[vakeiros]

Hi guys,

I need to build a new machine and would like some opinion to see if i'm in a good way.

I'm from Portugal and here it's a pain to get the materials to this kind of stuff so i'm dependent from the Bay and that kind of sites.

Last year I'd bought a Chinese TS3040 H80 and I'd learn ALOT with this machine but I need something bigger, stronger and better.

I Have some ideas for the structure but where my big concerns are the ball screws and linear guides. I'm thinking to make a machine that can work about 800-900mm * 500-600mm * 200-250mm

I first thought about this set:
3 SBR20 300/600/1000mm Linear shaft support sets+3 ballscrews RM1605+3 BK12/ BF12 Ball screw Support +couplering for CNC CNC010-in Ball Screws from Industry & Business on Aliexpress.com | Alibaba Group

it has 16mm ball screws and 20mm SBR guides but after reading very posts here on this forum everyone say that the "square guides" are much better so I'm on the wind again.

now I'm thinking about this:
China made good quality 6 sets linear guide HGH15CA+ 3 sets SFU1605 ball screw kits for cnc router-in Ball Screws from Industry & Business on Aliexpress.com | Alibaba Group

well this kit has the same 16mm ball screws (1000mm 650mm and 350mm) and HGH15 guides (1000mm 700mm 300mm) now these are really my max budget for the guides and screws so what do you think?

the spindle i'm thinking on an Hertz 1.5kW or an 2.2kW with an Hitachi VFD (I've no clue where to get these but these are the ones I want) on my TS3040 I mounted one of those Chinese 2.2kW WC spindles and I must say that I'm very happy with it.. but I'd heard many good things about that Hertz and Hitachi VFD.

about the steppers well i'm sure i'll go for the wantai 425OZ + DQ542MA drivers on a 48V PSU + 36V PSU, I've some 270oz of these and I'm very happy with them, and these might be enough for this machine but I tend to be a bit overkill on my stuff XD

well this is pretty much it, I used your help before an my TS3040 upgrades now here I am again... this time i'll ask before buy anything XD hehehe lesson learned...

best regards and thanks in advance

[awerby]

I'd stick with the 270 oz-in motors if I were you. Those 425s have too much inductance (9 mH/phase) to give you good performance. You generally want to choose a motor with less than 3 mH/phase for a machine this size.

[vakeiros]

yes, you're are right, you think the 270OZ are enough? I have no notion of the required force to the motors on these machines... I have these 270OZ on my little TS3040 and they break a carbide tool without any effort so probably they'll do the job on this machine...

what about the rails am I choosing right?

[vakeiros]

Hi,

I forgot to say, this CNC it's mainly to cut PVC and Aluminum, yes i know to cut aluminum it has to be very stiff and that's why i'm buildint a new one, my TS3040 cut's aluminum but it vibrates and the finish it's poor...

I want to try to cut brass too (i think it's not much harder than alu is it?).

after a bit more research i'd found out that you're right awerby, 270Oz it's enough for this machine so one less thing to decide!

the winner steppers are these:
【Germany SHIP Free SHIP】3Axis CNC NEMA 23 Wantai Stepper Motor 270oz 3A Driver | eBay

now my main question is about the linear movement...

between these too what do you recomend?
China made good quality 6 sets linear guide HGH15CA+ 3 sets SFU1605 ball screw kits for cnc router-in Ball Screws from Industry & Business on Aliexpress.com | Alibaba Group

or

3 SBR20 300/600/1000mm Linear shaft support sets+3 ballscrews RM1605+3 BK12/ BF12 Ball screw Support +couplering for CNC CNC010-in Ball Screws from Industry & Business on Aliexpress.com | Alibaba Group

about the structuer i«m thinking something like this:



what do you think? I'm thinking using 40mm aluminum profile for the structure.

thanks for all

regards

[plcamp]

I'd stick with the 270 oz-in motors if I were you. Those 425s have too much inductance (9 mH/phase) to give you good performance. You generally want to choose a motor with less than 3 mH/phase for a machine this size.

The 425 oz-in motors should be good if you keep the shaft speed at 5tpi or less. At this speed the motors most likely will not run long enough to see the high inductance characteristic to these motors.

[PaulRowntree]

The 425 oz-in motors should be good if you keep the shaft speed at 5tpi or less. At this speed the motors most likely will not run long enough to see the high inductance characteristic to these motors.

@plcamp : Could you please explain this ? I always thought that the high inductance affected the voltage/current necessary to get a clean step, every step, not the long-term running state of the motor.

