have been doing some research (cnc router)

[planescott]

Hello again,

Well i have been doing alot of research, previosly i was going to go with making a smaller machine but what i think sounds good has made me decide to go with making a bigger machine.

I am thinking of going with the 20 degree 8 or 12 pitch rack and spur gear
as it (i think) would save me alot of $ initially and would be something i could change later , but not really sure if it is a good idea.

I am also not sure about what powersupply i would need for this set up.

1) click automations- (3) nema34 2 phase 1076 oz in 3.5amp

2) mach3 software

3) would like to use geckos don't know which ones would go good with
the motors

(anyone know approx. what ipm range this would be in)

I am looking to build a fairly nice machine that will last and am trying not to jump into to something i am not going to be satisfied with.
Everyones opions are greatly appriciated and i look forward to hearing them.

thanks,
scott

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[Evodyne]

Scott,

Hi! Looks like you've made some good, solid choices. The motors I'm not familiar with-do you have a link? While your at it, what dimensions are you considering, what machine configuration (moveable gantry, fixed gantry, etc), and what will you be machining? Wood, aluminum, other? The more info you can provide, the better others can help. If you go to the Geckodrive site Marris has a .pdf file on power supplies-might be a good place to start. I've got the G210 units and absolutely love them. He has since released newer, updated units though. The answer to your IPM question depends on some design variables. The size of the spur gear, power supply, quality of build, and the PC's ability to output an adequately fast pulse train to the Geckos, among others. Come back with some details!

Lance

[planescott]

Hi Lance,

The motors are at clickautomation.com part #n2034510350b
I am considering a 4'x6' (odd size) only because i can't find a rack longer than 6'
I will be cutting mostly wood but would also like to work with aluminum.

Do you know if mach3 will turn dxf files into g code or do i need other software for that.
I did download the mach3 demo and did the test on my computer that they show you on their video, mine was as good as theirs.
i just got my computer a few months ago so i think it should do pretty good.

Thanks, scott

[Evodyne]

Hi! The motors look nice-good price too. Highest you'll probably want to go with Gecko's is 70 Volts for the supply. Their rated for 80, but 70 is a better choice. The 3.5 amps is for unipolar use. Geckos are bipolar. motors are fine, but you now need to decide on parallel or series bipolar. Parallel for that motor is 5A phase, while it's 2.5 amps/phase for series. One gives better power, one better speed, but I can't remember which is which. Sorry! BTW, the Geckos are good to 8 amps, so either serial or parallel is doable. Sounds like you and I are at about the same "know it level": I can't asnwer your Mach 3 question. Nice size machine-not so big you need a new pole barn, yet big enough. Good luck!

Lance

[planescott]

Hey Thanks Lance, I guess i will be going with bipolar series clickautomation has a powersupply #21598 65v/4amp is that a good choice.

scott

[Evodyne]

Scott,

Verify if series is what you want-the whole power/speed thing. If it turns out parallel is better, you'd likely need more current from the supply, or more than one supply (I have one supply per drive. Had lots o parts just sitting around so it made more sense). The 65 volts is darn near perfect. Geckodrive says you can go 4 to 20 times the motors rated voltage so long as your above 24V (I think) and under 80 (aim for 70). Also, get the power supply .pdf off of the Geckodrive site. Marris explains what current X a drive will use to drive a motor at a current Y-they are NOT the same. Another thing that has been discussed on the site is that at a given time its rare that all three motors will be pulling maximum current. So if each motor is 5 Amps, you really don't need 15 Amps at the supply. What is a safe value? Again, don't know if I'm qualified to answer. But if you know some of the issues you can ask the right questions, huh? Search through the back posts-some of these questions come up again and again.

Lance

[ger21]

Parallel for that motor is 5A phase, while it's 2.5 amps/phase for series. One gives better power, one better speed, but I can't remember which is which. Sorry! BTW, the Geckos are good to 8 amps, so either serial or parallel is doable.

Actually, both series and parallel should have just about the same holding torque. But bipolar parallel will have much more torque at higher rpm. I think the only benefit of bipolar series is that you still get full holding torque, but only need half the current. Bipolar parallel is almost always the preferred method.

Gecko's are rated for 7A, btw.

[ger21]

Almost forgot. When using Gecko's, you only need 2/3 of the motors rated current.

2/3x5x3 = 10A for 3 motors.

