If your microwave’s waveguide cover is scorched, cracked, greasy or missing, it should be replaced before using the appliance again. The cover helps protect the waveguide and internal components from food splashes and moisture.
If we don’t sell a pre-cut cover to fit your oven, you may be able to make a replacement using suitable MICAS microwave mica sheet or MICAL microwave mica sheet, provided the material is intended for microwave waveguide covers.
What you’ll need
- A suitable MICAS sheet or MICAL sheet
- The original waveguide cover, if available
- Pencil or fine marker
- Ruler or measuring tape
- Scissors, a sharp craft knife or tin snips
- Fine sandpaper or a nail file
- A screwdriver, if the cover is screwed in place
- Safety gloves and eye protection
Do not use ordinary plastic, cardboard, paper, aluminium foil or other household materials. The replacement must be made from proper microwave waveguide mica sheet.
Important safety advice
Unplug the microwave before removing the waveguide cover.
Only work from inside the cooking cavity. Do not remove the microwave cabinet or touch any internal components. Microwave ovens contain high-voltage parts that can remain dangerous even after the appliance has been unplugged. If the cover is difficult to access, the oven has sparking or burning damage, or you need to remove the outer casing, use a qualified microwave repair technician.
1. Remove the damaged cover
Check how the original cover is held in place. It may be secured with a screw, clip or retaining tab.
Remove it carefully and keep the screw or fixing safe. If the cover is stuck because it has melted or become greasy, do not force anything into the waveguide opening.
Clean away loose food residue from the surrounding area using a damp cloth, then allow it to dry fully.
2. Trace the original shape
Place the old cover on the MICAS or MICAL sheet and trace around it.
If the old cover is badly damaged or no longer available, measure the mounting area carefully. The new cover should match the original shape and cover the waveguide opening completely without pressing against the cavity wall.
Make sure you mark:
- The overall length and width
- Any angled corners or cut-outs
- The position of screw holes
- The direction the cover is fitted
The shape and fixing points need to match the original. A cover that is too small, loose or incorrectly positioned may allow grease and moisture into the waveguide.
3. Cut the new cover
Cut along the marked line using scissors, a sharp craft knife or suitable snips.
Take your time and avoid bending the sheet sharply. The finished cover should be flat, with no cracks or splits.
Smooth any rough edges with fine sandpaper or a nail file. Remove all dust and small fragments before fitting the cover.
4. Check the fit
Place the new cover over the waveguide opening without fixing it yet.
Check that:
- The opening is fully covered
- The cover sits flat
- No edges are folded or sticking up
- The screw or clip holes line up
- The cover does not touch the turntable, grill or other moving parts
- There is no large gap around the waveguide opening
Do not force the cover into position. If it does not fit correctly, remove it and adjust the shape carefully.
5. Fit the replacement cover
Refit the original screw, clip or retaining tab. Tighten a screw only enough to hold the cover securely, as overtightening can crack the mica sheet.
The cover must not be loose, bowed or able to move during use.
6. Inspect the microwave before testing
Before reconnecting the appliance, inspect the cooking cavity. Do not use the microwave if you find:
- Burn marks or holes in the cavity
- Peeling or damaged internal coating
- A damaged door, seal or hinge
- Evidence of arcing around the waveguide
- Burnt wiring or damage around the cover opening
These faults require professional inspection.
7. Test the microwave
Once the cover is fitted securely, place a microwave-safe cup containing water inside the oven and run it briefly.
Stop immediately if you see sparks, hear unusual buzzing or crackling, smell burning, or notice smoke. Unplug the appliance and arrange a professional inspection.
Never operate the microwave without a waveguide cover fitted.
Can I reuse the old screw?
Usually, yes, as long as it is the original fixing and is clean and undamaged. Do not replace it with a random screw, especially one that is too long or made from an unsuitable material. If the original fixing is missing, ask a qualified repair technician to identify the correct replacement.
Final advice
Making a replacement waveguide cover can be a practical solution when a pre-cut part is unavailable, but the material and fit are important. Use only proper microwave waveguide mica sheet such as MICAS or MICAL, copy the original shape accurately, and never use the appliance if the new cover does not sit securely.
If you are unsure about the material, measurements or condition of the microwave, it is safer to have the appliance checked by a qualified technician.
