Thursday, 29 October 2015

Halloween 2015

I saw this in our local Home Sense and thought it looked like a great project for a laser cutter or 3D printer:
First off I drew it up in Sketchup
I made a plate that could be cut on my laser cutter (when it is finished)
but ultimately scaled it down and printed the pieces individually.

Here is the finished article, with an orange LED tea light inside it, which I believe was from a pack of 8 bought at Wilko for £2.00.
I have also uploaded the Sketchup source as well as the STL files to Thingiverse.

I also decided to print Makies Jack-O-Lantern from Thingiverse.
Here is my one with an LED tea light inside it:

Saturday, 3 October 2015

TCT Show 2015

The TCT show was held at the NEC in Birmingham over 30th September and 1st October 2015, I attended on the last of the two days, arriving at about midday and expecting to be on my way home by about 14:00 - how wrong I was!

I new in advance that most of the exhibitors were going to be big business looking to sell their products or services, but was surprised at how many smaller firms, individuals and other new start-up people were there, along with elements of the reprap community.

I was also surprised at how many of the larger company representatives were more than happy to talk to someone who was highly unlikely to be in the market for one of their machines.

As expected Stratasys had one of the largest displays and many of the other print bureaus were also using their machines to promote their own business.

Autodesk were promoting their Ember resin based 3D printer - a snip at $5995.00 (£3870.00).
This is most likely competing with the likes of Formlabs and their new Form 2 printer which currently retails for €3299.00 (£3000.00).
Another highly impressive piece of equipment on display was Renishaw's Equator, their high speed delta comparative gauge for parts inspection.
I am always interested in what Renishaw are doing as my brother-in-law works for them, and I went to school with the son of the owner of the company.

I had a long discussion with the guys from ReprapWorld about the sliders I am using on my Kossel Mini printer, this is an area that they would like to explore further for use on one of their larger designs.

I would like to thank them once again for the spools of copper and bronze PLA they gave me at the end of the show as part of their raffle.

Another area that caught my eye was the kideville product from the start-up company kidesign, this is a collaborative city design project for schools, that incorporates design, CAD, 3D printing and teamwork, each student has a design spec for one element of the city that is eventually printed and then included in the city on the grid board.
Towards the end of the show I spotted the Roland iModela, which for £499.00 ($750.00) can mill, engrave and 3D print in it's 86x25x26mm build envelope and pretty much every part is available as a spare in their parts store.

I would also like to thank Sam Deng of 3D Elements for kindly providing me with a half a dozen 50g (about 12m) samples of their PLA filament to try out after some very interesting discussions regarding their various filaments, some of which reacted to light and others to temperature.

Tuesday, 16 June 2015

Mini Kossel Build Part 4 - Spool Holder and End Stops

My new E3D hot end clone turned up the other day for my Mini Kossel, this cost £7.49 ($11.60) with free P&P from ebay seller digital_store_2014.
I will replace the thermistor with a ATC Semitec 104GT-2 so that it is a known quantity, rather than the complete unknown that came with the hot end.

Based on the issues I had in the early days with my Prusa I3 printer and having to manually turn a spool of filament, I decided to get ahead of the game this time and print a spool holder.

I particularly like the look of this minimalist spool mount and guide on Thingiverse

As there are really only 2 different items to print, I need 3 of one of them and they are all pretty small, I decided to print them all at once.
In total this used 5767mm of filament for a cost of £0.216.

To make them up required 6 x 625 bearings, 5 x M5x20mm screws, 3 x M5x10mm screws, 1 x M5x30mm screw, 6 x M5 nuts, 3 x M5 T Nuts and 11 x M5 washers.
The 625 bearings were £1.61 ($2.50) for 10 from ebay seller warm_tech, the screws, nuts and washers were all from Orbital fasteners, and the T-nuts were $7.50 (£4.85) for 100 from robotdigg.

This makes the total cost (6 x 0.161) + (5 x 0.0484) + (3 x 0.0394) + 0.0697 + (6 x 0.0041) + (3 x 0.0485) + (11 x 0.0041) = £1.61 ($2.50).

These were then installed on the top of the frame and adjusted to fit one of my spools of filament.
I then relocated the extruder stepper motor and fitted the hot end and a length of 4mm OD, 2mm ID PTFE tubing between the push fit connector on the extruder and the one on the hot end.
I am still deciding on how thick an acrylic printing surface I want to use, I will either settle on 10mm, or 5mm and a 2mm aluminium sheet underneath it for additional rigidity.

5mm will be cheaper at half the price, but also half the rigidity.

I have designed some end stops for use with my hall effect sensors and magnets in Sketchup.
For some reason Slicer did not like the countersinks I had put in the holes, it was convinced that there was a hole in the solid, so I decided to print them without and manually countersink them afterwards.

The slot for the hall effect sensor curves upwards towards the rear to help the pins exit the hole.

Here are the end stops hot off the printer.

The 3 end stops used 1572mm of filament for a total cost of £0.06.

Here  is one with the hall effect sensor installed and held in place with some blue tac.
I have pre-insulated the pins with some electrical tape to prevent unwanted contact of the neighbouring pins.

