Printrbot+ Printbed Assembly

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These instructions assume you have done the assembly prep step and assembled the base.

Before you proceed

This part of the instructions differs substantially from Brook's videos. In addition it expects use of glass on the heat-bed and some heat insulation below the heat-bed PCB.

Also consider this forum post by CL1 about using a cork insulator, shims, then glass with binder clips to hold it all together.

Simple heatbed

If you want to go the with the easiest assembly and don't use the glass and heat insulation. Use the heating PCB with the wire side facing down (to the plywood) and with the "printrbot" logo facing up. Be aware that the photos show the opposite view because they will be using glass. The disadvantages of this are that you will have a hard time getting a completely flat because the PCB will flex as it heats. Without the insulation it will heat up slower and expend more energy maintaining the bed temperature. You will also be missing the bed-leveling screws, so it will be harder to level your bed and keep it level.

If you still want to continue with the basic way, you will need:

  • 1x Heat-bed
  • 1x the LC heat-bed plywood
  • M3 bolts + nuts for heat-bed + washers (4x M3x16mm bolt + 4xM3 nut or 4xM3x20mm + 12x M3 nut (+ 12x washer), see text below)
  • 4x Bolt - #6-32 0.5"
  • 4x Bolt - #6-32 1.25"
  • 1x Bolt - #6-32 1.25" for end-stop?
  • 8x Nut - Hex - #6-32
  • 1x the shorter belt
  • 1x heat-bed thermistor
  • 1x zip-tie
  • 2x 13_Shaft_8mm 8mm x 13" Smooth Rod
  • printed (or perhaps, cast) parts: 2x CLIP - belt clip, 3x YBAR Y-bar holder, 1xYBARBH Y-bar with bolt hole

However I don't recommend doing it.

If you still don't want to bother with the heat insulation, or the leveling screws, or the glass; simply tape (ideally with Kapton) the thermistor onto the side of the PCB with the heating grid, then use M3x16mm bolts with M3 hex nuts to bolt the PCB to the plywood.

Optional heat-bed leveling screws, heat insulation, glass

In the following steps I will describe how to assemble the heat-bed with some insulation between the plywood and the heating PCB and with the glass (200 x 200 x 3mm large) on top of the PCB. If you insert some insulation between the PCB and the plywood, you need to add some "spacers" on the bolts as well. You can use this to add a set of nuts allow "leveling" of the heat-bed in the future (allowing to make it as parallel as possible to the plane of the head movement). You also gain some space which can be used for the clamps securing the glass.

Pbp assy printbed 01 03.jpg Pbp assy printbed 01 05.jpg

Step 1: Attach the Thermistor

Required parts:

  • 1x Heat-bed
  • 1x heat-bed thermistor
  • 1x M3x20mm screw, with nut and washer (only if building the levelable version)

Tape the thermistor in the middle of the side of the heat-bed that will go down. It's not really necessary to cover the the thermistor completely with Kapton tape.(But it won't harm anything and may prevent a short-circuit in the future.)

If building the simple version without glass on top the thermistor should go on the "wire side" of the PCB (the one with no logo in it). And this side should be facing down towards the plywood.

If building the level-able version use the M3x20 bolts with nuts and washers as the picture shows.

Pbp assy printbed 01 01.jpg Pbp assy printbed 01 02.jpg

Step 2: Under the bed

Required parts:

  • M3 bolt nuts for heat-bed + washers (see text above)
  • Heat insulation (optional)
  • 1x Zip Tie
  • 4x Bolt - #6-32 0.5"
  • 4x Nut - Hex - #6-32
  • Printed (or cast) parts: 2x CLIP - belt clip
  • Plywood print-bed LC part

If desired, attach some heat insulation between the heat-bed PCB and the print-bed plywood. Add the nuts and washers on the bolts in heat-bed (see a few pictures above) if assembling the leveling heat-bed. Lead the wires through the big hole in the plywood part (be careful not to break the wires off from the PCB board) and bolt the PCB to the plywood. Make sure that the two holes in the front of the PCB are on the right hand side of the print-bed.

Pbp assy printbed 01 04.jpg

Zip-tie the wires from the heat-bed and thermistor to the plywood. The Kapton tape is there in order to have things more "nice and tidy" and hopefully it will help prevent the wires below the zip tie from breaking.

Pbp assy printbed 01 06.jpg

Attach the belt clips (CLIP) to the bottom of the print-bed. The orientation doesn't matter that much right now, but I'd say make it same on both sides. (Ignore the bar end in the top right corner, I accidentally left it there when taking the photo.)

Pbp assy printbed 01 07.jpg

Step 3: Prepare the Base

Required parts:

  • 4x Bolt - #6-32 1.25"
  • 1x Bolt - #6-32 1.25"? (something for end-stop, hard to guess the size from the video, I'll adjust this after I get the bot running)
  • 4x Nut - Hex - #6-32
  • 1x the shorter belt
  • 2x 13_Shaft_8mm 8mm x 13" Smooth Rod
  • The assembled base
  • Printed (or cast) parts: 3x YBAR Y-bar holder, 1xYBARBH Y-bar with bolt hole. On late 2012 machines, the Y-bar holders are lasercut wood.
  • "The shorter" timing belt

Insert the timing belt. It's much easier to do it now than later on. Carefully insert the smooth rods in the linear bearings. Gentle wiggling while inserting may help. Be careful because it is not that hard to break the bearings if you push the rod in at the wrong angle with too much force.

Pbp assy printbed 01 08.jpg

Remember that the arrows on the base parts point to the front of the bot. Attach the Y-bar holders as shown on photo. The one with the extra bolt (#6-32 1.25") for triggering the y-end-stop should go in the front left corner. Obey the orientation of the bar holders. The "bolt side" should go inside. If you put washers below the nuts securing the heating PCB in place, you might need to file the edges of the front two holders. (On the photo you may see that I first filed the wrong edge first. Only the inside one should be filed. ;) )

Pbp assy printbed 01 09.jpg Pbp assy printbed 01 010.jpg

Some late 2012 machines may need[1] to raise the print bed, by inserting washers under each Y-bar holder.

Step 4: Attach Bed to Base

Use the #6-32 1.25" bolts and 6-32 nuts and bolt the print-bed plywood to the y-bar holder.

Pbp assy printbed 01 011.jpg

If you assembled everything correctly so far, you should have the y-bar holder with the end-stop bolt on the left side (and if you move the bed backwards the bolt should hit the free end of the metal strip of the end-stop switch). On the right side of the heat-bed you should have the belt clips.

Step 5: Thread the Belt

The belt should go through one slot in the clip forth and through the other one back. When attaching the belt to the printbed the belt should be as parallel with the threaded rods as possible. So choose the way through the holes with respect to that. You might even try to rotate the belt clamps, they're not symmetrical. ;)

A correctly tightened belt should make a low noise when you pluck it, like a big guitar string. But you don't worry much now, you can retighten the belts later on if you find out your round prints don't come out round, or on the edges there is backlash or overshoot.

Pbp assy printbed 01 012.jpg

Before you put your assembly aside and will continue with the extruder, check that the y-endstop switch is correctly hit with the bolt.

Pbp assy printbed 01 013.jpg

Next Step

The next step is to assemble the Extruder.