More injection molding updates, more photos, the head unit
The Y Carriage
Leonid and his team have continued to help refine, redesign, and get the plastic parts ready to be injection molded parts of a quality far superior (while also saving on molding costs) to what they ever could have been otherwise - once again a HUGE thank you to them!
Leonid has spent a good deal of time on several revisions of the Y carriage part - a part that looks very simple as a 3d printed part:
But as an injection molded part is very complex because it has some many holes, going so many directions, all in a compact form factor.
First the part was redesigned as two identical parts - however this led to some concerns about the cost of making twice as many vs a more complex mold - as well as possible alignment issues when putting the two parts together.
Next it was redesigned back into a single part - but this would require a more complex mold then the two parts and the method of retaining the bearing (screws) was very different then the Z carriage presented in the last update -
Leonid and I then brainstormed on how we could get the best of both worlds - simple mold, simple assembly, and one part - he suggested some changes that would allow this and I've spent the last several days (among many other things) seeing if these changes will work with the rest of the printer and ensuring they'll have a minimal impact and no negative impact.
By moving the two idlers wheels toward the head unit (and some other spacing adjustments) - whereas one used to be forward and one set back - the part can be made such that the bearing can snap in and be secured by zip ties - this also makes for a simpler mold as well. This does change the belt path but in order to keep the belts straight where they need to be - all that is required is moving the back idlers (that are mounted to the main body of the printer) inward slightly.
I've now asked Leonid if he wouldn't mind making those changes so we can see if that will work to make it a single simple part - while I make the changes to the acrylic panels and such to accommodate the different spacings.
The Head Unit
There is one part left that Leonid nor I have yet to fully dive into in the way he has with these other parts - that is the head unit. The Head Unit is the most challenging part to turn into an injection molded parts and so we asking any backers with some basic knowledge of injection molding (or not) and any ideas to help us brainstorm.
Here is some essential info about the head unit:
The flat top of the head unit is where both the head unit circuit board (see below) and the print cooling fan mount (they share a screw hole). This should remain flat and at least similar in dimensions.
The front of the head unit holds the Hotend and also makes up the part cooling fan funnel - which is perhaps the hardest part of it to redesign - how do we direct a flat 30x30mm fans output down (or with the fan mounting on the side of the head unit would also be OK) and aim it roughly at the end of the hotend nozzle? and make that easy to injection mold. Likely it will take a second part - but who knows what creative solutions might be possible?
The hotend holder can certainly be optimized for injection molding without too much difficulty - the hotend itself is retained by an aluminium piece that screws into the two holes - the little tongue below it help keep it tight against the retaining piece.
The hotend is aligned to the holes on the back for the Z level sensor but this can be adjusted slightly without any negative effects (because we can adjust the offset in the software).
The back plate holds the laser module - two holes top and bottom on left and the Z level sensor - two holes side to side on right. The middle hole is the hole for tightening the bearings into place - see the side view to understand that.
The back needs these holes in these positions more or less - and a solid flat area (or at least some ribs or similar on the same plane as the holes) to the right of the laser mount holes and below the Z level sensor holes - for those modules to be supported. But that's it - this doesn't have to be a big solid plate, it can have holes in it or be split up or be changed completely beyond those requirements. Possibly the bearings could be snapped in from this side and then zip tie retained?
This shows the two bearing holes - the bearings ride on the two 8mm X axis rods that the Y carriages hold. It would be preferable for these to change to snap in and zip tie retained similar to the other redesigned parts.
One note: This part is slightly simplified in that the method of holding the belts is removed - we have several options for how the belts are retained at the head so they likely can work with any redesign.
You can download the STEP file shown here: https://robotic.industries/HEADUNIT.stp
If you want to help with the brainstorming:
1. Please read the above section and ensure your suggestions wouldn't break any of the required placements/supports/etc.
2. Offer your ideas in this update's comment thread - not the main project comment thread.
OR - contribute here: https://github.com/digistump/BuildOne/issues/5
PCB Photos and Minor Heatbed Issue
Currently a round of PVT PCBs is being made and assembled - these include some fixes that we've made in the last few months - and also are the first to bear the final colors, some of the final text, etc.
As of this morning the factory head not yet done the Through Hole parts assembly, but we got some photos of the boards with the surface mount parts on them and wanted to share.
As to why the through hole assembly hasn't been done - it is because the factory is waiting for new heatbed PCBs - they identified an issue (you can see it if you look carefully) that they had an easy suggestion to solve - the heat beds aren't very flat (actually they are just ever so slightly wavy - but relative to nice dead flat PCB that the factory is used to) and that's OK because we have active z leveling - but their engineers found a simple solution and asked if they could try it. The wave is caused by the aluminum plate and the PCB both being thick and both trying to warp in their own ways when heated. The factory is trying reducing the thickness of the PCB (just the fiberglass part) by 1/2 - and they think that will reduce the waviness which means less work for the z leveling - they'll have the new ones in the next day and then continue with the assembly of everything (using the thinner ones if it works, the thicker ones if it doesn't).
That is all for tonight - but we will be back hopefully even sooner this time with more updates - thank you all and please contribute some ideas for the head unit if you'd like to!