Nice troubleshooting - great detective work finding the skewed lower-back skull and fixing the frame. Those photos help a lot.

A few quick suggestions and checks while your new low-back skull prints, and things to try after you assemble:

What to verify after printing

• Dry-assemble first (no glue or screws) and tighten only the problem screws a little at a time to watch how the geometry shifts.
• Place the assembled head on a known-flat surface (glass or a table) and check for gaps/rocking.
• Use calipers to measure critical mating features (arm lengths, nut pocket width, hole centers) and compare to the STL if possible.

Nut / slot recommendations

• If you’re designing pockets for a hex nut (typical M3 nut ~5.5 mm across flats):
  • Make pocket width 5.7-6.0 mm (0.2-0.5 mm clearance)
  • Pocket depth nut thickness + 0.3 mm so the screw head can seat flush or slightly recessed.
• For repeatable assembly I recommend heat-set inserts for M3 where possible (clean, strong thread), otherwise a snug pocket for a hex nut or using hot glue for quick fixes is fine.

Tolerance guidance (what I usually do)

• Press-fit (tight): 0.1-0.2 mm clearance
• Sliding fit: 0.2-0.4 mm clearance
• Easy assembly / removable: 0.5-1.0 mm clearance
  Start with +0.2-0.3 mm on mating faces where you had interference.

Print / slicer tips to reduce surprises

• Print orientation: orient mating surfaces to minimize warping (flat on bed when possible).
• Reduce extrusion multiplier by 2-4% if parts come out oversized.
• Lower print temp / increase cooling to reduce filament squish.
• Print a small test coupon (10-20 mm of the mating area) before printing the full part.

Design tips if you need to tweak the STLs

• Add small chamfers (0.5-1 mm) to mating edges so parts ramp into place instead of hitting a sharp corner.
• Add 0.8-1.0 mm alignment pins/holes to force correct registration of the panels.
• If a side arm is slightly shorter, add a 0.2-0.5 mm offset to that arm or a washer/shim area to compensate.

Would you like me to:

• Edit any of your STL files (low-back skull / frame / side panel) to add nut slots, change clearances, or add alignment pins? If yes, tell me the target clearance and whether you use M3 nuts or heat-set inserts.
• Or do you want to upload photos of the new printed low-back skull after it finishes and I’ll review fit/clearance?

Reference for uploading/managing 3D parts on Synthiam: https://synthiam.com/Support/ARC-Overview/Project-Menu/3D%20Parts

Nice progress - once your test print is done post the pics and I’ll help tune any remaining fit issues.

howdy roboteers

some more interesting stuf. i notest that the left side head of the frame was thicker then the right side .

so i have to adjust that .

and now the heads touching at desame time the frame .

maybe there wil be a wacher needed between the mask and frame .

Nice detective work - those photos make the issue clear. The thicker left "head" is forcing both the mask and frame to contact at the same time, which explains the binding and misalignment. You’re on the right track thinking a washer/shim might help, but there are a few better long-term and short-term options. Below I’ve listed quick fixes, preferred design corrections, slicer checks, and exact next steps I can take for you.

Short-term fixes (fast, no CAD changes)

• Add a thin washer/shim between the mask and frame where they contact.
  • Measure needed thickness with a feeler gauge or stack of printer paper (one sheet 0.08-0.12 mm).
  • Use a metal washer (M3) or print a 0.2-0.5 mm PETG/PLA shim circle with a 3.2-3.4 mm hole for the screw. PETG will be a bit more durable.
  • Tighten screws slowly and evenly while checking alignment on a flat surface (glass/table).
• If you want a single printed part shim, I can make and upload a tiny washer/shim STL sized for the mating geometry.

Preferred (recommended) fixes - edit the STL

• Reduce the left head thickness or subtract a small offset on that one side so both heads contact evenly. Target values:
  • Start with 0.2-0.3 mm reduction (typical printer compensation).
  • If the part was ~1.5 mm off, try ~0.5-1.0 mm to be conservative, then test.
• Add small chamfers (0.5-1 mm) or lead-ins to the mating edge so the parts ramp into place rather than hitting a hard corner.
• Add a 0.8-1.0 mm alignment pin + matching hole to force correct registration when the mask seats on the frame.
• If you need nut retention, add keyed nut pockets sized nut + ~0.2 mm or a recess for heat-set inserts.

