support 2500 lb loads up to 30 foot for precision sawing equipment. It's definitely the thickest walled extrusion I have ever seen and I have enough in free pieces to make it work.

Option 1 would be epoxy granite filling the extrusion and option 2 would be of course to replace with a beam made steel.

The only reason this thing hasnt been started is I'm still struggling with the motor selection. Every calculator thrown at me tells me something different. One will say this motor works...other will say it doesn't. Maybe some insight on size of motors would be super helpful. Not sure the days I've lost sleep haha

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[skubajon]

So does this look correct?

The motors I'm looking at are dc servo motors.
1.2nm constant
6.0nm peak
4200 rpm
Terminal voltage 72vdc
Cont current 7.5a
Peak current >30a
Torque constant .01791nm/am
Volt constant 18.75v/100 rpm
Resistance .085 ohm
Inductance 2.35mh
Inertia 3.39kg/cm^2

Of course gear reduction to get me down the the desire speed. Probably be between 2.5 and 2 to 1 ratio




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[ger21]

You plan on spinning your screws at 2000 rpm? (4200rpm/2)

[skubajon]

Yes. I only really need 300 ipm rapids and according to this that means I'm at about 1500 rpm and my screws are good for 3000. So 2000 rpm will allow me to go faster or I can use the extra ratio for more torque

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[skubajon]

Well I won't push to many volts through. 2k max would be fine. Trying to find a good middle ground where servo size and speed meet in the middle. I'd like to keep costs down so using a small servo with right gearing is where I'm leaning

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[skubajon]

Here is another that I put through calculator and got a green light. Maybe I'm entering stuff in wrong?

This motor is a nema 23 sized dc servo motor. Cont torque of .353nm and 3.5a. Peak of >20a and 2.47nm. Essentially a 350oz motor.

So I figure 2.35 gear reduction for easy math. If torque is .102nm per amp and I figured 15a for running then this motor is also a compatible choice

Or is this calculator wrong or am I wrong? Do I add the continuous torque here or the peak torque or use math to figure out what torque would be at said amps

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[bhurts]

Size your servo for continuous torque. Peak torque is only used for acceleration and break away. It should only go above continuous current for fractions of a second at a time. When you make your calculations don't forget to include your screw pitch as part of gearing. Those smaller motors will probably work fine for x and y. Z you could use a larger motor or some kind of spring assist.

Ben

[skubajon]

Alright so almost everything is ordered except electronics

4 750w ac servo
4 servo drives
3 20mm ballscrews with all the fixings
1 16mm ballscrews with all the fixings
6 hiwin rails 1000mm
2 hiwin rails 450mm
16 hgr bearing blocks
All the cables for encoders, servo power etc
2.2kw spindle
2.2kw vfd

2280 dollars!!

Now to choose best motion controller and breakout board.

I've been thinking about smooth stepper and their breakout board I think was c32

What do you guy recommend?

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[louieatienza]

Yes. I only really need 300 ipm rapids and according to this that means I'm at about 1500 rpm and my screws are good for 3000. So 2000 rpm will allow me to go faster or I can use the extra ratio for more torque

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If they are the infamous LMB2008 rolled ballscrews, I'd be leery about running them past 2000rpm let alone 3000. Maybe under PERFECT conditions, with fixed-fixed end fixity, maybe. I have a few precision ground ballsctews and their critical speed is around 3400-4000rpm.

But generally the more reduction you run, the more efficient your machine can be and with better acceleration...

[skubajon]

No these are the sfu ballscrews fixed on one end and supported on other

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[skubajon]

Well I'm still struggling to find a good supplier for belts and pulleys. Also a little nervous because if a belt snaps I don't think that will fault system and could cause major damage

With the 750w motors 3000 to 5000 rpm I've been thinking I'll just go 2 to 1 with it. That will give me all the speed I could ever need.

Anyone have a good lead on belts and pulleys? I thought about running a laser type anti racking system on the back side of my x carriage blocks so that way if one screw stops turning the machine then the laser wouldn't hit the sensor and halt the machine as an estop. Similar to my tool height probe

Where's a good place or vendor for belts?

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[louieatienza]

Well I'm still struggling to find a good supplier for belts and pulleys. Also a little nervous because if a belt snaps I don't think that will fault system and could cause major damage
Ugh
With the 750w motors 3000 to 5000 rpm I've been thinking I'll just go 2 to 1 with it. That will give me all the speed I could ever need.

Anyone have a good lead on belts and pulleys? I thought about running a laser type anti racking system on the back side of my x carriage blocks so that way if one screw stops turning the machine then the laser wouldn't hit the sensor and halt the machine as an estop. Similar to my tool height probe

Where's a good place or vendor for belts?

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The aforementioned machine I work with has a 2:1 belt reduction and square style belt teeth and they're the original ones. Nowadays they have special rounded teeth profile and even steel and Kevlar reinforced. Likely your belt supplier will help you choose the right size and profile.

Try SDP/SI, Misumi, Motion Industries (though expensive)... You might get a list of distributors from companies like Gates.

[louieatienza]

No these are the sfu ballscrews fixed on one end and supported on other

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I wouldn't run them more than 1800-2000rpm max.

[skubajon]

See the company I work for owns motion industries lol. And they weren't much help so I was kind of bummed

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