As far as plans go - this is probably as good a place to start as anywhere..
Original Mendell construction
(again - this assumes the Botmill model you are getting is this version of Mendell - pics on the Botmill page certainly look like it.)
One of the links is to the "Mendel solid model files". If you haven't already, then get OpenScad (free 3D CAD, scripted rather than GUI - you'll learn to love it ! ) - as the files are in that format.
There are also assorted notes on checking the mechanical assembly.
I can't find any obvious single wiki item for "steps for first time you switch on", this was my approach..
There may well be better procedures out there somewhere - or provided with particular commercial products.
Also - these were my "starting point" - you will find plenty of advice on refining all of this from the experienced reprappers on the forums.
- use a small level and plumbob (e.g. nut on cotton) to check the horizontal and vertical bars are just that.
( and also the bed should be initially approximately levelled, before precise levelling below)
- the extruder rotates freely - (eccentricity in printed gears can cause tight spots)
- the bolt hobbing is lined up with the filament feed holes
- you can insert a piece of filament and wind it through manually, and the hobbed bolt grips well,
- the X & Y belts should be firm ( supposedly taut enough so that when tweaked should hum at about 100hz)
- ensure the travel on the 3 axes does not foul anything, and doesn't have "tight spots" (lightly lubricate smooth rods)
- the limit switches are positioned ok
(if micro-switches, they click before the bed Y movement or X carriage run into the framework, or Z runs into the bed,
if optical, then the flags seat correctly in the opto-sensors (see note below) )
After the endstop checks, you will have found winding Z up and down by hand is fairly tedious.
At this point I center the X carriage & the Y bed, raise Z a few cm, and apply power.
Make sure the power switch is readily accessibly just in case anything odd happens.
The usual power supplies found in repraps (often ATX PC PSUs) will shut themselves down if there is something serious like a short.
Optionally measure the 12v supply - if it's around 12v, then there's no major problem yet.
With the printer connected to your PC by USB then the host s/w should now be able to communicate with the firmware on the printer.
There will be a manual movement control panel on the PC S/W. They pretty much all have similar functions.
Select +10mm on X. Ensure the X-carriage moves to the right.
Same on Y, the bed should move away from the endstop.
For Z - it should move up.
If any of these are reversed, either reverse the wiring to the relevant stepper, or, usually easier (for some) edit the firmware, locate the relevant axis INVERT definition, alter, recompile, reload firmware to printer.
ALWAYS TURN POWER OFF BEFORE TOUCHING STEPPER ELECTRICAL CONNECTORS - inductive spikes kill stepper drivers. Expensive.
Test Homing. If there was to be a problem with the Home end-stop detection, it's too late to find out when the carriage or bed hits the stop and tries to keep going. So I "fake" an end-stop hit well before then.
Either put your finger near the end-stop microswitch, or hold a piece of card or similar (opaque) close to the opto-sensor - (having practiced inserting it)
Now hit the Home-X control. The carriage should start moving towards the end-stop. Fairly quickly press the end-stop micro-switch, or insert the card into the opto-sensor slot.
The carriage should stop, and will usually "bounce", i.e. it reverses away from the stop position a few mm, then retries. (I think this is to counteract any error due to a possibly higher initial "home-seek" speed. )
Be prepared to hit the power switch if it ignores the activated end-stop - because it is likely to just keep going and try to step right through the frame. (in fact, apart from some belt and pulley stress, it is not catastrophic for a stepper to hit the wall for a short time. It just grumbles loudly. )
Do the same with Y.
If they acknowledge the end-stops correctly, it should be safe to try the X & Y home controls for real.
Z is another kettle of fish.
- initial Bed level check: ( you first need to determine how your bed height adjustments are made. Often a screw at each corner.)
If the bed has not been precisely levelled before, e.g. if you have opto end-stops and this is the first "power-on Z-home",
you don't want to take the extruder tip all the way down to Z-home under power before ensuring there will be positive clearance. Negative clearance is a bad thing. The extruder is likely to be damaged by being driven into the bed. This will be less so if the bed is sprung.
With X & Y at the home positions, use the control panel to move Z down until the extruder tip is a few mm from the bed.
Then *while observing the tip clearance* gradually drive Z down to 1mm then in 0.1mm steps until the end-stop switch clicks or the opto flag enters the opto-sensor. The firmware *should* refuse to drive another 0.1mm once the end-stop activates.
If the tip gets less than 0.2mm from the bed before the endstop kicks in,
then you need to either take the endstop up some, or adjust the opto flag down
or use the bed adjustment to lower that.
You are aiming for about 0.2mm clearance between tip and bed when the Z end-stop activates. (actually about 0.1mm less than your intended print layer height, I use 0.3mm)
You need a Clearance Gauge - I just use a folded piece of copy paper. Two thicknesses is fairly accurately 0.2mm, and should just slide under the tip. Three thicknesses should not. (you do of course have that core reprapper's tool, a digital caliper? (from jaycar for us Australasians)
Once you have that clearance at X/Y home, then you must go round the periphery of the bed.
Take the Z-axis up until the smooth part of a drill bit neatly fits (rolls) between the extruder tip and bed at the X/Y home position.
( arbitrary drill size e.g. 3mm - a handy reliable size guauge, at this stage it's just to ensure there is the same level round the bed, at a safe enough height to avoid scrapes if there is a signifcant level difference first time round)
I then move X & Y round the corners of a rectangle a couple of cm in from each edge, and adjust the bed corners to get the same 3mm clearance.
You should go round twice - as each corner adjusted affects the others slightly.
Finally you can repeat the careful 0.1mm-at-a-time step check of full Z-home at X/Y home, and then run round the corners getting the same.
You need to check that levelling after any significant mechanical work - like removing and replacing the hot-end, or even an energetic digging off of a printed object well stuck to the bed. Possibly also after after a filament jam where you have had to put pressure on the extruder to get filament out, or pressed down to get flowing again.
( Opto endstops note: You can't tell when an opto has activated unless it has power applied. You could apply power, without actually commanding any stepper motion, put a meter on an end-stop, note how the voltage varies when you put a card in the sensor.
Look for the same indication on the meter when manually running the axis to its end-stop. )
For steps/mm calibration - see forum topics e.g.
How to calibrate a reprap
Synopsis. Home an axis. command it to drive +10mm. Use digital caliper to measure distance of carriage or bed from a fixed piece of frame, both before and after. If the difference is more than a few % from 10mm, modify the relevant axis steps per mm in the firmware. This will be either dynamically settable from the PC S/W into firmware EEPROM storage, or more primitively will require recompilation of the firmware with altered source constant definitions. (If you have to do the latter, consider switching to a more modern firmware)
Once this gets close for a 10mm test, do a 100mm test. (The reason for not going straight to a 100mm test: if the value is badly out, you may be trying to drive off the end of the rods.)
With no hot-end in place, check a 100mm feed through the extruder.