Cheap 3D printers

Like Steve, I like the flexibility of a heated bed as I print nylon and PETG, I think it's the weak point of the Cetus, but it would be easy to add a heated bed, especially if it uses a RAMPS system.

Even if the printer controller doesn’t have any circuitry for the heated bed one could be cobbled together easily enough enough and probably be better than what is on most printers as well !

The problem is the bed temperature should ideally be controlled by the same box so printing doesn't start until it's hot and it cools afterwards - plus you may want to cool slightly after the initial layers.

It just means you have to control it manually - pia i know but if your printer wasn’t made to have a heated bed there is little choice and it is always wiser to buy a printer with the feature just incase . I bought one of those cheap cnc engravers from China and wanted to add limit switches and after opening the box i found the break out board had the facilities for that but that area was unpopulated so i had to add 4 opto isolators and 8 resistors which added up to about $5 - i had the parts in stock so it really cost me nothing , i then checked the cable that connects the board to the machine and found it was missing th 5 wires needed to hook up 3 ends tops and a touch probe - another Job done for no cost. What i found odd is the 4th axis connectors are on the board ready to use if i buy a driver to run the steppers and a four pin plug to the case , i found this strange as they had skimped on a few dollars worth of parts but fitted the 4th axis break out board to a 3 axis machine . They must have to order that board and cable with the unpopulated end stop area and missing wires from the manufacturer specifically- surely the cost saving wouldn’t be worth it. I would have thought they would have sold the unit ready to go with the full breakout board minus the 4 th axis controller , the fully wired cable and limit switches and then had them listed as upgrades .

Neil

I take your point about some of my mods not making much difference but take issue on the 'mistake of replacing threaded rod with ball screws' . A machined ball screw can provide greater precision and at least equal resolution as long as you also upgrade the stepper driver.

There are many variable when 3d printing and I think it is good practice to reduce as many as you can for piece of mind if nothing else!

John

I take your point with regards the precision of a ballscrew compared to a rolled threaded rod from a manufacturing point of view, but am struggling with how the ballscrew provides the same or better resolution.

Assuming a standard stepper motor with 200 steps per revolution, 1/16 uStep and a gear ratio of 1:1 (direct coupled)

For an M5 threaded rod (0.8mm pitch) you have 4000 steps/mm

For an Acme 1/4-16 (1.5875mm pitch) you have 2015.75 steps/mm

A Stepstick A4988 can do 1/16 uStep and currently costs £1.00 or less on Ebay, unless you are looking at 1/32 or better uStep which will cost much much more, you are not going to beat the threaded rod for resolution.

On my Prusa i3 clone I built from a set of printed parts I have M5 threaded rod with pvc tube as a coupling and have no issues with resolution and have only twice had issues with the coupling coming loose - I have had more issues with the original printed parts failing and needing to be replaced with items that have more infill.

Edited By Zebethyal on 15/11/2018 14:09:42

It's the stepper, rather than the stepper driver you need to replace to restore the resolution, as ever finer microsteps rarely deliver real world increases in precision.

Going from a pitch of 0.75mm to 4mm (typical for ballscrews sold for 3D printers) is reducing the vertical precision by a factor of more than five, as most printers use 16-microsteps already, you would need to go to at least 128 microsteps to get better results and I don't think any affordable stepper is going to deliver even 64 steps with comparable accuracy to 8 or 16.

Neil

Would some of that lost precision be regained by the better accuracy of the ball screw/nut combination compared with a bit of studding and whatever is used as the nut?

I can see that with a finer pitch you get better resolution but if that is say +-0.01 for studding vs say +-0.001 of a ballscrew you have gained as much as you have lost

Edited By JasonB on 15/11/2018 15:14:39

I have some parts to make and the idea of an affordable (less than £250 say) printer rather appeals to me because making the part in the picture on the milling machine is a pain (I need about 50 of them) in about three weeks time. Currently I use Delrin because it machines nicely but the material is really not critical, although black is preferable.

Its about 20mm long and the protruding peg is 5mm diameter, am I being realistic in expecting to buy and assemble a printer and get usable results without a long learning curve?

Ian P

I have several Aldi hand and power tools, all of which do 'what it says on the tin', but are not pretending to be high-end products. With that in mind, what would the forum think of this:

https://www.aldi.co.uk/balco-3d-printer-/p/086887240233900

John

What are peoples views on 3D printing model kit sprues that are no longer produced? Is it frowned upon? Is it legal?

I bought one of the ALDI printers and I am very pleased with it. The only problem that I have had is that the springs on the bed for the levelling screws are too short and they do not hold the bed in a reproducable position. I 3D printed some spacers to fit under the springs and everything is better now.

Mike

If you do it for your own purposes and don't sell them I doubt anyone would object. Depending on how old the design is any copyright may have expired anyway.

I bought one of the ALDI Balco 3d printers a few weeks back. It was brain dead on arrival - would not power up. After customer support led trouble shooting they advised that the power supply must be dead. Unit was returned and full refund issued without a problem.

A week after I returned it I noticed they had reduced them by £50 to £250 but now I see they are back up to £300 again.

Rik

Edited By Rik Shaw on 07/02/2019 12:08:40

One lesson i learned the hard way was to be mindful of the fact a cheap printer will have a cheap build surface that more than likely won’t be flat . This causes some headaches when you start using the whole build plate and i had a lot of trouble getting descent bed adhesion even with a raft, i changed over to pyrex for a build plate but discovered this was also warped . I have some new pieces coming from a different supplier and i hope they are at least reasonably flat , i havent measured how out of kilter the other pieces of glass are other than lay a straight edge over them and on one side it became a see saw and the other side had a substantial gap in the middle - maybe half a mm or so . The mk 2 heat bed i fitted is way better than that but it if i lay a straight edge across it at 90 deg to the sides it has at a guess a 5 thou dip in the middle that decreases as it heats up to near perfect at 70 degrees but laythe straight edge diagonally it is much worse so maybe some of the corners have dog eared ,might take it down the workshop and give it a rub on the surface plate with some blue and see how f i can sort that out as well.