K8200 x,y axis drive

K8200 3D Printer K8200 - Your printer, creations, and ideas for imp
1

Thanks for a tremendous product.

I would like to replace the xy belts with (2)Z axis modification kit K8204.
Hardware looks easy. Can you help me with firmware.
Primary benefit would resolution per step.

Thank you
Michael Pell

2

Did you take into account that the Speed will be almost unusable with a leadscrew of that low lead?

3

I was going to leave the math for later, it just seemed like it would work.
I suppose though, it’s prudent to run some numbers.

2000 steps per sec. = 600 rpm (or won"t these motors run that fast?)
K8204 pitch looks like about 2.5mm (approx .1").
600 RPM / .1" = 60 ipm.

I’m still building, but when I look at k8200fannozzle.gcode
and see [ G1 X123.240 Y123.640 F1530.000 E5.10947 ]
I’m assuming that means 1530 mm per minute or about 60 ipm.

Further, a gilmer belt from motor to lead screw,
instead of direct drive, as in ‘Z’, can
allow something other than 1:1. (Which would increase feed)
And provide side benefit of more motor/chassis packaging arrangements.
I’ve seen pulley arrangement on many CNC’s because a large motor
wouldn’t fit between the ways.

I realize with electric motors driver circuitry is key.
Am I wrong expecting 2000 steps per sec.?
Or do you see some other error in my calcs.?

Thanks

Mike:)

4

One of the errors I found: The pitch of K8204 is AFAIK 1.5 mm and not 2.5 mm, as this is Tr8 and Tr8 has a standard Pitch of 1.5 mm.
You will need X/Y Tr only for CNC Milling of Metal. There is a reason, why CNC milling machines have trapezoid spindles, and not 3D printes.

5

I was only guessing because I couldn’t find spec.
Where did you find it? Do you have a link to it?

That would change feed rate from 60 ipm to 36 ipm at 600 rpm with 1:1 pulley ratio.

Is 36 ipm to slow? And is 600 rpm achievable.
If steppers can’t do that, or if 36ipm is to slow, I can always run some overdrive ratio in the pulleys.

What about firmware?

Thanks,
Mike:)

6

Do you want to run the steppers in full step mode?

The motors have 200 Steps/turn.
The drivers are set to 32/th microstepping as default.
So that will give you 6400 steps/turn.

With a lead of 1.5mm/turn that will give you 108373.3333333333 steps/inch.
Assuming 10000 steps/s that will give you about 5.5 inch/minute.
Not very reasonable, i think.

I woulf change the belt drives to GT2 2mmPitch belts with 16 tooth pulleys.
That gives you about 100 steps/mm. And reasonable fast speeds.
The printer won’t even be able to be as accurate as 1/100th mm for mechanical reasons at all.
So precise enough?

7

I didn’t know print feed was so fast.
Experimentation is required.

Thanks,
Mike

8

As i said, i would better stick with a belt drive.

9

I changed all my belts out with GT2 16, and it made a HUGE difference in quality of print. This is in conjunction with the z leadscrew from velleman, and a GT2 extruder pulley (printed the receiving gear).

Night and day, with very good results at reasonable speeds. GT2 is the way to go in X, Y, and E axis.

Here’s the link to the pulley: thingiverse.com/thing:339928

10

One of the nicest filament based printers I’ve seen uses high lead screws for the motions.

In conjunction with a rigid structure, there’s very little ‘ringing’ at the corners as a result.

The machine is the 3DP; 3dpunlimited.com/

If I get the chance to build a printer, I’ll be going with high lead screws.

11

Sure, high lead screws are more precise than belt drives.
But they also need better drives. Stepper motors below NEMA 24 won’t drive them successfully.
And for the needed Speed you would probably have to go for SERVO Motors.
Those are quite expensive. Also you would need a 32 bit controller to keep up with the Servo motors.
A cheap 8 bit AVR won’t do for such applications.

BTW. The z axis of the printer you posted seems not very rigid.
It is made up out of 2 small footprint aluminum extrusions.
If it goes to higher prints it will be unevitable that the whole assembly goes “rattle and shake”.
At least for reasonable speeds, i fear.

12

[quote=“MichaelPell”]I was only guessing because I couldn’t find spec.
Where did you find it? Do you have a link to it?

That would change feed rate from 60 ipm to 36 ipm at 600 rpm with 1:1 pulley ratio.

Is 36 ipm to slow? And is 600 rpm achievable.
If steppers can’t do that, or if 36ipm is to slow, I can always run some overdrive ratio in the pulleys.

What about firmware?

Thanks,
Mike:)[/quote]
de.wikipedia.org/wiki/Trapezgewinde
But its german.
I learned this in the school, and there are special versions like that used in CD ROM drives to transport the head. The problem is as mentioned before: The faster you move, the more power you loss.