Builders/Lasercut Hints

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Tips to remember before starting

This page documents some tips for people building Builders/LaserCut RepStraps.

Remove the protective film?

Beware there are some acrylic parts from which the blue cling film or backing paper should not be removed, as the fractions of a millimeter thickness are needed in the construction, such as to ensure fit for moving parts. For all other parts, it is advisable to remove the blue cling film from the parts just about before you put them in place. If you already know during assembly that you will need to remove a specific part again later, you may decide to leave the backing paper or film on that specific part as a reminder, and then remove the film during final re-assembly.

Buy a 5mm spanner

There are a lot of 5mm nuts. Getting a 5mm spanner will save time as long as you do not over tighten.

Keep all the bits

Ian has done a good job of getting the most out of the plastic. Unfortunately some bits that look like they should be thrown away are actually required. Personally I had a special reprap bin which had all the offcuts in it. So far I have gone through it about three times looking for missing parts. Fortunately they were all there safely in the bin.


It is tempting to go for "good enough" when it comes to accuracy on your first build. But getting it right first time saves a lot of time in the long run as the reprap simply will not work if it is out of alignment. (especially the Z axis) you will be faced with the soul destroying prospect of pulling it all apart to get it done right.

Over tightening

Careful when tightening any screws or bolts, Acrylic does not show stress very well. Resist the urge to give it one more turn. Remember if it is tight enough to hold the parts in place there is no need to go any further. You also can always come back and re-tighten something if it comes loose. A small acrylic spanner is included in the current 3mm sheet; it is more than sufficiently strong to crack the acrylic parts!

Fixing Cracked parts

If you do happen to over-tighten a piece and it cracks do not worry too much.

  • First make sure you have all of the broken bits.
  • Test your glue. If you bought the kit from Ian use some of the scrap border pieces to test your glue. Some super glues will work on Acrylic. Let the test part sit for several hours to make sure it really holds.If you want to make sure it works. Use an acrylic solvent such as "Plastic Weld" Or "Weld-on 4". (Most acrylic solvents do contain hazardous chemicals so use gloves and in well ventilated areas.)
  • Carefully glue one piece at a time. Hold the glue piece in for at least 30 second with light pressure. Let it dry/cure for a few minutes before gluing another piece.
  • Let the now fixed part dry completely. Read the label for the curing time (usually 24-36 hours)
  • I know you may want to rush this part but it is better to take your time and do it right once rather than have to redo it several times.

Lowering The Cost

You can reduce the cost of the Ponoko RepRap by cutting the MDF bed on cardboard as a template, then hacking your own out of your preferred bed material. This is also useful if you want to experiment with alternative bed materials.

Cutting Threaded Rod


  • Always wear leather/cloth protective gloves when handling metal that even MIGHT have sharp edges.


  • After cutting threaded rod, the threads at the point of the cut may have burs, dents, bends, etc that prevent a nut from moving smoothly, making it difficult to place a nut on the rod after cutting.
  • To prevent this problem, thread two nuts onto the rod above and below the cut (only one may be necessary depending on the condition of the outer ends of the rod before cutting, how many lengths to cut from a single rod, etc. - apply common sense).
  • More later.


  • OK. So cut the rod.
  • If your saw skips and jumps across the threads, use a file to put a small "V" into the rod where you want to cut.
  • Depending on your access to tools, patience, etc, you may find that girdling the rod with a v-groove using a file, then carefully bending the rod to break it is easier than cutting (use the nuts from STEP 1 to hold the rod close to the cut so you don't damage threads or bend the rod).


  • One tapers the end of the rod after the cut so that the nut easily centers on the rod.
  • Files have grooves. Threaded rods have grooves. Grooves lock into grooves. If this occurs while filing, frustration and potential injury (when the locked grooves suddenly jerk free while all your strength is applied to the file) may result.
  • Instead, use a sharpening tool: Arkansas stone, diamond tool sharpener, etc. Use one a little on the coarse side.
  • If you cut the rod with a filed v-groove (STEP 2), then half the tapering is already done. Slide the sharpener over the surface of the end (like chalking a pool cue) so as to smooth it into the rounded shape of a, er, shiva linga (look it up on wikipedia).


