Sunday, 4 December 2011

Frame Assembly

I now have enough parts to start on the frame.

Short work was made of cutting the lengths of studding by using the chop saw attachment for my angle grinder, worth every penny of whatever I paid for it at Aldi.

Having chopped the six 1m lengths according to the cutting regimen, I then proceeded to drill the various holes in the cast parts using my pillar drill (something that has paid for itself several times over, mine was from Wickes, current price is £65.00, pretty sure I paid no more than £45.00)

All was going very smoothly, indentations in the parts to start the drill in the right spot, until I put too much pressure on one of the Z axis motor mounts:

Still, all is not lost, after the application of some superglue to re-attach the broken pieces, I was able to finish drilling this piece, and unless you look very close, you cannot even see the join.

Having finished with the drilling, I started putting the frame together, the two sides were completed in hardly any time:

When I came to put the top bars on I discovered an issue with the parts: The hole drilling locations on the parts do not all actually line up! The Z axis motor mounts are supposed to slide on to the top bars, however the holes drilled in the top frame piece are too close together to allow this.

So off came the top bars, and top frame piece and the holes were suitably "adjusted" on the drill so that they were the right distance apart.

I had to leave out a couple of nuts and washers next to the Y axis motor mount, as the shafts on my motors are a bit on the short side.

I measured all of the vertices and all seem to be the correct lengths, however the frame will still not sit level. This is again probably an issue with slight differences in hole locations and differences in thickness of the various parts. I will worry about this some more when I have the smooth rails and I am ensuring that axes will travel smoothly.

Thursday, 1 December 2011

Parts start arriving

Well I have now amassed most of the items required.

My Clonedel parts from Metrix Create:Space turned up the day after I chased them, took just over a month to arrive, they are definitely colourful and some of them are designed in a slightly different manner to a printed set. Surface finish is a bit rough as the originals are produced on a powder printer before molds are taken.

I ended up buying 4 Pololu boards complete with heatsinks from Ebay at just under £7.00 each, instead of the StepStick boards I mentioned last time, these arrived in a couple of days from Denmark, costing £1.27 for postage.

I have just about collected all of the parts for my Sanguinololu, I just need to solder it all together, total cost of the board and associated electronics was £13.25. Parts for the opto endstops came to about £1.00 each for 6, making a grand total of £47.28 for all of the electronics, so well within my estimate of £50.00-60.00.

608-ZZ Bearings also from Ebay at £1.20 for 10, delivered next day.

My studding, nuts and washers order has arrived from Orbital Fasteners, 1m lengths of M8 BZP studding at £0.75 each, M8 nuts at £1.36 per 100, M8 form A flat washers at £0.59 per 100 (all inclusive of VAT), and because I live in the delivery area for their van and placed an order for over £20.00 worth of parts, next day delivery was free as well (I almost never just buy for the current project).

The stepper motors all came with a metal 16 tooth T2 gear attached which will be a shame to remove, so I am looking at alternative belt options, which will ultimately give me better print results anyway.

I can buy 5mm wide open length T5 belting from Belting Online for £2.25 per meter, which is the standard belt for use on a Prusa, but would prefer to buy the T2 belts to use with my stepper gears. Unfortunately the longest length they supply is 710mm (£6.27) and I potentially require 2 lengths of around 900mm, so would either need to buy one of these and a 200mm belt (£3.21) or a 600mm (£5.68) and a 280mm (£3.54), 292mm (£3.60) or 320mm (3.71) length to join together, so around £9.50 per 900mm belt (all prices are ex VAT). I may yet ask them if they can do me an open length of belt for a similar sort of price.

I am also moving towards the idea of a bowden extruder, as again I can make use of the already attached gear on the stepper motor squeezing the filament past a bearing. This method allows for less moving mass on the printbed, which allows for faster printing. The eMaker Huxley design already uses a Bowden cable from a modified Wades Geared Extruder.

