Well I might be biased because my machine has a six micron step size but I think you are better off putting effort in to increase the accuracy of the XYZ system than adding a fourth redundant axis. That way all shapes benefit rather than just circles which are a special case of an ellipse which is special case of a curve. It may be worth adding a curve drawing function to the firmware rather thaby nophead - General
You can express a circle in Cartesian coordinates to 0.1mm accuracy with Darwin. That is the same as the thickness of a piece of paper. With the current filament size and accuaracy of deposition are you really going to notice the difference going to a turntable? My point was that when making a tube it would be better to lay down a coil rather than a stack or circles, but that does not fit in witby nophead - General
The current software approach is to slice and dice objects, but to make a hollow tube a continous spiral would produce a better result.by nophead - General
Yes, I don't think it would be a problem with RepRap control boards, or any through hole components for that matter, but my machine for example has 100Mbit Ethernet so that will involve frequencies well above 100MHz.by nophead - General
I am thinking of hundreds of MHz and surface mount components as that is where most things are at these days. Digital signals have harmonics way above their fundamental. In fact it is the edge rate that important, so if you run some fast logic at a low clock speed you will still get high frequency signal components. When running power to, and decoupling high speed circuits, short lead length isby nophead - General
Not quite the same when it comes to high frequencies. The extra distances will add to the inductance and there is also the skin effect.by nophead - General
I think the electrical conductivity of solder is about 10 times less than copper. Presumably thermal conductivity is similar. For a lot of simple low power circuits this will not matter, but may be a problem for high power, high frequency or low noise circuits.by nophead - General
The wiki page suggests this is done under parafin. I have also seen parafin recommended as a lubricant when machining aluminium. I have always wondered why it does not ignite in the presence of heat and sparks? I have some parafin, maybe I should try an experiment outside before I put it in HydraRaptor which is largely made of wood!by nophead - General
I was re-reading Adrian's blog article about etching PCBs with electrolysis and a movable electrode. The main problem seemed to be that a small electrode etches a hole much bigger than itself. I read that spark erosion can produce very accurate shapes . How about replacing the electrolyte with oil, moving the electrode very close to the work and apply a large voltage. The electrode will wear downby nophead - General
Like Eric, I think we should be cooling the work piece, not warming it. Doesn't Vic use a fan to cool down the object being made? I know he is using lower temperature CAPA, but rather than trying to keep the work warm perhaps we should do the opposite. If the deposited layer has cooled fully before the next layer is placed on top of it then it might be stronger and able to resist the contractionby nophead - Plastic Extruder Working Group
I don't know much about carbs but what I can remember from the Ladybird book I read at school is that these nozels form a valve closed off by a needle attached to a float. For that reason they have a concave end to receive the needle. I think the extruder needs to have a convex nozel otherwise the outside of the nozel will collide with the plastic already laid down.by nophead - General
Yes I would only need XY tool motion, the reason I was proposing attaching the tool to Z is that it is a convenient way to hold it at the right height. If you take a look at the layout of my machine you will see that the way I have mounted the XY table means a tool attached to that would have to reach out over the y motor to get to the lathe. Easier to place the lathe and its motor on a heavy plaby nophead - Reprappers
Hi Bart, Not a bad idea. I would have to mount the tool post on the XY table as the other heads only move in the vertical direction. Or I could mount the whole lathe and its motor on the XY table and the tool post on the Z. It might be just as easy to couple a pair of stepper motors to the cross slide of the lathe though. For now the priority is to make a CNC mill to make the extruder body anby nophead - Reprappers
Thanks Forrest, The lathe was a lot nicer when my father had it! Foolishly I lent it to my brother-in-law who let it go rusty, broke some bits and lost others . I had to clean it up for this project and I need to make a new tool post. The one in the picture is not the original which was a nce chromed thing. I always planned to CNC it with some of the steppers I had collected but I have a betby nophead - Reprappers
Hi, I have been making my RepStrap machine for a couple of months now and it is starting to take shape. I decided this weekend to blog my progress at . The blog is historical at the moment but I intend to catch up to real time with an article or two per day for the next week or so. Chrisby nophead - Reprappers
As I understand it the comms board takes the RS232 levels from the PC down to TTL levels to send around the ring of PICs. As the PIC boards are distributed around the machine their ground leads must drop some voltage due to the motor currents flowing down the same path. This voltage gets added or subracted from the comms levels between the boards.by nophead - General
It has always seemed unwise to me that the RS232 comms are converted to TTL levels to be sent around the ring of PICs. TTL only has guaranteed noise immunity of 0.4V. CMOS is a bit better, but you have heavy currents sharing the same ground connection from the stepper motors and broad-spectrum noise from the DC gear motors. I always remember an EMC expert telling me that motors with commutators eby nophead - General
Thanks Forrest I will stick with that.by nophead - Reprappers
Hi, I am just commisioning the cartesian engine of my RepStrap effort. I currently have the axes of my machine as follows: X axis left(-) to right(+), Y axis front(-) to back(+) and Z bottom(-) to top(+) is this correct? It is not as AOI but I am sure other people have referred to the Z axis of their machines as the vertical one.by nophead - Reprappers
Any chance you could make the developer's forum show a whole thread or is there a reason why it is different.by nophead - General