What extruder do you have on your printer kram?

 

Kram,

When do you think that you will have the files for the side and gantry plates up?

The plates are the long pole in the tent for make the OX.

 

Good job, Mark. You are almost at the finish line!

Two points I would like to make!
When will be able to see the Garolite plates in the stores for people like me who have no access to a machine shop. I tried McMaster-Carr and they have the material but only in square pieces (12"x12"( being the smallest. Since Garolite is a trade name for reinforced-Phenolic material I also looked for Bakelite but so far no luck. So, please let us have the plates (especially for the Z-axis at the store).

I did some searching on the electronics also. I was planning on using TinyG from Synthetos but realistically they cannot be used with Nema23 drawing near 3amps. In fact I discussed this with Synthetos and they finally decided to recall my board when I pointed out some shortcomings.

Most Stepper Motor driver chips are run using constant current driver stage - meaning the current through the motor is held constant independent of supply voltage variations. TinyG and its sibling GRBL(pronounced garble) Shield are limited to 2.5amp max. Indeed you can run multiple motors connected to one output as you have suggested especially when microstepping is used where full current is NOT applied to motors. But the total current output from the axes will still be maxed out at 2.5amps. The electeronics, of course, will not be damaged since its power dissipation(current through the part) is limited.

At full power, these chips will get hot and the heatsink is at the BOTTOM of the board - this means adequate cooling is required at the BOTTOM of the board - or else there will be a thermal shut down by the chip.

Anyway, when you connect multiple motors running at high current the current from the axis output is shared by the two motors and they will provide LESS TORQUE - defeating the purpose of using TWO Nema23 motors to drive the Y-axis which carries max load in the OX design.

So I am opting for different electronics for the drivers - one suggestion I have made here is to go with a design by massmind.ord that uses THB6064 with 4.5amp capability. They sell parts for those who are good with soldering, or assembled parts for about $35/axis. Other options are also available. (see http://www.massmind.org/Techref/io/stepper/THB6064/index.htm).

Now there are newer electronics coming to market - ST Microelectronics have announced a new chip ST6472 which is a fully integrated axis with SPI interface - Arduino chips support such a communication. But here is something one can get from eBay:
http://www.ebay.com/itm/ST-L6472-Ba...d=100011&prg=1005&rk=2&rkt=5&sd=230891366885&

Anyway, OX is a great mechanical engineering design - and I feel members who are good at electronics should come up with a solid electronics BOX to complement this.
Gopal

 

The E3D - version 5 extruder is from UK and their website is: http://e3d-online.com/index.php?route=product/product&path=20&product_id=51

Robert, you should also look into their multi-head design the Kraken.

I have actually ordered a 5head unit from ORD Solutions located in your part of the world and should get it next month or so!!!

By the way, have you thought about beefing up your spindle motor design using R8 with a through central hole?
The reason I suggest is that if you then mount it horizontally, it can be used as a quick and easy jig for grinding acme screww rods, ha ha!

Gopal

 

R8 brushless ?
I used my drill press and a 608zz bearing block setup to grind my old leadscrew when I first started lol
I will post a pic for ya later

 

Like I feel, it is not fair that some people have all the fun in their lives. I lived in a cacoon for the past 40 some years theorizing in particle physics - now the butterfly is out but the body is no longer willing!!!

Besides, I have a 3yr old (!!!!) and my better half has given us the same amount of budget for our toys - he has a roomful of toys and I cant get one on my desk!

What impresses me about your efforts is that you seem multi-talented - mechanical, RC toys, electronics, Laser engraving, 3D printing and what else?

Gopal

 

I agree with both your points!
Yes, running both ends of the gantry is indeed a good design when the spindle torque when at one end and take a good plunge cut can exert a twist to the whole gantry. I also realize that by having two motors with slightly variable belt tension or tooth position on the drive wheel can reduce overall backlash.

I am just pointing out the limitations of the motor drive and may have overstated on the required force
Also, I am urging memebres to come forward and hold out a helping hand with the electronics part also. Mark has done a terrific job on the mechanical design but we tend to want him to do everything for us and I noticed that from his posting of the spindle motor mounting post. This is an evolving build and I wish I had the wherewithall to jump-in and do my portion of supporting the efforts.....
Gopal

 

Mark, the motor mounted board is indeed a bad idea but I posted that to show that the ST chip is being implemented in a design. I have often seen Steppers with heat sink mounted on them! And read at many places that the motor heats up SOONER than the drive boards! But was thinking that with steppers mounted on Nylon (?) standoffs the board cound find a place as part fo the motor but away from heat issues- my imagination is to put a wireless (Xbee??) along with the drive electronics thereby reduce wires running to the motors - even day-dreaming about a low voltage electrified rail (having built such things for my kids Thomas Train collection - can't afford batteries at the rate he is using them up) on each axis to totally eliminate flying leads....Oh well.
Gopal

 

No 3d printer experience yet, but it is the last tool I want for my hobbies and and kids to play with. Their future will be so different.
Teach them young
Printing body parts , just awesome!
I'm a jack of all master of none
As they say here in Canada
They should at least find ya handy if not handsome eh!

 

Mark, you had mentioned switching to GT3- belt & pulley - point to a source, please!

