My Rotary Axis

[ThothLoki]

So, after trying the same rotary axis that Nottingham did, I found it to be overly complicated for my purposes. While the design is was very simple (4 rollers, 2 gears and 1 motor), I don't think the parts were designed well. Ah, the joys of Thingiverse

I am in the process of designing my own rotary axis. I am going for a direct drive chuck version.

This thread will show the joys and pitfalls I have during the process

I designed, printed and assembled the piece that will support the other end of the round object as you can see in the picture. I found out I have some calibration to do on my 3D printer as the holes for the bearings and screws were of the incorrect size. Also, the part that slides in had to be filed down a fair amount to get it to slide freely.

I designed it to have an adjustable height to accommodate various odd sized round objects such as wine glasses and bottles.

I have not released the stl files into the wild yet as I have yet to determine how much of the issues I had were my design or my printer. I am willing to share the files of anyone would like these, but remember there are known issues with the current setup.

I am in the process of designing the other end now. Hopefully I will have time this week to finish it and get it printed. Will post more as the updates come.

[nottingham82]

neat

[ThothLoki]

I am still designing the other side. It doesn't look like much now, but I hope it will do what I need later. I am sure some redesign will be necessary as I go.

Nottingham, how is your rotary axis treating you?

[nottingham82]

its in my lap and im tweaking it to get it all straight.  hopefully in a few hours it will be working.  I have my calipers out and I had to swap out a few parts.

[ThothLoki]

Sounds a lot better than what I am doing (sitting at work.....working )

Can't wait to see it in action.

[Stonemull]

Its a known. fact that all cool things are made with orange PLA.
So I have no doubt it will be awesome.
I am guessing you intend to raise the bottom of the object up and maintain the same focus height ?

[ggallant571]

I think that if you have a 0.4mm nozzle and no kerf compensation your part will be 0.2 larger in both X & Y on both extremes. You could also expect the inside holes to be 0.4mm less in diameter. That is assuming your holes are aligned vertical. When the hole is perpendicular to the Z they will be oblong depending on the layer height.

This is from a complete newcomer to the 3D printing game but is the result of doing some medium sized prints with cutouts and measuring the results

[Stonemull]

That is pretty accurate, a correctly calibrated printer should produce the correct size holes, however even temperature will affect them.
The slicer might put the nozzle in the correct spot but as it extrudes hot plastic and draws a small circle it drags the filament inwards towards the centre. Lowering temperature and speed on articles with small holes can help.

Personally if I want a hole for a 3mm bolt I print it 3.5mm, 2.5mm for a tapped hole.

[ThothLoki]

>> Its a known. fact that all cool things are made with orange PLA.
DUH!!! That's why I did it I am almost out of black, so had to pop in the orange roll. I still have some purple though, but that is saved for anything made for my wife or child.

>> I am guessing you intend to raise the bottom of the object up and maintain the same focus height ?
I made that piece to be adjustable height to maintain a level work space. When I get my other half done, I am going to test on a 1.5" wood dowel, a wine glass and a wine bottle. Being that most wine glasses and bottles vary in dimensions, I wanted something versatile.

 ggallant, you and I are in the same boat (or benchy?) when it comes to 3D printing. I know my settings are not perfect. Most items that I have printed, it did not matter if the scale was off by a hair. This is the first piece that I did that required more exacting measurements. obviously, I know it is not spot on. Before I just enlargen the holes in the STL file, I am going back to the drawing board with a 20mm cube for some testing of different settings. I guess it is high time I start that process (as everyone else most likely did it when they got the printer). 

The one problem I have noticed is that when you look to calibrate your machine, it all depends on your software. If I am using Cura, I find that I will have a harder following steps for calibration if the youtuber/poster is using Slic3r. While we are talking about the same thing, it seems the settings and some of the language is different between slicing software. I am using Cura now (I only use the MP version to view, I do not like their flavor of it but cannot get the real Cura to work on that computer) and know that Slic3r offers more setting out of the gate. Cura has them, but you have to check a lot of boxes.

[Lob0426]

When you drew the holes did you take into account the nozzle size?

If you are using a .4 nozzle then you have to open the "hole" .4diameter, .2 radius. The slicer programs do not use any type of "tool size" compensation. Even then the bottom layer will be off as it is purposely mashed into the bed for better adhesion.

This should help you get more accurate hole sizes.

[ThothLoki]

When you drew the holes did you take into account the nozzle size?

If you are using a .4 nozzle then you have to open the "hole" .4diameter, .2 radius. The slicer programs do not use any type of "tool size" compensation. Even then the bottom layer will be off as it is purposely mashed into the bed for better adhesion.

This should help you get more accurate hole sizes.

I thought I did. I am going to go through my settings again and start doing test cubes. I am doing a print now and noticed that the pla was not sticking to the bed. I reduced my bed temp and everything is working fine.

I know there are many settings that can affect a print. Again, I finally need to just sit down and print the same thing over and over to get my settings correct. Also, this will help me understand the settings more as well as what settings are not shown in my cura that should be shown.

[Lob0426]

3D extrusion machine just not super accurate. But they are often accurate enough. I follow all holes with the right size drill bit.

[Stonemull]

When you drew the holes did you take into account the nozzle size?

If you are using a .4 nozzle then you have to open the "hole" .4diameter, .2 radius. The slicer programs do not use any type of "tool size" compensation. Even then the bottom layer will be off as it is purposely mashed into the bed for better adhesion.

This should help you get more accurate hole sizes.

I am about 95% sure this is incorrect, slic3r has settings for extrusion width for first layer and then other layers. Cura has settings for different sections, infill, skin, support etc.
This affects how soread apart the lines are and obviously, their position.

Also, looking in the wrong place to calibrate, you need to look at the machine settings first, for instance my latest machine had steps/mm on the X and Y set to 81 when it should be 80.
My guess is they did that to compensate for PLA thrinking 0.5% but it is the wrong way to go about it, scale the print in the slicer by 0.5% if you have to, the X shoukd move 80mm if you tell it to, not 81mm.

You adjust the machine so it does what the slicervis telling it first, then toy with settings in the slicer to get the results you want, that is the point of calibration.


edit: the new central spar for my robot chassis just completed actually (2:45 print), the 2 bearings are 11mm outside diameter and are a push fit with a vice but can then be removed by hand, the central bush for the bearing to 6mm bolt needed rework, the outside is 8mm and I shoukd have designed it 8.2 to cope with shrink, it is a tiny bit loose in the bearing, the 6mm centre hole I had to drill out to fit over the bolt, the bit next to it is what was removed. A trick for drilling pla to not tear it up is to operate the drill backwards, then it will remove much thinner amounts of material.

[ThothLoki]

Stoney, I am going through my slicer settings again. I messed them up by changing them around and not keeping track. Time to start over and go from there..

The first thing I did when I got my machine powered up was check that the setting were at 80mm. They were

[ThothLoki]

So, I know my printer settings are good as well as the physical setup.

I made a new profile and scoured the nets of inter for people with my machine and what their settings were. I think I found a setup that works. I printed a test shape that has a circle and square. The walls were designed to be 1mm wide. My caliper shows 1.06. Looks good to me!