[vakeiros]

The 425 oz-in motors should be good if you keep the shaft speed at 5tpi or less. At this speed the motors most likely will not run long enough to see the high inductance characteristic to these motors.

I'll go for the 270Oz ones, it's enough for what i need.

i'll have to decide about the rails... I think i'll get the "square" ones... don't really know if 15mm rails are enough... I have ZERO experience on this field..

[plcamp]

@plcamp : Could you please explain this ? I always thought that the high inductance affected the voltage/current necessary to get a clean step, every step, not the long-term running state of the motor.

Inductance reduces a stepper motor’s high speed torque performance. Inductance is the reason all motors eventually lose torque at higher speeds. Each stepper motor winding has a certain value of inductance and resistance.

The “electrical time constant” is the amount of time it takes a motor coil to charge up to 63% of its rated value. If a stepper motor is rated at 1 amp, after one time constant, the coil will be at 0.63 amps, giving the motor about 63% of rated torque. After two time constants, the current will increase to 0.86 amps, giving the motor about 86% of rated torque.

t = L/R

Inductance “L” (mH), divided by resistance “R” (&), gives the electrical time constant “t” (ms).

At low speeds, high inductance is not a problem. Current can easily flow into the motor windings fast enough that the stepper motor has rated torque. At high speeds, however, sufficient current cannot get into the winding fast enough before the current is switched to the next phase, thereby reducing motor torque. Increasing the driver voltage can fight this loss of torque at higher speeds by forcing current into the windings of the motor at an increased rate. In summary, the current and the number of coil turns in the windings determine a motor’s maximum torque output, while the voltage applied to the motor and the inductance of its windings will affect the speed at which a given amount of torque can be generated.

A high inductance motor will provide a greater amount of torque at low speeds and lower torque at higher speeds, thus you design your 'drive' system to keep the motor speeds low.

My 2 cents worth of info, hope this is of some value....Paul L.

[PaulRowntree]

Thanks Paul, I misunderstood. I thought your were connecting inductance to thermal properties of the motor, with 'not run long enough ...' referring to overheating etc

[awerby]

I don't know about that particular vendor, but the HiWin 15mm profile rails should work fine for you; much better than the equivalent round rails. Just figure out a way to shield them from the dust and chips.

[vakeiros]

I don't know about that particular vendor, but the HiWin 15mm profile rails should work fine for you; much better than the equivalent round rails. Just figure out a way to shield them from the dust and chips.

thanks for your input about this, yes the rails are Hiwin, I asked the seller if he could provide 20mm rails and the price goes up about $170 so my question now is, does it woth it?? it's a bit out of budget but if there's one thing i learnt with my chinese CNC machine is that I won't go cheap again on this matter. if the 15mm are enough that's great, if you say i should spend more 170usd and get the 20mm for this machine size than I won't be broke because of this :P

what about the structure am i going the right way if i build something like the photo?

best regards

[awerby]

If I were building this machine, I'd spend the extra money on giving it dual motors, screws and drivers for the X axis rather than on wider rails. The structure of the machine in the photos is okay, but it's not complete. The Z axis doesn't seem to be worked out yet, for one thing. The 80-20 extrusions are handy, but they're pretty expensive; you don't really need to build the whole thing out of aluminum unless you're planning to move it a lot. You can save money by building the base from steel - just provide some very flat plates to screw the rails to.

[vakeiros]

If I were building this machine, I'd spend the extra money on giving it dual motors, screws and drivers for the X axis rather than on wider rails. The structure of the machine in the photos is okay, but it's not complete. The Z axis doesn't seem to be worked out yet, for one thing. The 80-20 extrusions are handy, but they're pretty expensive; you don't really need to build the whole thing out of aluminum unless you're planning to move it a lot. You can save money by building the base from steel - just provide some very flat plates to screw the rails to.

that's a good idea too, I'll see about the 80-20 extrusions price (I've no idea abot that), And my father is a blacksmith (according to google translator :P, he makes steel gates, doors, etc... works a lot with steel)

I liked that Idea of dual motors on the X but I have one Doubt about the connections... So I'll get the Extra motor/driver/ballscrew and how do i connect them? I mean, do I connect both enable/direction/signal together?

I have to study this one :P

but glad to ear nice opinions.

regards

EDIT: well I guess i'll heve to slave an axis on Mach3 to have twin motion am I right?

[UA_Iron]

With a 5mm pitch you'll want to operate in a higher RPM range than what is typical of a lot of "high holding torque" cheap chinese stepper motors. Holding torque is a bad metric to size a motor, the motor should be sized to the dynamic application. If the holding torque is insufficient, then you can look at a brake or some other means to stop movement when it is static.

