Saturday, May 12, 2012

Frame Assembly

Before the 1.5 version of the Mendelmax came out, I was not intending on really going into any depth on the frame assembly as Techpaladin had done a stirling job of documenting the process. However, as Kludgineer has changed so many things in the 1.5 design, I'll attempt to document the build process. I suspect that someone else is out there, with more time and inclination, doing the same thing except better. Oh well.

Anyway, first things first. Before building the frame you need to have some bits from which to build it. These bits should include:

  • Misumi (or similar) Aluminium extrusions, cut to length.
  • Mendelmax 1.5 printed parts
  • 8mm and/or 10mm smooth rod, cut to lengths as follows: Z axis - 2 x 350mm, Y axis - 2x 450mm, X axis - 2 x 445mm. I strongly recommend you check these for your flavour of Mendelmax as they can differ dependent on the build.
  • A lot (maybe 120) of M5 10mm machine screws, similar numbers of M5 half nuts/pressed nuts (or the Misumi T-slot nuts if you're made of money), M5 washers, and then 4 x  40mm  M5 machine screws. NB. Some of the printed parts for the 1.5 will only accomodate for screws with a small head diameter such as hex-socket screws, so if you use M5 machine screws like me, you will also need 20-odd of these smaller headed screws (like this).
You should find, amongst the files on the Mendelmax 1.5 Thingiverse page, a PDF that, if opened with the latest version of Acrobat, will provide a 3d model of the 1.5 Mendelmax that you can rotate, zoom into etc. This is extremely useful in getting an understanding of what goes where. In saying that, what it lacks is labels, in particular labels indicating which piece of Aluminium Extrusion goes where - OK, this is a lie, if you expand the Model-Tree in the PDF every thing is nicely labelled but it's still not an easy thing to refer to when you're holding screwdrivers etc. So, for my own benefit I produced this:

The Mendelmax frame components are symmetrical front to back so I've only labelled the front facing ones on the diagram.
So, first of all, a few holes need drilling and some holes may need to be tapped.  The top horizontal 420mm pieces (A) each need 6mm holes drilled through them in order to attach the 340mm pieces (B), hole centres are 70mm in from each end. I recommend you print the 70mm jig that is on the 1.5 Thingiverse page as it makes it pretty hard to screw up the hole placement, if you can't work out how to use the jig you may want to try an easier project. If you don't have a drill-press and instead use a handheld drill, it may be worth drilling from either side of the extrusion so the holes meet in the middle to ensure you have alignment as close to square as possible. Next, you need to tap M5 holes in both ends of all 4 of the 300mm extrusions (C) and either one end or both ends of the 340mm extrusions  (B), if you tap both ends of the 340mm pieces, you won't need to use a self tapping screw to secure a printed part later on. Tapping holes is one of those things that you can easily screw up (hah!) if you've not done it before so I recommend practicing on some of the parts that don't need tapping, the bottom set of 420mm extrusions (D) would do nicely. The YouTube also has some good videos showing how to tap a hole.
Right, once holes are drilled and taps are tapped, assembly may commence.
I started with the base of the frame, consisting of 4 x 300mm extrusions (C) and 4 x 420mm extrusions (D). It's all pretty simple from this point onwards, it won't take you long to work out how to get your chosen M5 nut into alignment in the slots on the extrusion to accept a machine screw and after that it's all gravy (for a while).

Rather than exhaustively going through the build step by step, here are some pretty pictures instead:

Only thing to note about putting the front and back together is that if you use the same Y-mounts as I did then you're best to install them first, then put the L shaped printed corner pieces on.

Here's the completed base with one of the upper pieces placed on top, the 420mm extrusions (A) are attached via 40mm M5 screws through the 6mm holes drilled in the cross member and then into tapped holes in the ends of the 340mm pieces (B).

Once the two diagonal sections are assembled, they need to have the 'lower vertex upper ' printed parts attached to the ends of the 340mm extrusions (B) using either self tappers or M5 screws dependent on your prefs (I used M5). You should do this before joining the front and back diagonal assemblies together. Again it's all pretty simple from this point onwards and you'll soon end up with something looking like this:

Oh yes, very pleasing.

Ok, I know I have skipped describing several crucial steps here; Like installing the smooth rods, building the X ends and the extruder but I will cover those bits in a future post, probably.
I think this will do for the moment.

Saturday, April 21, 2012

Blog GO!