How I can edit the STL (tools & steps)

• Quick boolean offset method (Meshmixer): create a thin rectangular block positioned to cut the extra thickness, then boolean-difference to remove it. Add chamfers with the "Sculpt / Flatten" tools.
• Precise method (Fusion 360): import STL, convert to BRep, use Modify Offset Face or direct face edits for exact mm adjustments.
  Tell me which approach you prefer and I’ll produce an edited STL.

Slicer / printer checks (to avoid future surprises)

• Extrusion multiplier: reduce 2-4% if parts print oversized.
• Horizontal expansion (Cura): try a negative value (-0.1 to -0.3 mm) to reduce outer dims.
• Print temperature / cooling: reduce temp or increase cooling to cut filament squish.
• Print orientation: put mating faces on the bed where possible to minimize warp.

Assembly tips

• Dry-assemble and snug screws evenly (don’t fully torque one side first).
• Use a flat glass or table to check that the head sits without rocking.
• For captive nuts, heat-set inserts (M3) give the cleanest long-term result; otherwise make a snug pocket for a hex nut + 0.2 mm clearance.

Next steps - pick one and I’ll do it

1. I can create a small shim/washer STL sized to your screws so you can print and test quickly. Tell me screw size (looks like M3?) and desired shim thickness (0.3 mm recommended).
2. I can modify the left head STL (or the whole frame) and add a 0.25-0.5 mm offset + chamfer/alignment pin. Tell me which STL you want edited (low-back skull / frame / side panel / mask).
3. If you prefer slicer tweaks first, tell me your filament (PLA/PETG), nozzle size (0.4 mm?), and typical layer height so I can recommend exact values.

Which option do you want? If you want an STL edit, upload the specific file name(s) or confirm the three you listed earlier (Eye Support Complete / Frame Mod / Jaw Hinges Mod) and your preferred clearance. I’ll prepare the file(s) and post them back for a quick test print.

@athena

with a spacer or wacher 4,1 MM it fit perfect , the frame and mask . do here's another problem i saw . the holes for the mask to the frame , doesn line up . bolt doesn line up .

short video

https://www.youtube.com/shorts/DvS3z2sSkEA

Nice find - that misaligned bolt hole explains why you needed the 4.1 mm spacer. Glad the spacer fixed the fit temporarily. Below are practical short-term and permanent fixes, exact edit options I can do for you, and questions so I can prepare the correct STL.

Short-term fixes (quick, no CAD changes)

• Use a longer bolt + washer so it can reach and thread even if hole centers are off.
• Ream or enlarge the printed hole with a drill bit (hand drill, Dremel, or drill press). Use the bolt diameter or a slightly larger bit (bolt dia + 0.2-0.5 mm) for clearance.
• Make the hole a slot: Carefully use a round file or rotary tool to elongate the hole in the direction of misalignment (2-3 mm long, width = bolt dia + ~0.3 mm).
• Keep the spacer (4.1 mm) as a temporary shim if it’s working well.

Permanent fixes (preferred)

• Edit the STL to move the hole center so bolts line up exactly. This is the cleanest fix.
• Or convert the hole to a slotted hole (elongated slot) sized for the expected alignment tolerance (slot length 2-4 mm depending on error, width = screw dia + 0.3-0.5 mm).
• Add a small alignment pin + matching hole to force perfect registration when assembling (0.8-1.0 mm pin/hole).

Recommended tolerances

• Standard clearance for screw holes: bolt diameter + 0.2-0.5 mm.
• Slot width = bolt dia + ~0.3-0.5 mm.
• If parts have been printing slightly oversized, allow +0.2-0.3 mm in the STL for holes.

How I can help (pick an option)

1. I can edit your STL(s) to shift the hole(s) so they align. Tell me which file(s) to edit (Frame Mod / Mask / low-back skull / other) and which hole(s) are misaligned.
2. I can create a slotted-hole variant of the part (slot length & direction based on how it misaligns).
3. I can design a small printed washer/shim set sized for your screws (if you want a nicer printed shim rather than a store washer).
4. I can prepare a "test coupon" STL (small section with the hole/slot) for a fast 10-20 mm test print so you can verify fit before printing the whole part.

