My First Build Question

[teamloks1]

hi its my first time trying to build cnc last time i just bought workbee cnc now i prefer to go play aluminum so here my question

i got 400w JMC Servo 20Bit and 2005 Ground Ball Screw C5 should i use reduction and which ratio is better for it?

Thanks

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[ger21]

If it's a 3000 rpm servo, than I would direct drive it.

[teamloks1]

ok thanks sir for fast answer

[teamloks1]

owh btw i got hand on 2005 2010 2020 c5 ground ball screw which 1 should i get and better if using with reducer to get best performance

[ger21]

What type of machine, and how big is it?
For a larger router, I'd use 2020 or 2525, and belt reduction.

[teamloks1]

its only 2x2 machine so its ok to use 2005 only? btw have you heard about new inwin linear rail CG series i think

[HuguesP]

5mm x 3000 RPM, = 15 000 mm/min. Wich is for a diy router, 2x2, maybe a little fast. you could gear it down, but this is not an obligation. The use of software limitation and /or limit switches would be mandatory.

As for the size, According to this table, a rigid ( 2 bearings) - Simple ( one bearing block) will allow you the 3000 RPM with a 12mm diameter ballscrew. so your 20mm ballscrew is way over designed. Internet is full of 1605 ballscrews, so unless you already own them, you may want to reduce the size. It is also easier to design a small machine with smaller components.

just my 2 cents iam not an expert.

[teamloks1]

5mm x 3000 RPM, = 15 000 mm/min. Wich is for a diy router, 2x2, maybe a little fast. you could gear it down, but this is not an obligation. The use of software limitation and /or limit switches would be mandatory.

As for the size, According to this table, a rigid ( 2 bearings) - Simple ( one bearing block) will allow you the 3000 RPM with a 12mm diameter ballscrew. so your 20mm ballscrew is way over designed. Internet is full of 1605 ballscrews, so unless you already own them, you may want to reduce the size. It is also easier to design a small machine with smaller components.

just my 2 cents iam not an expert.

thanks for answer yes i already got all the part i wonder is my design is good or not for now this is my stuff

1.TBI BALL SCREW OFU(DFU) C5 2005
2.JMC MOTION 20 BIT Servo
3.HIWIN CGW20CC
4.100*200 Extrusion
5.100*100 Extrusion
6.80*160 Extrusion
7.C5 ballscrew holder with angular bearing
8.for z axis im using linear actuator i got for free its with 2005 screw and hiwin 15mm block

i hope can get good suggestion since this is my first build

[dberndt]

Why not use the RPM's you've got. If you want to go reasonably quick for a hobby machine pick something like 250Inches Per Minute and do the calc.

With a 5mm ball-screw, that works out to ~1270 RPM. As per some of the above, thats a somewhat reasonable ball-screw RPM.

But your servo probably goes to 3000rpm rated, 4500-5000 max. Why not use a 3:1 ratio gearbox or belt and get ~3x the torque? Without the gearbox you're leaving %60 servo watts on the table.

If we ignore linear motion losses, ballscrew efficiency, etc. The linear force calc is something like:?
2pi x r = 5mm
5mm/2pi= r = 0.795mm moment arm, convert to inches because North America= .031"
A 400w servo has ~11b-in rated, ~33ln-in peak
11/.031=354lbf thrust rated, 1064lbf peak thrust

With a 3:1 gearbox/belt, ignoring losses, you can roughly triple those thrust forces.

If you want to take optimizing these things, and including real world efficiencies, inertias, etc. Then a good software VisualSizer from CopperHill Tech, you can find it around the web. You can mock up your setup and motion profiles and see the required power.

[teamloks1]

are there any suggestion for 3:1 belt type should i get?

[multivactubes]

are there any suggestion for 3:1 belt type should i get?

In my build I used Gates timing pulleys and a Gates timing belt. The pulleys I am using are GT series with a 5mm pitch. The belt is GT3 type. I am not sure where you are located but in the USA stock drive products sells them. http://www.sdp-si.com

[wizard]

are there any suggestion for 3:1 belt type should i get?

In this context I don't think there is a huge difference in performance from one timing belt series to the next. In the distant past I worked on some diamond turning lathes that used old fashion trapezoidal timing belts and they worked just fine. This was optical work in polymers and at the time we did inspections with optical tools and Taylor Hobosn Talysurfs. You would see more surface imperfections from the air bearing spindles than anything else on the machine. Usability comes down to "tuning" the belts with optimal belt tension.

