First print(s)/post

Hi all,

From the moment I read about this project about 2 months ago, I knew I had to be a part of it. I have spent the last month (weekends and such) setting up a mendel in my basement. As a total newbie to the project I wanted to put the documentation to the test: not asking the forum until all other resources were exhausted.

Tonight I finally had what I consider to be a successful print. I am using gen3 electronics, ABS filament, wade's geared extruder, reprap host software and a cold aluminum print bed (insert).

The results - assembly went well, I only had 2-3 major road blocks in getting the system running.

1 – Extruder stepper motor.
At one point I had everything moving, except the extruder stepper motor. As it turns out, the I2C connection had not been made. The “testing reprap electronics” page seems to give information on everything except wiring I2C and testing an extruder stepper motor. I have added a note to hopefully help any future newbies from this pitfall.

2 – Getting plastic to stick to the print bed.
I tried just about everything short of a heated bed to get the plastic to stick.
Yellow masking tape: didn't even start to stick.
Kapton tape: sort of a waste.
Cheap double-stick tape: this sort of started to work, but eventually the corners would curl and the part would break free.
Blue masking tape: not much better than yellow.
90W flood lamp: BAD IDEA. I want to build a heated bed using only what I had on hand. It didn't work with ASB. I left this on while I loaded a different filament. Everything was powered to keep the hot end hot. After shining on the stepper drivers providing holding current for about 10 minutes. Two of them were fried. (my third road block)
Acrylic adhesive strip: this stuck really well, still had lifted corners, but my first completed part (ybar_clamp_10off). This is very expensive at $10 for a 50 ft roll and it is impossible to reuse.
Styrene sheet: cheap, but brittle.
Acrylic sheet: By itself – unpredictable. Sometimes it wont even start to stick. Sometimes it works, sometimes there are lifted corners. Sometimes the part breaks about half way through. Sometimes it sticks so hard that the part breaks when you try to remove it.

I experimented by extruding the usual 250 unit bursts (clicking extrude) onto acrylic at Z=0.0mm, 0.5mm and 1.0mm, testing the strength of the bond:
1.0mm: fair bond, no damage to acrylic.
0.5mm: good bond, slight damage to acrylic.
0.0mm: bond too strong, plastic ball must be broken and there is damage to the acrylic.

Having done this I decided to hack my gcode to put one of these welds (100units at 0.0mm) on each corner of my part (nopheads/wades idler block beefy). I lightly oiled the surface to prevent the center from sticking and printed the part. This actually worked well. All four corners stayed down and the welds were easily broken at removal time.

I am going to try to modify the host software to add this functionality as I get time. This might take a while as I have not written java in some time and no longer have a compiler installed. Does anyone know if this has been tried before? I have yet to try any other software. I hear skienforge has a “raft” feature, but I have yet to try it.

I will try to add some pictures tomorrow as it is very late here.

Interesting post, thanks. I'll be having the same problems soon too, when my extruder is finished.

Which oil did you use? PTFE?

Here are some photos of some of my prints gone bad using tape, then acrylic, then finally my only good one.

The oil I used was just residue from touching some of the oily steel parts. I noticed a slight sheen after handling the acrylic and debated wiping it clean. I figure this could be the difference between the plastic sticking too strong or too weak. The point of the spot welds is to push through the oil and determine precisely where the part should stick.

I am still open to other solutions to getting printing working a consistant basis. I would however, like to avoid a heated bed. Does a heated print bed even help that much anyway? After reading [blog.onshoulders.org] I have decided to give skeinforge a try. If it works as well as this says it will, I think it should be at least mentioned in the mendel build instructions.

-Bill

I don't remember anybody being able to print ABS on a cold bed without a raft. I think you need either a heated bed or rafts and a heated bed produces much flatter objects and allows you to print much bigger objects.

If you want to not use a heated bed then PLA is more suitable.

Edited 1 time(s). Last edit at 12/07/2010 05:52AM by nophead.

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[www.hydraraptor.blogspot.com]

nophead Wrote:
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> I don't remember anybody being able to print ABS
> on a cold bed without a raft.

I was afraid of this, but I hadn't read anything to confirm it until now. I need to research heated beds.

> I think you need
> either a heated bed or rafts and a heated bed
> produces much flatter objects and allows you to
> print much bigger objects.

I will have to try my corner weld technique on a large object to see if it is worth investing any more time into. I was impressed with the initial results on the one object I printed this way.

I installed skeinforge last night to print rafts, skeinforge kinda makes my head spin. I don't think I found the correct link for ktclk, I ended up downloading and installing activePython instead. Anyway it sortof works, the gcode it creates crashes the electronics if I don't comment out the lines starting with (<. There are no E-commands in the gcode so if I run it, the print nozzle just moves, very slowly, around the print area, extruding nothing. Still some work to do.

> If you want to not use a heated bed then PLA is
> more suitable.

I have a sample of PLA I have tried on blue making tape without success. I will have to try it again

Sadly, I am allotted only about 2 hours on occasional weeknights to research and experiment, only giving me time to setup and print one small test part. I should be able to test some of these things this weekend.

Thanks for your advice
-Bill

Quote
Bill
I installed skeinforge last night to print rafts, skeinforge kinda makes my head spin. I don't think I found the correct link for ktclk, I ended up downloading and installing activePython instead. Anyway it sortof works, the gcode it creates crashes the electronics if I don't comment out the lines starting with (<. There are no E-commands in the gcode so if I run it, the print nozzle just moves, very slowly, around the print area, extruding nothing. Still some work to do.

In Craft - Dimension - check "Activate Dimension (Absolute)" to generate E-commands.
In Craft - Export - check "Activate Export" and select "Delete Crafting Comments" or "Delete All Comments".

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Bob Morrison
Wörth am Rhein, Germany
"Luke, use the source!"
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