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Re: PCB production with spark erosion - 16 years ago

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

PCB production with spark erosion - 16 years ago

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 down

by nophead - General

Re: Coefficient of Expansion - 16 years ago

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 contraction

by nophead - Plastic Extruder Working Group

Re: Carburetor Jet as Nozzle - 16 years ago

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

Re: Many headed monster - 16 years ago

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 pla

by nophead - Reprappers

Re: Many headed monster - 16 years ago

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 an

by nophead - Reprappers

Re: Many headed monster - 16 years ago

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 bet

by nophead - Reprappers

Many headed monster - 16 years ago

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. Chris

by nophead - Reprappers

Re: Vic's comms errors - 16 years ago

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

Vic's comms errors - 16 years ago

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 e

by nophead - General

Re: RepRap axes conventions - 16 years ago

Thanks Forrest I will stick with that.

by nophead - Reprappers

RepRap axes conventions - 16 years ago

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

Re: These forums are very slow - 16 years ago

All sorted, thanks Simon.

by nophead - General

Re: These forums are very slow - 16 years ago

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

Re: These forums are very slow - 16 years ago

Yes its much better now, thanks.

by nophead - General