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Optimum parallel arm width

Posted by etfrench

etfrench

Optimum parallel arm width
December 30, 2014 09:58PM

Registered: 9 years ago
Posts: 483

Other than ensuring the hot end and fans, etc. fit between all of the arms, what criteria should be used to determine the width of the parallel arms? Is there an optimum distance based on the print bed size?

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hercek

Re: Optimum parallel arm width
December 31, 2014 04:16AM

Registered: 10 years ago
Posts: 732

The more far away the two parallel diagonal rods are from each other the better. It has no relation to the bed size but it is limited by the platform size. (Platform is the plastic part which holds hotend.)

The bigger distance makes both:

small errors in diagonal rod length less important,
and force load on diagonal rods smaller.

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dc42

Re: Optimum parallel arm width
December 31, 2014 04:29AM

Registered: 10 years ago
Posts: 14,672

On the other hand, increasing the size of the effector (platform) reduces the print radius. So the effector size is a compromise between getting a good print area and getting the parallel rods far apart.

Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

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etfrench

Re: Optimum parallel arm width
December 31, 2014 08:50PM

Registered: 9 years ago
Posts: 483

Interestingly enough, in my current design, increasing the width 10mm only increases the DELTA_RADIUS about 3mm. That seems like it would be a worthwhile tradeoff.

Thanks for the replies.

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dc42

Re: Optimum parallel arm width
January 01, 2015 03:38AM

Registered: 10 years ago
Posts: 14,672

Quote
etfrench
Interestingly enough, in my current design, increasing the width 10mm only increases the DELTA_RADIUS about 3mm.

Increasing the radius of the effector by some amount should reduce the delta radius and the print radius by the same amount, if the towers are kept in the same position. By "radius of the effector" I mean the distance between the mid point of the joints connecting a pair of parallel rods and the centre of the effector.

Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].