I am not sure this is correct, but I believe this is the same stepper motor you referenced:
http://www.wantmotor.com/WebEditor/U...2594119192.gif

torque falls off fast - now thats at 30V, it should do better at 48V.

Now if your machine was going to do 200in/min rapid cuts - this would put you at the 1000RPM range (1016 to be exact) with a 5mm ball screw.

check out these offerings at automation direct (I don't work for them, I swear).

http://www.automationdirect.com/stat...stepmotors.pdf

At 1000RPM, and 32V, the STP-MTRH-23079, STP-MTRH-34066 and STP-MTRH-34097 are all nearly equal at 100oz-in. The other motor isn't even rated that high.

At 100in/min we're at 508RPM and 32V:
STP-MTRH-23079 = ~162oz-in
STP-MTRH-34066 = ~210oz-in
STP-MTRH-34097 = ~250oz-in
57BYGH115-003 = ~57oz-in

50in/min, 254RPM 32V
STP-MTRH-23079 = ~178oz-in
STP-MTRH-34066 = ~280oz-in
STP-MTRH-34097 = ~400oz-in
57BYGH115-003 = ~177oz-in

It all depends on what RPM you need your torque. I gave you solutions that were a lot more expensive than what you were originally looking at. Sizing should be done off your use cases; what torque will you need at what RPM then size ~30-50% larger for margin.

I've said this in other threads, the increase in stack # of the motor increases the inductance, it's a physical phenomenon as you will end up with more metal mass causing that inductance. This equates to greater low RPM torque and a decrease in high RPM torque. I equate it to a diesel motor vs. a gasoline engine motor with similar horsepower ratings - one will have that torque and hp at a lower rpm, the other at a higher rpm. The power band is what we're interested in for usability.

This spiraled out of control quick, didn't it?



Your 15mm linear guides and screws should be adequate for what you want to do. With the linear guides you will want to mount it to a stout surface - their rigidity is largely dependent on the mounting surface.

[vakeiros]

With a 5mm pitch you'll want to operate in a higher RPM range than what is typical of a lot of "high holding torque" cheap chinese stepper motors. Holding torque is a bad metric to size a motor, the motor should be sized to the dynamic application. If the holding torque is insufficient, then you can look at a brake or some other means to stop movement when it is static.

I am not sure this is correct, but I believe this is the same stepper motor you referenced:
http://www.wantmotor.com/WebEditor/U...2594119192.gif

torque falls off fast - now thats at 30V, it should do better at 48V.

Now if your machine was going to do 200in/min rapid cuts - this would put you at the 1000RPM range (1016 to be exact) with a 5mm ball screw.

check out these offerings at automation direct (I don't work for them, I swear).

http://www.automationdirect.com/stat...stepmotors.pdf

At 1000RPM, and 32V, the STP-MTRH-23079, STP-MTRH-34066 and STP-MTRH-34097 are all nearly equal at 100oz-in. The other motor isn't even rated that high.

At 100in/min we're at 508RPM and 32V:
STP-MTRH-23079 = ~162oz-in
STP-MTRH-34066 = ~210oz-in
STP-MTRH-34097 = ~250oz-in
57BYGH115-003 = ~57oz-in

50in/min, 254RPM 32V
STP-MTRH-23079 = ~178oz-in
STP-MTRH-34066 = ~280oz-in
STP-MTRH-34097 = ~400oz-in
57BYGH115-003 = ~177oz-in

It all depends on what RPM you need your torque. I gave you solutions that were a lot more expensive than what you were originally looking at. Sizing should be done off your use cases; what torque will you need at what RPM then size ~30-50% larger for margin.

I've said this in other threads, the increase in stack # of the motor increases the inductance, it's a physical phenomenon as you will end up with more metal mass causing that inductance. This equates to greater low RPM torque and a decrease in high RPM torque. I equate it to a diesel motor vs. a gasoline engine motor with similar horsepower ratings - one will have that torque and hp at a lower rpm, the other at a higher rpm. The power band is what we're interested in for usability.

This spiraled out of control quick, didn't it?



Your 15mm linear guides and screws should be adequate for what you want to do. With the linear guides you will want to mount it to a stout surface - their rigidity is largely dependent on the mounting surface.

