Voron Switchwire Linear Rail Kit — Complete Conversion Guide

Upgrades Switchwire Linear Rails

The Voron Switchwire is unique among Voron printers — it's the only model that uses a y-axis with V-slot wheels on an aluminum extrusion rather than linear rails. While this works well for an Ender 3 conversion platform, upgrading to proper linear rails is one of the most impactful mods you can make. Last updated: May 2025.

This guide covers everything you need to convert your Switchwire to full linear rails on the Y axis (and optionally the X axis). We cover rail selection, mounting hardware, printed parts needed, belt path adjustments, tuning after conversion, and what print quality improvements you can realistically expect.

Why Upgrade to Linear Rails?

The stock Switchwire uses POM (polyoxymethylene) V-slot wheels running on a 4040 aluminum extrusion. While functional, this system has inherent limitations:

• Wear: V-slot wheels develop flat spots over time. The Switchwire's bed is heavy (typically 3-5kg with the cast aluminum bed), accelerating wheel wear significantly.
• Friction variation: Wheel tension that is too tight causes binding; too loose causes wobble. Finding and maintaining the sweet spot requires frequent adjustment.
• Debris sensitivity: V-slot wheels pick up dust and filament particles, which become embedded in the wheel surface and create high spots. This causes Z-band-like artifacts on Y-axis features.
• Limited acceleration: The rolling friction of V-slot wheels limits practical acceleration to around 3,000-4,000 mm/s^2 before wheel bounce becomes an issue.

Linear rails solve all of these problems. MGN9C or MGN12H rails on the Y axis provide consistent low friction, high load capacity, and no wear-induced flat spots for tens of thousands of hours of use.

Linear Rail Kit Contents

A typical Switchwire linear rail conversion kit includes:

• 2x MGN9C or MGN12H linear rails (Y-axis, length: 300-350mm depending on build size)
• 1x MGN9C linear rail (X-axis, optional, length: 250-300mm)
• 4-6 carriage blocks per rail (pre-assembled or separate)
• M3 and M5 mounting hardware (screws, T-nuts, washers)
• Rail alignment jig (3D printed, included in some kits)
• Linear rail lubrication oil

Not included: You'll need to print the modified Y carriage and X carriage parts (files available on the Voron User Mods repository). Most kits assume you already have a printer to produce these parts.

Choosing the Right Rails

MGN9C vs MGN12H for Y-Axis

For most Switchwire builds, MGN9C is sufficient and easier to fit. Use MGN12H if you plan to run a heavier bed (e.g., a thick cast aluminum bed with a PCB heater) or want maximum rigidity.

MGN9C for X-Axis

The X-axis on the Switchwire is already linear-rail based from the factory on most kits, but early Switchwire builds or budget kits may use V-slot wheels on the X axis too. If your X axis is already on an MGN9C rail, the conversion only covers Y. If not, add an X-axis rail to your kit.

Installation Procedure

Preparation

1. Print the modified Y carriage and X carriage parts. Recommended materials: ABS or ASA for all structural parts.
2. Gather tools: 2.5mm, 3mm hex keys, torque wrench (for rail bolts), digital calipers, machinist square, sharp knife or deburring tool.
3. Clean the rail surface with isopropyl alcohol. Do NOT remove the plastic protection strip until just before installation — rails arrive coated in oil and easily collect debris.
4. Apply a thin coat of lubrication oil (Krytox GPL-205 or Super Lube) to the rail surface and cycle the carriage back and forth 10-20 times to distribute.

Y-Axis Rail Installation

1. Remove the bed assembly from the printer. Set it aside on a clean, flat surface.
2. Remove the V-slot wheels, eccentric spacers, and wheel mounts from the 4040 Y extrusion. Keep the hardware for potential reuse.
3. Clean the 4040 extrusion surface thoroughly. Remove any adhesive residue from the V-slot wheel mounts using isopropyl alcohol.
4. Position the MGN9C or MGN12H rail on the extrusion. The rail must be perfectly parallel to the extrusion's T-slot. Use a dial indicator or the printed alignment jig to check.
5. Drill and tap M3 holes in the extrusion at 60mm intervals, or use M5 T-nuts if the extrusion slots are accessible. For a cleaner install, drill and tap.
6. Mount the rail starting from the center and working outward. Use a cross-tightening pattern and torque to 0.8 Nm (do not overtighten — M3 bolts in aluminum extrusions strip easily).
7. Check carriage smoothness: the carriage should slide freely with no binding. If there is binding, loosen the bolts, re-align, and re-tighten.
8. Install the second rail on the other side of the extrusion following the same procedure.
9. Check parallelism: both rails must be parallel within 0.1mm over their full length. A misaligned pair will cause binding and wear.

