Couple of questions about Dolly

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JonJahaerysSnow
Posts: 5
Joined: Wed Aug 16, 2017 6:46 am

Couple of questions about Dolly

Post by JonJahaerysSnow » Wed Aug 16, 2017 7:11 am

Hey guys, I'm John. I'm new to 3d printing, but I have a background in programming and a little electronics. I have a Tarantula (I know) and while I've enjoyed and learned tons from assembling it, I don't really feel it as mine. So I'm ready for the next step and I'm looking to build my own printer from scratch. I'm still trying to decide between a couple of printers, but I'll most likely end up building a Dolly. But before I embark in the adventure, I would like to ask a couple of questions if you guys don't mind.
  • In the part list for Dolly, it lists 1m of M5 threaded rod. However, unlike the other rods, this one doesn't say how long my cuts should be. Does anyone know?
  • I am biased towards chinese brass nuts (not linked because that would look like spam). If I print a different set of X ends, will I still be able to do the build? I REALLY don't want to drill on my printed pieces to fit a nut.
  • I'm really interested in a mk42 clone. Is the 9 point bed calibration process exclusive to genuine Prusas or is that something I can achieve on an everyday RAMPS setup?
  • While I'm planning to salvage some parts from the Tarantula (steppers, genuine e3dv6, mks board), my spreadsheet tells me that most of my budget will be spent on screws. Like having to get a 50 pack of screws when I only need 5. Aliexpress is generally cheap, but the screws are starting to add up to a little too much. Is there a cheaper way to source them?
  • More like a forum suggestion, but there should be a subforum dedicated to Dolly.
Thanks a lot everyone!
Last edited by JonJahaerysSnow on Fri Aug 18, 2017 4:31 am, edited 1 time in total.

slippyr4
Posts: 224
Joined: Thu Jun 15, 2017 10:24 am

Re: Couple of questions about Dolly

Post by slippyr4 » Thu Aug 17, 2017 9:05 am

Disclosure: I didn't build a dolly but a more faithful mk2s clone.

The dolly project was all about building a i3 ish printer for absolute rock bottom pricing. If you have a little bit more money you could get a much better printer.

To answer some (but 'not all) of your points:

Yes you can use prusa firmware with your MK42 clone - but for ramps you should use my port (see link in my signature). Personally I would recommend and MKS BASE or MKS GEN over ramps, it's all in one and a lot less hassle although Lin compatible with ramps. And you get an extra mosfet which you can use for the extruder cooling fan. And an axtra stepper driver you could use for Z2.

If you can afford it, get steppers with integrated leadscrews for the Z axis. They should be 320mm lead screw length. It'll be a better printer with them instead of metric threaded rod.

I made a modified set of x ends that work properly with the Chinese lead screw nuts, but my ones don't have the mods that tom did for the endstop boards. However, I don't really understand why he went with those boards: the genuine prusa uses plain micro switches, and they are dirt cheap too. So if you buy micro switches you could use my x ends.

Screws are expensive. If you're lucky a local hardware store might have them, or maybe eBay will be more cost effective.
Self-built Prusa i3 MK2 clone
My things: https://www.thingiverse.com/slippyr4/designs
My Prusa firmware port for ramps & MKS : https://github.com/slippyr4/Prusa-Firmware

chumm
Posts: 176
Joined: Thu Jun 15, 2017 11:24 am

Re: Couple of questions about Dolly

Post by chumm » Thu Aug 17, 2017 10:37 pm

Hi John,

If you're in the US, I found Mr. Metric to be the perfect supplier for a bunch of weird quantities of screws. They have a flat shipping rate of $7.50 or free shipping if you order more than $50, and each item can be ordered to any quantity you like. I did find that the bill of materials on Tom's site was way incorrect for screws, but I ordered them before he started assembling his, he may have updated it since then. In particular there were too many large screws and not enough M3s, maybe just get 10 more of each M3 to be safe, they are always handy for small printed stuff anyway.

Agreed that you should definitely get 8mm leadscrews, I built my Dolly with M5 threaded rods for the Z axis and it was horrible. I drilled my parts when I made the upgrade and it was terrible lol, so I'd definitely recommend finding the X parts with the proper nut setup.

JonJahaerysSnow
Posts: 5
Joined: Wed Aug 16, 2017 6:46 am

Re: Couple of questions about Dolly

Post by JonJahaerysSnow » Tue Aug 22, 2017 7:14 am

Hey guys,

I'm sorry for the very late reply. I am between jobs working retail and my schedule is all over the place. Thank you very much for your answers.
slippyr4 wrote:
Thu Aug 17, 2017 9:05 am
I didn't build a dolly but a more faithful mk2s clone
Do you have a link/bom to that build or was it something you prefer to keep private? Would love to check it out and compare.

I also decided against the mk42 clone for the moment because I'd like to experiment with Marlin in its most vanilla version and I'd like to be able to update quickly. I also want to keep the cost low, but I will definitely check your port in an eventual additional build because it looks awesome.

Speaking of the heatbed, I have an extra 300x200 bed laying around still in its original packaging. Could I use that one for my build? I notice most builds use a smaller 200x200 bed. Would I need to change the size of the XY stage screws if I still go with the bigger one?
chumm wrote:
Thu Aug 17, 2017 10:37 pm
I found Mr. Metric to be the perfect supplier for a bunch of weird quantities of screws.
That looks like an invaluable source, I just bookmarked it and will be the first thing I'll use when I start ordering my parts.

Regarding the steppers, I already have the ones from the Tarantula and those are the ones I'm planning to use to keep it cheap. If this build goes well, I'll build another version with better parts. Will still use lead screws+couplers on this build though.

Thanks a lot guys and again excuse the late reply.

slippyr4
Posts: 224
Joined: Thu Jun 15, 2017 10:24 am

Re: Couple of questions about Dolly

Post by slippyr4 » Tue Aug 22, 2017 11:16 am

JonJahaerysSnow wrote:
Tue Aug 22, 2017 7:14 am
Do you have a link/bom to that build or was it something you prefer to keep private? Would love to check it out and compare.
See https://www.dropbox.com/s/ii80dalrywpodvv/bom.xlsx?dl=0

But don't trust it 100% - the screw quantities aren't really right. They came partly from tom's dolly bom and partly from work by peter ellens.

TBH it's not that hard to build a pretty faithful clone. I bought the frame in, and smooth rods. Then all the other bits & printing and there you are.

My openscad for the electronics case is in customiser on thingiverse so if you use a board like MKS BASE or MKS GEN then you can print yourself a tweaked case that will fit the printer.

I've also got an openscad for a parametric PSU cover I worked on which will allow pretty much any PSU to fit the frame.

There's some pictures of mine in the show us your printers thread in general.
Self-built Prusa i3 MK2 clone
My things: https://www.thingiverse.com/slippyr4/designs
My Prusa firmware port for ramps & MKS : https://github.com/slippyr4/Prusa-Firmware

Jim JKla
Posts: 21
Joined: Mon Jun 26, 2017 12:01 pm

Re: Couple of questions about Dolly

Post by Jim JKla » Thu Sep 07, 2017 12:12 pm

Just a heads up for anyone in the UK there's an ebay supplier Bolt Base thats in Scotland and does vairious sizes and quantities and free delivery.

I have no connection with them but its just a supplier I found when thrashing around trying to find a supplier for hardware. N.B. they don't do the screwed rods.

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