Ending a TIG weld can be just as important as starting one. If the arc stops too abruptly, it’s easy to leave behind a small crater that can crack later or create a weak spot at the end of an otherwise perfect bead.
That’s where understanding what is down-slope on TIG welder becomes valuable, especially if you’re aiming for cleaner, stronger welds.
Many TIG welders include a down-slope setting, but it’s one of the most overlooked controls on the machine. Instead of cutting the current off instantly, it gradually reduces the amperage, giving the weld puddle time to solidify smoothly. The result is better crater fill, improved bead appearance, and fewer defects that require grinding or repair.
Whether you’re welding stainless steel, aluminum, or mild steel, knowing how and when to use the down-slope function can noticeably improve your weld quality.
I’ll explain what down-slope does, how to adjust it correctly, and the situations where this simple setting makes the biggest difference.
Image by preferredmachinellc
What Exactly Is Down-Slope and How Does It Work?
Defining Down-Slope in TIG Welding
Down-slope is a programmable feature on most modern TIG power sources, like Miller Dynasty models, Lincoln Precision TIGs, or affordable inverters from YesWelder and Everlast popular in US home shops. It works alongside upslope (ramp-up at the start) and often crater fill functions.
The Mechanics Behind the Feature
Here’s how it works: When you release the torch trigger (in 2T or 4T mode) or lift your foot off the pedal, the machine doesn’t snap the current from your main welding amperage straight to zero. Instead, it linearly or in steps decreases the output over your chosen time—typically 0.5 to 10 seconds or more.
Many machines also let you set an end amperage, like 10-30% of peak, so the arc tapers gently before extinguishing.
This gradual reduction gives the molten puddle time to cool and accept filler metal. Without it, the puddle shrinks rapidly, pulling in on itself and forming a depression or “crater” that can crack as it solidifies. On thin materials or high-nickel alloys, that crater becomes a stress riser.
Practical Machine Setup Tips
In practice, I set down-slope based on material thickness and joint type. For 1/8″ aluminum, I might use 2-4 seconds with end amps around 20-30. For thicker stainless pipe, 5-8 seconds helps manage heat. Your machine’s manual will show exact parameters, but real-world testing on scrap beats theory every time.
Why Down-Slope Matters More Than Most Welders Realize
Real Impact on Weld Quality and Integrity
Think about the last time you welded a thin stainless exhaust tube or an aluminum tank. You nail the bead, but the end looks like a volcano crater. That defect isn’t just ugly—it compromises strength. Craters trap contaminants, promote cracking, and fail dye penetrant or X-ray tests in professional work.
Benefits for Everyday Welding Tasks
Down-slope addresses this by controlling heat input at termination. It minimizes distortion on thin sheets, reduces tungsten contamination risk, and improves overall bead appearance. For hobbyists building roll cages or pros doing sanitary welds, it’s a game-changer for consistency.
I’ve seen beginners crank amps and rely on speed to “outrun” the heat, only to leave nasty ends. Pros use down-slope to weld cleaner and faster overall because they spend less time fixing mistakes.
When and Why You Should Use Down-Slope
Ideal Situations for Down-Slope
Use down-slope almost anytime you’re not running full manual foot-pedal control on every weld. It’s essential for thin materials (under 1/8″), aluminum and stainless, longer runs or production work, and repair jobs.
When to Skip or Modify It
Skip it on very thick sections where you might want abrupt stops, or when using a foot pedal for total real-time control. Even then, many pedal users combine it with down-slope for the final taper.
Why? Because abrupt arc extinction causes rapid cooling. The puddle contracts, and without enough filler or controlled heat, you get shrinkage voids. Down-slope lets you keep feeding rod while amps drop, filling the crater perfectly.
Setting Up Down-Slope on Common US TIG Machines
Basic Configuration Steps
Most US hobby and pro machines handle this similarly. Start with your base settings: Select TIG mode (DC for steel, AC for aluminum), choose 2T or 4T trigger mode, set pre-flow, main amperage, down-slope time, end amperage, and post-flow.
Testing and Fine-Tuning Your Settings
On a Miller or similar, you’ll see dedicated knobs or menu options for slope times. Test on scrap: Strike the arc, weld a short bead, trigger the end, and watch the puddle. Adjust until it fills flat without sinking.
Pro tip from the shop floor: Always clean your tungsten and use the right cup size. Gas turbulence at the end can ruin a good taper if post-flow is too short.
Step-by-Step TIG Welding with Down-Slope
Mild Steel Example Walkthrough
Let’s walk through a typical repair on 1/8″ mild steel plate—common in fab work. Joint prep: Grind clean, bevel if needed, tack with low heat. Use 3/32″ tungsten and ER70S-6 filler. Settings: 90-120 amps main, 2-second down-slope, 20% end amps, post-flow 8 seconds.
Weld by starting with upslope if available. Maintain tight arc, add filler steadily. As you near the end, release trigger. Keep the torch in place and dab filler as amps drop. Watch the puddle shrink smoothly.