[smarbaga]

what are you going to cut with this 4' x 6' machine
do u plan to do a lot of tabletops or engraved aluminum truck beds.
i said to myself, well a small 12" x 12" for starters, well maybe 12 x 16 .... inched it up untill it got to be 4' x 8' ( in the plans that is)
then i came to reality, an accurate 16" x 36" would be better ( for me ) than a monster, where i would have to cut corners ( due to cost ) and really how many 4' wide single cuttings will i do?

[planescott]

I will mostly be doing woodworking with it furniture, etc.
but no truck beds (lol)
so can anyone recommend where i could get a powersupply that would be
just right for this, going with bipolar parallel. i read that unregulated is the best choice.
i seen a 115vac 65v/8amp would that work well.

thanks again for the bits of info, don't think i would ever build a machine if
this site didn't exist

scott

[Evodyne]

Actually, both series and parallel should have just about the same holding torque. But bipolar parallel will have much more torque at higher rpm. I think the only benefit of bipolar series is that you still get full holding torque, but only need half the current. Bipolar parallel is almost always the preferred method.

Gecko's are rated for 7A, btw.

Thanks Gerry! Kinda figured that if I at least meantioned to Scott the need to decide on the series/parallel options one of you smarties would step in, fill in the blanks, and bail me out. Oops on the extra amp Scott, Gerry's correct: 7 Amps max on the Geckos.

Almost forgot. When using Gecko's, you only need 2/3 of the motors rated current. 2/3x5x3 = 10A for 3 motors.

Ah! Thanks AGAIN Ger! Scott-this is what I was referring to when I said to look in the power supply .pdf from Geckodrive. Looks like you've gotten a good bit of info at this point. Have fun!

Sincerely,

Lance

[Evodyne]

what are you going to cut with this 4' x 6' machine
do u plan to do a lot of tabletops or engraved aluminum truck beds.
i said to myself, well a small 12" x 12" for starters, well maybe 12 x 16 .... inched it up untill it got to be 4' x 8' ( in the plans that is)
then i came to reality, an accurate 16" x 36" would be better ( for me ) than a monster, where i would have to cut corners ( due to cost ) and really how many 4' wide single cuttings will i do?

smarbaga,

Boy does this sound familiar-mental feature creep. Due to some buys I couldn't pass up I even ended up with the parts for a biggy. But then I really looked at the space I've got and it wouldn't make sense. And after really thinking about it, the stuff I'm interested in making doesn't even require it. So once I got out of dreamland I'm downsizing too. (But I'm holding onto the othe parts in case I win the lottery and put up a pole barn ). What kind of things do hope to make? And for the 16" by 36" X and Y, how much Z travel are looking at? Just curious.

Sincerely,

Lance

[smarbaga]

my design is kinda square horse shoe shaped with the 'y' screw drive at the side.
this gives me an open work area. i will be able to clamp the machine anywhere on a large or thick workpiece, if necessary ( like a truckbed, lol), but i guess about 3 " of z, depends on the slides and screw i find.
i think the z axis will be the easiest and cheapestpart.
but i've got this thing planned to death, and don't think i could draw another line on it.
now its time to committ and spend, spend spend
ps : my little 12" x 12" machine would have ended up needing a $20,000 20' x 40' garage built around it, until i woke up .
i've seen machines bigger than my livingroom with a 1/8" drill bit on them
what a machine size to job ratio

[jcc3inc]

Sir,

While I like your choice of 20 degree pinions, I'd like to suggest that you consider 24 dp rack instead of 8 or 12 pitch. Since the minimum tooth count which has NO undercutting of the pinion is 18 teeth, suppose you chose 20t; the distance traveled per rev would be 2.618 inches; a more practical size might be 30t which gives 3.927 inches per rev. With 8 pitch, the 20 tooth distance becomes 7.854 inches, a 30 tooth yields 11.781 inches per rev. Thus you can see the increased gear reduction required for each motor. In practice, we used 12 pitch only for very large gantries with dual sided drive.

Regarding travel length, it is common practice to butt 6 foot lengths together using a short 3" section of inverted rack to establish min error at the rack joint before bolting down the pieces.

Happy to make further comments on gear rack drives, mounting, gearboxes, etc.

Regards,
Jack C.

[Evodyne]

jcc3inc,

"Happy to make further comments on gear rack drives, mounting, gearboxes, etc." Please do! If you have a great deal of experience with this, would you consider a "best practices" or "how to for dummies" or "tutorial"? Something along the lines of swede's fine ball screw overview.

Lance