Im new, am a 3D designer. Need a New cnc machine and need advice and guidance

Hello again, Right After going thourgh more of the build logs..Updated teh design of my gantry...people using 10mm 2D cut steel and wled it all together, Im using 6mm and have just reinforced it allot... Simply for cost. When it comes to driving the belts, I have done the drive system using the belts and Pulleys Jazz reccomended(your real name?) I did the basic calculation to get the mtor shaft to pulley distane and added a couple holes where i can add tensionsers if the tensions isnt quite right..

When it comes to the X axis, Its currently using two motors...but reading around Im seeing a fair few people having issues with losing steps (similar to z axis on 3D printers) how much of an issue is this? If so Ill redesign for a big belt using one Nema 34 motor driving both ballscrews (cant find it but saw a diagram you posted Jazz...)

Help? :victorious:

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Originally Posted by FlyHighRC

When it comes to the X axis, Its currently using two motors...but reading around Im seeing a fair few people having issues with losing steps (similar to z axis on 3D printers) how much of an issue is this? If so Ill redesign for a big belt using one Nema 34 motor driving both ballscrews (cant find it but saw a diagram you posted Jazz...)

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Ok well don't worry about losing steps. Those who are losing steps have usually either overtuned the motors or have mechanical issues. If you use decent electronics and don't be greedy regards tuning then you won't have any issues. Regards electronics then get out your head any relationship to 3D printers and absolutley don't look to buy electrics intended for 3D printers they are far removed from each other.

Single motor and belts do give peace of mind about not racking and do allow faster feeds has they can be run closer to the motors limits with worrying about stalling. But like you will have seen me say before if you've read other posts if twin motors are setup correctly and run comfortably within the motors torque capabiltys then you don't have any problems for majority of work. If running very long 3D work(15hrs+) then I prefer twin belts as you know one motor can't run out of sync with other.!

Keep reading and you'll find my Name. .:thumsup:

Awesome, Ill stay away from 3D printer electronics then :)

'If running very long 3D work(15hrs+) then I prefer twin belts as you know one motor can't run out of sync with other' By this do you mean the single motor system?

Here is the machine so far, The gantry side are completely different though the Y axis section is similar with some ugly looking supports, Might do what another member said about one 40x80mm piece running the length... Also still need to add laser cut steel peices for mounting the ballscrew supports at either end of the X axis...Pay no attention to the other side of the machine...I mate everything on one side then mirror and remate on the other...saves inserting the same parts over..

Attachment 12550

If this is approved Ill Take this over as a build Log :)

How are you getting the steel the rails are sitting on flat? If you're going the epoxy route you might want to give consideration ax to how you're going to get the joining bridge between the rails?

Sent from my Galaxy S5

If you go with 2 motors on one axis, remember there are 2 kinds of stepper drivers. When you power up some will remember the last coil pattern used and some won't.

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Originally Posted by Robin Hewitt

If you go with 2 motors on one axis, remember there are 2 kinds of stepper drivers. When you power up some will remember the last coil pattern used and some won't.

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Would you mind expanding on that, as I don't understand. ..Clive

A stepper motor has two sets of coils, say A and B. If you home the twin-motor setup, it might be that the home positions correspond to A on one and B on the other energised. Switch off, switch on again, and some drivers (I suspect all analogue drivers) will energise A rather then remembering the last coil used, so the gantry will be slightly off-square. I'm assuming that a rehome operation will reset this, but the moral is that you can't rely on the system remembering exactly where it was when it was switched off. Slightly more complicated if you are using micro-stepping but the principle is the same. Small effect if you do it once, but the error could accumulate over a number of on/off cycles unless you rehome at the start of each session.

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Originally Posted by Neale

A stepper motor has two sets of coils, say A and B. If you home the twin-motor setup, it might be that the home positions correspond to A on one and B on the other energised. Switch off, switch on again, and some drivers (I suspect all analogue drivers) will energise A rather then remembering the last coil used, so the gantry will be slightly off-square. I'm assuming that a rehome operation will reset this, but the moral is that you can't rely on the system remembering exactly where it was when it was switched off. Slightly more complicated if you are using micro-stepping but the principle is the same. Small effect if you do it once, but the error could accumulate over a number of on/off cycles unless you rehome at the start of each session.

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Thanks for that Neal I would assume that most people would home each time they fired the system up and if they did not have home switches they would zero on the part. So generally would not be an issue. ..Clive

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Originally Posted by Robin Hewitt

If you go with 2 motors on one axis, remember there are 2 kinds of stepper drivers. When you power up some will remember the last coil pattern used and some won't.

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Doesn't make a Jot of difference if using Home switches which you really should use with Twin motors.
It's good practice to home the machine when first switched on and Most industrial machine won't let the machine function untill the machine as been homed. This ensures your setup and square so any step jumps on startup doesn't come into play.
It's also best to home the machine between every job if not shutting down just to remove any errors that may have crept in over period of the last job. This is why I prefer single motor/belts on machines that will be running single jobs for 12hrs +.

Thats the only issue with the design, I noticed exactly what your talking about...Well alteast i think haha, The gantry... when adding all the components to the gantry ill have to do so in a certain order...and if say the whole gantry is assembled and i need to removed the ballscrew but then id have o dismantle the whole thing... the only issue i can see.

I will be having the machine welded up then going ahead with the expxy method..

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Originally Posted by JAZZCNC

Doesn't make a Jot of difference

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I can tell you have never had to write the manual :toot:

Problem with writing the manual is you have to cover all the bases, because you know some geek is going to figure out the problem and ask you why it isn't a problem. You have to try and out geek the geeks by spotting all the snags before they do. Patting a geek on the head and saying, "Don't worry about it sonny" does not work. They can smell fear.

Let's suppose your driver(s) are the forgetful step pattern kind. They always fire up on the same pattern, a pattern that will repeat every 1.8 degrees.

Now suppose you parked the machine 0.9 degrees out of phase to that so when you power up it can leap either way.

Suppose one leaps CW and the other CCW, both equally valid. The gantry is now out of square. You can bump every home switch in Christendom but the most you can do is detect the error, you can't fix it unless you can drive the motors independently.

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Originally Posted by Robin Hewitt

Suppose one leaps CW and the other CCW, both equally valid. The gantry is now out of square. You can bump every home switch in Christendom but the most you can do is detect the error, you can't fix it unless you can drive the motors independently.

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Yes agreed but you obviously have no experience of how twin axis slaving works with home switches. They do move the motors independant so I'll say it again "It doesn't make a Jot of difference if you use home switches" Your argument only works if you don't use home switches and when slaving motors you should always use home switches.
Now to clear the Geek fear manual you have, which is unfair to geeks really, i'd call them fucking idiots my self then I'll clarify by saying "Separate home switches on Slaved axis motors"

Can someone clarify what a "twin axis" is please, I've tried to find information on it but everything I found relates to minerals or more specifically crystals.

I even tried "twin axis slaving" but I already new about setting up slaved motors in Mach 3, so those results didn't really help, the correlation please.

.Me

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Originally Posted by Lee Roberts

Can someone clarify what a "twin axis" is please, I've tried to find information on it but everything I found relates to minerals or more specifically crystals.

I even tried "twin axis slaving" but I already new about setting up slaved motors in Mach 3, so those results didn't really help, the correlation please.

.Me

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Lee if you don't know by now then you need to hang up your boots mate. . :loyal:

Suppose Twin Axis is wrong really.? Should be "Single Axis Twin motors slaved together" . . . . . Try that it will probably come up with Match.COM.!!