I completely understood you but WOW, i wasn't expecting that 200ipm that's about 5mpm... currently I had my small machine at 1.6mpm that's about 63ipm LOL

but now that you talk about that... I'm curious... my main problem is to get that kind of steppers from Europe, first it's the shipping cost, steppers are heavy... these chinese ones i can get them from Germany so no taxes here... and i have already 3 of them here at my little machine so i can at least try them and see if they work ok on this machine...

so other thing is decided.15mm rails is enough... now the question remains about the 1 or 2 motors on the X axis... this is a tought one, the incremental value is not much... my guess is about 60usd for the extra ballscrew+accessories, extra motor and driver arround 100usd... I would need an extra 48V PSU but I have one here so no expenses here.

honestly I don't think that i would need the 2nd moter but if you guys sugest it... you have far more experience here than me...

[vakeiros]

well I've been working out of town and this project was very forgoten but here I am again.

Have made some decisions, so if you have something to add or advices to improve I really want to ear it.

Motors: 4x Wantai 270Oz/in (1 on X, 1 on Z and 2 on Y, now I really only though on this now, awerby you said you would bet on dual motors on X axis, don't you mean the Y, meaning 2 motors moving the gantry back and forward? well I guess it's a matter of perspective... right? XD)
Drivers: 4x DQ542MA
PSU: 48V 350W (For Z and X) + 48V 480W (for Y and A [when use it])

Ballscrews on all axis (16mm dia, 5mm pitch, 1000mm & 650mm & 300mm YXZ)
HIWIN linear rails HGR 20mm (1000mm + 700mm + 30mm) + 12x HGH20CA blocks

Structure materials:
Base made of steel tube 80*40*3mm i think this will make a stiff and heavy base.
Gantry not decided yet but i'm thinking on 2 aluminum 12mm plates on the sides (reinforced with some U profile), one steel tube 80*40*3 on the bottom where the ballnuts are attached, and the X and Z axis base not planned yet.

I'm designing the whole thing on Solidworks, and I'll post images soon as I finish it.

one question, the ballscrew/linear rails set I'm buying include the 12 blocks for the HIWIN rails, 2 of them together measure 15.5cm length if I use them all on my Z Axis I'll have very little movement on the Z. the total length of the ballscrew is 300mm, the machining itself is 65mm so only remains 235mm, the HGH20CA block has 77.5mm each, if I use one it'll be 157.5mm of travell (not bad), if I use them both only will have 80mm... so the question is, will it be ok using just one HGH20CA on each rail? or even better question, should i get 15mm rails on the Z axis and use only one HGH15CA (these have 61.4mm length) so my Z travell would increase to 173.6mm... doing this it would be a bit cheaper using just 2 blocks on the Z and lighter rails...

waiting for your answers/comments

best regards

[pippin88]

I'd strongly recommend 10mm pitch screws at least.

Where are you looking at buying Hiwin rails? I've just received a shipment from BST Automation on aliexpress and can recommend them, I'm very happy with the transaction. They will do custom orders to exactly what you need.

15mm rails are vastly stronger than you'll ever need. If you want more travel on the Z just get longer rails.

I don't understand your maths. The ballscrew is 300mm, minus 65mm for the bearings etc. So 235mm travel. The rails are 300mm, minus 77.5mmx2 for the carriages leaves you with 145mm travel. So when you put the screw and rails together it is the rails that will limit you (to 145mm travel).

[vakeiros]

thanks pippin88,

the 1605 will be replaced by 1610. I'll stay on the 15mm rails then if it's enough that's good...

about the Z I'll ask if they have 400mm instead of 300mm. I'll buy the rails from FY Bearing Co.,Ltd they are good (worked with them already).

[vakeiros]

guys, need some input about the gantry side pilars and bridge... was thinking about some 150mm U profile for that.. what do you think? good idea? bad idea? overkill idea? weak idea? or dumb idea? XD

another question is about Z axis, it's 400mm long and I need to know if 15mm thickness aluminum plates are enough or will I need to go 20 or 25mm? I'll provide a picture soon.

thanks for everything... tomorrow I should have some screens from the project to show how it's going...

[vakeiros]

well guys, just finish (rough finish yet, a few things missing), well this is just how I picture my future machine, I'll add some 30x60mm 3mm thickness tubes bolted on the gantry sidepilars (don't know exactly eith right term for that) to reinforce the stiffness (I think 15mm aluminum plate it's too weak for the gantry).

anything else I think it's prety good (the spindle plate it's kind of oversized I think, I'll have to analise the Hertz spindle dimensions for future, because at first I'll run a chinese WC 2.2kh that I own already.

well what do you expert guys have to say?