Sketch

Hi Sander The problem resembles what is known as backlash and due to the shape that is makes, it looks as if the problem is with the Y axis. The image above gives an indication of the shape (or at least distribution of shape) produced. In a nut shell when the Y axis reverses in direction, it does not react in the desired manner to produce a perfect circle. This is a matter of calibration / setting of the stepper motor, assuming no other inefficiencies in the slide rails, belts etc. I did rather think it may just be a machine limitation. As for Horizontal Expansion, I use this all the time for sizing of models but this will have no effect at all on the issue, as it is for size in both X and Y simultaneously. Basically I get the same problem but on a slightly bigger or smaller diameter. Maybe worth suggesting this to the powers that be, as a possible addition to UM machines, to allow fine tuning of stepper motor behaviour. Maybe an additional calibration feature. If I have any other breakthroughs, I will add to the post, or if anyone else has any other ideas, it would be great to hear them. Many thanks anyway.

Hi SandervG: Thanks for getting back so quickly. This issue is 0.15mm (150 microns), so is not detectable to the human eye. I've added a couple of pics anyway. Largest diameter visible is 65.0mm. This is an assembled component consisting of. Black ABS - Main Body. Silver ABS - Disk Insert (This will be replaced by Turned and Milled PEEK in the final use part - not printed). Black Nylon - Centre Locator. There are other Stainless Steel inserts and fixings present (not printed). The ovality encompasses both X and Y to almost equal degree (i.e. both axis combining to give ovality). Ovality is consistent in both magnitude and direction (therefore this indicates actual mis-calibration). The machine is stable and does not rock or move. Machine is in humidity and temperature controlled environment. I have the additional Accante top enclosure to aid temperature stability. I print with pretty much every type of material (PLA, ABS, PP, PET, Nylon, PC, PET CF, PAHT CF, PP GF, PA GF etc. etc.) and always found the print quality to be very good. Only other issues I have had, has been blocked nozzles and dirty feed wheels which accidentally trigger material out alarm. However, both of these issues are to do with printing composite materials and are simple cleaning jobs. Aside from this, the machine is kept clean and is looked after. I gentle wipe the slide rails clean and oil them once every few weeks, along with greasing the lead screw and cleaning the feeders. I first noticed the issues several weeks ago and found that the main culprit to be loose short belts. However, this got me looking and digging deeper, trying to improve the ovality (roundness) issue. Can't say for sure how long it has been there before this, as have not had to do such a size and shape sensitive part until now. It may well have been there since the start. This type of problem is usually calibration related on most CNC machines and can usually be adjusted in soft settings to cure the problem. Obviously with the S5 being a far simpler device, I would imagine that the adjustment is only possible by hardware, hence asking. However, if stepper motor calibration is possible, this may be the answer. Many thanks. Sketch

Hi. I have issues with ovality when printing diameters, both internal and external and of all sizes. The direction and distribution between X & Y of this ovality is always the same. This is not to do with the short belts or out of alignment of the print head rails. To start with and ignoring any small print seams left, I was getting about 0.4mm ovality on a 50.mm external diameter. After adjusting the short belts and aligning the print head rails I have reduced this to 0.15mm. To align the print head slides I used a precision 100.mm engineering calibration slip and used this to align each rail in 4 places (at each end and at both limits of axis travel) to its relevant drive / slide rail. Both X and Y were done in this manner until not discernible error could be detected. I have repeated this procedure several times with no further change. Still got 0.15mm ovality. So, effectively I need to know if there is a method to 'dial' out this last 0.15mm of ovality. Is there a further hardware related issue I do not know about? Or, can this axis error be adjusted with a setting or software? I really do need to find a solution, as I use our S5 to make Engineering fixtures that are used directly in a Automotive production environment.