View from underneath.
Here are all three after I removed the sensors and then manually countersunk for the M4 screws with an 8.5mm drill and then re-assembled.
I actually turned the drill by hand rather than under power on my mini mill to give me more control of how much material was being removed.

I have two sets of very sharp, precision ground HSS metric drills, from Chronos in 0.1mm increments covering 1-6mm and 6-10mm respectively. I use these whenever I require a very sharp or accurate drill, most of the rest of the time I use a more generic set of drills.

The hall effect sensors were $4.00 (£2.58) for 10 from ebay seller gc_supermarket, the M4 T-nuts were $7.50 (£4.85) for 100 from robotdigg, and the countersunk M4 screws actually came with hinges I bought for my laser cutter where I used some slightly longer screws instead, so these were effectively free.

The total cost for the completed endstops is therefore 0.06 + (3 x 0.258) + (3 x 0.0485) = £0.882 ($1.35).

Here are some coils of wire I made up for the endstops, they are each about a metre long and are made from 3 cores of a 50m reel of 6 core alarm cable I bought from Wickes for £12.49 ($19.35) back when I was building my Prusa I3, so about £0.25 each.
Mixing up the various cores allows each cable to either be the same or different depending on what you require at the time.

I tend to leave the outer protective sleeve on for the 4 core motor wires, but twist any signal wires to help avoid any cross talk interference, should the signal wires need to run together with the motor wires.

Saturday, 2 May 2015

Mini Kossel Build part 3 - The Spider

I decided to simply bite the bullet and make all of the carbon tubes the same length, so I set up an end stop on my milling machine and held the shortest and one other tube in the milling vice, whilst I cut the longer one down with my Dremel.

Next I made myself a quick jig to ensure that all the rods were exactly the same length once assembled.

This was simply a piece of left over laminate flooring with two 3mm holes drilled through it 228mm apart (it would have been 230mm if I had not needed to cut the tubes down) and then some long M3 screws secured through the holes to act as guides for the rod ends.
I then tried several different glues to attach the rod ends, there must be something wrong with my cheap Wilko brand super glue, because the only thing it seems capable of sticking these days is skin!

It had no interest in securing the grub screws to the carbon fibre tubes, in fact it was not even interested in drying out!

I eventually decided to use hot glue, this worked fine, although there was very little working time before it set.

Here are three of the completed arms mounted on the jig.
Next, I attached one end of each of the arms to the effector to make a 'spider'.
Then finally attached the spider to the sliders on the frame.
The level of lateral movement on the sliders has now vastly reduced.

At most I can move the effector 0.2mm in a circle without actually moving the sliders up or down, but since nothing will be attempting to push the effector out of position, it remains to be seen if this causes issues when printing.

I have been designing some mounts for the hall effect sensors in Google Sketchup, although I am not 100% convinced I like them yet.
Here it is shown on the model in relation to the slider.
The wires from the hall effect sensor would come out in front of the screw and then be hidden within the 20x20 profile slot.

I would prefer the wires to come out at the back, but then I have no way of routing them past the T-nut, or past the T shaped base of the slider, that would be blocking the path of the wire.

Instead I will route the wire to the top of the frame and then back down the side of the 20x20 profile.

I likewise can't use the centre of the profile  for routing wires, as this has a foot screwed into it at the bottom, blocking the egress of the wires.

I may yet also have issues routing the wires past the tensioning screws at the top of the frame.

Monday, 27 April 2015

Mini Kossel Build Part 2 - Frame Again

Because I am trying out the Delrin profile slider from Motedis, I don't really have any choice other than to design my own carriage.

I used ideas and dimensions from a couple of other carriages on Thingiverse, but that is about where the similarity ends, my carriages were designed from the ground up to work with my sliders.

Here is the final version of the model I designed in Sketchup:
The idea is that the belt is retained all the way around the toothed fixture, that combined with tight slots for the belts should mean that it is unlikely that the belts will pull out.

The holes in the ends are for magnets that I will use with hall effect sensors as limit sensors, just like I use on my Prusa I3.

The carriages took 10397.1mm (25cm3) of filament each for a combined cost of £1.17 for 3.

Here are the 3 printed carriages ready to be attached to their sliders:
The original holes in the sliders are about 2.5mm, so I drilled them out to 3.2mm and  tapped them M4.

I then attached the carriages to the sliders with 3 x M4x20mm socket head cap screws.
I decided to remove the anti-vibtarion mounts from the stepper motors and also attach them with 4 rather than 2 x M3x8mm button head cap screws.

Previously I had been unable to tighten the motor screws as there was not enough space for an allen key to fit, even a ball end allen key was at too much of an angle to connect properly.

So I decided to modify one of my spare 2mm allen keys I had received for free with something or other.

Initially I thought I would cut it down with a hacksaw, but this would not even mark the hardened allen hey. Heavy duty wire cutters just about made an indentation.