Bed and Y Carriage Mounting

1. Attach the printed Y carriage to the linear rail carriages. Most mods use 4 carriage blocks (2 per rail) with M3 screws.
2. Mount the bed to the Y carriage. Check that the bed is level relative to the rail using a machinist square. Shim if necessary using thin washers.
3. Adjust the bed height to maintain proper Z clearance. The Switchwire Z endstop position changes slightly with the taller carriage.
4. Install the Y belt. The belt path on a linear-rail Switchwire is usually identical to stock — the belt attaches to the Y carriage and loops around an idler pulley at the rear and the motor pulley at the front.
5. Tension the Y belt. Target frequency: 95 ± 5 Hz for a 250mm Switchwire build.

X-Axis Rail Installation (If Applicable)

1. Remove the X gantry from the Z extrusions.
2. Remove the V-slot wheels from the X extrusion.
3. Mount the MGN9C rail to the front face of the X extrusion using M3 bolts and T-nuts.
4. Install the X carriage block on the rail.
5. Mount the toolhead (StealthBurner or Mini StealthBurner) to the X carriage.
6. Reinstall the X gantry and check X-axis smoothness.

Tuning After Conversion

After the mechanical conversion, several printer settings must be updated:

Mechanical Adjustments

• Z offset: The bed height changes due to the taller Y carriage. Re-run Z endstop calibration and Z offset calibration.
• Bed mesh: Generate a new bed mesh. The new carriage may apply different pressure distribution, altering the bed's warp pattern.
• Belt tension: Re-tension the Y belt. The linear rail system has less static friction than V-slot wheels, so the same belt tension feels different.

Klipper Configuration Updates

• Update position_min and position_max if the Y carriage changes the toolhead's range of motion.
• Re-run SHAPER_CALIBRATE — the resonance frequencies of the Y axis will change significantly with linear rails. Expect Y frequency to increase by 20-40%.
• Re-run PID_CALIBRATE for the bed if the Z offset change affected the bed's thermal characteristics.
• Update max_accel — you can typically increase Y acceleration by 50-100% with linear rails. Try 5,000 mm/s^2 as a starting point and increase from there.

Expected Print Quality Improvements

• Ghosting reduction: 30-50% reduction in Y-axis ghosting due to higher resonance frequency and better damping.
• Surface finish: Elimination of periodic artifacts caused by V-slot wheel flat spots. Y-axis surfaces will be as smooth as X-axis surfaces.
• Acceleration: Practical Y acceleration increases from ~3,500 mm/s^2 (V-slot wheels) to 6,000-8,000 mm/s^2 (linear rails) with good input shaper tuning.
• Consistency: Print-to-print repeatability improves because the linear rails do not develop wear-induced geometry changes over time.

Troubleshooting

Binding After Installation

If the Y axis binds: (1) check that both rails are parallel — use a jacking screw or shim method to adjust, (2) verify the carriage blocks are mounted at the correct spacing (too close together causes binding, too far apart causes rocking), (3) check that the extrusion is not bent — a bent 4040 extrusion will cause binding regardless of rail alignment.

Belt Skipping

If the Y belt skips under acceleration after conversion, the lower friction of linear rails may be masking a loose belt. Increase Y belt tension by 5-10 Hz above the stock recommendation. The lower static friction means the belt needs to be tighter to prevent the carriage from "bouncing" on direction changes.

Bed Wobble

If the bed wobbles after mounting to the Y carriage: (1) ensure all carriage block screws are tight, (2) check that the Y carriage is rigid — some printed carriage designs flex under load, (3) consider adding a cable chain support to prevent the cable chain from pulling the carriage sideways.

Maintenance After Conversion

• Every 200 hours: Wipe the linear rails clean and re-apply lubrication oil. Cycle the carriage a few times to distribute.
• Every 500 hours: Remove the carriage blocks, clean the bearing balls with solvent, inspect for wear, re-grease with lithium grease or PTFE grease.
• Every 1000 hours: Check rail straightness with a dial indicator. If the rail has developed a bow (unlikely with proper installation), replace it.

Summary

Converting your Switchwire to linear rails is a major upgrade that transforms the printer's performance. The Y axis becomes as smooth and precise as the X axis, acceleration limits increase substantially, and the print quality improvement is immediately visible on Y-oriented surfaces. The conversion takes a weekend for an experienced builder, including printing the modified parts. For the cost of rails and hardware ($30-60), it's one of the highest-value upgrades you can make to a Switchwire.