1 Topic by Downeasta

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Topic: Chain drive?

I am curious about using #25 chain as opposed to using the rubber belts?  My theory is that we are trying to take out the free movement of the printers so that we get a precision print.  I am under the impression that if metal chain were used it would eliminate the flex from the rubber and also eliminate the stretchy factor.

#25 chain means that the links are 1/4" between links. Or 6.35 mm for you metric readers.
http://i21.geccdn.net/site/images/n-picgroup/BRM_25-1R10FT.jpg


What are your thoughts?

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2 Reply by Downeasta

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Re: Chain drive?

Mind you the links are not what sets the traverse.  As it is still the stepper motor.

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3 Reply by adrian (edited by adrian 2013-06-19 14:57:55)

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Re: Chain drive?

Because you'll have backlash issues - its horrendous
Backlash will also change based on wear and stuff like gravity deflection of the chain....
It weighs more, so will have acceleration and inertia (deceleration) issues.

Chains are good for torque applications - not rapids with precision.
The happy medium would actually be Synchromesh drive...
http://sdp-si.com/web/html/newprdbelts6.htm
http://www.minibearings.com.au/catalogu … romesh.pdf

There is a reason only very early Reprap Darwins even entertained chain drive.... wink

4 Reply by Downeasta

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Re: Chain drive?

Well thankyou for saving me money on something that has been realized can lead to bad results.

So if chain is a bad idea.  Why arent we using screw drives?  Since the z axis has it.

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5 Reply by ronsii (edited by ronsii 2013-06-19 15:13:30)

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Re: Chain drive?

Downeasta wrote:

Well thankyou for saving me money on something that has been realized can lead to bad results.

So if chain is a bad idea.  Why arent we using screw drives?  Since the z axis has it.

the z screw drive only has force applied to it in one direction(downward) so backlash isn't as apparent but if you used a same drive in x or y the results would be immediately noticeable [EEK] now if you used a ballscrew instead it would be a lot better but then again it costs a lot more wink

6 Reply by iowajames

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Re: Chain drive?

Downeasta wrote:

Well thankyou for saving me money on something that has been realized can lead to bad results.

So if chain is a bad idea.  Why arent we using screw drives?  Since the z axis has it.

The screw cannot produce fast rapid movement either.

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7 Reply by IanJohnson

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Re: Chain drive?

An alternative to belts is fishing line which has worked well. The Tantillus uses it- www.tantillus.org.

8 Reply by elmoret

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Re: Chain drive?

iowajames wrote:
Downeasta wrote:

Well thankyou for saving me money on something that has been realized can lead to bad results.

So if chain is a bad idea.  Why arent we using screw drives?  Since the z axis has it.

The screw cannot produce fast rapid movement either.

QU-BD would like to have a word:

http://www.youtube.com/watch?v=CDqWurM9hPs

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9 Reply by Staffordknot (edited by Staffordknot 2013-06-19 17:06:26)

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Re: Chain drive?

Thats one mama of a stepper motor!

Lead screws are the way forward, i'm talking to a local engineering company at the moment but by all account a high precision lead screw as used in cnc machines are not a cheap option. Threaded rod is cheap however but crap

10 Reply by downeym

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Re: Chain drive?

elmoret wrote:
iowajames wrote:
Downeasta wrote:

Well thankyou for saving me money on something that has been realized can lead to bad results.

So if chain is a bad idea.  Why arent we using screw drives?  Since the z axis has it.

The screw cannot produce fast rapid movement either.

QU-BD would like to have a word:

http://www.youtube.com/watch?v=CDqWurM9hPs

wow...That is awesome, but it uses 7 leadscrews! the leadscrews alone cost mode than a brand new solidoodle 3.

but I still want one! smile

11 Reply by Downeasta

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Re: Chain drive?

The ball screws has some possibilities for me.  The company I deal with for most of my purchases does carry them

http://www.mcmaster.com/#ball-screws/=n9hspf

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12 Reply by adrian (edited by adrian 2013-06-20 06:34:02)

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Re: Chain drive?

Downeasta wrote:

The ball screws has some possibilities for me.  The company I deal with for most of my purchases does carry them

http://www.mcmaster.com/#ball-screws/=n9hspf

I'm not continuing the imperial vs SI units discussion.. but I will point out... its a fairly well known issue with using imperial threaded rods and stepping values (basically, it doesn't divide properly).  Despite your personal preference to deal in Imperial - theres a reason that the screws and rods used on *most* printers are Metric... and its often been observed this is one of the 'issues' with the stock Solidoodles use of 5/16" rod and why it suffers banding and backlash so badly. And despite you insisting otherwise, a Micron is just as accurate as a Mil, Arguably greater, as it can deal with far less decimal places for the same precision  wink

Google it by all means - but you are best advised to avoid any thinking of using imperial drive components if you don't want to spend months chasing banding issues and other associated problems.

So make sure you scroll down that page to the "Metric" section big_smile

And as an added bonus, you'll get to speak to people using internationally accepted SI units big_smile big_smile

13 Reply by lawsy

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Re: Chain drive?

THat linked video printer is impressive but it uses ball screws, not threaded rod or lead screws.

Fast and accurate with lash but very expensive.

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14 Reply by adrian

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Re: Chain drive?

lawsy wrote:

THat linked video printer is impressive but it uses ball screws, not threaded rod or lead screws.

Fast and accurate with lash but very expensive.

And still retains belts - the motors drive the screws using 2 loop-belts... just like on our Y-Axis.... Besides the design elements of their motor placement, I'm surprised they didn't just go direct-drive...

15 Reply by tealvince

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Re: Chain drive?

adrian wrote:

I'm not continuing the imperial vs SI units discussion.. but I will point out... its a fairly well known issue with using imperial threaded rods and stepping values (basically, it doesn't divide properly).

That's not consistent with what I've experienced. 

There's nothing inherently metric or imperial about the motion of the stepper motor or Z axis; the only thing that *is* metric is our choice to typically print in .1 or .3 mm layer heights, which is just a convention.  Thus, if one simply printed using imperial layer heights (say, .141mm = 1/180"), the banding *should* go away entirely if it were due to stepping roundoff.  Unfortunately, that never worked at all for me, which tells me that microstepping was not the major cause of my banding.  The only thing that worked was to go to *finer* thread pitch.