In the end I ground down the short arm on my bench grinder to about half of its original length whilst holding the allen key in a pair of mole grips to protect my fingers.
The motor screws could now be tightened to a satisfactory level and were more likely to line up with the top pulley.
I assembled the top pulley from 2 x 623 flanged bearings (£4.59 ($7.00) for 10 inc P&P from Ebay seller link-fortune), suitably spaced with M3 washers and an M3 nut.
And then attached the belts to the carriages
I will trim the top piece of belt once I am satisfied with the tension.

I fitted the M3x30mm tensioning screws with some M3x12mm penny washers to the top of the frame.
After suitably tensioning the belts, I tested moving the carriages up and down the 20x20mm profile by hand.

At this point I discovered that something was very wrong with one of the motors, I was feeling some very pronounced 'cogging' and on closer inspection discovered that the shaft for this motor was in fact bent!

I swapped it out for another motor and all is now fine.

I suppose I can't complain too much, the motors are used and 5 of them cost me $30.00 (£20.00) + $20.00 (£13.00) P&P, admittedly prices have come down recently - 40mm Nema 17 steppers can be had for $6.80 (£4.38) from Robotdigg.

There is a small amount of sideways rotational movement possible on the sliders, I have yet to determine if this is going to be an issue once the arms have been assembled.

I was about to assemble the effector arms, but thought I would check they were all the same length first.
I was a bit disappointed to find such a variety of lengths ranging from 178mm to 182mm, when they were all supposed to be 180mm.

I have complained to Derek at Robotdigg about this poor level of quality control, +/- 2mm or 10% is a bit much in my opinion, there is 4mm (20%) difference between the longest and shortest of my tubes.

To be fair, if I ignore the shortest one, the others are all 180mm or over and could all become 180mm with very little effort, however lengthening a carbon fibre tube is less straight forward.

Tuesday, 17 February 2015

Mini Kossel Build Part 1 - The Frame

My order from Motedis arrived yesterday, this was mostly pieces for my CO2 laser cutter project, but I added in the pieces for my Mini Kossel build as well as it barely affected the overall cost of the order.

Motedis include any left over pieces if you choose to have your items cut from standard 2, 3, 4 or 6m lengths, instead of specifying individual lengths.

I used GoNest 1D to optimise my cutting plan and allow for the kerf/waste generated by each cut.

This is 4 x 6m lengths of 20x20mm and 2 x 960mm lengths of 20x40mm aluminium extrusion cut according to my requirements.
Here are the pieces for the Mini Kossel, 3 x 660mm and 9 x 240mm pieces of 20x20mm extrusion:
This is a total of 4140mm of extrusion, although you need to allow around 25mm per cut and ensure the remainder is more than 50mm. These pieces were actually cut from 2 different 6m lengths to minimise waste in the overall cutting plan.

A 6m length of 20x20mm extrusion from Motedis costs £17.21 ($26.50), so about £13.00 ($20.00) for the Mini Kossel parts

Here are the sliders that actually have surprisingly little slop and slide really smoothly on the rails, these were £2.09 ($3.25) each, they are injection molded from Acetal/Delrin/POM.
I have already pre-attached the T-Nuts and various other screws to the frame ends, to speed up the assembly process.
The M5 T-Nuts came from RobotDigg @ $7.50 (£4.80) for 100.
The M5 screws came from Orbital Fastners @ £3.95 for 100 M5x10mm and £4.06 for 100 M5x12mm screws. 36 of the M5x10mm and 6 of the M5x12mm  screws were required, the rest will be used on the CO2 laser cutter project.

First I attached a 240mm length of the 20x20mm extrusion to each of the top mounts
then joined them all together
then attached 2 x 240mm lengths of 20x20mm extrusion to each of the motor mounts
and joined those together.
Checked the top and bottom frames for squareness relative to each other.
Next Inserted the 660mm lengths of 20x20mm extrusion into the motor frame
and finally attached the top frame.
You can also see the sliders in place in this picture.

The top frame is not in its final position just yet, the top mounts need a little more TLC so that they can be attached/removed a little better, they are still very stiff at present.

I also need to have a think about modifying the carriages so that they can be attached to the sliders and still line up with the pulleys and motors.

A while back I bought a set of 8 M6 feet, for use with my CO2 laser cutter project, for £3.21 ($5.00) from ebay seller gadgetskingdom, I only actually need 4 for the laser, so I decided to use 3 of the remaining 4 feet for the Mini Kossel.
The end of the extrusion is designed to be tapped M6, however because of the gaps around the central hole, it is not really designed to be tapped with conventional straight flute taps as they may break when all of the teeth try to re-engage after the gap.
Instead this type of hole should be tapped with a machine or spiral flute tap. These taps also eject any continuous waste upwards, like a drill, so they can be used on blind holes without the risk of filling the hole with chips.

I bought a set of Europa spiral flute taps for £50.00 ($77.50) at the recent Model Engineering Show at Alexandra Palace, the set comes with the correct size drill for each tap size.
These made short work of tapping the extrusion and left some perfect threads for installing the feet.
3 feet will always self level, but the adjustment is useful for making the build platform level on however uneven a surface the unit may be placed on.