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New to reprap

Posted by alex199020 
New to reprap
June 01, 2014 08:12AM

I am beginning a long term reprap project. Long term for a few reasons but mainly because I want to design my own (money is also something I lack of at the moment but that doesn't mean I can't start all the pre work which I think i'll have a lot of!). I've been doing a fair bit of reading but do have some questions that hopefully you'll be able to answer.

To start with i'll talk about vibration, its something that seems to pop up here and there and obviously costly to printing accuracy. What are the best ways to reduce this, i've seen people talk about the microstepping of the motors to increase smoothness but are there any 'mechanical' ways that can be incorparated into the frame itself. Clearly I can't go adding damping springs to the axis as this will introduce inaccuracy but I was thinking along the lines of mounting the whole thing on rubber/sprung feet to absorb some of the vibration?

Jumping to microstepping/half stepping etc, being new to electronics this will be the hardest part of the build for me i think. I understand that the smaller steps allow smoother movement by fiddling the pulse to be a sinewave (is that the essence of it?) but is the motor able to hold at every step between two full steps and how accurate is the position of the microstep?

Also, I am about to begin learning a programming language. I was going to do C as I have dabbled in this before at uni so thought it'd be a good place to start. I'm not 100% sure what language the popular firmwares for repraps are written in but would C be usefull in this project or should I consider another language that would be more useful to my reprap project.

In terms of actually printing, how easily do parts warp. I understand that a heated bed will help stop the lower layes cooling too quickly but what about the middle layers of a build which cool according the environmental temperature? Clearly an enclosure for the whole thing with a controlled ambiant temp. would be the best solution? And if so what sort of temps would the enclosure need to reach?

This is going to be a very long build so I'm not even considering the final product yet just storming ideas. My plan is to design my own frame and use standard reprap electronics to start before adjusting them to my tastes aswell!

Thanks in advance

Re: New to reprap
June 03, 2014 04:32PM
Vibrations can be mitigated in a few ways. One is damping as you mentioned. Rubber washer here and there wouldn't hurt. Also, there are some stepper mounts specifically to reduce vibrations.

Another way to reduce vibrations is to increase the rigidity of the machine. This doesn't always work because a lot is going on here. With more rigidity, the natural frequency will increase. The farther the natural frequency is from the driving frequency, the smaller the amplitude of the vibrations. (Note: it is possible to increase the rigidity and get worse results if your natural frequency and the driving frequency align.)

It is advisable to damp and increase rigidity. Vibrations will rip the machine apart if there isn't any damping no matter how rigid it is but in reality there are tons of places in a machine to turn vibrations into harmless heat.

1/16 or 1/32 is about the standard now days. It doesn't add much in the way of accuracy. From any position or microposition you will have a 1/2 step of wiggle room. Microstepping makes the machine a little quiter and marginally improves the prints. When you do your calculations use +/- 1/2 step for your error.

C will be great to help you write firmware. A scripting language like Python would also be handy. I use Python to post process gcode for Wally and GUS and even CoreXZ. Learning any language will help you learn others in the future.

Warping is a function of your bed material, print medium, size of print, surface preperation, room temp, bed temp, etc. You get the idea. I use PLA on a hairspray coated piece of heated glass. I never have any problems. ABS I am told has more issues.

Good luck!!!

Wally, GUS Simpson, LISA Simpson, THOR Simpson, Sextupteron, CoreXZ
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