The idea of tuning a belt applys to any size servo driven axis. For example Cincinnati Milarcron ATC mold machines ran rather huge FANUC servos, driving very large leadscrews with HTD style belts. Even here the tension in the belt is a factor in proper operation of the machine, this evne on a belt that might be around 6" wide.

I'm not a big fan of the AT series of belts. So I wouldn't go that route.

[teamloks1]

In this context I don't think there is a huge difference in performance from one timing belt series to the next. In the distant past I worked on some diamond turning lathes that used old fashion trapezoidal timing belts and they worked just fine. This was optical work in polymers and at the time we did inspections with optical tools and Taylor Hobosn Talysurfs. You would see more surface imperfections from the air bearing spindles than anything else on the machine. Usability comes down to "tuning" the belts with optimal belt tension.

The idea of tuning a belt applys to any size servo driven axis. For example Cincinnati Milarcron ATC mold machines ran rather huge FANUC servos, driving very large leadscrews with HTD style belts. Even here the tension in the belt is a factor in proper operation of the machine, this evne on a belt that might be around 6" wide.

I'm not a big fan of the AT series of belts. So I wouldn't go that route.

if i got budget is planetary gear more better?

[ger21]

If you want to go reasonably quick for a hobby machine pick something like 250Inches Per Minute

250ipm is not "reasonably quick". I'd argue that it's quite slow.
I think direct drive, or 1:1 belt is the best choice.

if i got budget is planetary gear more better?

No, they will have more backlash than good belts (GT2 or GT3).

[teamloks1]

250ipm is not "reasonably quick". I'd argue that it's quite slow.
I think direct drive, or 1:1 belt is the best choice.



No, they will have more backlash than good belts (GT2 or GT3).

i think i go with direct for now and is bellow coupling is good? and i even think about gt2 but its hard to find 14mm bore for my servo

[skrubol]

Bellows couplings tend to be pretty pricey I think. From my reading Oldham's tend to be the best compromise. They're 3-piece, so it tends to be easier to find the combination of input and output shaft sizes. Lovejoy's (spider,) are similar, but tend to have a bit more backlash.

[teamloks1]

Bellows couplings tend to be pretty pricey I think. From my reading Oldham's tend to be the best compromise. They're 3-piece, so it tends to be easier to find the combination of input and output shaft sizes. Lovejoy's (spider,) are similar, but tend to have a bit more backlash.

i already bought bellow and gt2 belt 10mm diaemter still thinking to direct or making 2:1 ratio

[peteeng]

Just asking but whats the issues with an AT belt? Peter

[wizard]

Honestly I’d have to say no!

At work I’m involved in a project to replace gear boxes on mold machine extractors that are not available anymore. Frankly gearbox’s don’t last very long and can go out of production or simply be hard to find in the USA. In one case the gear boxes have been replaced several times and the belts being driven never or maybe once.

Now one might argue that the gearboxes where not sized correctly when the machines where designed. That is possible but I’ve seen all sorts of gearbox failures across many machines. At this point I would not design in a gear bloc unless I needed a ratio not easily obtained with a single level belt reduction.

It might be noted that many of these gear box failures are in machines that are sealed grease lubed. Oil bath boxes seem to perform much better. Then again oil bath gearboxes will leak required by seal replacement. Beyond all of that timing belts and pulleys are cheap.

if i got budget is planetary gear more better?

[teamloks1]

Honestly I’d have to say no!

At work I’m involved in a project to replace gear boxes on mold machine extractors that are not available anymore. Frankly gearbox’s don’t last very long and can go out of production or simply be hard to find in the USA. In one case the gear boxes have been replaced several times and the belts being driven never or maybe once.

Now one might argue that the gearboxes where not sized correctly when the machines where designed. That is possible but I’ve seen all sorts of gearbox failures across many machines. At this point I would not design in a gear bloc unless I needed a ratio not easily obtained with a single level belt reduction.

It might be noted that many of these gear box failures are in machines that are sealed grease lubed. Oil bath boxes seem to perform much better. Then again oil bath gearboxes will leak required by seal replacement. Beyond all of that timing belts and pulleys are cheap.

thanks i already go with ger suggestion by using gt2 belt 2:1 ratio 45:90 tootht