Aluminum-Specific Technique
For 1/8″ 6061 aluminum, use AC balance around 60-70% EN, frequency 100-150 Hz, down-slope 2-4 seconds. Move the torch in small circles or back-step slightly while downslope runs. This distributes heat and fills evenly. Common mistake: Pulling the torch away too soon.
Stainless Steel and Other Materials
Handling Stainless with Down-Slope
On 304 or 316 stainless, down-slope shines for color control and corrosion resistance. Use 4T mode for longer welds. Set longer slopes (4-8 seconds) because stainless holds heat longer. Purge the back side if possible to prevent sugaring.
Exotic Alloys and Special Cases
For exotic materials like Inconel in repair work, precise down-slope combined with pulse settings keeps the heat-affected zone minimal.
Common Mistakes and How to Avoid Them
Beginner Pitfalls
Beginners often set down-slope too short, forget to add filler during the ramp-down, ignore joint fit-up, or use dirty metal.
Even Pros Slip Up Sometimes
Pros slip up by over-relying on automation without watching the puddle, using the same settings across all thicknesses, or neglecting tungsten prep.
Fix these by practicing on coupons and logging settings that work for your machine and materials.
Down-Slope vs Foot Pedal: Which Should You Use?
| Aspect | Down-Slope (2T/4T) | Foot Pedal Control |
|---|---|---|
| Ease for Beginners | High – automated taper | Steeper learning curve |
| Precision | Good for consistent ends | Best for variable heat input |
| Thin Material | Excellent crater control | Superior if skilled |
| Production Speed | Faster setup for repetitive welds | More fatigue on long runs |
| Crater Prevention | Reliable with proper settings | Excellent with practice |
Both have places. Many welders use pedal for bodywork and slopes for pipe or fixtured jobs.
Joint Preparation, Filler, and Amperage Essentials
Preparing Joints Properly
Cleanliness is non-negotiable. Grind or wire-brush to bright metal. For aluminum, use a dedicated stainless brush. Match filler to base metal.
Recommended Amperage Ranges
- Mild Steel (DCEN): 1/16″ tungsten – 50-90A; 3/32″ – 80-150A.
- Aluminum (AC): Similar ranges but higher for oxide cleaning.
- Stainless: Slightly lower than steel to control heat.
Electrode diameter affects current density. Always match to your machine’s capabilities.
Safety Considerations in TIG Welding
Wear proper PPE: helmet with good lens (9-13 shade), leather gloves, jacket. Ensure good ventilation—especially with stainless or aluminum. Down-slope indirectly helps safety by reducing spatter and hot metal pops at termination. Never weld without post-flow.
Real-World Applications and Advanced Techniques
Shop Examples That Prove It Works
On a recent exhaust repair for a classic truck, down-slope let me tie into existing thin tubing without blowing holes. For a custom aluminum fuel cell, consistent 3-second downslope across dozens of seams prevented leaks.
Combining Features for Better Results
Pulse TIG plus down-slope is killer for thin materials. Some machines offer “crater fill” as a dedicated mode—essentially enhanced down-slope.
Troubleshooting Crater and End Defects
- Crater still forms: Increase slope time or add more filler.
- Tungsten contamination: Extend post-flow, check gas flow (15-20 CFH).
- Porosity: Clean better, check for drafts.
- Uneven bead: Practice trigger timing in 4T mode.
Building Consistent Skills with Down-Slope
Practice short beads on scrap daily. Vary thicknesses and note settings in a shop notebook. Over time, you’ll dial in instinctively. Down-slope isn’t a crutch—it’s a tool that frees you to focus on puddle control, travel speed, and rod dipping.
After years of running beads on everything from mild steel to exotic alloys, one thing stands out: the best welders control heat from start to finish. Down-slope gives you that control at the most vulnerable moment. Experiment on your machine, watch the puddle like a hawk, and you’ll produce stronger, prettier welds with less frustration.
Keep your tungsten sharp, your metal clean, and your settings dialed. The next time you’re wrapping up a bead on a critical joint, that smooth taper will remind you why these features exist.
One pro-level tip I’d give any welder heading into the shop: Treat the end of the weld with as much respect as the start—because that’s often where failures begin. Master down-slope, and you’ll weld with confidence on any job that comes your way.
FAQ
How long should I set down-slope on my TIG welder for aluminum?
For 1/8″ aluminum, start with 2-4 seconds and 20-30% end amperage. Thinner material needs shorter times; test and adjust while watching the puddle shrink evenly without sinking.
Can I use down-slope without a foot pedal?
Yes. In 2T or 4T trigger modes, down-slope works independently. Many entry-level inverters shine here for hobbyists without a pedal.
Why am I still getting craters even with down-slope?
Common causes: too short slope time, not adding filler during ramp-down, dirty metal, or insufficient post-flow. Increase time and practice feeding rod until the arc extinguishes.
Does down-slope work on all TIG machines?
Most inverter TIGs have it, but basic transformer machines may not. Check your model’s manual—higher-end US brands like Miller and Lincoln offer robust controls.
What’s the difference between down-slope and crater fill?
Down-slope is the time-based ramp; crater fill often includes automatic filler addition or specific end current settings. Many machines combine them for best results.