So, I'd pretty much decided not to record my progress in putting together a Mendelmax variant of the RepRap family of 3d printers, but then Kludgineer released an improved set of parts for Mendelmax (V1.5). He's made raft of improvements on the version 1 Mendelmax and after doing some googling it became apparent that no-one (that I can find) has documented a 1.5 build yet, so, here is my (likely feeble) attempt.
I don't have the time and inclination to start from first principles with respect to build process, prerequisites etc, there's plenty of information out there for those who might be inclined to find it. However, in saying that, if you have stumbled across this in an effort to find some starting point on a journey to building your own printer, I'll do my best to put down what I have learned so far.
Anyway, a couple of months ago, I had a passing understanding of 3d printers and was under the impression that they were awesome but also prohibitively expensive for the married man with small child. Then randomly, I came across the RepRap family and suddenly realized I could build my own printer. I came very close to starting construction on a Prusa Mendel but at the last moment, discovered the Mendelmax, which to my eye, provided the maximum rigidity and ease of assembly. I'm sure this is probably not everyone's opinion but, it seemed that folks with Prusas would 'upgrade' to Mendelmax. So, with that decision made, I started looking at where to source the various 'Vitamins' required to build a Mendelmax.

Living in new Zealand, as I do, it became apparent that the vast majority of the components that I wanted to purchase were not readily available in NZ. If you live in Europe or the States, It should be pretty easy to source all the bits you need. There's a bill of materials available  that details the majority of the components here. Depending on your choice of components, there can be some extra bit's you'll require. I will, at some stage list the places that you can source parts from in NZ.

There are some choices to make when you start speccing up a machine so, in my case, here is what I went for (after a lot of research):

Basic Mechanics
  • Mendelmax spec extruded aluminium from Misumi
  • GT2 belts and pulleys for y and X axis - these are apparently the ones to go for if you want optimum accuracy as exhibit extremely low 'backlash', won't go into the specifics of it here but an explanation of what backlash is and why you don't want it is here.
  • Acme Lead Screws and nuts for the Z axis - this is a better alternative than just using threaded rod and nut's as threaded rod is not designed to be used in moving parts, has lower tolerances, is made of mild steel/stainless etc etc.
  • Self lubricating brass bearings - can't remember why I decided on these over all the other choices out there but there was a reason, it may even have been a good one.
  • 8mm smooth stainless steel rod for x,y,z - In hindsight, I might have gone for 10mm for the Z axis because that's what Kludgineer recommends for the 1.5 but there is mixed anecdotal evidence that it makes a huge difference - I've printed Z parts that accomodate for 10mm and then some 10-8mm reducers where required so I can always upgrade later. This is just high grade stainless rod - not 'Drill Rod' as some recommend, so we'll have to see how it performs with the brass bushings.
  • Some other things TBC when i remember them.
  • 608 skate bearings, screws, nuts, more screws, washers etc etc.
Printed parts.
  • Vanilla Mendelmax 1.5 components as found here. I've used the X ends found in the .zip file for the parts because they looked pretty more than anything, mistake in hindsite as it turns out they're designed for  specific type of leadscrew nut that I didn't purchase :(. Not great show stopper as I'll just fabricate some sort of temporary adaptor and then print a permanent one once the machine is working.
  • X carriage for the 8mm brass bushings found here
  • Y rod ends to allow me to move the y rod spacing in the future without printing new ones, found here.
  • Y carriage saddle brackets for the 8mm brass bushings found here. I'll produce a proper y-carriage at some stage but these will suffice in the mean time.
  • Greg's Wade Reloaded Extruder - Found here.
  • Nima 17 stepper motors.
  • Polulu stepper drivers
  • RAMPS 1.4 stepper interface board
  • Some sort of end stop switch for z axis (TBC)
  • Arduino Mega controller/IO/processor/brain type-thing.
  • Lot's of bits of wire, heat shrink, connectors etc.
Right then, so, that's the plan. I have already bought the majority of the mechanical parts and borrowed a friends UP! 3d printer to produce the requisite printed parts. Annoyingly, all I'm waiting for now is some friking M5x10mm machine screws (which you need loads of), I could have just bought these off the shelf but instead  included then in an order to RS but for some reason they are being shipped from the UK and now I have to twiddle my thumbs while I wait for them - I know I could just go and buy some but it's the principal at stake here.

So, that, I think, will do for now. To conclude, here is pretty picture of all the bits I've got so far, I am disconcertingly excited about joining all these bits together to make a shiny machine!