Questions I need to prepare the right edit

• Which exact STL file should I edit? (Frame Mod or Mask or another file you posted)
• Which hole(s) do not line up - describe location or upload a close photo showing the two holes and the gap/offset.
• Screw size you’re using (looks like M3?). Bolt diameter and length.
• How much offset did you measure between hole centers? (If unknown, a close photo with a ruler or a caliper measurement helps.)
• Filament type and nozzle size (PLA / PETG and 0.4 mm nozzle) - I’ll set clearances accordingly.

Tools & quick references

• If you want to edit yourself: Fusion 360 (convert mesh->BRep, then edit hole positions) or Meshmixer for quick slot/cut edits.
• If you want to ream/slot manually: use a drill bit or round file sized bolt dia + 0.2-0.5 mm.

Upload or confirm and I’ll do the STL edit

• If you want me to edit an STL, tell me the filename (from your earlier uploads) and the choice of fix (move hole / slot / add alignment pin / create shim). I’ll prepare the modified STL and post it back for a quick test print.

Also - if you want, I can make a small printed shim/washers STL set sized to 4.1 mm thickness so you can print a tidy spacer instead of using random washers.

Next step: which part do you want me to edit (and provide the hole details)?

howdy roboteers and  @athena

little update for a sunday . small wacher for the center servo .  els you have the possebility to damage the mount from the servo. M4x20 MM screws .

Nice update - good catch adding a washer to protect the servo mount. That’ll prevent the screw head from digging in and help keep the mount flat when you torque the M4x20 screws.

A few practical tips and options you can use now, plus longerterm fixes if you want a cleaner part.

What works well right now

• Use a metal washer under the screw head (and/or under the nut) to spread the load.
  • Washer inner diameter: 4.3-4.5 mm for an M4 screw.
  • Outer diameter: 8-12 mm depending on available area.
  • Thickness: 1-2 mm (1 mm typically OK; 2 mm for extra protection).
• If you print the washer, use PETG or Nylon for strength and slight flex - PLA can crack under compression.
• If screw sits proud of the surface, add a thin printed counterbore or chamfer so the washer sits flush.
• If the screw threads into printed plastic (no nut), consider a heatset insert or a brass/helical insert for M4 for reliable repeated tightening.

Permanent/better fixes

• Integrate a larger bearing boss or washer recess into the servo mount STL so a washer becomes captive - prevents wandering and looks cleaner.
• Add a nut pocket or designed recess for a heatset insert so the M4 threads into metal instead of plastic.
• Add ribs/fillets around the servo boss to spread stress and reduce chance of cracking.

Exact sizes & tooling

• Drill/ream printed hole for M4 clearance: ~4.3-4.5 mm.
• Heatset insert hole (approx): check the insert spec (typical M4 brass insert needs a tight hole ~6-6.5 mm depending on style) - I can set exact sizes if you tell me which insert brand/type.
• Printed washer file: inner hole 4.3 mm, OD 10 mm, thickness 1.0 mm (I can make 0.5/1/2 mm variants).

Installation tips

• Tighten screws slowly and evenly. Snug progressively rather than full torque on one screw first.
• Use medium thread locker (blue) if vibration is an issue, or nylock nuts on throughbolted connections.
• If you use heatset inserts, warm them with a soldering iron and press in straight for best results.

Want me to prepare files?

• I can create a small printed washer STL set (0.5 / 1.0 / 2.0 mm) sized for M4 right now.
• Or I can modify your servomount STL to add a captive washer recess + nut pocket / insert pocket and post the updated STL for test prints.

If you want an STL edit, tell me:

• Which file (Frame Mod / Mask / lowback skull / servo mount filename).
• Whether you want a printed washer or an integrated recess & insert pocket - and whether you use heatset inserts or nuts.

Reference for uploading/managing 3D parts on Synthiam: https://synthiam.com/Support/ARC-Overview/Project-Menu/3D%20Parts

Which option do you want - quick washer STL or an edited servomount with nut/insert pocket?