I am currently thinking I will use something along the lines of the Wildseyed Simple Hot End, I am also thinking of utilising some pneumatic fittings at either end of the Bowden tube, they are pretty cheap £1.63 each for an all metal one, this should be an easy fit to the air hose fitting, used with this Hot End as they are both available with a 1/4 BSP thread, and then a length of 6mm PTFE tubing will be a simple push fit.

Current estimate for the total cost for this project is around £135.00.

I don't really subscribe to the idea that a RepRap should be capable of self replicating, and as far as I can see, certain areas of the project seem to be rapidly moving away from this ethos as well. Firstly, most of the electronics seem to be heading towards surface mount components, which are not exactly beginner hobbyist friendly, and good luck milling the pcb on your 3D printer. Second, until it is possible to print the various bar items, threaded or otherwise, nuts, stepper motors, etc the goal is a bit far fetched.

Choosing printable items over cheap vitamins is also often a false economy, yes you may be able to print a given part, but if the equivalent purchased part is cheaper than the cost of printing it - why bother?

I am all for reducing the parts count and think that the Printrbot variant has a good handle on this concept, one of these, or an eMaker Huxley, will probably be the first child of my Prusa.

Wednesday, 21 September 2011

Opening Thoughts

This blog will be following the development of my Reprap Prusa Mendel, from parts source contemplations, through the build process and on to things I eventually get around to printing and all the highs and lows in between.

The main issue for all people joining this 3D printer revolution is how to build your first machine, building the second one, or first child, is relatively straight forward - you just use your existing printer, but when you don't already have a printer you have a couple of options:
  • Build some sort of bootstrap (repstrap) machine, extruder attached to a CNC machine of some sort  to print out the parts for your printer.
  • Buy a full or partial kit of parts that someone else has put together
Now whilst I am all for supporting the reprap community, I am also a cheapskate and object to paying some of the prices being charged for these kits, I am perfectly happy sourcing the vitamins, motors, electronics, etc from the cheapest suppliers I can find, rather than paying the premium for someone else putting it all together in a kit.

I have been researching parts suppliers, electronics options, etc. for quite a few months now and have made a few decisions and actually splashed out and bought a few items.

To that end I have decided to go with a cast set of parts including a Wades Extruder from Metrix Create:Space at $50.00 and $15.00 shipping to the UK (£42.20), these parts may not last forever, and will need drilling, but I am sure they will last long enough for me to print at least one child's worth of parts, probably many more, but they are a whole lot cheaper than the going rate of about £80.00 for an equivalent set of printed parts.

I have decided to go with the Sanguinololu approach for the electronics, mainly because I feel it is a neat and compact solution. I like the RAMPS idea for Arduino, but believe the Sanguinololu can be built for less, has a smaller footprint and looks neater. I also really like the Repic approach and will probably try this for my next controller - all through hole construction, PCB can be milled on the printer, PIC can be obtained for free (if you request a sample), but is still in development and is quite a steer from the ATMEGA based controllers that are currently the norm.

Rather than buy a ready built one, complete with drivers for £99.00, I have bought a 1.3a circuit board from Ebay for £4.50, and a couple of FTDI chips again from Ebay for £2.54 each, with free or minimal postage costs. I am thinking about some StepStick drivers from Ebay at £8.29 each. The remainder of the electronic components will be coming from Rapid or from various multi packs of resistors and capacitors I have previously bought from HK - total cost should be around £50-60.00 and doing my own soldering. I'll add it all up properly when I have all the parts, along with the total cost of this build, just to see what it actually cost me.

The stepper motors I have bought, in keeping with my cheapskate nature, are used rather than new items, again from Ebay, under £30.00 for 5 Nema 17 steppers, I actually bought a set of 5x29 oz/in steppers and a set of 4x55 oz/in steppers as I need one with with the higher torque for the extruder. I will use the others, either on a second Prusa, or on a heated wire foam cutting CNC machine.