  • Grasping the rod and (STEP 1) nut with gloved hands (may need pliers/visegrips on nut, depending upon how badly the threads got buggered), run the nut down the rod to the cut end.
  • Thread nut about half off rod. Thread back onto rod. Iterate until nut slides easily, like rose petals on silk, over the entire length of cut/tapered section of rod. Now remove nut.


  • If this did not produce a rod end that easily accepts a nut, just forget I said anything.

Ordering from Ponoko

Ponoko should be offering pre-configured packages in the near future, but in the meantime you'll have to register, download the designs yourself from here, and upload them back to Ponoko in MyPonoko Account -> My Designs -> Add a new design. The following material configurations should be used:

  • 5mm-laser-acrylic.eps: Acrylic plastic, 4.5mm thickness, 790.0 mm x 384.0 mm sheet size
  • p2-3mm-parts.eps: Acrylic plastic, 3.0mm thickness, 384.0 mm x 384.0 mm sheet size
  • p3-bfb-extruder-beds.eps: Acrylic plastic, 8.0mm thickness, 790.0 mm x 384.0 mm sheet size

Note that clear acrylic may aid assembly, and not all colors are available in the needed thicknesses. Using clear acrylic and without shipping, this currently costs USD$385.41. If you get hold of Vik he can arrange a discount on the cutting.

Checking the rods for straightness

You should verify that your 500mm rods are straight. If they're not, you will be very unhappy. On a flat surface, lay two rods parallel about 400mm apart. Place the rod you are checking between those two rods. Take a fourth rod, and lay it on top of the rod being checked, parallel to the two rods. Use it to roll the rod back and forth. If the rod is not straight it will not roll smoothly. Bend it gently until it is straight.

English vs. (American)

  • grub screw (setscrew)
  • studding (allthread)

Grubs and nuts

The nuts with grub screws in don't really want to stay in place. You may wish to use a touch of hot-melt glue to hold them while you manipulate everything else.

McMaster-Carr Shopping List

This is a preliminary list of McMaster part numbers. There may be mis-buys. This list may not be complete if you're using NEMA 17 motors and/or are using bolts instead of studding in the Y-Axis Assembly.

Builders/McMaster-Carr Part Numbers

List of studding and rod lengths

This is a quick reference list of lengths of studding and steel rod used in the Ponoko design. Since my rods & studding came in 6 feet lengths, I made a reference guide so I could cut them all at once.


  • 1 x 110mm Extruder
  • 1 x 80mm X idler assembly
  • 2 x 70mm Y axis assembly
  • 1 x 500mm Y drive rod assembly
  • 4 x 400mm Bed Mounts / Y Axis Idler assembly (one will be shortened by the height of your z motor e.g. length is 290mm for NEMA23)
  • 1 x 290mm Z drive rod
  • 2 x 650mm Frame Base Bracing
  • 8 x 600mm Frame Side Bracing

Rod (steel 8mm)

  • 4 x 500mm Frame Base
  • 4 x 500mm Frame Sides
  • 4 x 500mm Frame Top
  • 4 x 500mm X Axis (make 2 x 520 if using NEMA23 motor)


  • 4 x 80mm Y Axis motor mount clamp (either rod or studding or a mix of both)

Extruder Assembly

Drive bolt thread

For reliable extrusion of HDPE the thread of the drive bolt needs to be deeper than the standard screw thread and have a sharp top edge to cut into the filament. One way to achieve this is cut the thread to at least 1.5mm deep using a small hacksaw.

PTFE tube

In use, the PTFE tube tends to bulge at the hot end, becomes shorter and then the extruder leaks. One way to reduce this is to drill out a big nut and press it over the end of the PTFE tube to hold it in shape.