 

Don't be fooled by the 7amp rating of the st6472, it is a max peak current rating with a max pulse duration of <1ms. Not very useful in stepper applications. The ThB6064 has a peak current rating of 4.5amps with a max pulse duration of 100ms, which is a more reasonable specification. The fact is both drivers are rated at 5 watts and have similar on resistances. Therefore, they both will generate the same amount of heat for the same amount of current. The real variable is the size of the heatsink which will determine how much current the driver can sink without overheating. The ThB6064 was designed to be mounted on any size heatsink. This is not true of the st6472.

The Spi port interface means additional software has to be developed to configure and control the st6472. I have designed Spi port stepper motor drivers for the Auto industry. They work fine in some applications but are susceptible to noise problems if the wires are not routed and shielded properly. I would also recommend keeping the wire lengths as short as possible. Spi based stepper solutions are designed to run open looped, meaning that you send a goto position to the driver and a step rate and it goes to that position. This presents a problem and controlling three different axis that need to be synchronized. The st6472 overcomes this problem by allowing the software to send a Spi port direction command which puts the driver in single step mode which is stepped via a stck pin similar to the step input pin on many drivers.

I think I will stay with the ThB6064, which could be soldered to the step, dir, and enable pins on the TinyG board. The on board drivers would not be used. However, I have my eyes on the CNC USB Controller MK2 board in the parts store. I know it cost, but the hardware and software supports a lot on nice features that I plan to use.

Comments welcome.

Mark, when will the MK2 be back is stock? I noticed that it shows in stock at your other store with free delivery, is that true?

 

Scored some 1/4 plate for my end plates
Nothing like having friends in the metal biz lol
Its 6061 econo plate so should clean up nice after milling 10" by 4' $20

Going to hold off a bit here and see what works before I start milling as I'm sure a few design changes are still going to happen

 

Thank you so much for all that useful info. I am truly a noobe with all this and my edification is through browsing and reading data sheets and more from reading posts like yours. In all my ignorance if I can kindle enough participation and interest in developing a good and reliable product that we all can use and enjoy, then I feel gratified.

All these urging also have another personal interest (ulteriro motive) - to develop a six channel stage similar to the Stewart design to be used as an articulated platform to see if it can help children with spatial balancing problems due to congenital problems (pediatric vestibular disorders). I feel that the expensive toys that we develop can be converted to something more useful than just engraving and carving.

Robert touched upon something when he said future may see body parts being printed using 3D type printers - actually there a few people already pushing that -prosthetics- envelop).

But then again I am just a dreamer and have rely heavily on people like you, Mark & Robert to guide me along.

Thanks for putting up with my flailings here in the forum
Gopal

 

To dream is simply a way of making things reality, E=MC2 was thought up by an un-schooled dreamer and I feel that the largest problem in the education system is that if your not as they say book smart and learn their garbage you are over looked.
Yet that same persons dreams if given the chance could be the cure to cancer or many other issues in this place we call reality.
we suppress them gifted under sights when we should be helping them grow.
Anyway so off topic lol
If I can do it so can anyone else

 

I would like to take the engine from the TinyG controller and have it a on a separate board. Have the signals come from it to drive separate drivers. If any one of your drivers goes down you could swap in another driver and your back up. As new drivers are developed you can easily upgrade. Also would like a MicroSD card so you could put your files to be cut. Just my thoughts. Robert you said your from Canada ? I am in Ontario.

 

Yes I live in the busy city of Toronto.
I'm a generator service tech, going on 18 years now.
Tinkering is my hobby and way of letting my imagination free.
I rather build something that way if it breaks I know how to fix it.
I started in the cnc sence when I got a chin board that the z axis IC went bang on and decided to turn their junk into something that worked

 

Mark, I have also included the 9 axes board in my wishlist (not for any discount) but it may be something that I can use in my dream project. My inspirations, besides coming from all of you folks and your work, also have to do from suggestions like this:


My intention is to use magnetic spheres for the lower and upper (not visible) universal joints and use the belt & pinion drive with constant rate springs to balance forces. (nothing new here except for the application perhaps)
Gopal

 

I am in Windsor, across from Detroit Mi. I've been an Electronics Technician for 30+ years now. Time flies. When I order from Mark, I'll have it shipped to a Detroit mail service, drive over and pick up the stuff. Cheaper that way. Watching this site closely.

 

Dave,
Correct me if I am wrong but isn't that what they did with the grblShield? The Arduino Uno is the controller board and the grblShield stepper driver board sets on top. Just use the Arduino Uno to drive external driver boards. Of course you would have to make your own header connector or find a board with screw terminals.

 

Thanks Mark,
I will keep a eye out for the MK2. I like it when a plan comes together, just a few details to work out now.

 

Another source for Arduino+GRBL+stepper drive as a replacement for Arduino shiled + GRBL Shield

http://www.panucatt.com/product_p/mcnc-3az-328p.htm

They have other products also.

Gopal

 

Can't the tinyg power an external stepper driver? It has 4 drivers on the board, and at least 2 other outputs for external drivers. Does anyone know some compatible stepper driver options that could output more amperage to connect to the tinyg and the larger stepper motors or dual output stepper motors? even a commercial option such as a gecko?
http://www.geckodrive.com/geckodrive-step-motor-drives/g250x.html
http://www.geckodrive.com/geckodrive-step-motor-drives/g201x.html
depending if one needs 3.5 amps or 7 amps?