How fast should a RepStrap run?

I am about to print my first parts this weekend and have a question about the speed of my RepStrap. I have been building a CNC router for a while now and since it is just about complete I decided to mount the extruder head onto it to print parts to build a RepRap. However, I am curious if it will be able to move quick enough to print parts effectively.

I am using a 200 step / revolution motor, with a half stepping controller. The motor is connected to a 1/2"-10 acme screw. (Ten turns per inch screw). So it takes 4000 steps per inch of travel. I have tested my machine and it runs fine at 10 inches per minute. I might be able to bump that up a little, but I lose torque at higher frequencies and at some point it become to high a frequency for the motor and controller.

Is 10 inches / min of travel fast enough to print parts?

Thanks in advance,
Nightwork

That is about 4mm/s, which will work, but not very quickly.

I get 16mm/s extrusion with 40mm/s moves and some Darwin parts take about 4 hours each and 100 hours in total.

---

[www.hydraraptor.blogspot.com]

nophead,

Thanks for the response. It is nice to have an idea of what speed I should shoot for. I am still trying to figure out a way to up my speed. Does anyone know what the maximum frequency the average 200 step / revolution stepper motor can handle. I am not sure where the bottle neck is at.

Nightwork

... my 1.8°-steppers with 2Amps (@60V-f/h, @30V-microstepping) can drive safe until 2kHz with fullstep, 5kHz with halfstep and until 10kHz with microstepping (max. steprate of my controller/drivers ).

So with direct driving and a 5mm/rev-spindle i have 50mm/s @full-, 62.5mm/s @half- and the same speed at 1/4- and every slower (but more accurate) at higher microstepping-ratio ...

Viktor

Edited 1 time(s). Last edit at 09/15/2009 06:16AM by VDX.

Viktor,

Thanks for your numbers. I guess I am running my motors at about the correct values. I should have choose a acme screw with less turns per inch. I thought the motor would be able to run at much higher RPM then it can. It shouldn't be too hard to upgrade to a different screw. But for now I will try running my machine at the slow speeds. If I can print enough parts to make my first RepRap it will be worth it.

Nightwork

Viktor (et al)

Interesting speed numbers. What drivers are you using that can handle 60 volts for full/half step? That's considerably (5x) higher than the 12 volt rail used by the stock reprap stepper boards (both current and prev generations) and a bit higher than the H-bridge chips I've used to date.
I'm looking for a different power supply so I can try running my steppers faster.

-- Larry

---

Larry Pfeffer,

My blog about building repstrap Cerberus:
[repstrap-cerberus.blogspot.com]

Hi Larry,

... its an Isel C-142 controller which is capable of 6A@70V and 10 kHz maximum steprate.

Additionally i have three IMS-1/256-microstepping-drivers with 3A@30V, and max. 10 kHz too, which i can exchange with the Isel drivers for higher accuracy.

In my 'scrapery' there are some IMT901-drivers and a SMC11 from nanotec - all 2A@30V and 1/8 microstepping with more than 10 kHz.

My controllers are the Isel-interfacecard with its own software and CAD/CAM, an Arduino mega and some AtMega168-boards i'm combining for lasercutting, milling and dispenser-fabbing with the CNC-mill and different toolheads ...

Viktor